Digital Camera And Shutter Operation Estimating Method

Abstract

A shutter blade is traveled to block light arriving at an image sensor at which light has arrived. Movement of a predetermined amount from traveling start of the shutter is detected (time) and a movement operation of the shutter blade is estimated based on a detection timing of the movement of the predetermined amount of the shutter blade, and a correction amount is set. The shutter is traveled at a travel start timing earlier than a basic travel start timing only by a timing correction amount correction amount based on the correction amount set until the previous time. Thus, an exposure period can be adjusted more properly.

Description

CROSS REFERENCES TO RELATED APPLICATIONS

The entire disclosure of Japanese Patent Application No. 2011-048739, filed Mar. 7, 2011 is incorporated by reference herein. The entire disclosure of Japanese Patent Application No. 2011-051445, filed Mar. 9, 2011 is incorporated by reference herein.

BACKGROUND

1. Technical Field

The present invention relates to a digital camera and a shutter operation estimating method.

2. Related Art

In general, an imaging apparatus applicable to a digital camera includes an imaging element that accumulates received light as charge and a focal-plane-type shutter that is traveled to block the imaging element from light. In the past, an imaging apparatus was suggested which adjusts an exposure period by controlling a start time of charge accumulation scanning of the imaging element corresponding to travel of an anterior curtain and a start time of shutter travel corresponding to travel of a posterior curtain, when a still image is photographed (for example, see Japanese Patent No. 3988215 (JP-A-11-41523).

Further, an electronic camera using an electronic shutter and a mechanical shutter together has been suggested. Such an electronic camera adjusts an exposure period deviation caused due to an individual difference of the mechanical delay from reception of an instruction of a closing operation of the mechanical shutter to start of the actual closing operation by executing previous and subsequent adjustment of a charge accumulation start timing or a shutter driving start timing of the electronic shutter while evaluating an exposure amount based on a signal integrated value corresponding to one-screen bright data (for example, JP-A-11-234574).

In digital cameras, adjusting an exposure period properly is one of the important tasks. In the method of adjusting the exposure period in the latter camera described above, however, it is necessary to photograph a light source determined under a given environment in order to adjust the exposure period deviation caused due to the individual difference of the mechanical shutters. Further, when the mechanical shutter changes over time, a user may not easily adjust the exposure period. Therefore, the user may not obtain a proper photographed image in some cases.

SUMMARY

An advantage of some aspects of the invention is that it provides a digital camera and a shutter operation estimating method capable of adjusting an exposure period of an image sensor more properly.

According to an aspect of the invention, there is provided a digital camera including: an image sensor that generates an image signal based on an exposure amount; a shutter that is moved in a predetermined direction to block light arriving at the image sensor; a movement control unit that moves the shutter to block the light arriving at the image sensor at which the light has arrived; a movement detecting unit that detects the shutter moving by a predetermined amount from movement start; and an operation estimating unit that estimates the movement operation of the shutter based on a detection timing of the movement detecting unit.

In the digital camera according to the aspect of the invention, the shutter blocking the light arriving at the image sensor in the predetermined direction is moved to block the light arriving at the image sensor at which the light has arrived. It is detected that the shutter moves by the predetermined amount from the movement start and the movement operation of the shutter is estimated based on the detection timing of the movement of the shutter by the predetermined amount. Accordingly, when it is detected that the shutter moves by the predetermined amount from the movement start and the estimation result of the estimated movement operation of the shutter is used to control the exposure period of the image sensor, it is possible to adjust the exposure period of the image sensor. That is, it is possible to adjust the exposure period of the image sensor more properly. Here, the movement detecting unit may detect that the shutter moves and reaches a detection position between the end of the shutter in an open state on the side of the image sensor and the end of the image sensor on the side of the shutter. Further, when only a partial region (referred to as an effective pixel region) of an image sensor circuit is effective, the image sensor described here means the image sensor circuit of the effective pixel region.

The digital camera according to the aspect of the invention may further include a reset control unit that starts reset scanning of the exposure amount of the image sensor in the predetermined direction in response to the movement operation of the shutter estimated by the operation estimating unit until the previous time. Then, by adjusting a timing at which the exposure amount of the image sensor is reset, it is possible to adjust the exposure period of the image sensor more properly. In this case, the reset control unit may execute the reset scanning of the exposure amount of the image sensor in the predetermined direction in accordance with a change in a speed corresponding to the movement operation of the shutter estimated by the operation estimating unit until the previous time. Alternatively, the reset control unit may start the reset scanning of the exposure amount of the image sensor in the predetermined direction at a timing corresponding to the movement operation of the shutter estimated by the operation estimating unit until the previous time. Here, the reset scanning of the exposure amount in the predetermined direction is executed by executing the reset of the exposure amount of the image sensor in sequence in the predetermined direction. The reset of the exposure amount includes executing reset of the exposure amount in a state where the reset of the exposure amount is not executed, finishing the reset of the exposure amount in a state where the reset of the exposure amount continues to be executed and finishing the reset as the finishing result of a reading process or the like by executing the rest as the result of the reading process or the like.

In the digital camera according to the aspect of the invention, when the movement operation of the shutter estimated by the operation estimating unit until the previous time is later than a predetermined operation, the movement control unit may start moving the shutter at a timing earlier compared to a case where the estimated movement operation of the shutter is earlier than the predetermined operation. In order words, the movement control unit may start moving the shutter at a timing of a tendency in which the movement operation of the shutter is earlier as the estimated movement operation of the shutter is later (for example, a proportional or step-like (gradual) tendency in which the movement operation of the shutter is earlier as the estimated operation of the shutter is later). Thus, by adjusting the timing at which the movement of the shutter starts, it is possible to adjust the exposure period of the image sensor more properly.

In the digital camera according to the aspect of the invention, the operation estimating unit may estimate a current-time movement operation of the shutter based on the movement operation of the shutter estimated by the operation estimating unit until the previous time and a current-time detection timing of the movement detecting unit. Thus, it is possible to estimate the movement operation of the shutter more properly.

In the digital camera according to the aspect of the invention, the movement detecting unit may detect the movement of the shutter by detecting an operation of an interlocking member interlocking with the movement of the shutter.

In the digital camera according to the aspect of the invention, the movement detecting unit may detect movements of a plurality of amounts including movement of a first predetermined amount and movement of a second predetermined amount larger than the first predetermined amount. The operation estimating unit may estimate the movement operation of the shutter based on a plurality of detection timings for the movements of the plurality of amounts of the shutter. Thus, it is possible to estimate the movement operation of the shutter more properly.

In the digital camera according to the aspect of the invention, when the exposure period is shorter than a period threshold value, the reset control unit can start the reset scanning of the exposure amount of the image sensor in the predetermined direction at the timing which corresponds to the detection of the movement detecting unit after the movement start of the shutter and corresponds to the detection of the movement detecting unit after the movement start of the shutter before the previous time. When the exposure period is longer than the period threshold value, the reset control unit can start the reset scanning of the exposure amount of the image sensor in the predetermined direction at the timing which does not correspond to the detection of the movement detecting unit after the movement start of the shutter and corresponds to the detection of the movement detecting unit after the movement start of the shutter before the previous time.

According to another aspect of the invention, there is provided a shutter operation estimating method of a digital camera which includes an image sensor that generates an image signal based on an exposure amount and a shutter that is moved in a predetermined direction to block light arriving at the image sensor. The shutter operation estimating method includes: moving the shutter to block the light arriving at the image sensor at which the light has arrived; detecting the shutter moving by a predetermined amount from movement start; and estimating the movement operation of the shutter based on a detection timing in the detecting of the movement of the shutter.

