Abstract: A method of adjusting the maximum intensity of a laser exposure mechanism for irradiating laser light to the surface of a photoreceptor to which a uniform potential is being given by a corona discharger. Photoreceptor surface portions are exposed to laser lights of a plurality of laser intensities obtained by coarsely dividing an optional laser intensity, and the potentials of the photoreceptor surface portions are detected (coarse-division potential detecting step). In the vicinity of the laser intensity corresponding to the potential closest to the desired preset potential, the predetermined laser intensity is further finely divided to set a plurality of laser intensities, photoreceptor surface portions are exposed to laser lights of the plurality of laser intensities thus set, and the potentials of the photoreceptor surface portions are detected (fine-division potential detecting step).

Abstract: A linefeed calibration method for identifying media advancement errors utilizes plural test patterns, including both a base pattern and an overlay pattern that are printed overlying each other to form an interference pattern. A sensor detects overall alignment of the interference pattern. That overall alignment is compared to alignment of at least a second interference pattern to identify a linefeed advance error. The error is correlated to a position on a media advancement mechanism such as a roller. A processor then adjusts the media advancement mechanism to correct the identified media advancement error. Under-advance errors, over-advance errors and skew errors may be identified using the described method.

Abstract: An electrophotographic device with a laser power correction device (and method therefor) includes a laser power detection sensor retractably disposed relative to a laser beam optical path of a laser beam, a laser power adjusting device for controlling laser power of the laser beam based on an output from the laser power detection sensor, and a controller for inserting the laser power detection sensor into the optical path and applying laser power correction when a total laser beam activation time has reached a predetermined time and printing is stopped.

Abstract: In a digital copying machine using a multi-beam optical system, a sensor pattern senses a light beam directed onto the photosensitive drum and generates current according to the amount of light. The current is converted into a voltage by an operational amplifier acting as a current/voltage conversion amplifier. The output voltage of the operational amplifier is integrated by an integrator. The output of the integrator is converted into a digital signal by an A/D converter, thereby producing luminous energy sensing information. According to the luminous energy sensing information, a laser oscillator is controlled. Between the operational amplifier and integrator, a variable resistor is inserted which absorbs variations in the sensitivity of the sensor pattern or variations in the conversion characteristic of the operational amplifier.

Abstract: In a photographic printer using a laser scanning unit for exposing a latent image corresponding to an image data on a sensitized surface of a photographic paper, intensities of the laser beams exposing the photographic paper are adjusted corresponding to a variation of an actual sensitivity of the photographic paper and deterioration of a developer with respect to nominal values of them. At least the intensities directly emitted from laser light sources, or values of optical modulation data for modulating the laser beams corresponding to the image data are varied. Alternatively, transmittances of optical elements such as polarizing beam splitters provided on optical paths are varied for adjusting the intensities of the laser beams.

Abstract: An image forming apparatus comprises a memory which stores test pattern data. The test-pattern data are configured for detecting a density of image data formed on a photo conductor. The image forming apparatus comprises a laser unit which forms a plurality of test patterns on the photo conductor by utilizing a plurality of a first laser powers based on the test pattern data stored in the memory. The image forming apparatus comprises a detector which illuminates each test pattern formed on the photo conductor by the plurality of the third laser powers, receives each light intensity reflected by the test patterns, and outputs output values corresponding to each received light intensity. The output values defines a first range of output values. The image forming apparatus comprises a controller which compares each output value with a first predetermined value.

Abstract: This invention provides an exposure apparatus capable of properly reading an electrical signal from a photoelectric sensor by using the time interval between emission pulses even at a high emission frequency of the light source. A photoelectric sensor attached to an exposure apparatus which exposes a substrate to a pulse beam emitted by a light source for generating a pulse beam has a plurality of photoelectric converters (29-1-29-n). The photoelectric converters (29-1-29-n) are divided into a plurality of blocks. While charges are read from each block by using one time interval between pulse beams, charges in all the photoelectric converters (29-1-29-n) are read by using a plurality of time intervals between pulse beams.

