Abstract: A bi-directional transmission mechanism is provided for an image scanner to increase the scanning speed. The bidirectional transmission mechanism provides a first transmission device for driving a sheet table in a first direction, and a second transmission device disposed below the sheet table for driving an image reading device in a second direction. The two transmission devices are moving towards opposite directions and at the same time when the scanning operation is enabled. The present invention mainly encompasses a sheet table for placing a document sheet. A first transmission device is provided for supporting and connecting to the sheet table for driving the sheet table from a first direction to a second direction. An image reading device disposed under the sheet table reads the image information of the document sheet.

Abstract: In an analog front end (FE) IC chip having a CDS (Correlated Double Sampling) function and an AGC (Automatic Gain Control) function, a clamp circuit for clamping an output signal during a black reference signal period is equipped with a mechanism for suppressing the effect of noises contaminated from a power source, external circuits, etc.

Abstract: A device and process which eliminates potential moiré patterns in digitized images by employing a one-dimensional sensor array and a sampling method of the sensor signals which produces a data set of non-uniformly spaced sensor positions. This allows the spacing of the sensors to avoid having a strong “harmonic” which may interfere with details or harmonics present in the image source, which eliminates the occurrence of moiré patterns and the need for application of image processing to remove moiré patterns. Sensors are non-uniformly spaced along a first axis according to a predetermined scheme or function. Sensors are sampled during scanning according a non-uniform function in order to realize a non-uniform sampling scheme in a second dimension. Linear interpolation is applied to the non-uniformly spaced data set, synthesizing a uniformly-spaced data set for use in common imaging formats and processing.

Abstract: A contact image sensor (CIS) for scanning a document is disclosed. The CIS includes a housing having an opening, a first slide and a second slide, a light guide installed on the housing through the opening and the first slide for scanning the document and generating a reflective image, a rod lens installed on the housing through the opening and the second slide for receiving the reflective image and generating a focused image, a PCB installed on the housing and having a sensing array for transforming the focused image into an image signal, and a spring cover fixed on the opening for fixing the light guide and the rod lens in the housing to form the CIS.

Abstract: There is disclosed an illumination device in which a light guide is adapted to emil the light from a face thereof and is provided with an area, on a face opposite to the light emitting face, for diffusing and/or reflecting the light introduced into the light guide from an end face thereof or is provided with uneven light emitting characteristics along the longitudinal direction of the light guide, and the center of the light source positioned at the end of the light guide is placed at a position aberrated from the normal line to said area, whereby attained are compactnces, a low cost, a low eleotric power consumption, a high efficiency of utilization of the light emitted by the light source, and excellent and uniform illumination characteristics. There are also disclosed an image reading device and an information processing apparatus, equipped with the above-mentioned illumination device.

Abstract: A document-guiding device that clips onto the image sensor of a document scanner ensures that documents to be scanned are introduced into the scanner at an optimal angle and are applied to the transparent surface of the image sensor at an optimal pressure, thereby avoiding scratching and soiling the sensor glass surface. Moreover, the deep input guide clip includes a sharp edge that acts as a scrapper to remove or flatten protruding impurities to further reduce soiling the sensor transparent surface. The deep input guide clip has the added benefit of stopping parasitic ambient light and protecting the image sensor against hard falling objects thus avoiding breakage of the transparent surface. The deep input guide clip forms a compact enclosure that may also hold a set of document proximity sensors and associated control electronics for precisely detecting the leading edge of the document when it is introduced in the scanner, its width and its trailing edge.

Abstract: Provided is an image reader which is constituted by an image sensor having a plurality of image sensor ICs mounted therein linearly, wherein the plurality of image sensor ICs are divided into a plurality of blocks to read image signals of the blocks in the same period, and adjacent light receiving elements of the adjacent image sensor ICs between the blocks are arranged so as to be slipped from each other in a sub scanning direction in such a way that the reading areas of the image signals which are to be read in the same period in the sub scanning direction become identical to each other. Thus, no continuousness of an image is injured even in a joint between the adjacent blocks.