When the estimation result of the movement operation of the shutter estimated by the shutter operation estimating method of the digital camera according to the aspect of the invention is used for the control of the exposure period of the image sensor, the exposure period of the image sensor can be adjusted. That is, it is possible to adjust the exposure period of the image sensor more properly. Further, in the shutter operation estimating method of the digital camera, the units of the above-described digital camera according to the aspect of the invention may be used and realizing each function of the above-described digital camera according to the aspect of the invention may be further included. According to a still another aspect of the invention, there is provided a computer program causing a camera to realize the above-mentioned functions and a recording medium of the program. Of course, a recording medium of the computer program may be a magnetic recording medium, a magneto-optical recording medium, or any recording medium developed in future.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.

FIG. 1 is a diagram illustrating the overall configuration of a digital camera according to an embodiment of the invention.

FIG. 2 is a diagram illustrating a shutter mechanism viewed in a light incident direction.

FIG. 3 is a diagram illustrating a case where an image sensor is exposed.

FIG. 4 is a flowchart illustrating an example of an exposure processing routine.

FIG. 5 is a diagram illustrating a case where shutter travel starts after reset scanning starts.

FIG. 6 is a diagram illustrating a case where the reset scanning starts after the shutter travel starts.

FIG. 7 is a flowchart illustrating an example of a correction amount setting routine.

FIG. 8 is a diagram illustrating a case where the reset scanning starts after the shutter travel starts.

FIG. 9 is a flowchart illustrating an example of another exposure processing routine.

FIG. 10 is a flowchart illustrating an example of another correction amount setting routine.

FIG. 11 is a diagram illustrating the configuration of another shutter mechanism.

FIG. 12 is a flowchart illustrating an example of an exposure processing routine according to a second embodiment.

FIG. 13 is a diagram illustrating a case where the shutter travel starts after the reset scanning starts.

FIG. 14 is a diagram illustrating a case where the reset scanning starts after the shutter travel starts.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, embodiments of the invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating the overall configuration of a digital camera 10 according to an embodiment of the invention. FIG. 2 is a diagram illustrating a shutter mechanism 23 viewed in a light incident light. FIG. 3 is a diagram illustrating a case where the image sensor 22 viewed in the light incident direction is exposed.

The digital camera 10 according to the embodiment includes: an electronic imaging unit 20 that outputs a signal for a photographed image based on an image signal generated through photoelectric conversion of a subject; an image processing device 60 that inputs the signal output from the electronic imaging unit 20, executes predetermined image processing, and generates image data or an image file of the photographed image; a display control device 70 that displays the image data input from the image processing device 60 on an EVF (Electronic View Finder) 72 or a liquid crystal monitor 74; an operation button group 80 that includes various kinds of buttons operated by a user; a memory card 50 that is capable of storing the image file generated by the image processing device 60; a battery 55 that supplies power to each unit of the digital camera 10; and a main controller 40 that controls the entire apparatus.

The electronic imaging unit 20 includes a photographic lens 21 that is mounted on the body of the digital camera 10 so as to replaced through a lens mount (not shown), an image sensor 22 that converts light input via the photographic lens 21 into an electric signal through photoelectric conversion; a shutter mechanism 23 that is disposed between the photographic lens 21 and the image sensor 22, an analog front-end (AFE) 28 that converts the electric signal output from the image sensor 22 into a digital signal and outputs the digital signal; and a pulse generating circuit 30 that outputs a clock signal to the image sensor 22 or the image processing device 60.

The photographic lens 21 includes a group of a plurality of lenses configured by convex lenses and concave lenses and a diaphragm mechanism 21a that adjusts the amount of light incident on the image sensor 22 or an auto-focus mechanism 21b that executes focusing based on information from a range-finding sensor (not shown) or the photographic lens 21. The diaphragm mechanism 21a or the auto-focus mechanism 21b is controlled by driving a motor of each mechanism in accordance with a signal from a main controller 40.

The image sensor 22 is configured as a COMS image sensor that includes a plurality of photodiodes (not shown) arranged in a matrix form and forming an imaging surface 22a (see FIG. 3) or includes a plurality of amplifiers (not shown) installed in each photodiode. The photodiode is a photoelectric conversion element that converts light into charge when the photodiode is exposed and is installed in each pixel. The photodiode is configured such that the charge flows into a substrate (not shown). The amplifier executes an amplifying process so that the charge accumulated by the photodiode can be read as a signal. The image sensor 22 outputs a signal of one of red (R), green (G), and blue (B) from each photodiode via the amplifier by using color filters on the imaging surface 22a. Each photodiode of the image sensor 22 is supplied with a horizontal scanning clock (a horizontal driving pulse) from a pulse generating circuit 30 and is also supplied with a vertical scanning clock (a vertical driving pulse) generated by the pulse generating circuit 30 and modulated in frequency by a vertical driving modulation circuit 32. In the embodiment, the clock supply from the pulse generating circuit 30 and the modulation of a clock frequency by the vertical driving modulation circuit 32 are controlled by a signal from the main controller 40. Reset scanning of the exposure amount of the image sensor 22 outputting the charge accumulated by the photodiode is executed together with the adjustment of a scanning speed. Further, the reset scanning of the exposure amount of the image sensor 22 functions as an operation of an electronic anterior curtain.

The shutter mechanism 23 functions as a mechanical posterior curtain with respect to the electronic anterior curtain. As shown in FIG. 2, the shutter mechanism 23 includes a ground plate 24 that is held by the body of the digital camera 10 in the front direction of the axial direction of the image sensor 22 and has a rectangular opening 24a, a plurality of rectangular shutter blades 25, and a driving arm 26a and a driven arm 26b that are connected to one ends of the respective shutter blades 25 and form a parallel link mechanism together with the shutter blades 25. The driving arm 26a and the driven arm 26b are rotated about axes 26c and 26d at the ends to which each shutter blade 25 is connected and at the opposite ends. The driven arm 26b is connected to the driving arm 26a by a connection member (not shown), and thus is rotated together with the driving arm 26a. The shutter blades 25 travel in the rotation of the driving arm 26a as follows. That is, when the shutter blades 25 are in an open state (a state in FIG. 2), the driving arm 26a first keeps not to be rotated by conduction to an electromagnet (not shown). When the conduction to the electromagnet is cancelled by releasing a locking member (not shown) by the driving a motor (not shown), the driving arm 26a can enter the rotatable state at any time. Subsequently, when the driving arm 26a starts rotating by the cancellation of the conduction to the electromagnet, the shutter blades 25 travel from the downward direction to the upward direction (direction indicated by a thick arrow in FIG. 2) of the vertical direction of the digital camera 10 by the urging force of a spring (not shown). When the shutter blades 25 travel, the light incident on the image sensor 22 from the opening 24a of the ground plate 24 is blocked, so that the light blocking state is realized. Thereafter, when the driving arm 26a is rotated again in the opposite direction by the driving of the motor, the shutter blades 25 are returned to the original position (the position of the shutter blades in FIG. 2) and the driving arm 26a is not rotated by locking the locking member (not shown) locks by the driving of the motor.