Abstract: An image processing apparatus, comprising: an exposing device for exposing an image forming material so as to form a latent image on the image forming material based on image data; a thermal developing device for developing and visualizing the latent image on the exposed image forming material so as to form an image; a measuring device for measuring the image density of the image on the developed image forming material; a calibrating device for forming a table to define a relation between an image signal and image density on the basis of plural different test image data and measured-image densities thereof; a counting device for counting the number of the image forming material developed within predetermined time; and a controlling device for controlling the exposing device, the thermal developing device, the measuring device, the calibrating device and the counting device; wherein the controlling device stop forming the table for predetermined time when the counting device counts the number of the developed

Abstract: An exposure head is provided in which light beams from light emitting parts 63 pass through a transparent substrate 62 and are projected on an image carrier. The transparent substrate 62 has plain faces substantially parallel to each other, one of the faces being a face on which the light emitting parts 63 are formed and the other being a face from which light beams are projected. The transparent substrate 62 is provided, at position(s) other than the face on which the light emitting parts 63 are formed and than the face from which light beams are projected, with light quantity detecting means 100 for detecting the quantity of light emitted from said light emitting parts 63.

Abstract: A laser drawing apparatus according to the invention calibrates the accuracy of a first light quantity monitor in detecting the quantities of laser beams, based on results of detection by a second light quantity monitor of the quantities of laser beams emitted from an imaging optical system to a drawing stage, when a characteristic deterioration of or adhesion of foreign matter to optical components of the first light quantity monitor has resulted in variations in the optical characteristic of the first light quantity monitor, and variations in the detection by the first light quantity monitor of the quantities of the laser beams. The quantities of the laser beams emitted to a printed circuit board (image-receiving object) is thereby adjusted to a proper value, to maintain high-quality, high-definition drawings requiring a high degree of light quantity precision.

Abstract: The method of the invention includes: determining the beam profiles of plural LED elements (light-emitting elements) including joints of LED chips (light-emitting chips); determining the distance between the LED elements at the joints of the LED chips from the distance between peaks of the beam profiles; comparing the determined distance between the LED elements with the resolution pitch of the printhead; raising the light amount of the LED elements of at least one side of the joints of the LED chips when the determined distance between the LED elements is longer than the resolution pitch; and lowering the light amount of the LED elements of at least one side of the joints of the LED chips when the distance between the LED chips is shorter than the resolution pitch.

Abstract: There is provided an image recording apparatus able to form images without fluctuation of image dot intervals in the main scan direction.

Abstract: SLED (Self-scanning type Light Emitting Diode) array chips of 56 pieces and one driving circuit which generates signals to drive the 56 SLED array chips are provided. A signal is generated by another driving circuit. A driving current control resistor which is connected in series to a common base of driving transistors is provided to variably adjust an input voltage value acting as a control signal of the driving circuit. Thus, a light emission array head, a driving level adjustment method of a driving signal for this head, and an image formation apparatus containing this head can be simplified.

Abstract: When a light beam scans a scanned surface in a horizontal scan direction, a sensor is arranged on the scanned surface or a position equivalent to the scanned surface. The sensor converts a light quantity of the light beam into an electric signal to be output. The light beam's passage position is gradually moved in a vertical scan direction to detect a maximum value of the electric signal output from the sensor. When the detected maximum value is smaller than a specified reference value, the light beam is determined to be defocused.

Abstract: An image forming apparatus includes a light emitting array composed of a plurality of light emitting elements that emits light fluxes. An imaging element array may be provided so as to perform imaging with the light fluxes on a prescribed plane. A three dimensional exposure intensity distribution of the light flux is obtained per each light emitting element. A prescribed attribute is obtained from each of the exposure intensity distributions. A plurality of comparison values for the entire exposure valid region may be obtained from different units which consist of two or more successive attributes. Prescribed light emitting quantities enabling all of the comparison values to fall within a prescribed range may be determined and set to respective light emitting elements.

