Abstract: System and method are devised to produce an optical recording medium suitable for identification and management. A recording layer formed in the optical recording medium is irradiated with writing light by a pickup. A visible image pattern suitable for identification, management or the like is formed on the optical recording medium by generating changes in optical characteristics of a portion irradiated with light and a portion not irradiated with light in the recording layer.

Abstract: A light-scanning optical system comprises a light source, a first optical system, a light deflector having a deflection surface, a second optical system, a photodetector and a luminous flux delimiting member. A luminous flux emitted from the light source is trimmed and imaged as a linear luminous flux extending in the main scanning direction by the first optical system. The deflection surface of the deflector is arranged near the imaging position of the first optical system so that it reflects and deflects the linear luminous flux for scanning operation. The deflected luminous flux is then imaged on the plane to be scanned by the second optical system that establishes a substantially conjugate relationship between the deflection surface and the plane to be scanned.

Abstract: Magnification data for designating a recording magnification of an overall image along a horizontal scanning direction, magnification balance data for designating the balance in the recording magnification of left and right partial image regions, and write position data for designating the timing of starting the recording of an image are inputted on the basis of results of measurement of the positions of registration marks formed at the center and both ends of an image recording range. A phase selection circuit and a LSYNC generating circuit adjust the timing of starting the recording of an image on the basis of the write position data.

Abstract: An image forming apparatus includes a light beam generating and modulating device which generates and modulates a light beam in accordance with an image signal, a light beam deflecting device which deflects the modulated light beam and scans an image carrier so as to form an image.

Abstract: An optical scanning apparatus has an incident optical system for causing a light beam from a light source to be obliquely incident in a sub-scanning cross-section on a deflecting surface of an optical deflector, and an imaging optical system for forming, on a scanned surface, an image of the light beam deflected by the deflecting surface.

Abstract: A raster output scanner in which both the start-of-scan and the beam intensity of a laser beam are determined using a single photodetector. The raster output scanner has a laser source for generating a laser beam; a rotating polygon for sweeping the laser beam along a scan line plane, an optical fiber with a light receiving end positioned at a known position in the scan line plane and which intercepts at least a portion of the sweeping laser beam, and a photodetector for converting the intercepted laser beam into a beam current. The raster output scanner further includes both a scan detection circuit for producing a star-of-scan signal from the beam current and a beam intensity circuit for producing an electrical output which depends upon the magnitude of the beam current.

Abstract: When the image-forming modes are switched over, the difference between the scan speeds of image-forming modes before and after the mode switching is checked. If the difference is not less than a predetermined set value, the adjustment of a laser beam is executed first, and then image formation is started. If the difference between the scan speeds of image-forming modes before and after the mode switching is less than the predetermined set value, the image formation is started immediately without making adjustment of the laser beam.

Abstract: A dot pattern is generated by using scalable font data on the basis of received print data, and then printed. One scalable font set corresponds to two kinds of dot pattern generating modes. One generates a dot pattern with quality being given precedence, and the other generates a dot pattern with speed being given precedence and for printing at high speed, though quality inferior. The two modes are switchable to perform printing to fit user's needs.

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: A method and apparatus for forming an image reduce the processing load on a video controller. A CPU causes a counter to start counting the optical beam detection signals of a photodiode in accordance with a signal which indicates the leading edge of a sheet of recording paper received from a TOP sensor. Comparators compare the count value issued from the counter with the values set by the CPU at registers. Based on the comparison result, an F/F sets Q output. Thus, a BD signal is issued through a gate during a period specified by the values set at the registers. The use of the BD signal reduces the processing load on the video controller which generates and transfers an image signal.

Abstract: A method of aligning print images of an electrophotographic machine on a print medium includes providing a plurality of rotating photoconductive drums in the electrophotographic machine. Each of a plurality of laser beams is reflected off of a respective one of a plurality of reflectors. Each reflector rotates relative to the respective laser beam to thereby scan the laser beam across a respective one of the photoconductive drums to produce a scan line in a scan direction. The relative rotation between the laser beams and the respective reflectors is cyclically repeated to thereby produce a plurality of substantially parallel scan lines on each photoconductive drum. Each scan line is displaced from an adjacent scan line by a scan line separation distance in a process direction perpendicular to the scan direction. Toner is applied to each scan line on the photoconductive drums. A moving toner transfer medium contacts each photoconductive drum at a respective toner transfer nip.