Abstract: What is described here is a method of analog signal processing of video signals from picture elements arranged in an array, which are adapted for discrete scanning in terms of time, using a resistive network, the so-called electronic retina, having a two-dimensional field structure including a number of lines m smaller than the number of lines p of the picture element array, wherein the video signals are transmitted from the picture elements in the electronic retina by lines in such a manner that, starting with the first line of picture elements, the video signals are transmitted into the first line of said electronic retina until after the transmission of the video signals from the m-th line of the picture element arrays into the m-th line of said electronic retina the picture elements of the m+1st line of the picture element array are transmitted into the electronic retina, starting again with the first line, until the p-th line of the picture element array is transmitted in a roll-over manner into the

Abstract: According to the present invention, there is provided an image sensor for receiving light reflected from an original copy on which the light has been irradiated and for converting the received light into electrical signals, the image sensor having a simple configuration, no residual image, a small fluctuation in the dark outputs, and a good S/N ratio. In order to achieve such an image sensor, an output terminal of a photodiode is reset to a constant voltage, and an image signal output of the photodiode and the reference voltage output immediately after the photodiode is reset are performed succeedingly, using a clamping circuit.

Abstract: A contact image sensor includes a light sensitive optical detector and a light source mounted on a mounting surface. A light guide is located under the light source and is oriented to direct a light path from the light source to a scan line region under the light sensitive optical detector.

Abstract: An image reading device includes a control unit for controlling an image reading unit so as to perform a reading operation within a range obtained by adding predetermined widths m and n to a reading range set after prescanning by a setting unit so that the relationship of X2=X1+m and Y2=Y1+n holds at main scanning, where m and n are constants, X1 and Y1 are the lengths of the set reading range in the x-axis and y-axis directions, and X2 and Y2 are the lengths of an actual reading range in the x-axis and y-axis directions, respectively. As a result, it is unnecessary to perform troublesome operations, such as reassigning a reading range, and again performing a reading operation.

Abstract: A dynamic threshold two-level A/D converter, also termed a tracking digitizer circuit. The module circuitry includes a comparator circuit and a tracking low-pass filter circuit. The dynamic thresholding module takes the output signals from a CIS module and develops a tracking (variable) background signal. The tracking background signal is then compared to the output signals from the CIS in a comparator. The comparator outputs a two-level (binary) output digital signal. The circuit is designed to be used in conjunction with a scanning device, particularly a CIS system. The circuit can be used in a wide variety of applications that require pre-processed digitized video signals. The dynamic thresholding module's circuitry can be implemented quite simply. Moreover, the circuit provides a very low cost and a low parts density module that can easily be incorporated with existing CIS modules without substantially increasing the size of the CIS module or the cost to manufacture the unit.

Abstract: A structure of a CMOS image sensory device is described. A photodiode sensory region and a transistor device region are isolated from each other by an isolation layer formed in the substrate. A gate structure is located on the transistor device region, and a source/drain region is in the transistor device region beside the side of the gate structure. A doped region is in the photodiode sensory region. A self-aligned block is located on the photodiode sensory region and a protective layer is formed on the entire substrate.

Abstract: A circular optical reflection apparatus to be used in an optical image capturing device for receiving light ray from a light source and reflecting the light ray at least twice inside the apparatus then projecting the light ray to a lens set for forming an image on an image forming device. The apparatus includes a cylindrical optical member which has its outside surface coating with a reflective material and has an axial cutaway section to serve as a light inlet and a light outlet. Light ray enters through the light inlet into the cylindrical optical member and reflects inside at least twice then emits out through the light outlet. It may obtain an optical path needed for image forming with less number of reflection mirrors. It is smaller size and may be produced and assembled with less time and cost. It can also eliminate accumulated reflection angle tolerance that might otherwise happen to the conventional ones that use reflection mirrors.

Abstract: An imaging device includes plurality of illumination elements interspersed among a plurality of light sensing elements so that each illumination element is adjacent to a light sensing element. The illumination elements each include a ferroelectric liquid crystal element positioned over a LED. The light sensing elements each include a photodiode. The illumination elements and the light sensing elements are arranged so that adjacent to each illumination element is a light sensing element. Illumination control logic can selectively illuminate each of the illumination elements. The light sensing elements are coupled to analog shift registers. The light sensing elements generate charges related to the intensity of the impinging light. Sensor control logic is used to load the charges generated by the light sensing elements corresponding to the illuminated illumination elements into the shift registers. The charge data in the shift registers is sequentially shifted to the input of an amplifier.