Abstract: A method is provided for enhancing a digital image without distortion of the color. The result is an adjusted image which preserves the essential color of each and every dot in the input digital image while varying the effective light gathering power—like a virtual flash. The image enhancement is performed in RGB color space and comprises determining the maximum strength of the R,G, and B of a dot's RGB triplet and similarly for all dots. The dot maximums are scaled through a scaling function which is constrained in domain and range to the system's dynamic range. The same scaling factor that is applied to a dot maximum is also applied to each of R,G and B in the triplet. Preferably, a continuous scaling function is provided which smoothly approaches the minimum and maximum of the system's dynamic range for providing an aesthetically pleasing enhancement while maintaining true color.

Abstract: In a laser beam scanner of used for exposing a latent image on a photographic paper, intensities of the laser beams are maintained in predetermined range by compensating amplitude of driving signals supplied to acousto-optic modulators when intensities of the laser beams emitted from laser light sources are varied. The intensities of the laser beams passing through the modulators are sensed by photo sensors and compared with predetermined standard value. When any of the intensity of the laser beam is discrepant from the standard value, a difference between them is calculated and an optical modulation data for controlling the amplitude of the driving signal is compensated by subtracting the difference value from the standard value. Thereby, the amplitude of the driving signal of the modulator is compensated.

Abstract: A calibration system is disclosed for use with an imaging system including a laser line illumination source. The calibration system includes an imaging head, a mask having a calibration opening through which a portion of the line of laser illumination may pass, and a calibration unit. The imaging head is movable along a slow scan direction with respect to an imaging surface for imaging a line of laser illumination in the slow scan direction. The calibration opening has a width in the slow scan direction that is larger than a full width half maximum distance of an imaging spot of a smallest addressable picture element of the line of laser illumination. The calibration unit is for receiving a portion of the line of laser illumination through the calibration opening and for processing the received portion of the line of laser illumination.

Abstract: A printer head for computer-to-plate printing includes a linear array of individually addressable diode-lasers and a linear array of photodetectors. The number and spacing of the photodetectors is the same as the number and spacing of the diode-lasers. The diode-lasers emit in forward and reverse directions. The diode-lasers and photodetectors are aligned parallel to each other such that reverse-emitted light output of each diode-laser is incident on a corresponding photodetector. Each photodetector output is monitored by a dedicated controller/driver sub-circuit that regulates drive current supplied to the diode-laser. The drive current is regulated according to a comparison of the monitored photodetector output with a reference current individually calibrated in each sub-circuit. Calibration data for each sub-circuit is obtained from a measurement of forward-emitted output power of its corresponding diode-laser compared with a desired target forward-emitted power.

Abstract: A printhead having a plurality of exposure elements (18) with improved non-uniformity correction. Spatial variance of the energy emitted by the exposure elements (18) is measured and used to establish spot size characteristics for each exposure element. A sensor (26) scans multiple points along the pixel area written by each exposure element (18) and measures a corresponding output power value at each point. The output power values are evaluated to determine a maximum output power value for the exposure element (18) and to obtain a spot size for the exposure element (18) based on full-width at half-power values. Both spot size data, which can thus be obtained and stored only once, and output power values are then used to correct for non-uniformity's between the exposure elements (18).

Abstract: Uniformity of light output from an LED printbar is achieved by current sensing or image sensing of auxiliary LEDs on the LED printbar. A photodetector measures the light output from the auxiliary LEDs and a comparator will compare the auxiliary LED data to determine if the entire LED printbar has to be compensated to make the light output more uniform.

Abstract: When a light beam scans a scanned surface in a horizontal scan direction, a sensor is arranged on the scanned surface or a position equivalent to the scanned surface. The sensor converts a light quantity of the light beam into an electric signal to be output. The light beam's passage position is gradually moved in a vertical scan direction to detect a maximum value of the electric signal output from the sensor. When the detected maximum value is smaller than a specified reference value, the light beam is determined to be defocused.