Abstract: In a digital copying machine using a multi-beam optical system, a light beam position detector situated on a line extended from the surface of a photosensitive drum detects the passing position of each light beam scanned by a polygon mirror rotated by a polygon motor. A CPU calculates control amounts for galvanomirrors by using a beam position detector output processor, on the basis of the detection result of the beam position detector. Based on the calculated control amounts, galvanomirror drive circuits drive the galvanomirrors, thereby to control the positions of the beams in a sub-scan direction. The passing positions of the beams can be precisely detected with no special precision in assembling the optical system. In addition, the positions of the beams in the sub-scan direction can be controlled at predetermined positions, even if some change occurs in the structure of the optical system due to a variation in ambience or a variation with the passing of time.

Abstract: An embodiment of an edge placement device is supplied with transition data to generate transitions during a pixel time period corresponding to the transition data. The transition data is supplied by pulse code logic that converts pixel data to the transition data. The embodiment of an edge placement device includes first edge placement logic coupled to taps from a first clock delay chain and second edge placement logic coupled to taps of a second clock phase delay chain. Also included is a phase splitter that generate a first and a second clock phase coupled, respectively, to the first and the second clock delay chain from a clock corresponding to a pixel time period. The first and the second clock phase have rising edges on alternate cycles of the clock. The first and the second edge placement logic each include a plurality of D flip flops.

Abstract: An image forming apparatus and method wherein a writing device writes information of an image on a photoconductive body traveling in the sub-scanning direction to form an electrostatic latent image of the image thereupon by driving a light source to emit luminous flux, in response to an image signal corresponding to the image information, using a write clock and scanning the luminous flux from the light source with a scanning device in the main scanning direction on the photoconductive drum. The electrostatic latent image on the photoconductive body is developed by a developing device to a toner image, a transfer sheet having a size in the main scanning direction is selected by a selecting device, and the toner image on the photoconductive body is transferred by a transfer device to the selected transfer paper.

Abstract: A method and system are disclosed for improving performance of adjustable printer clock signals in an electrophotographic device. A source clock signal is output having a source frequency. A first clock signal is output having a first frequency. The first frequency is substantially related to the source frequency by a ratio of n1:m1. An alignment signal is generated for adjusting a first printer clock signal with respect to a second printer clock signal. In response to the first clock signal and the alignment signal, the first printer clock signal is output having a first printer frequency. The first printer frequency is substantially related to the source clock frequency by a ratio of n1n2:m1m2.

Abstract: A photodiode is positioned outside an image recording region and receives light from a light source portion prior to image recording processing. When the photodiode detects light at the time of the first main scan, the pulse number of a stepping motor is reset, 0, and thereafter, the pulse number is used to control the driving of the stepping motor. For this reason, an output timing of an image signal in the second and subsequent main scan operations does not depend on the detection of light by the photodiode and allows output of an image signal at a predetermined pulse number. The scan operation based on the control of the pulse number is effected for each image, and at the scan start time of a subsequent image, the pulse number is reset again when light is detected by the photodiode. Accordingly, it is possible to eliminate inconsistency of the start time of each main scan, which is caused by a variation in the time of detection by a sensor for controlling a scan start timing.

Abstract: The present invention has been made for the purpose of obtaining an optical apparatus which avoids the necessity for changing a control unit for appropriate control of a light source or making a modification to the control unit even when the type and specifications of the optical apparatus are changed, whereby costs for designing the control unit may be reduced. In the case where a comparative table stores therein LEND signal times and data starting times respectively corresponding SYNC signal periods of three apparatuses of different types, a CPU searches for a SYNC signal period coincident with the measured SYNC signal period from among the SYNC signal periods which are stored in the comparative table, and executes control of signals for an optical unit by using the obtained LEND signal time and data starting time corresponding to the searched SYNC signal period.

Abstract: A method and apparatus for determining a line start writing position of a scanning light beam in a scanning light beam writing system. A first detector and a second detector are positioned in the scan path of the scanning light beam for detection of the scanning light beam. The information obtained from the detector is used to determine the line start for commencing writing on a media and for monitoring and controlling the power level of the scanning light beam.

Abstract: Four beams are caused to scan a scanning surface in the main scanning direction in parallel. The beams expose the target area between two optical sensors, not the surface of a photosensitive drum, to produce correction data to correct shifts in the exposure positions of the four beams in the main scanning direction with an accuracy of less than a small fraction of one pixel. On the basis of the correction data, an actual image formation area is set on the photosensitive drum. This makes it possible to always control the relative exposure scanning position accurately even when the relationship between the main scanning positions of the light beams is unknown.