In the shutter mechanism 23, the shutter blades 25 travel to block an area broader than the opening 24a of the ground plate 24. Therefore, as shown in FIG. 2, a margin al is ensured between the vertical upper end (hereinafter, referred to a front end) of the shutter blades 25 and the lower end of the opening 24a in the open state of the shutter blades 25. Further, in a light-blocking state by the shutter blades 25, the front end of the shutter blades 25 is located upward by a margin α2 from the upper end of the opening 24a. Since the digital camera 10 according to this embodiment uses a mirror-less structure which has no mirror along a light incident path of the image sensor 22. Therefore, when the shutter blades 25 enter the open state, the light can be instantly emitted to the image sensor 22. In FIG. 2, a position sensor 25a is installed so that a position between the front end (the end of the shutter blades 25 on the side of the image sensor 22) of the shutter blades 25 in the open state and the lower end (the end of the imaging surface 22a on the side of the shutter blades 25) of the imaging surface 22a of the image sensor 22 in the front side of the optical axis direction of the ground plate 24 is a detection position. Before the front end of the shutter blades 25 blocks the light at the lower end of the imaging surface 22a, the position sensor 25a detects that the front end of the shutter blades 25 starts to move from the open state and travels upward by a predetermined amount, and reaches the detection position. For example, a contactless sensor such as a proximity switch using an electric field or a magnetic field can be used as the position sensor 25a. The meaning of the predetermined amount will be described again.

The image processing device 60 include various kinds of image processing function blocks (not shown) that execute general image processing of a digital camera such as a color interpolation process or a white balance process of RGB pixels, a color reproduction process, re-size processing, a gamma correction process, or an image file generation process. The image processing device 60 inputs the digital signal output from the electronic imaging unit 20 and input the clock signal from the pulse generating circuit 30, and executes the image processing to generate a photographed image, or converts the generated photographed image into an image with a predetermined format and adds photograph information to generate an image file. The image processing device 60 sequentially inputs the digital signals output from the electronic imaging unit 20 at a predetermined period interval and generate a live-view display image.

The display control device 70 displays the photographed image generated by the image processing device 60 on the liquid crystal monitor 74 or executes a live-view display process of sequentially displaying the live-view display images generated by the image processing device 60 on the EVF 72 or the liquid crystal monitor 74.

The operation button group 80 includes a shutter button 80a that outputs an instruction to photograph a subject to the main controller 40 when the user presses down the shutter button, a plurality of setting buttons 80b that set various setting values for the photographing such as a shutter speed, a stop value, and an exposure value, and a power button 80c that gives an instruction of power-on or power-off.

The main controller 40 is configured by a microprocessor which includes the CPU 42 as a main unit. The main controller 40 includes a ROM 44 that stores processing programs and various tables, a RAM 46 that temporarily stores data, a flash memory 48 that is capable of writing data and keeps data even when power is turned off, and an input/output port (not shown). The main controller 40 is supplied with detection signals (ON and OFF signals) from the position sensor 25a that detects the shutter blades 25 traveling by a predetermined amount from the movement start of the shutter blades 25, various kinds of operation signals from the operation button group 80, information regarding the photographic lens 21, image files read from the memory card 50, various kinds of images from the image processing device 60, and the like. Further, the main controller 40 outputs a driving signal for the photographic lens 21, a control signal, which is used to control the motor (not shown) or control the conduction to the electromagnet, for the shutter mechanism 23, a control signal for the pulse generating circuit 30, a control signal for the vertical driving modulation circuit 32, an image file written into the memory card 50, an image processing instruction for the image processing device 60, a display control instruction for the display control device 70, and the like.

Various setting values such as a shutter speed are set in the digital camera 10 having the above-described configuration according to the embodiment. When a photograph instruction is output in response to an operation of the shutter button 80a, the main controller 40 executes various kinds of exposure controls to control the rest scanning of the exposure amount of the image sensor 22 or the travelling of the shutter blades 25 and read scanning of the image signal from the image sensor 22. Finally, an image file generated from the output signal of the electronic imaging unit 20 by the image processing device 60 is stored in the memory card 50. According to various kinds of exposure controls on the imaging surface 22a of the image sensor 22, as shown in FIG. 3, the reset scanning position (line) is first moved upward by the reset scanning of the image sensor 22 to operate the electronic anterior curtain, the position (hereinafter, referred to as a shutter front end position) corresponding to the front end of the shutter blades 25 is subsequently moved upward, so that the mechanical posterior curtain blocks the light, and then the read scanning position (line) of the image sensor 22 is finally moved upward in sequence. Accordingly, when one point of the image sensor 22 is noticed, a shutter speed (exposure period) is a period in which the reset scanning position corresponding to the rear end of the electronic anterior curtain passes through the one point, so that the exposure start, and then the shutter anterior position corresponding to the front end of the mechanical posterior curtain passes through the one point, so that the light is blocked. By adjusting this period, it is possible to adjust a period in which a subject image is emitted onto the imaging surface 22a of the image sensor 22. At this time, a region (a region indicated by a diagonal line in the drawing) between the rest scanning position on the imaging surface 22a of the image sensor 22 and the shutter anterior position is a charge accumulation region of the image sensor 22. When the exposure period is short, this region is a slit-shaped region. Further, the reset scanning in the vertical upward direction of the exposure amount of the image sensor 22 is executed by executing the reset of the exposure amount of the image sensor 22 in the vertical upward direction in sequence. In the embodiment, the reset of the exposure amount may be executed instantly when the reset of the exposure amount is not executed. Alternatively, the reset of the exposure amount may be ended when the reset of the exposure amount continues to be executed temporally. Further, the reset of the exposure amount may be executed as the result of another process such as read scanning.

Next, an operation of the digital camera 10 having the above-described configuration, particularly, an exposure operation will be described according to this embodiment. FIG. 4 is a flowchart illustrating an example of an exposure processing routine executed by the CPU 42 of the main controller 40. The exposure processing routine is executed when the main controller 40 inputs a photograph instruction in response to an operation of the shutter button 80a. Further, it is assumed that various setting values for the photographing such as a shutter speed, a stop value, and an exposure value are set until the main controller 40 inputs the photograph instruction.

When the exposure processing routine is executed, the CPU 42 of the main controller 40 first inputs data necessary for an exposure process, such as a set exposure period Tex or a timing correction amount ΔT of a travel start timing of the travel (hereinafter, referred to as shutter travel) of the shutter blades 25 (step S100). Here, the exposure period Tex set as a shutter speed when the user operates the setting button 80b or set by an automatic exposure processing routine (not shown) may be input. The timing correction amount ΔT is calculated as an average value or a median value of the delay periods caused due to, for example, the temporal change in the shutter travel operation estimated at the previous three-time photograph times. The timing correction amount ΔT will be described in detail later.

Next, a reset timing of the reset scanning of the image sensor 22 and the a basic travel start timing, which is a basic value of the travel start timing of the shutter blades 25, are set based on the input exposure period Tex (step S110). A timing obtained by correcting the set basic travel start timing so as to be earlier by the timing correction amount ΔT is set as the travel start timing (step S120). In the embodiment, the reset timing is set to a time at each position (each line) of the imaging surface 22a in a vertical direction when the photograph instruction is input, and the basic travel start timing is set to a time after the photograph instruction is input. In the embodiment, the reset timing and the basic travel start timing are set by determining a relation between the exposure period Tex and the reset timing and the basic travel start timing, from which the exposure period Tex in the default state at the shipment of the digital camera 10 is obtained, in advance by an experiment or analysis, storing the relation as a timing set map in the ROM 44, and deriving the corresponding reset timing and the corresponding basic travel start timing from the timing set map when the exposure period Tex is given. When, the corresponding reset timing and the corresponding basic travel start timing are derived from the stored timing set map. Even when the basic travel start timing is corrected to be earlier only by the timing correction amount ΔT, the timing set map may be determined so that the travel start timing is not a timing earlier than the current timing. Alternatively, when the travel start timing is a timing earlier than the current timing, both the reset timing and the travel start timing may be made to be later by the earlier time.