Abstract: To obtain an excellent image signal, an image sensor having a plurality of photoelectric conversion devices each including a plurality of light-receiving elements includes a resolution switching circuit for switching a resolution of a signal read from the light-receiving element, a scanning circuit for reading a signal from the light-receiving element in accordance with the resolution switched by the resolution switching circuit, and a start timing control circuit for controlling a start timing from one of the photoelectric conversion devices to the next photoelectric conversion device in accordance with the resolution switched by the resolution switching circuit.

Abstract: A method for enhancing scan resolution, suitable for the application of a scanner with a sensor. The range that a detecting cell in the sensor can detect is the original pixels with a predetermined number. The scanned result of the detecting cell is called the scanned pixels. In the method for enhancing scan resolution, a smooth image region is scanned to obtain a smooth image data. The smooth image region includes at least the above original pixels with the predetermined number. The smooth image region has a uniform brightness. According to the smooth image data, the scanned pixels obtained from scanning the document are processed.

Abstract: In order to improve the reliability of apparatus and to attain signal outputs with high S/N ratios, a driving method of photoelectric conversion apparatus has a first mode for performing drive of photoelectric conversion elements, irrelevant to reading of information, and a second mode for dealing with reading of information, and transition to the second mode is carried out after a lapse of a desired time from the first mode.

Abstract: A method for super-resolution scanning in a image capturing device includes capturing a first color component of the image at one-half of a full resolution, capturing a first luminance component at one-half of the full resolution, and generating a first color-luminance output signal therefrom; capturing a second luminance component of the image at the full resolution and generating a luminance output signal therefrom; capturing a second color component of the image at one-half the full resolution, capturing a third luminance component of the image at one-half the full resolution, and generating a second color-luminance output signal therefrom; converting the first and second luminance components of the first and second color-luminance output signals and the third luminance component signal to a luminance component signal of 2X full resolution; and processing the full resolution output signals and the 2X full resolution output signal to form a combined output signal.

Abstract: An original reader such as an image scanner for inputting image information, provided with a optical source for illuminating an original, a lens unit (8) capable of optically changing resolution, and a solid-state image sensor substrate placed on an image forming plane (10) of the lens, wherein the lens unit (8) includes a plurality of lenses that can deal with a plurality of different resolution and one lens corresponding to a specified resolution is selectively moved into a light path. The lens unit and the solid-state image sensor substrate are independently movable in the direction of optical axis for focusing.

Abstract: A dynamic threshold two-level A/D converter, also termed a tracking digitizer circuit. The module circuitry includes a comparator circuit and a tracking low-pass filter circuit. The dynamic thresholding module takes the output signals from a CIS module and develops a tracking (variable) background signal. The tracking background signal is then compared to the output signals from the CIS in a comparator. The comparator outputs a two-level (binary) output digital signal. The circuit is designed to be used in conjunction with a scanning device, particularly a CIS system. The circuit can be used in a wide variety of applications that require pre-processed digitized video signals. The dynamic thresholding module's circuitry can be implemented quite simply. Moreover, the circuit provides a very low cost and a low parts density module that can easily be incorporated with existing CIS modules without substantially increasing the size of the CIS module or the cost to manufacture the unit.

Abstract: An optical imaging assembly comprises a mounting surface and at least one semiconductor die having a face and an edge portion. The edge portion of the at least one semiconductor die is mounted to the mounting surface. A light sensitive optical detector is located on the face of the at least one semiconductor die. An optical system is mounted to the mounting surface adjacent the at least one semiconductor die.

Abstract: The present invention is made to provide a fixing structure for solid state image forming device made inexpensively and easily by simple caulking adhering method with keeping high positional accuracy, by which it is achieved that the solid state image forming device can be separated easily from the image focusing lens holding member when the image focusing lens holding member has a defect, In the fixing structure of present invention, an image focusing lens holding member 3 and an intermediate holding member 6 are adhered by caulking adhering method.

Abstract: Data representing the characteristics of a honeycomb CCD are stored on a ROM. The image of a subject is sensed by the honeycomb CCD and image data representing the image of the subject is recorded on a memory card. The data representing the characteristics of the honeycomb CCD is read out of the ROM and is recorded on the memory card in association with the image data. When an image is reproduced, correction of the image data can be performed comparatively accurately utilizing the characteristics data.

Abstract: The divided one-dimensional solid-state imaging device includes photodiode arrays having photodiodes for individual pixels arrayed in a line, output transistors for outputting electric charges from the respective photodiodes and transfer paths for transferring the outputted electric charges to output terminals. In the imaging device, the photodiode arrays is divided into a plurality of sections differing in the number of pixels in a photodiode arraying direction, the respective divided sections connecting to the corresponding ones of the transfer paths and the output terminals, and pixel rows in the respective divided sections are read out in parallel at the same time from the output terminals corresponding to the respective divided sections.