Abstract: A laser drawing apparatus according to the invention calibrates the accuracy of a first light quantity monitor in detecting the quantities of laser beams, based on results of detection by a second light quantity monitor of the quantities of laser beams emitted from an imaging optical system to a drawing stage, when a characteristic deterioration of or adhesion of foreign matter to optical components of the first light quantity monitor has resulted in variations in the optical characteristic of the first light quantity monitor, and variations in the detection by the first light quantity monitor of the quantities of the laser beams. The quantities of the laser beams emitted to a printed circuit board (image-receiving object) is thereby adjusted to a proper value, to maintain high-quality, high-definition drawings requiring a high degree of light quantity precision.

Abstract: In an optical recording apparatus, a detecting section detects disk identification information of an optical disk for selecting a constant which relates to the detected disk identification information. A test OPC section performs test writing operation for OPC at a predetermined linear velocity prior to recording of data so as to obtain a test value. A formulating section formulates an equation expressing a target value in function of a recording linear velocity based on the constant, the predetermined linear velocity and the test value. A running OPC section performs running operation of OPC by monitoring an actual value while irradiating a laser beam for the recording of data at the recording linear velocity. A controlling section controls the power of the laser beam such that the monitored actual value coincides with the target value which is determined by the equation with respect to the recording linear velocity.

Abstract: In an image recording apparatus 1 which records an image on a recording medium 9 by moving an optical head 10 while rotating the recording medium 9 held by a holding drum 7, a photodetector 2 having a plurality of photodetector elements 21 is provided in a range of movement of the optical head 10. In correcting beam intensity, the optical head 10 is positioned so precisely that the photodetector 2 can receive the signal light beams. This constitution makes it possible to detect signal light beams from the light modulator with high S/N ratio as compared with a conventional case where one photodetector element sequentially receives the signal light beams, and therefore possible to correct the beam intensities with high accuracy.

Abstract: A system for printing on a print media. The device comprises at least one high energy emitting device and a parameter estimation device. The parameter estimation device is coupled to the high energy emitting device and is adapted to classify the print media and quantify an amount of energy per time to be emitted by the high energy emitting device during printing.

Abstract: The emission level of a laser source at the non-imaging time when image data “0” is input and the emission level at the imaging time when image data “1” is input are controlled so that each of them becomes a desired level. The light output intensity is stabilized at all times regardless of variations in ambient temperature. As a result, images uniform in density can be obtained.

Abstract: A calibration station (34) for a printhead (20) adapted to provide a beam of electromagnetic radiation from a variable electromagnetic energy source onto a sensitive radiation medium, the calibration station (34), incorporates a sensor (26) disposed for sensing the beam (16) provided by the printhead (20), wherein the sensor (26) provides an output sensor signal indicative of the sensed power of the beam (16). A control circuit is adapted to accept the output sensor signal from the sensor and adjusts the variable electromagnetic energy source. A filter is disposed in the path of the beam (16) between the printhead (20) and sensor (26), adapted to transmit to the sensor (26) a portion of incident electromagnetic radiation over a predefined range of wavelengths, dependent upon a measured response characteristic of the radiation-sensitive medium.

Abstract: In a solid scanning optical writing device that writes images on a photoreceptor by turning ON/OFF many light shutter elements aligned in an alternating fashion in two rows in the main scanning direction, single-row illumination and double-row illumination of the light shutter elements are alternately performed on a time sharing basis prior to the image writing in order to perform high-quality light amount correction. The positions of the light shutter elements are identified from the light amount data obtained from single-row illumination, and the transmitted light amount for each light shutter element during double-row illumination is sought from the light amount data obtained from double-row illumination. Calculation for shading correction is then performed from these sets of data.