In this way, when the reset timing of the reset scanning of the image sensor 22 and the travel start timing of the shutter blades 25 are set, it is determined whether the shutter travel starts earlier or the reset scanning of the image sensor 22 starts earlier based on the set values of the reset timing and the travel start timing (step S130). When it is determined that the shutter travel starts earlier, the reset scanning of the exposure amount of the image sensor 22 starts at the set reset timing (step S140), and then the shutter travel starts at the set the travel start timing (step S150). The reset scanning is executed by outputting the control signals to the pulse generating circuit 30 and the vertical driving modulation circuit 32, respectively. The shutter travel starts by outputting a control signal for instructing the start of the travel to the shutter mechanism 23. FIG. 5 is a diagram illustrating an example of the exposure when the shutter travel starts after the reset scanning starts. In FIG. 5, the horizontal axis represents a time and the vertical axis represents a position in the vertical direction. A shutter front end position (a posterior curtain opening position), the lower end of the imaging surface 22a, the upper end of the imaging surface 22a, and a shutter front end position (a posterior curtain light-blocking position) in a light-blocking state are shown in order from the upper side to the lower side of the vertical axis. As shown in FIG. 5, the reset scanning starts at a time t1 (see a one-dot chain line). Thereafter, when an instruction to start the shutter travel is given at a time t2 (see a solid line), the reset scanning is executed in accordance with the set reset timing so that the exposure period Tex is ensured along the trajectory of the shutter front end position during the movement of the shutter front end position from the lower end to the upper end of the imaging surface 22a. Then, when the reset scanning ends for all of the lines at a time t3, the read scanning of the image sensor 22 then starts at a time t4 in order from the line in which the shutter travel ends (see two-dot chain line).

In this way, the read scanning is executed from the line in which the shutter travel ends, and then when the read scanning ends for all of the lines (step S180), the exposure processing routine ends. When the reset scanning starts earlier than the shutter travel, that is, the exposure period Tex is relatively long (the shutter speed is relatively low), the exposure of the image sensor 22 can be executed through the above process for the set exposure period Tex.

When it is determined that the shutter travel starts earlier than the reset scanning in step S130, the shutter travel starts at the set travel start timing (step S160), and then the reset scanning starts at the set reset timing (step S170). Finally, the read scanning is executed (step S180) and the exposure processing routine ends. FIG. 6 is a diagram illustrating an example of the exposure when the reset scanning starts after the shutter travel starts. In the example of FIG. 6, the reset scanning starts at a time t5, and then an instruction to start the shutter travel is given at a time t6. When the shutter travel starts earlier than the reset scanning, that is, the exposure period Tex is relatively short (the shutter speed is relatively fast), the exposure of the image sensor 22 can be executed through the above process for the set exposure period Tex. The exposure process has hitherto been described.

Next, setting of the timing correction amount ΔT used to correct the basic travel start timing will be described. FIG. 7 is a flowchart illustrating an example of a correction amount setting routine executed by the CPU 42 of the main controller 40. The correction amount setting routine is executed when the main controller 40 inputs a photograph instruction in response to an operation of the shutter button 80a.

When the correction amount setting routine is executed, the CPU 42 of the main controller 40 again stores a correction amount ΔT1 set at the time of executing the previous correction account setting routine and stored in a predetermined region of the flash memory 48 and a correction amount ΔT2 set at the time of executing the previous correction account setting routine and stored in a predetermined region of the flash memory 48, which are basis values of the calculation of all the timing correction amounts ΔT, as correction amounts ΔT2 and ΔT3, respectively, in the predetermined region of the flash memory 48 (step S200), and then input the correction amounts ΔT2 and ΔT3 stored again (step S210). Here, the correction amounts ΔT1, ΔT2, and ΔT3 are amounts estimated as a delay period caused due to the temporal change or the like of all the shutter travel operations. The correction amount ΔT1 is a value set by executing the correction amount setting routine at the current time. The correction amount ΔT2 is a value set by executing the correction amount setting routine at the previous time. The correction amount ΔT3 is a value set by executing the correction amount setting routine at the time before last. Of course, the number of correction amounts to be stored is not limited thereto, but one or three or more correction amounts may be stored.

Subsequently, the input of the detection signal transmitted from the position sensor 25a is waited (step S220). When the detection signal transmitted from the position sensor 25a is input, a necessary detection period Td is set as a period elapsed after the start of the shutter travel by the use of a period measured by a timer (not shown) (step S230). In the embodiment, a predetermined amount of movement of the shutter blades 25 to be detected by the position sensor 25a is a movement amount which is determined in advance by an experiment or the like and is necessary for grasping a change tendency in which the travel of the shutter blades 25 is delayed or advanced due to an individual difference or a temporal change of the shutter mechanism 23.

The correction amount ΔT1 set in the correction amount setting routine of the current time is set based on the necessary detection period Td of the set position sensor 25a and is stored in a predetermined region of the flash memory 48 (step S240). The average value of the correction amounts ΔT1, ΔT2, and ΔT3 is set as the timing correction amount ΔT and is stored in a predetermined region of the flash memory 48 (step S250), and then the correction amount setting routine ends. As the timing correction amount ΔT, the median value of the correction amounts ΔT1, ΔT2, and ΔT3 may be used, a weighted average value obtained by weighting the correction amount ΔT1 may be used, or a value obtained by another calculation may be used. In the embodiment, the correction amount ΔT1 is set by determining a relation between the necessary detection period Td of the position sensor 25a and the correction amount ΔT1 in advance by an experiment or analysis, storing the relation as a correction amount setting map in the ROM 44, and deriving the corresponding correction amount ΔT1 from the stored correction amount setting map when the necessary detection period Td is given. A setting example of the correction amount ΔT1 and the meaning of the timing correction amount ΔT will be described later.

FIG. 8 is a diagram illustrating an example of the exposure when the reset scanning starts after the shutter travel starts. In FIG. 8, a solid line indicates the trajectory of the shutter front end position in a default state (basic state) of the shipment of the digital camera 10 indicted by a solid line. The trajectory of the shutter front end position indicated by a dashed line in a comparative state is delayed with respect to the trajectory of the shutter front end position due to, for example, the temporal change or the like of the electromagnet or the spring (not shown) of the shutter mechanism 23. The delay of the shutter travel can be understood as a delay period with respect to the trajectory of the shutter front end position in the basic state. In the example of FIG. 8 for example, a period Td1 from a time t7, at which an instruction to start the shutter travel in the basic state is given, to a time t9, at which the shutter blades 25 reach the lower end of the imaging surface 22a from the posterior curtain opening position at the time t7, becomes longer in the comparative state. Further, a period Td2 from the time t7 to a time t10, at which the shutter blades 25 reach the upper end of the imaging surface 22a from the posterior curtain opening position at the time t7, becomes longer in the comparative state. That is, both the periods Td1 and Td2 have a tendency to become longer as the necessary detection period Td is longer (the detection timing is late) from the time 7 to a time t8 (detection timing) at which the shutter blades 25 reach the detection position. Accordingly, in the embodiment, the correction amount setting map is determined so that the larger correction amount ΔT1 is obtained as the detection timing of the position sensor 25a is later.