Abstract: A method for digitally controlling power from dual laser diodes in a system that forms a plurality of scan lines in a transverse direction across the width of a photosensitive member by reflecting modulated beams from a plurality of facets of a rotating polygon by detecting the beginning of a scan line and providing a start of scan (SOS) signal representing the detection. Power is digitally controlled from the laser diodes by controlling the power from each of the laser diodes for video ON exposure control and controlling the power from each of the laser diodes for video OFF bias control in order for the bias control to enable constant exposure power during SOS detection.

Abstract: A multiple light beam scanning optical system includes a plurality of light sources, driving circuits, collimator lenses, cylindrical lenses for focusing light beams emitted from the collimator lens in sub-scanning directions, a beam splitter, and a deflector. The deflector has a deflection surface disposed near a point at which a light beam emitted from the beam splitter is focused by the cylindrical lens. A scanning lens, a synchronizing detector, and a sensor unit enable detection of position information of sub-scanning directions of the plurality of light beams. A control circuit drives and controls a cylindrical lens by processing an output signal from the sensor unit, and a light path correction mechanism moves a cylindrical lens on the basis of a control signal from the control circuit.

Abstract: An imaging system having a raster output scanner that produces high quality scan lines comprised of evenly spaced pixels. The raster output laser device is modulated in accordance with a variable frequency pixel clock that is derived from a high frequency oscillator using a dual modulus programmable divider that is controlled by a state machine. In turn, that state machine is controlled by information stored in a memory. The variable frequency pixel clock compensates for scan line nonlinearity, polygon facet errors, and/or scan line magnification.

Abstract: In an image forming apparatus for forming an image by scanning a rotating photosensitive member with modulated light based on an image signal, a PLL circuit generates a high-frequency clock having a frequency n (n is an integer that satisfies n>2) times that of an oscillation output from a reference oscillating circuit. A frequency dividing circuit generates an image processing clock synchronized with the high-frequency clock and a detection signal from a scan light detecting mechanism. A latch circuit, a parallel/serial conversion circuit, and the like generate an image modulating signal by modulating image data on the basis of the high-frequency clock.

Abstract: A reference frequency and facet to facet correction circuit utilizes a phase locked loop which includes a digital phase detector to measure the time difference between the end of scan and the end of count of each facet and store them in a lookup table. The phase locked loop continuously generates an average time value form the time differences of all the facets of the polygon. The phase locked loop also adds the errors of each facet to the average time value and uses the result to correct the frequency of a pixel clock generator for both the reference frequency and facet to facet errors.

Abstract: An image recording system for deriving a recorded image from an image signal by producing a positional-deviation amount indicative signal representative of a positional deviation in a sub-scanning direction of a scanning line forming a recorded image. The system corrects the positional deviation of the scanning line on the basis of the positional-deviation amount indicative signal. The system also corrects a density deviation of a recorded image due to the correction of the positional deviation on the basis of a pixel pattern of the image signal. A method is also provided for detecting a relative positional deviation between images of different colors in a color image recording system.

Abstract: Disclosed is a thin-film transistor which can be operated even if a high voltage is applied thereto. The thin-film transistor consists of a first and a second thin-film transistor. Each thin-film transistor has an offset region between an active region and a drain region whose conductivity is controlled by a sub-gate electrode. Each thin-film transistor has a sub-gate insulator between a sub-gate electrode and the offset region which is thicker than a main-gate insulator between the main-gate electrode and the active region. The thickness of the main-gate insulator of the second thin-film transistor is thicker than the thickness of the main-gate insulator of the first thin-film transistor.

Abstract: A recording apparatus records data on a sensitive material with a laser beam. The recording apparatus includes a data storage unit for storing data, a laser illumination unit for generating the laser beam, and a laser beam scanning unit for scanning the laser beam, which is generated by the laser illumination unit, at a predetermined position. The recording apparatus further includes a transporting unit for transporting the sensitive material to the predetermined position, a laser control unit for controlling the laser illumination unit to generate the laser beam on the basis of the data stored in the data storage unit, and an intensity change-over unit for changing over the intensity of the laser beam illuminating the sensitive material at the predetermined position, in dependence on the type of the sensitive material.