Abstract: A printhead having a plurality of exposure elements (18) with improved non-uniformity correction. Spatial variance of the energy emitted by the exposure elements (18) is measured and used to establish spot size characteristics for each exposure element. A sensor (26) scans multiple points along the pixel area written by each exposure element (18)and measures a corresponding output power value at each point. The output power values are evaluated to determine a maximum output power value for the exposure element (18) and to obtain a spot size for the exposure element (18) based on full-width at half-power values. Both spot size data, which can thus be obtained and stored only once, and output power values are then used to correct for non-uniformity's between the exposure elements (18).

Abstract: An image forming apparatus and a method of controlling turn-on of light source used therefor are capable of conducting stable image forming operation and maintaining high effective scanning rate while switching the rotation control of the polygonal motor between the internal control by the internal encoder of the motor and the external control by the horizontal synchronous signal outside of the motor. With the apparatus and method, the period of detecting the timing of start of the fast scanning (referred to as SOS period) is T when the driving motor rotates at a predetermined number of revolutions. T becomes shorter by T2 due to the switching from the internal control to the external control. During the shift from the internal control to the external control, the light source is turned on so that the period T1 from turning-on the light source for detecting the SOS timing to the detection of the SOS signal becomes longer than T2.

Abstract: In a digital copying machine using a multi-beam optical system, a sensor pattern SH for sensing the power of each of the light beams a to d scanning the surface of a photosensitive drum and sensor patterns SB1 to SF1, SB2 to SF2 for sensing the passing positions of the beams are provided in a light beam position sensing unit. The sensor patterns SB1 to SF1, SB2 to SF2 are arranged linearly in the sub-scanning direction at intervals corresponding to two resolutions. The power of each light beam on the surface to be scanned is controlled so as to be in a specific range. Even when the light beams are scanned with different resolutions, they can be controlled with high accuracy so as to constantly have an ideal positional relationship between them. This always assures high picture quality.

Abstract: An optical printer head capable of increasing a level of a light amount for exposure emitted from luminous dot trains in view of an end cool phenomenon of filamentary cathodes and reducing loss of exposure energy. A light source includes luminous dot trains each constituted by a plurality of luminous dots each including an anode arranged on an anode substrate and a phosphor layer deposited on the anode, as well as filamentary cathodes arranged above the luminous dot trains so as to extend along the trains. A memory device is arranged so as to store therein correction information for ensuring uniform luminescence of the luminous dots. Light-amount correction is carried out on the luminous dots other than those positioned in proximity to each of both ends of the luminous dot trains excluded from light-amount correction, to thereby obtain correction information on the former luminous dots, which is then stored in the memory device.

Abstract: There is provided an image forming apparatus which can implement digital control of a laser beam scan (analog amount) that moves at high speed, without using any high-speed, multi-bit A/D converter. Upon executing a digital process on the basis of analog detection value Vo corresponding to the passage position or light beam power of a light beam with which a photosensitive drum is irradiated, comparator CMP0, comparison reference value (threshold value) Vr of which changes in correspondence with detection value (integration output) Vo, is used. New comparison reference value Vr is supplied to comparator CMP0 on the basis of digital data BMDA corresponding to output CMPOUT of this comparator.

Abstract: An optical write head which drives a plurality of light shutter elements arranged in a main scanning direction individually to write a multi-tone image on a recording medium. Prior to the image writing, while the light shutter elements are driven for reproduction of tone levels of 0, 48, 160 and 240, the quantities of light outputted from each of the elements are measured with a sensor, and from the measured values, an approximate expression indicating the output characteristic of each of the elements is calculated. The difference between the recording medium and the sensor in spectral sensitivity is made up, for example, by changing the intensity of light of each of the three primary colors emitted from a lamp by switching the voltage applied to the lamp between at the time of measurement and at the time of exposure or by changing the sensitivity of the sensor in receiving each of the three primary colors by switching the accelerating voltage applied to the sensor.