Accordingly, the process of setting the correction amount ΔT1 based on the necessary detection period Td of the position sensor 25a in step S240 can be said to be a process of estimating that the shutter travel is later as the detection timing of the position sensor 25a is later. In the correction amount setting map, for example, the average value or the like of a delay period of the timing, at which the shutter blades 25 reach the lower end of the imaging surface 22a, from the basic state and a delay period of the timing, at which the shutter blades 25 reach the upper end of the imaging surface 22a, from the basic state can be set as the correction amount ΔT1. Further, the correction amount of the shutter travel start timing can be obtained more properly by setting, as the timing correction amount ΔT, the average value or the median value of the estimated correction amount ΔT1 and the correction amounts ΔT2 and ΔT3 estimated at the previous photograph time. In the digital camera 10 according to the embodiment, it is possible to determine the exposure period of the image sensor 22 more properly, since the shutter travel start timing is adjusted at the subsequent photograph time by the use of the calculated timing correction amount ΔT. Further, since the timing correction amount ΔT can be set with a positive value or a negative value, it is possible to adjust the exposure period of the image sensor 22 properly in accordance with a change in the shutter travel method due to the individual difference of the shutter mechanism 23 or the temporal change.

Here, a correspondence relation between the constituent elements of this embodiment and the constituent elements of the invention will be described. The image sensor 22 of this embodiment corresponds to an “image sensor” of the invention. The shutter blade 25 corresponds to a “shutter.” The main controller 40 that controls the shutter mechanism 23 to start traveling the shutter blades 25 at the set travel start timing and executes the processes of step S150 and step S160 of the exposure processing routine of FIG. 4 corresponds to a “movement control unit.” The position sensor 25a that detects the shutter blades 25 moving by the predetermined amount from the movement start and the main controller 40 that executes the process of determining the detection by the position sensor 25a in step S220 of the correction amount setting routine of FIG. 7 correspond to a “movement detecting unit.” The main controller 40 that executes the process of step S240 of the correction amount setting routine of FIG. 7 in which the larger correction amount ΔT1 is set as the detection timing of the position sensor 25a is later corresponds to an “operation estimating unit.” Further, in this embodiment, an example of the shutter operation estimating method of the digital camera according to the invention can be clarified by describing the operation of the digital camera.

In the digital camera 10 described above in this embodiment, the shutter blades 25 travel to block the light arriving at the image sensor 22 at which the light has arrived. Then, the movement of the predetermined amount from the start of the shutter travel is detected, the movement operation of the shutter blades 25 is estimated based on the detection timing of the movement of the shutter blades 25 by the predetermined amount, and the correction amount ΔT1 is determined. Further, the shutter travel starts at the travel start timing earlier than the basic travel start timing by the timing correction amount ΔT based on the correction amount ΔT1 set until the previous time. Thus, it is possible to adjust the exposure period of the image sensor 22 more properly.

The invention is not limited to the above-described embodiment, but may be, of course, modified in various forms within the technical scope of the invention.

In the above-described embodiment, the correction amount ΔT is set to set the travel start timing of the shutter travel based on the detection timing of the position sensor 25a. Instead, a timing correction amount may be set to set the reset timing of the reset scanning of the image sensor 22. In this case, the exposure processing routine of FIG. 9 may be executed instead of the exposure processing routine of FIG. 4 and the correction amount setting routine of FIG. 10 may be executed instead of the correction amount setting routine of FIG. 7. The same reference numerals are given to the same processes as those of the exposure processing routine of FIG. 4 among the process of the steps of the exposure processing routine of FIG. 9 and the detailed description thereof will not be repeated.

In the exposure processing routine of FIG. 9, data of the set exposure period Tex, the timing correction amount ΔT(y) of the reset timing of the image sensor 22, or the like are input (step S300). Then, a basic reset timing and a travel start timing of the shutter travel which are basic values of the reset timing are set based on the input exposure period Tex (step S310). A timing corrected by delaying the back reset timing only by the timing correction amount ΔT(y) is set as a reset timing (step S320). Then, the reset scanning and the shutter travel start depending on the determination result whether shutter travel is executed earlier and the read scanning is executed (step S130 to step s180), and then the exposure processing routine ends. Here, the basic reset timing, the timing correction amount ΔT(y), and the reset timing is set as a period of each position (each line) of the imaging surface 22a in the vertical direction after all the photograph instructions are input. The basic travel start timing is set as a period after the photographing instruction is input. The variable y of the timing correction amount ΔT(y) indicates the position of the imaging surface 22a in the vertical direction. The basic reset timing and the travel start timing are set by the use of a timing set map determined by a relation between the exposure period Tex and the basic reset timing and the travel start timing, from which the exposure period Tex in the default state at the shipment of the digital camera 10 is obtained, in advance by an experiment or analysis.

In the correction amount setting routine of FIG. 10, correction amounts ΔT1(y) and ΔT2(y) stored in predetermined regions of the flash memory 48 until the correction amount setting routine is executed until the previous time and ends are again stored as the correction amounts ΔT2(y) and ΔT3(y) in the predetermined regions of the flash memory 48 (step S400), and then the correction amounts ΔT2(y) and ΔT3(y) stored again are input (step S410). Subsequently, as in the processes of step S220 and step S230 of the correction amount setting routine of FIG. 7, the input of the detection signal transmitted from the position sensor 25a is waited (step S420). When the detection signal transmitted from the position sensor 25a is input, a necessary detection period Td is set as a period elapsed after the start of the shutter travel (step S430). The correction amount ΔT1(y) set in the correction amount setting routine of the current time is set based on the necessary detection period Td of the set position sensor 25a and is stored in a predetermined region of the flash memory 48 (step S440). The average value or the median value of the correction amounts ΔT1(y), ΔT2(y), and ΔT3(y) is set for each variable y as the timing correction amount ΔT(y) and is stored in a predetermined region of the flash memory 48 (step S450), and then the correction amount setting routine ends. Here, the correction amount ΔT1(y) can be set by the use of a correction amount setting map in which a relation between the detection timing of the position sensor 25a and the correction amount ΔT1(y) is determined in advance by an experiment or analysis. In the correction amount setting map is determined so that the larger correction amount ΔT1(y) is obtained as the detection timing is later, by estimating that the shutter travel is later as the necessary detection period Td of the position sensor 25a is longer (as the detection timing is later).

Thus, the correction amount of the reset timing of the reset scanning of the image sensor 22 can be obtained more properly by setting, as the timing correction amount ΔT(y), the average value or the median value of the estimated correction amount ΔT1(y) and the correction amounts ΔT2(y) and ΔT3(y) estimated at the previous photograph time. By adjusting the reset timing at the next photograph time by the use of the calculated timing correction amount ΔT(y), it is possible to determine the exposure period of the image sensor 22 more properly.

In the above-described embodiment, the travel start timing of the shutter travel is adjusted by setting the timing correction amount ΔT based on the detection timing of the position sensor 25a. However, each timing may be adjusted by dividing the timing correction amount ΔT set in the same manner at a predetermined division ratio (for example, a value of ½) between adjustment by which the travel start timing of the shutter travel is made to be earlier and adjustment by which the reset timing of the image sensor 22 is made to be later.

In the above-described embodiment, the timing correction amount ΔT is set based on the correction amount ΔT1 set in the correction amount setting routine and the correction amounts ΔT2 and ΔT3 set in the correction amount setting routine until the previous time. However, the correction amount ΔT1 may be set as the timing correction amount ΔT without use of the correction amounts ΔT2 and ΔT3.

In the above-described embodiment, the position sensor 25a, which detects that the front end of the shutter blades 25 starts moving in the open state, travels upward by the predetermined amount, and reaches the detection position, is used as a sensor that detects the shutter blades 25 moving by the predetermined amount from the movement start. Instead, for example, a rotation position sensor or the like may be used which detect the rotation position of the driving arm 26a of the shutter mechanism 23.