Abstract: In a laser drawing apparatus, a pattern is drawn on a workpiece by scanning the workpiece with at least one laser beam. The laser beam is modulated on the basis of raster-graphic data, in accordance with a series of clock pulses. A calculator calulates clock-pulse-phase-shift location data, indicative of where a phase of the clock pulses should be shifted, with a unit of less than 2.PI.. The calculation is made on the basis of pixel-dot-pitch discrepancy data measured along a scanning line defined by the scanning laser beam. A clock-pulse-outputting controller controls outputting the clock pulses so that the phase of the clock pulses is shifted, with the unit of less than 2.PI.. The shift occurs whenever the laser beam reaches each of the clock-pulse-phase-shift locations, represented by the clock-pulse-phase shift location data, during scanning of the workpiece with the laser beam. Consequently, a pixel-dot-pitch discrepance in the scanning line can be corrected with a unit of less than a one-pixel-dot size.

Abstract: The present invention eliminates artifacts in an image formed using a plurality of imaging sources. Visible seams in the image are eliminated by randomizing the stitch point between the scan lines produced by each imaging source. The randomization may be optimized by additionally applying a method for relocating the random stitch point based on the data content of the scan line, adjacent scan lines, and other criteria. The present invention further compensates for in-scan and cross-scan errors caused by thermally induced errors, spinner synchronization errors, mechanical misalignment, and other factors associated with the use of a plurality of imaging systems. A photodetector system, comprising a mask having a pair of triangular openings, provides measurements of the in-scan and cross-scan errors.

Abstract: A recorded image is distorted on a printing plate when an image information for a computer is recorded in the form of a band with a band width of a plurality of image elements on a printing plate wound around a drum. This invention provides an undistorted recording on the printing plate, made possible by an arrangement that has a printing plate wound around a drum in the form of a right circular cylinder, an exposure unit that uses a light beam to record image information in the form of a band on the printing plate, a moving mechanism to move the exposure unit by one band width in the direction of the drum axis in relation to the drum while the drum makes a revolution, an image treating apparatus with the image information stored in the form of a right quadrangle, and an image modulator to rearrange and slant each band of image information readout from said image treatment apparatus by one band width in the opposite direction to the movement of said moving mechanism.

Abstract: A color image forming apparatus includes an image forming unit which forms a multicolor image on a second image support by sequentially transferring toner images related to a plurality of colors from a first image support to the second image support in an overlaying manner. A reference position detecting unit detects a reference mark signal every time a reference mark at a reference position on the second image support is sensed during rotation of the second image support. A laser scan start timing control unit controls a laser scan start timing for the image forming unit to start scanning the first image support by a laser beam, based on the reference mark signal. A phase error measurement unit measures a phase error between a line sync signal and the reference mark signal by counting system clocks before the laser scan start timing.

Abstract: A laser beam printer which detects the position of a laser beam in order to scan a photosensitive member. The laser beam is detected at a predetermined position, wherein the laser beam is detected at a time during which a rotating polygon mirror is rotating at a speed less than a predetermined speed. Laser beam detection signals are then output. A timing of the output of the detection signals is predicted, wherein the detection signals are not output at a constant interval because the rotating polygon mirror is rotating at a speed less than the predetermined speed. A signal to turn on the laser beam is generated based on the predicted timing. In another aspect, a line for the detection signals is completed or broken at a timing based on an output interval of the detection signals.

Abstract: A semiconductor laser array emits a plurality of laser beams. A polygon mirror deflects the plurality of laser beams together. A prism type reflector separates the deflected laser beams to different directions that are generally along an arrangement direction of a plurality of photoreceptors. The separated laser beams are input to the respective photoreceptors through mirrors and cylindrical lenses.

Abstract: A printer for use in exposing a photosensitive material and method of operation thereof. The printer includes a rotatable polygon mirror having a plurality of adjacent facets. The mirror includes a reference facet and signal generator for generating a polygon index signal which defines a reference position. A light source for directing a light beam is provided for reflection of the beam off each of the adjacent facets for exposing the photosensitive material and defining a writing path. A sensor is also provided for generating a line start signal for each of the facets in response to the light beam passing over the sensor. The printer is provided with a switch for placing printer in a first set-up mode or writing mode. When in set-up mode a counter measures a first time period T.sub.S from the polygon index signal to a first line start signal generated by the reference facet. A counter also measuring a second time period T.sub.

Abstract: A spindle unit control method controls a plurality of spindle units which rotate in synchronism with each other, and comprises with respect to each of the spindle units a first step of obtaining a phase error by comparing phases of a detection signal indicating a rotary reference position of the spindle unit and a first clock signal, a second step of generating a second clock signal having a phase which is adjusted by delaying or advancing the phase of the first clock signal by the phase error, and a third step of controlling the rotation of the spindle unit by a phase locked loop based on the detection signal and the second clock signal. The first clock signal is used in common with respect to each of the spindle units, and the second clock signal is independent for each of the spindle units.