Abstract: In a contact type image sensor having a sensor array mounting photosensors, a focussing unit for focussing light from an original upon the photosensors, and a frame for holding in position the sensor-array and focussing unit, the focussing unit abuts on the sensor array. In a contact type image sensor having a sensor array having a plurality of face-down sensor chips with a plurality of pixels mounted on a transparent substrate in line, a rod lens array for focussing light from an original, a light source for illuminating the original, and a frame for holding in position the sensor array, rod lens array, the transparent substrate is covered with a light shielding layer in an area other than an area on which the pixels of the sensor chips are mounted and an area corresponding to a focussing area of the rod lens array.

Abstract: An image reading apparatus includes a sensor IC having a group of photoelectric conversion devices which are linearly aligned, a sensor board on which the sensor IC is mounted, a lens for forming light information into an image on the sensor IC, a light source having electrical connection lines, an illumination unit consisting of a light guide for guiding light from the light source and outputting the light in a desired direction, and a frame for holding the respective members. The electrical connection lines of the light source are directly connected to the sensor board. Connector cables for the light source can be omitted, and the image sensor and the external system can be electrically connected through one connector. By simplifying the electrical connection, the influence of noise can be minimized.

Abstract: To reduce current consumption in a contact type linear image sensor of a multi-chip form, a control circuit controls a clock buffer circuit of the device so that the clock buffer is activated only when a picture signal from a corresponding linear image sensor IC is output. The control circuit inputs a control signal, operates the clock buffer, and drives a shift register when a picture signal is to be read out.

Abstract: The present invention is to provide an image reader including a transparent substrate, which can be used effectively for an extended lifetime. The image reader comprises a transparent substrate and a stationary image pickup opposed to the transparent substrate for reading an image of an original document while the document is being transported between the transparent substrate and the stationary image pickup. The transparent substrate can be turned around and/or upside down relative to the image pickup in order to use the transparent substrate for an extended its service time. Also, the transparent substrate includes at least one first indicator showing an arrangement order how the transparent substrate has been turned around relative to the image pickup.

Abstract: Improved circuitry for active matix image arrays which, in one application reduces the number of source or gate lines for a given number of pixels, and in another application extends the dynamic range of the imaging array without reducing the number of source or gate lines. Each circuit includes multiple electrodes per pixel and multiple thin film transistors for switching charge from the pixel electrodes to the data line.

Abstract: In order to prevent an image quality from being lowered by shading and or the like, an image pickup apparatus is provided which includes an image pickup area including a plurality of photoelectric conversion areas, a plurality of converging lenses for converging light on a plurality of photoelectric conversion areas, and a light shielding area having a plurality of opening areas through which light is incident upon the plurality of photoelectric conversion areas, wherein positions of the converging lens and opening area are shifted inward than a corresponding photoelectric conversion area.

Abstract: A sensor chip, an image reading sensor and an electronic device, which are capable of preventing poor image readings, are provided. The sensor chip is constructed such that the image reading sensor is constituted by mounting a plurality of sensor chips on a sensor substrate, and is provided with a notch at a lower corner of an end portion which faces with other sensor chip. The image reading sensor is constituted by mounting a plurality of sensor chips on a sensor substrate, and each sensor chip is provided with a notch at a lower corner of the end portion which faces other sensor chip. The electronic device contains the image reading sensor, which is constituted by mounting a plurality of sensor chips on a sensor substrate, and each sensor chip is provided with a notch at a lower corner of the end portion which faces other sensor chip.

Abstract: In order to prevent a decrease of yield due to a discontinuity of a wire or a short between upper and lower metal wires in production of a TFT matrix panel having pixel capacitors and TFTs and produce the TFT panel in a good yield without decrease of an aperture rate of the pixel capacitor portions even with increase in the size of the panel and with micronization of the pixel pattern, ends of bias lines on the opposite side to connection to a common electrode driver for application of bias are electrically connected to each other by a redundant wire.