In the above-described embodiment, one position sensor 25a is provided which detect the shutter blades 25 moving from the movement start by the predetermined amount. However, two or more position sensors may be provided. For example, as shown in FIG. 11, another shutter mechanism 123 may include not only the position sensor 25a that detects the shutter blades 25 moving from the movement start by the predetermined amount but also a position sensor 125b that detects the shutter blades 25 moving from the movement start by a second predetermined amount (greater than the predetermined amount) and a position sensor 125c that detects the shutter blades 25 moving from the movement start by a third predetermined amount (greater than the second predetermined amount). In this case, the trajectories of the shutter front end position from three detection timings of the position sensors 25a, 125b, and 125c are estimated, and a delay amount (for example, an average value or the like of the delay periods between the trajectories compared to each other) from the basic state of the trajectory of the estimated shutter front end position may be as a timing correction amount ΔT. At this time, the timing correction amount ΔT may be set without using the movement start timing of the shutter blades 25 based on a difference between the detection timings of the respective position sensors, that is, a period necessary when the shutter blades 25 are moved at the positions corresponding to the respective position sensors. Thus, it is possible to estimate the movement operation of the shutter blades 25 more properly. Instead of the position sensor 25a, the position sensor 125b or the position sensor 125c may be used as one position sensor that detects the shutter blades 25 moving from the movement start by the predetermined amount.

That is, the shutter mechanism may includes the position sensor 125b that detects the shutter blades 25 moving by the second predetermined amount, which is a movement amount of the shutter blades 25 from the movement start up to the position at which the light starts to be blocked in the imaging surface 22a, or the position sensor 125c that detects the shutter blades 25 moving by the third predetermined amount.

In the above-described embodiment, the larger correction amount ΔT1 is set as the detection timing of the position sensor 25a is later by the use of the correction amount setting map, that is, the correction amount ΔT1 is set to be larger proportionally as the detection timing of the position sensor 25a is later. Instead, the correction amount ΔT1 may be set to be larger stepwise (gradually) as the detection timing of the position sensor 25a is later.

In the above-described embodiment, the case has hitherto been described in which the photodiodes of the image sensor 22 are effective. However, all of the plurality of photodiodes may not be effective, but the photodiodes in a partial region (also referred to as an effective pixel region) may be effective. In this case, the photodiodes in a region other than the effective pixel region are covered to block light, are made not to read charge, or made to ignore the read charge or signal. Then, the shutter blades 25 are moved so that light arriving at the effective pixel region of the image sensor 22 at which the light has arrived is blocked, it is detected that the shutter blades 25 are moved from the movement start by a predetermined amount, and the movement operation of the shutter blades 25 may be estimated based on the detection timing of the movement of the shutter blades 25 by the predetermined amount.

In the above-described embodiment, the travel start timing of the shutter travel or the reset start timing is corrected based on the detection result of the position sensor. However, the forms indicated by the one-dot chain line in FIGS. 5, 6, and 8 may be changed so as to approximate the operation of the actual shutter blades by changing the timing itself of the rest operation, that is, the speed for the movement of the position of the reset operation. This method is effective since a difference in the exposure amount decreases particularly when the shutter speed is short. On the contrary, when the shutter speed is long, the effect of changing the speed for the movement of the position of the reset operation may become small. Therefore, it is switched whether or not the speed for the movement of the position of the reset operation is changed. The speed is changed when the shutter speed is short, whereas no speed is changed when the shutter speed is long. It is desirable to change the speed for the movement of the position of the reset operation so as to approximate to the more actual shutter operation when the shutter speed is short in comparison to the case the shutter speed is long. The speed for the movement of the position of the reset operation may be determined based on a function of the detection result of the position sensor and the shutter speed or a correspondent relation stored in advance.

In a digital camera 10 according to a second embodiment, shutter blades 25 travel to block light arriving at an image sensor 22 at which light has arrived. Before the shutter blades 25 start to block the light arriving at the image sensor 22, it is detected that the shutter blades 25 moves from the movement start by a predetermined amount. Before the shutter blades 25 start blocking the light arriving at the image sensor 22, the reset scanning of the exposure amount of the image sensor 22 in the vertical upward direction is started at a reset timing corresponding to a necessary detection period Td from the movement start of the shutter blades 25 to the detection of the movement by the predetermined amount and the above-described timing correction amount ΔT. In the digital camera 10 according to the second embodiment, an exposure processing routine of FIG. 12 is executed instead of the exposure processing routine of FIG. 4. The correction amount setting routine of FIG. 7 is executed. The description thereof will not be repeated to avoid the repeated description. The exposure processing routine of FIG. 12 will be mainly described below. The exposure processing routine of FIG. 12 is executed when the main controller 40 inputs a photograph instruction by operating the shutter button 80a. Further, it is assumed that various setting values for the photographing such as a shutter speed, a stop value, and an exposure value are set until the main controller 40 inputs the photograph instruction.

When the exposure processing routine of FIG. 12 is executed, the CPU 42 of the main controller 40 first inputs data necessary for an exposure process, such as a set exposure period Tex or a timing correction amount ΔT to which the degree of delay of the shutter travel up to the previous photograph time set in the correction amount setting routine of FIG. 7 is reflected (step S500). The CPU 42 executes a process of determining whether the input exposure period Tex is longer than a period threshold value Tref (step S510). Here, the exposure period Tex set as a shutter speed when the user operates the setting button 80b or set by an automatic exposure processing routine (not shown) may be input. In the embodiment, the period threshold value Tref is set to a value which is obtained by calculating a period (the shortest period in consideration of an individual difference or a temporal change) necessary for the travel of the shutter blades 25 until the light incident on the image sensor 22 is blocked from a timing at which the shutter blades 25 travel from the movement start up to the detection position of the position sensor 25a in advance by an experiment or the like and setting a value predetermined within the calculation period as a shutter speed (exposure period) (for example, 1/4000 second). When there are a plurality of shutter speeds (exposure periods), a larger shutter speed (for example, 1/4000 between 1/4000 and 1/8000) is used. The meaning of the period threshold value Tref will be described again.

When it is determined that the exposure period Tex is longer than the period threshold value Tref, the shutter blades 25 start traveling (hereinafter, also referred to as shutter travel). Thereafter, when the reset scanning of the image sensor 22 starts, it is determined that the exposure period Tex is not ensured. The reset timing of the reset scanning of the image sensor 22 and the travel start timing of the shutter blades 25 are set based on the exposure period Tex (step s520). The reset timing of the reset scanning of the image sensor 22 and the travel start timing of the shutter blades 25 may be set based on both the exposure period Tex and the timing correction amount ΔT. In the embodiment, the reset timing is set to a time at each position (each line) of the imaging surface 22a in a vertical direction when the photograph instruction is input, and the basic travel start timing is set to a time after the photograph instruction is input. In the embodiment, the reset timing and the travel start timing are set by determining a relation between the exposure period Tex and the reset timing and the travel start timing, from which the exposure period Tex can be obtained, in advance by an experiment or analysis, storing the relation as a timing set map in the ROM 44, and deriving the corresponding reset timing and the corresponding travel start timing from the timing set map when the exposure period Tex is given.