Abstract: An image forming apparatus includes a light emitting array composed of a plurality of light emitting elements that emits light fluxes. An imaging element array may be provided so as to perform imaging with the light fluxes on a prescribed plane. A three dimensional exposure intensity distribution of the light flux is obtained per each light emitting element. A prescribed attribute is obtained from each of the exposure intensity distributions. A plurality of comparison values for the entire exposure valid region may be obtained from different units which consist of two or more successive attributes. Prescribed light emitting quantities enabling all of the comparison values to fall within a prescribed range may be determined and set to respective light emitting elements.

Abstract: An optical scanning apparatus is constructed to detect one or more defective or damaged light emitting devices of a light source unit and forms images having substantially the same quality as that of the images formed when all of a plurality of light emitting devices of a light source of the apparatus are functioning normally even when any one of the plurality of light emitting devices are damaged or broken, without decreasing the image forming performance of the apparatus. The optical scanning apparatus detects one or more damaged or broken light emitting devices and then compensates for the light omitted due to the damaged or broken light emitting devices using the normally functioning light emitting devices without decreasing the image forming speed or quality of the optical scanning apparatus.

Abstract: The object of the present invention is to precisely correct the luminous energy of a laser beam on a scanned surface which varies according to scanning and varies according to an angle of incidence with the scanned surface when a laser beam emitted from a semiconductor laser for emitting a laser beam having luminous energy according to supply current is scanned on the scanned surface via a scanning optical system.

Abstract: At least two light beam detection units are spaced at a predetermined distance and provided in the scanning direction of a surface to be scanned. A light beam is emitted to the light beam detection unit provided on a scanning start side, by lighting a light beam source which is employed to scan the surface linearly during a scanning period equivalent to 1 dot during scanning. A light beam is emitted to the light beam detection unit provided on a scanning end side, by lighting the light beam source during the scanning period after elapse of a light-off period computed from a previously designed scanning speed and the predetermined distance. Based on a detection result of the light beam detection unit provided on the scanning start side and a detection result of the light beam detection unit provided on the scanning end side, scanning characteristics required of the light beam are evaluated.

Abstract: An electric photograph system for improving non-linearities of an exposing light intensity and an operating current at a low exposing level when performing analog printing operation. A range (saturable absorber) having a saturable absorbing characteristic is provided in a part of an optical path including a semiconductor laser as light source to improve the non-linearity of the operating current when the light intensity is weak. The saturable absorber may be made in the form of a non current injected area provided in a part of the semiconductor laser as the light source or a thin film layer provided partly in films coated on a facet of the semiconductor laser. Due to the provision of the saturable absorber, the light output power characteristic can exhibit its linearity in its low optical power range, the size of a printing dot can be arithmetically changed, and thus fine laser printing can be realized.

Abstract: A deterioration sensing device comprises a laser diode (LD), a voltage-current converter supplying electric current to the LD to radiate a laser beam which is received by a photo-diode, and an APC circuit outputting electric voltage in accordance with the intensity of the laser beam sensed by the photo-diode. The voltage-current converter is controlled based on the electric voltage so that the intensity of the laser beam is kept constant. An LD deterioration circuit is provided with a comparator, in which the electric voltage is compared with a reference voltage. An LD deterioration control unit is provided in the LD deterioration circuit to output a deterioration signal when the electric voltage becomes higher than the reference voltage, so that an alarm, indicating that the LD has deteriorated, is output, and the electric current supplied to the LD is decreased.

Abstract: A light beam scanner unit includes a light beam generating unit for generating light beams at a fixed power, a polygon mirror for reflecting light beams generated from the light beam generating means toward a surface to be scanned, thereby scanning it, and a light beam power sensing unit for sensing light beam power for scanning a surface to be scanned with the polygon mirror. This light beam scanner unit further has a mirror contamination sensing unit for sensing contamination of the polygon mirror by comparing a sensing result obtained from the light beam power sensing unit when light beams are emitted by the light beam generating unit with a preset reference value.