Abstract: It is an object to stably form a color image of a high quality without a color deviation by completing a phase adjustment in a short time so that a reference signal of a main scanning control system and a reference signal of a sub scanning control system have a predetermined phase. To accomplish the object, an output timing of an ITOP signal which is generated by a sensor 9 which detects a predetermined position of a photosensitive drum 5 which is rotated is compared with an output timing of a virtual main scanning sync signal BD' of a polygon mirror 3 for scanning a light beam onto the photosensitive drum 5 in the main scanning direction, thereby deciding an output timing of a reference clock SP. On the basis of the decided output timing, a PLL circuit 116 controls a rotational speed of a polygon motor 117 so that a difference between the reference clock SP which is outputted by a counter 83 and the ITOP signal have a predetermined phase difference.

Abstract: Disclosed is a photographic printer with bi-directional sweeping of a monochrome CRT to expose a photosensitive medium. Image data from a host system is received by the printer and stored in a data drive system. The data drive system converts the data into a series of rows of dot row data to produce the appropriate image desired. Linear deflection amplifiers sweep the CRT's electron beam across the face of the CRT to expose the medium utilizing the dot row data. The present invention sweeps and writes data bi-directionally, eliminating the retrace period associated with sweeping and writing in one direction, and without any hold periods once printing starts. The data in every other dot row is processed in reverse order so that the dot row data utilized in the reverse writing sweep will be exposed onto the medium in proper relationship to the rows written above and below it.

Abstract: Disclosed is a photographic printer with bi-directional sweeping of a color CRT to expose a photosensitive medium. Image data from a host system is received by the printer and stored in a data drive system. The data drive system converts the data into a series of rows of dot row data to produce the appropriate image desired. Linear deflection amplifiers sweep the CRT's electron beam across the color phosphor areas on the face of the CRT to expose the medium utilizing the dot row data. The present invention sweeps and writes data bi-directionally, eliminating the retrace period associated with sweeping and writing in one direction, and without any hold periods once printing starts. The data in every other dot row is processed in reverse order so that the dot row data utilized in the reverse writing sweep will be exposed onto the medium in proper relationship to the rows written before and after it.

Abstract: Thermochromic materials are incorporated into constructions that facilitate accurate reproductions of monochrome or full-color images having multiple gray levels. The invention utilizes thermochromic materials having different transition temperatures to facilitate their selective activation. The materials may be located in a single layer of a recording sheet, or in multiple layers. The invention also comprises thermal printing apparatus useful in imaging the foregoing constructions, particularly those exhibiting hysteresis.

Abstract: A fast scan error measuring system of a raster output scanner (ROS) is provided in order to determine whether the laser beam position in the fast scan direction is within acceptable operational parameters. A detector, for example, a linescan or area array camera, is used to acquire multiple successive images from each facet of the ROS as the unit is operating. For each rotating facet the position of a beam spot (centroid) at the end of scan line is measured. A sufficient number of centroids are collected so that a Fourier transform of the centroids will produce an accurate spatial frequency spectrum measured in cycles per millimeter. This spectrum can be easily compared to the product's fast scan error specification limits.

Abstract: A method of achieving line-to-line synchronization having a high degree of synchronization accuracy. Synchronization is performed by a specific high-speed block of logic which signals the beginning of scans to a PELCLK-based logic at pel boundaries, and provides sub-pel shifting as it passes data between the pel generation logic and a laser control signal. The synchronization error is made as small as propagation delays through a single multiplexer element. Such delays can be controlled to values less than 1/2 ns. The need to stop and restart the clocks is eliminated. All complex pel generation logic is clocked with the relatively low frequency PELCLK without regard to the synchronization task.

Abstract: Distortions, wherein a recording image is inclined relative to a printing plate, are removed when image data from a computer are recorded spirally in recording bands, having a predetermined band width, of a plurality of picture elements on the printing plate which is wound on a drum. Printing plate exposure apparatus comprises the printing plate being wound spirally on the drum such that an extension line of a side edge line of the printing plate is shifted a band width after one drum revolution. The printing plate exposure apparatus further includes: an exposure unit for recording the image data in the recording bands on the printing plate; a moving mechanism for moving the exposure unit by one band width along a drum axial direction relative to the drum during one revolution of the drum; and a timing mechanism for adjusting a band recording start position of the image data for each rotation of the drum so as to set a top edge line of the recording image parallel to a top edge line of the printing plate.