In this way, when the reset timing of the reset scanning of the image sensor 22 and the travel start timing of the shutter blades 25 are set, the reset scanning of the exposure amount of the image sensor 22 at the set reset timing starts and the shutter travel starts at the set travel start timing (step S530). Then, the exposure processing routine ends. The reset scanning is executed by outputting the control signals to the pulse generating circuit 30 and the vertical driving modulation circuit 32, respectively. The shutter travel starts by outputting a control signal for instructing the start of the travel to the shutter mechanism 23. FIG. 13 is a diagram illustrating an example of the exposure when the shutter travel starts, when the exposure period Tex is longer than the period threshold value Tref, and thus the shutter travel starts after the reset scanning starts. In FIG. 13, the horizontal axis represents a time and the vertical axis represents a position in the vertical direction. A shutter front end position (a posterior curtain opening position), the lower end of the imaging surface 22a, the upper end of the imaging surface 22a, and a shutter front end position (a posterior curtain light-blocking position) in a light-blocking state are shown in order from the upper side to the lower side of the vertical axis. As shown in FIG. 13, the reset scanning starts at a time t11 (see a one-dot chain line). Thereafter, when an instruction to start the shutter travel is given at a time t12 (see a solid line), the reset scanning is executed in accordance with the set reset timing so that the exposure period Tex is ensured along the trajectory of the shutter front end position during the movement of the shutter front end position from the lower end to the upper end of the imaging surface 22a. Then, when the reset scanning ends for all of the lines at a time t13, the read scanning of the image sensor 22 then starts at a time t14 in order from the line in which the shutter travel ends (see two-dot chain line).

In this way, the read scanning is executed from the line in which the shutter travel ends, and then when the read scanning ends for all of the lines (step S590), the exposure processing routine ends. When the exposure processing routine ends, the AFE 28 converts a signal read from the image sensor 22 into a digital signal, the image processing device 60 executes predetermined image processing, and an image file of the photographed images is finally stored in the memory card 50. When the exposure period Tex is longer than the period threshold value Tref, the exposure of the image sensor 22 can be executed through the above process for the set exposure period Tex.

When the exposure period Tex is equal to or less than the period threshold value Tref in step S510, the shutter travel first starts (step S540) and the input of the detection signal transmitted from the position sensor 25a is waited (step S550). When the detection signal transmitted from the position sensor 25a is input, a necessary detection period Td is set as a period elapsed after the start of the shutter travel by the use of a period measured by a timer (not shown) (step S560). In the embodiment, a predetermined amount of movement of the shutter blades 25 to be detected by the position sensor 25a is a movement amount which is determined in advance by an experiment or the like and is necessary for grasping a change tendency in which the travel of the shutter blades 25 is delayed or advanced due to an individual difference or a temporal change of the shutter mechanism 23.

Subsequently, the reset timing of the image sensor 22 corresponding to the timing correction amount ΔT and the necessary detection period Td is set based on the exposure period Tex (step S570). In the embodiment, as in the setting of the correction amount ΔT1 in step S240 of the correction amount setting routine of FIG. 7, the timing correction amount ΔT is updated by applying the necessary detection period Td to the correction amount setting map, setting a correction amount ΔT0 being in progress of the current-time photographing, and calculating the average value or the like of the correction amount ΔT0 and the timing correction amount ΔT so that the set correction amount ΔT0 is reflected to the timing correction amount ΔT. That is, the timing correction amount ΔT, to which the degree of delay of the latest shutter travel is applied, is updated by reflecting the correction amount ΔT0 during the photographing of the current time to the timing correction amount ΔT to which the degree of delay of the shutter travel until the previous photograph time is reflected. A relation between the exposure period Tex and the reset timing and the basic travel start timing, from which the exposure period Tex can be obtained, is determined in advance by an experiment or analysis, the relation is stored as a timing set map in the ROM 44, and the corresponding reset timing is derived from the timing set map when the exposure period Tex is given. In the timing setting map, the reset timing is set earlier as the exposure period Tex is longer, whereas the reset timing is set later as the timing correction amount ΔT is larger (the movement operation of the shutter blades 25 estimated until the photographing of the current time is late).

FIG. 14 is a diagram illustrating an example of the exposure when the shutter travel starts and the reset scanning then starts in a case where the exposure period Tex is longer than the period threshold value Tref. In FIG. 14, in regard to the shutter front end position, the solid line indicates a trajectory when the travel is delayed due to the individual difference or the temporal change (for example, the individual difference or deterioration of an electromagnet or a spring (not shown)) of the shutter mechanism 23. The dashed line indicates a trajectory when the travel is not advanced or delayed in the default state of the shipment of the digital camera 10. In FIG. 14, various times or periods indicated by solid lines are shown. For example, when an instruction to start the shutter travel is given at a time t15, and then the reset scanning starts at a time t17. As shown in the drawing, when the exposure period Tex is equal to or less than the period threshold value Tref, a ratio the delay period or the advance period of the shutter travel is large with respect to the exposure period Tex due to the individual difference or the temporal change of the shutter mechanism 23, and thus the individual difference or the temporal change of the shutter mechanism 23 have a considerable influence on the actual exposure period. For this reason, the reset timing is adjusted so as to be earlier for the trajectory of the shutter front end position as the set exposure period Tex is longer. Further, the reset timing is adjusted so as to be later as the detection timing of the shutter blades 25 at the detection position of the position sensor 25a is later, that is, the necessary detection period Td is longer. In FIG. 14, when a reference example indicated by a dashed line is compared to that indicated by solid line, a period Td1 from a time t15, at which the shutter travel starts, to a time t18, at which the shutter front end position reaches the detection position from the posterior curtain opening position, has a tendency to be longer as the necessary detection period Td from the time t15 to a time t16 is longer. Further, a period td2 from the time t15 to a time t19, at which the shutter front end position reaches the upper end of the imaging surface 22a from the posterior curtain opening position at the time t15, has a tendency to be longer as the necessary detection period Td is longer. In the embodiment, this tendency is grasped as a deviation in the detection timing and the exposure period is adjusted. Thus, the exposure period Tex can be ensured more reliably by setting the reset timing in accordance with the necessary detection period Td of the position sensor 25a and the timing correction amount ΔT. The reset timing is set to later as the updated timing correction amount ΔT is larger, and thus the reset timing can be set to be earlier as the updated timing correction amount ΔT is smaller. As understood from the example of the period threshold value Tref shown in the drawing, in the case where the exposure period Tex is longer than the period threshold value Tref, the exposure period Tex is not ensured even when the detection of the position sensor 25a is executed and then the reset scanning starts.

The period threshold value Tref can be used to determine whether the reset scanning may start after the detection timing of the position sensor 25a.

When the reset timing is set in this way, the reset scanning starts at the set rest timing (step S580) and the read scanning is finally executed (step S590). Then, the exposure processing routine ends.

In the digital camera 10 described above in the second embodiment, the shutter blades 25 travel to block the light arriving at the image sensor 22 at which light has arrived. Before the shutter blades 25 starts blocking the light arriving at the image sensor 22, it is detected that the shutter blades 25 moves from the movement start by the predetermined amount. Further, before the shutter blades 25 starts blocking the light arriving at the image sensor 22, the reset scanning of the exposure amount of the image sensor 22 in the vertical upward direction is started at the reset timing corresponding to the above-described timing correction amount ΔT and the necessary detection period Td in which the shutter blades 25 starts moving and the movement of the predetermined amount is detected. In this way, the reset scanning of the exposure amount of the image sensor 22 is started at the timing corresponding to the period in which the shutter blades 25 starts moving and the movement of the predetermined amount is detected. Therefore, when a variation occurs in the travel method due to the individual difference of the shutter mechanism 23 or the travel method is changed due to the temporal change of the shutter mechanism 23, the exposure amount of the image sensor 22 can be reset at the timing corresponding to the shutter travel method of each camera. Accordingly, it is possible to set the exposure period of the image sensor 22.