Abstract: The present invention concerns a method for operating a CMOS image sensor including a matrix of pixels (50) arranged in a plurality of lines and columns, each of said pixels including a photosensor element (PD) accumulating charge carriers in proportion to the illumination thereof and storage means (C1,55) able to be coupled to said photosensor element (PD) at a determined instant in order to generate a sampled signal representative of said charge carriers accumulated by the photosensor, the storage means (C1, 55) being intended to assure storage for the purpose of reading said sampling signal.

Abstract: An improved high resolution scanner for use in a conventional scanner housing. A plurality of mirrors, including a two-position switchable mirror adapted to sequentially scan a first column, and then a second column, is mounted on a carriage which also includes a conventional lens and CCD for sequentially scanning an object to be scanned in a two-pass scan. The resulting scanned portions, when combined, produce a high resolution image of the scanned image.

Abstract: To control the potential distribution generated in a well at the time of amplification and reduce a shading in a solid-state imaging device of amplification type, the amplification type solid-state imaging device of the present invention comprises a plurality of picture elements each including photoelectric conversion elements formed in a second conductivity type common well inside a first conductivity type substrate, wherein a plurality of well contacts are disposed inside a picture element array area.

Abstract: An image sensor has a plurality of sensor integrated circuit devices of the same configuration arranged in a row. Each sensor integrated circuit device has a plurality of light-sensing elements, a sensor circuit for successively outputting the outputs of these light-sensing elements, and an amplifier circuit. It further has a first output terminal for directing the output of the sensor circuit out of the sensor integrated circuit device, an input terminal for directing an external signal to the amplifier circuit, and a second output terminal for directing the output of the amplifier circuit out of the sensor integrated circuit device. The first output terminal of each sensor integrated circuit device is connected to the input terminal of a particular sensor integrated circuit device so that the output of every light-sensing element is amplified by the amplifier circuit of that particular sensor integrated circuit device alone.

Abstract: In a multi-element sensor calibration apparatus, an image signal derived from a multi-element sensor installed in a facsimile or a satellite is periodically calibrated based upon a zero level signal and a calibration signal having more than two uniform levels.

Abstract: A document sensing device for an image forming apparatus of the present invention is capable of sensing a document stably without being influenced by disturbing light, e.g., light ascribable to fluorescent lamps or similar illuminators illuminating a room. According to one aspect of die invention, optical elements are held by a jig rotatable about an optical axis. According to another aspect of the invention, a light receiving means or a photosensor means has at least four light-sensitive regions.

Abstract: An optical scanner for retrieving digital images of opaque and transmissive objects. The scanner of the present invention includes a scanner body, a docking port, and a removable scanning platform. An object to be scanned is placed on the scanning platform, which is subsequently loaded into scanner body for scanning. Inside the scanner body, a sensor module, including a first light source and an image-retrieving device, is disposed above the docked scanning platform; a support frame, on which is disposed a second light source, is disposed below the docked scanning platform. A connecting rod engages the sensor module and the support frame, and a driving device synchronously moves the sensor module and the support frame along a longitudinal axis. In a first embodiment, the scanning platform can include an adhesive tape for adhering an opaque object to be scanned to the surface of the scanning platform.

Abstract: An apparatus and a method for compensating the gray-scale values of an image scanned by a contact image sensor. The gray-scale compensating apparatus includes: a power supply for providing a fixed level of voltage source, a contact image sensor for scanning an image and outputting image voltages VIMG of pixels of the image, or scanning a white pixel and outputting the white-level voltage VP of the white pixel, an analog/digital converter, to receive the fixed voltage from the power supply and the image voltage VIMG or the white-level voltage VP, a microprocessor to calculate the average of n white-level values G(x, y), where n is an integer, and the average value G′(x)=(G(x, 0)+G(x, 1)+ . . . +G(x, n−1))/n. The microprocessor also determines the gray-scale values g′(x, y) of the image being compensated by calculating the gray-scale values g(x, y) of the image not compensated in accordance with the value of G′(x).

Abstract: An image reading apparatus having a partition module between an image sensor module and a heat source (e.g., a laser-beam printer) includes a partition module disposed between the image sensor module and the heat source. The partition module has two walls with a gap therebetween for thermally insulating the image reading module from the heat source. Preferably, the partition module has an air intake port, and an air exhaust port, and a fan for circulating cooling air.

Abstract: An image sensing device includes three photoelectric signal generators, each of which generates a photoelectric signal proportional to an intensity of incident light, and three converters which are connected with the photoelectric current generators, respectively. Each of the converters generates an analog signal which is logarithmically proportional to the photoelectric signal. A direct-current component of the analog signal, generated by each of the converters, is adjusted to perform a white balance adjustment before an A/D conversion.