Abstract: In a photographic printer using a laser scanning unit for exposing a latent image corresponding to an image data on a sensitized surface of a photographic paper, intensities of the laser beams exposing the photographic paper is adjusted corresponding to a variation of an actual sensitivity of the photographic paper and deterioration of a developer with respect to nominal values of them. At least the intensities directly emitted from laser light sources, or values of optical modulation data for modulating the laser beams corresponding to the image data are varied. Alternatively, transmittances of optical elements such as polarizing beam splitters provided on optical paths are varied for adjusting the intensities of the laser beams.

Abstract: The present invention relates to an electrophotographic apparatus which has a photosensitive member, first light emitting means and second light emitting means, detecting means, and control means and the control means variably adjusting the light emitting amount of the first light emitting means and the light emitting amount of the second light emitting means so that a ratio between the light emitting amount of the first light emitting means and the light emitting amount of the second light emitting means becomes a predetermined value.

Abstract: A solid scanning optical writing device has multiple optical elements which are aligned in a zigzag fashion to form two lines in a main scanning direction. Each of the optical elements is turned ON/OFF in accordance with image data to write an image. In the solid scanning optical writing device, the amount of light output from each of optical elements is corrected based on correction data. The correction data is obtained by detecting light amount distribution of each of the two lines and obtaining ridge light amount and trough light amount from the detected light amount distributions.

Abstract: An image recording apparatus includes a PLZT head. The PLZT head performs an interval exposure based on an interval exposure data between exposures of photosensitive material. Further, exposure data of a predetermined number of lines already used in an N-th and preceding exposures may be maintained in a RAM as a basis of correction to an exposure data for an N+1-th print. The PLZT head performs an exposure for an exposure time given by the corrected exposure data.

Abstract: An image forming apparatus for forming an image by modulating laser light in correspondence with an image signal. A pulsewidth modulation signal is generated in correspondence with input image data. A laser drive control circuit has a photosensor PD which detects laser light emitted from a laser diode LD and generates a detection current, a resistor which generates a detection voltage corresponding to the detection current outputted from the photosensor PD, a buffer in which the generated detection voltage is inputted, an amplifier which amplifies an output from the buffer, and a constant current source and a switch to add a predetermined current to the detection current for compensation for reduction of output voltage due to offset voltages of the buffer and the amplifier. Control data for controlling maximum and minimum pulsewidths in the pulsewidth modulation signal are obtained based on the detection voltage, and generation of the pulsewidth modulation signal is controlled.

Abstract: The present invention relates to an electrophotographic apparatus which has a photosensitive member, first light emitting means and second light emitting means, detecting means, and control means and the control means variably adjusting the light emitting amount of the first light emitting means and the light emitting amount of the second light emitting means so that a ratio between the light emitting amount of the first light emitting means and the light emitting amount of the second light emitting means becomes a predetermined value.

Abstract: In a laser beam scanner of used for exposing a latent image on a photographic paper, intensities of the laser beams are maintained in predetermined range by compensating amplitude of driving signals supplied to acousto-optic modulators when intensities of the laser beams emitted from laser light sources are varied. The intensities of the laser beams passing through the modulators are sensed by photo sensors and compared with predetermined standard value. When any of the intensity of the laser beam is discrepant from the standard value, a difference between them is calculated and an optical modulation data for controlling the amplitude of the driving signal is compensated by subtracting the difference value from the standard value. Thereby, the amplitude of the driving signal of the modulator is compensated.

Abstract: A light beam scanner unit includes a light beam generating unit for generating light beams at a fixed power, a polygon mirror for reflecting light beams generated from the light beam generating means toward a surface to be scanned, thereby scanning it, and a light beam power sensing unit for sensing light beam power for scanning a surface to be scanned with the polygon mirror. This light beam scanner unit further has a mirror contamination sensing unit for sensing contamination of the polygon mirror by comparing a sensing result obtained from the light beam power sensing unit when light beams are emitted by the light beam generating unit with a preset reference value.