In the above-described second embodiment, as the period threshold value, the shutter speed (the exposure period) is used which is determined in advance within the period necessary for traveling the shutter blades 25 until the shutter blades 25 start moving and then travel by the predetermined amount up to the detection position of the position sensor 25a and the light incident on the image sensor 22 starts to be blocked. However, the period necessary for traveling the shutter blades 25 may be used. A period slightly shorter than the shutter speed (the exposure period) determined in this way may be used.

In the above-described second embodiment, when the exposure period Tex is equal to or less than the period threshold value Tref, the reset timing of the image sensor 22 is set to be earlier as the exposure period Tex is longer, whereas the reset timing of the image sensor 22 is set to be later as the updated timing correction amount ΔT is larger. That is, the reset timing is set to be earlier proportionally as the exposure period Tex is longer, whereas the reset timing is set to be later proportionally as the timing correction amount ΔT is larger. However, the reset timing may be set to be earlier stepwise as the exposure period Tex is longer, whereas the reset timing may be set to be later in stepwise (gradually) as the updated timing correction amount ΔT is larger.

In the above-described second embodiment, the position sensor 25a, which detects that the front end of the shutter blades 25 starts moving in the open state, travels upward by the predetermined amount, and reaches the detection position, is used as a sensor that detects the shutter blades 25 moving by the predetermined amount from the movement start. Instead, another sensor such as a sensor detecting an operation of an interlocking member interlocking with the movement of the shutter may be used. As the interlocking member, for example, the driving arm 26a or the driven arm 26b of the shutter mechanism 23, the shaft 26c, the shaft 26d, or the spring operating the driving arm 26a can be used. As the sensor, a rotation position sensor or the like may be used which detect the rotation position of the driving arm 26a or the driven arm 26b of the shutter mechanism 23, the shaft 26c, or the shaft 26d. Further, a sensor may be used which detects deformation of the spring or the like operating the driving arm 26a. The number of position sensors is not limited to one, but a plurality of position sensors may be used to control the reset scanning based on the detection result. In this case, a position sensor may be also installed at a position on the movement end side (upper side of the upper end of the imaging surface 22a) of the shutter blades 25 and the detection result of the position sensor may be reflected on the control of the reset scanning at the subsequent photograph time.

In the above-described second embodiment, the case has hitherto been described in which the photodiodes of the image sensor 22 are effective. However, all of the plurality of photodiodes may not be effective, but the photodiodes in a partial region (also referred to as an effective pixel region) may be effective. In this case, the photodiodes in a region other than the effective pixel region are covered to block light, are made not to read charge, or made to ignore the read charge or signal. Before the shutter blades 25 starts blocking the light arriving at the effective pixel region of the image sensor 22, it is detected that the shutter blades 25 move from the movement start by the predetermined amount. Further, before the shutter blades 25 starts blocking the light arriving at the effective pixel region of the image sensor 22, the reset scanning of the exposure amount of the image sensor 22 in the vertical upward direction may be started at the reset timing corresponding to the above-described timing correction amount ΔT and the necessary detection period Td in which the shutter blades 25 starts moving and the movement of the predetermined amount is detected. Furthermore, after the shutter blades 25 start blocking the light arriving at the photodiodes in a region other than the effective pixel region, the detection of the position sensor or the reset scanning may start.

In the above-described second embodiment, the contents described as other examples of the first embodiment may be, of course, applied as long as the contents is applicable even when the contents are other examples of the second embodiment. For example, the timing correction amount ΔT(y) set in the correction amount setting routine of FIG. 10 may be used instead of the timing correction amount ΔT. Further, the same value as the correction amount ΔT1 may be set as the timing correction amount ΔT without using the correction amounts ΔT2 and ΔT3. As another shutter mechanism 123 in FIG. 11 is exemplified, two or more position sensors may be prepared and the timing correction amount ΔT may be set based on the detection timings of the plurality of position sensors. Further, the timing correction amount ΔT may be set by setting the correction amount ΔT1 which is larger stepwise (gradually) as the detection timing of the position sensor 25a is later. For example, the form indicated by the one-dot chain line in FIG. 14 may approximate to the actual shutter operation and may be changed by changing the speed (particularly, when the shutter speed is shorter) at which the position of the reset operation is moved.

In the above-described two embodiments, the shutter mechanism 23 has a so-called transverse structure in which the shutter blades 25 move transversely in the vertical direction. However, when the shutter blades are moved in a predetermined on the front side of the image surface 22a of the image sensor 22, shutter mechanism may have a longitudinal structure in which the shutter blades move in a horizontal direction. Further, shutter blades with other structure may be used. For example, shutter blades travel in a rotation direction. In this case, the type or mounting position may be selected appropriately according to the structure of the shutter.

In the above-described two embodiments, the invention is applied to the digital camera 10, but may be applied to a shutter operation estimating method of the digital camera. Further, one or a plurality of the above-described two embodiments and modifications thereof may be combined appropriately.

Claims

1. A digital camera comprising:

an image sensor that generates an image signal based on an exposure amount;

a shutter that is moved in a predetermined direction to block light arriving at the image sensor;

a movement control unit that moves the shutter to block the light arriving at the image sensor at which the light has arrived;

a movement detecting unit that detects the shutter moving by a predetermined amount from movement start;

an operation estimating unit that estimates the movement operation of the shutter based on a detection timing of the movement detecting unit; and

a reset control unit that starts reset scanning of the exposure amount of the image sensor in the predetermined direction in response to the movement operation of the shutter estimated by the operation estimating unit based on the detection timing in the movement operation of the shutter until the previous time.

2. The digital camera according to claim 1, wherein the reset control unit executes the reset scanning of the exposure amount of the image sensor in the predetermined direction in accordance with a change in a speed corresponding to the estimated movement operation of the shutter.

3. The digital camera according to claim 1, wherein the reset control unit starts the reset scanning of the exposure amount of the image sensor in the predetermined direction at a timing corresponding to the estimated movement operation of the shutter.

4. The digital camera according to claim 1, wherein when the estimated movement operation of the shutter is later than a predetermined operation, the movement control unit starts moving the shutter at a timing earlier compared to a case where the estimated movement operation of the shutter is earlier than the predetermined operation.

5. The digital camera according to claim 1, wherein the operation estimating unit estimates a current-time movement operation of the shutter based on the estimated movement operation of the shutter and a current-time detection timing of the movement detecting unit.

6. The digital camera according to claim 1, wherein the movement detecting unit detects the movement of the shutter by detecting an operation of an interlocking member interlocking with the movement of the shutter.

7. The digital camera according to claim 1,

wherein the movement detecting unit detects movements of a plurality of amounts including movement of a first predetermined amount and movement of a second predetermined amount larger than the first predetermined amount, and

wherein the operation estimating unit estimates the movement operation of the shutter based on a plurality of detection timings for the movements of the plurality of amounts of the shutter.

8. A shutter operation estimating method of a digital camera which includes an image sensor that generates an image signal based on an exposure amount and a shutter that is moved in a predetermined direction to block light arriving at the image sensor, the shutter operation estimating method comprising:

moving the shutter to block the light arriving at the image sensor at which the light has arrived;

detecting the shutter moving by a predetermined amount from movement start;

estimating the movement operation of the shutter based on a detection timing in the detecting of the movement of the shutter; and

starting reset scanning of the exposure amount of the image sensor in the predetermined direction in response to the movement operation of the shutter estimated in the estimating of the movement operation based on the detection timing in the movement operation of the shutter until the previous time.