Abstract: In a photoelectric conversion device for reading signals in succession from plural photoelectric converting elements (S11-S33), arranged two-dimensionally on a substrate, by successively scanning drive lines (g1-g3) in the X-direction thereby transferring signals charges along signal lines in the Y-direction, for reading the signals of the photoelectric converting elements in a partial area, only the arbitrarily selected drive lines for the plural photoelectric converting elements are scanned in succession while the remaining drive lines are not driven or are driven simultaneously for transferring the charges at a timing different from the timing of drive of the arbitrarily selected drive lines.

Abstract: An image scanning apparatus efficiently compresses and encodes image data obtained by scanning both sides of an original sheet by using a line memory storing three lines. Image data output from a first scanner and image data output from a second scanner are alternately output from a switching unit on an individual line basis. The line memory stores three consecutive lines of the image data output from the switching unit. The three lines include a current line, an immediately preceding line and a second immediately preceding line immediately preceding the immediately preceding line, the current line including a current pixel being encoded. Reference pixels are extracted from among pixels included in the current line and the second immediately preceding line. A pixel value of the current pixel is encoded by using a predicted pixel value of the current pixel as a parameter so as to output encoded image data corresponding to both sides of the original sheet.

Abstract: An electronic circuit apparatus comprises an array of M.times.N functional elements, M.times.N switching elements provided in a one-to-one correspondence with the M.times.N functional elements, a shift register having M output lines, and a selector having N select lines. M control lines are commonly connected in units of N elements of the M.times.N switching elements. The M control lines are connected to the M output lines of said shift register. N input and/or output lines are commonly connected in units of M elements of the M.times.N switching elements. The N input and/or output lines are connected to the N select lines of the selector. Transistors constituting the shift register are thin-film transistors. And, transistors constituting the selector are transistors each having an active region consisting of a single-crystal semiconductor.

Abstract: A CCD line sensor is adjusted to a dynamic range capable of reliably reading a maximum density (highest density) so as to ascertain the density distribution of an original image (prescan). Next, a pixel which outputs date having a density value higher than a predetermined density threshold value (for example, D=about 2.0 to 2.3 with a maximum density value D as 3 to 3.3) is extracted from image data obtained by one scanning. At the main scanning time, a liquid crystal shutter is operated, transmittance is reduced, and an original image is read only when light is received by the extracted pixel(main scan). An image reading method is provided as mentioned above, and also a scanner for restraining the deterioration of the S/N ratio from the low density area of the original image to the high density area thereof and reliably reading the original image is obtained.

Abstract: An apparatus and method for a large-format scanner. In a preferred embodiment, a device for scanning an image on a medium having a width and providing signals representing the image includes a frame, a transport, a lamp and a plurality of sensors. The transport is mounted to the frame and is used for moving the medium along a first axis transverse to the medium's width. The lamp illuminates the medium. The lamp has a first end and a second end wherein the first end and the second end are folded back approximately 180 degrees, so that the lamp produces uniform brightness across the width of the medium. The plurality of sensors are proximate to the transport, span the medium's width, and the sensors provide a signal representative of a portion of the image within the illuminated portion of the medium. The device may also include a focal length adjustor, mounted to the frame between the sensors and the transport, for adjusting the distance between the medium and the sensors.

Abstract: An image sensor is provided for reading images on an image carrying paper irradiated by light emitted from a light source. The image sensor includes a plurality of image sensor chips for receiving reflected light from the image carrying paper for output of image signals in accordance with the luminous energy of the reflected light. The image sensor also includes a light detector for receiving light directly from the light source for output of a detection signal in accordance with the luminous energy of the directly received light.

Abstract: An image sensor has a photoelectric conversion unit composed of an array of a plurality of sets of a photoelectric conversion element having one electrode connected to a power source line and a switching element connected to another electrode of the photoelectric conversion element to receive an output thereof. A shift register, operating in synchronism with a clock supplied thereto, generates a pulse to turn on the switching element. The current that the switching element outputs when turned on is stored in and converted into a voltage by a capacitor. When the switching element is turned on, a transistor that forms a discharging path for the capacitor is connected in parallel with the capacitor. This transistor is turned on with a pulse obtained by delaying the clock. Thus, the capacitor is cleared over a period including periods before and after the switching element is turned on.