Abstract: An image reading and recording apparatus includes a reading section for optically reading an image for output of image signals, and a recording section for generating and controlling a light beam to record the read image on the basis of the image signals. The apparatus further includes a light sensor for detecting the light beam at a predetermined position and for generating a record timing signal which determines start timing for control of the optical beam, a counter for determining lapse of a predetermined time since the generation of the record timing signal, and a read timing signal generator for generating, upon the lapse of the predetermined time, a read timing signal which determines timing for output of the image signals from the reading section.

Abstract: The current disclosure is directed to a multiple beam control unit for generating independent control signals each of which is used as a beam activation signal as well as a beam detection confirmation signal for a corresponding one of the multiple beams so as to accurately synchronize each of the beams. The multiple beams are thus independently ascertained to form a desired image at a predetermined location on am image forming surface.

Abstract: A laser beam printing machine according to the present invention includes a polygon mirror motor; a first control circuit which generates, in response to an error in rotation of the polygon mirror motor, a control signal which bring about the rotation of the polygon mirror motor to a target rpm and performs a PWM control; an output circuit which receives data for printing and, in response to the received data, outputs data for controlling a laser beam; a voltage controlled oscillator which generates clock pulses for determining the transmission timing of the data from the output circuit; and a second control circuit which controls, in response to the control signal, a control voltage of the voltage controlled oscillator to follow up the rotation fluctuation of the polygon mirror motor.

Abstract: Color banding resulting from facet-to-facet jitter in a color imaging device having a plurality of multifaceted polygons is reduced by matching the facets of the various polygons such that the composite image produced by the matched facets result in minimal color banding. The latent images are registered by starting each latent image with a selected "starting" facet such that the matched facets trace corresponding scan lines. Imaging offsets that would result from either advancing or retarding the exposure of a latent image such that the latent images begin with the correct facet are compensated for by moving a rotating cylinder mirror in each polygon such that the latent images are registered. Moving of the cylinder mirror is beneficially achieved using a controlled piezoelectric element.

Abstract: An optical scanning device is comprised of a light source unit, a rotating polygon mirror, an f.theta. lens, a photosensitive drum, a synchronization signal generating circuit 10, etc. Synchronization signal generating circuit 10 has a photodiode 6, and a resonance circuit 31, comprised of a parallel circuit of coil 32, capacitor 33, and resistor 34, is connected to photodiode 6 as its load circuit. An amplifier 35 is connected to the junction of photodiode 6 and resonance circuit 31, a capacitor 36 is connected to the output side of amplifier 35, and the other end of capacitor 36 is connected to the positive input terminal of comparator 38. A reference voltage generator 39 of variable reference voltage is connected to the negative input terminal of comparator 38 and a reference voltage is applied from this reference voltage generator 39.

Abstract: An optical scanning apparatus includes light beam emitter that emits a plurality of light beams, such as laser beams having different wavelengths, respectively; light beam deflector that deflects the plurality of light beams emitted by the light beam emitter that scans an object; guider that guides the plurality of deflected light beams so that the deflected light beams fall at about the same position on the object; light receiver that receives the reflected light beams reflected from the object of reading; and image information generator that generates image information representing the object based on the reflected light beams.

Abstract: An optical multiple-scanning device has a number of scanning laser light beams that scan along a scan path, are separated along the scan path by a predetermined pitch P, and produce an illumination spot of diameter D along the scan path. A synchronizing signal generating circuit for the optical multiple-scanning device includes a single photodiode and a signal processing circuit. The single photodiode has a width W along the scan path and generates a signal with maximums IMAX and minimums IMIN. If the condition W.ltoreq.P-D/4 is met, or if IMIN is less than or equal to 80% of IMAX, the signal processing circuit accurately generates a square-wave synchronizing signal such that successive rectangular pulses of the synchronizing signal cyclically indicate that successive scanning laser beams have reached a predetermined position along the scan path.

Abstract: In a laser printer wherein a photoconductive drum is scanned by utilizing a plurality of laser beams, there are detected spacings between the plural laser beams, such detection being confined to a blanking time. On the basis of the detected results, the spacings between the plural laser beams are controlled; and this state is maintained for a printing time. With this arrangement, it is possible to accurately detect the spacings between the plural laser beams thereby to obtain the practicable laser printer employing the plural laser beams.