Abstract: Printers that correct for polygon phasing errors. Such printers include a raster output scanner, a moving photoreceptor, a page sensor for sensing the position of an image area, a start-of-scan sensor for sensing the start of scan, a light valve array having a plurality of electrically controlled light valves for selectively passing light, and a system controller that controls the light valve(s). The system controller initially selects one of the light valves. When the page sensor senses the beginning of a page the system controller starts selecting sequential light valves at a controlled rate. After a start-of-scan occurs the system controller stops sequencing the light valves. The light valve that passed light when the start-of-scan occurred continues to pass light. Beneficially, the system controller monitors the photoreceptor motion. If the photoreceptor motion changes the system controller then selects a light valve that moves the scan line toward the proper position.

Abstract: A single laser crystal is driven with multiple pumping sources to obtain discrete, collimated outputs without substantial thermal crosstalk, so that the action of one pumping source does not adversely interfere with the action of another source driving the same crystal; that is, an imaging output emanating from one crystal region will neither defeat nor spuriously cause an imaging output in another region.

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: Image distortion is corrected in a color printer wherein print units for a plurality of colors are aligned to form a color image by superposing images formed by the print units. Images of the colors of a predetermined pattern formed by the print units are detected by a sensor. Based on the detection result, image distortion quantities and a setting error of the position of the sensor are detected. Then, the detected color shift on image forming is corrected according to the image distortion quantities and the setting error.

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: An optical scanning system for a printer, for example, includes: an optical scanning unit for scanning light onto an image print region of a photosensitive belt; a photodetector disposed at an edge of the photosensitive belt for receiving the light emitted from the optical scanning unit, and for outputting a pulse signal in response to the received light; a belt position calculator for counting a hold time of the pulse signal output from the photodetector in order to calculate an edge point of the photosensitive belt; a memory for storing information about the delay time from an end point of the pulse signal to a point in time at which the optical scanning unit starts scanning light onto a start point of the image print region of the photosensitive belt; a delay time setting unit for accessing the memory in order to locate delay time information, corresponding to the edge point of the photosensitive belt, output from the belt position calculator; a scanning start signal generator for counting a time duration

Abstract: The invention provides an optical head which provides between a photosensitive member and a position detector a sufficient distance over which the photosensitive member and the position detector are not brought into contact with each other readily by thermal expansion of the apparatus or a like cause.

Abstract: The objective of this invention is to provide an apparatus which can form a high-quality image by reliably adjusting the superposing positions of frame images when a single image is formed by superposing a plurality of frame images, and especially, the objective of this invention is to reliably adjust the superposing positions of frame images and form a high-quality image by controlling a rotary polygon and image carrier to operate in association with each other. To achieve such objectives, the apparatus of this invention generates a first signal indicating that the light beam coming from the rotary polygon has scanned a predetermined position, also generates a second signal independently of that detection, and moves the image carrier by selectively using the first and second signals as needed. In this apparatus, by rotating a driving means N times on the basis of a reference signal obtained by frequency-dividing the first signal, the image carrier completes one rotation.

Abstract: The method for positioning an array with periodic structures, for forming an image thereon, comprises the following steps: (a) providing a first beam of light by a first light source; (b) passing this first beam of light through the array; (c) forming a light line corresponding to the first light source with the first beam of light after the first beam of light passes through the array such that the light line is perpendicular to long axes of the periodic structures; (d) rotating the array to rotate the light line across a first detector; (e) producing a signal when the light line sweeps across the first detector; (f) determining when maximum signal is produced by the first detector; and (g) rotating the array to a proper position based on angular position corresponding to this maximum signal.

Abstract: An image forming apparatus includes an image carrier, a laser diode for generating a plurality of light beams, and a rotating polygonal mirror for simultaneously scanning the image carrier in a primary scanning direction along respective lines which are parallel to each other in a secondary scanning direction. The image carrier is scanned once for each of a plurality of different colors to thereby form a color image on the image carrier. A photosensitive sensor is provided for detecting an amount of deviation of the plurality of light beams in the primary scanning direction with respect to a first color of the plurality of different colors, and deviations among the plurality of light beams in connection with scanning for each of the plurality of different colors are corrected according to the detected amount of deviation with respect to the first color of the plurality of different colors.

Abstract: In a method of driving a plurality of optical output media aligned in one direction in an optical writing apparatus that drives activation and deactivation of the optical output media based on image data to thereby perform optical writing onto an object onto which writing is to be performed, it is determined whether the number of optical output media that are writing-driven based on the image data in order to perform optical writing onto the object is smaller than the total number of optical output media, and when the number of writing-driven optical output media is smaller than the total number of optical output media, non-writing driving of optical output media other than the writing-driven optical output media is performed. The non-writing driving is a driving in which optical writing is not performed onto the object.

Abstract: A light beam is made to scan and expose a photosensitive drum in the main scanning direction and the passing position of the light beam in the sub-scanning direction is sensed. On the basis of the result of the sensing, the light beam is shifted in the sub-scanning direction when the beam is made to scan by a scanner so that the passing position may come in a target range, which brings the passing position to the proper position. After the position control, the passing position of the light beam is confirmed and controlled so that the passing position may fall on the proper position a specific number of times consecutively. When the light beam is shifted in the sub-scanning direction, the passing position of the light beam is brought into a final target range in such a manner that the target range is forced to converge stepwise in a first range and then in a second range narrower than the first range.

Abstract: A method for positioning an array with periodic structures, for forming an image thereon, comprises the following steps: (i) producing a light beam along fast-scan axis; (ii) translating the array in a direction substantially perpendicular to the fast-scan axis; (iii) detecting the light beam alternatively by a pair of detectors, the detectors being located near opposite edges of the array along the fast-scan axis; (iv) providing substantially periodic signals by the pair of detectors in accordance with their detection of the light beam; (v) determining relative phases of the periodic signals, the relative phases corresponding to misalignment of the array; (vi) sensing phases of the periodic signals and rotating the array such that the long axes of the periodic structures are substantially parallel to the fast-scan axis.

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: An image forming apparatus and method that provides a laser beam oscillator that provides a laser beam corresponding to an original image, reflects/scans the laser beam, transmits a first part of said laser beam to a photoconductive element to write thereupon an image indicative of the original image, accepts a second part of the laser beam as to control and synchronize a write timing sequence of the laser beam on the image carrying element.

Abstract: An apparatus and method for correcting top edge sheet misregistration using a sensor array. An array sensor is placed in the paper path prior to transfer. A signal is generated indicating the position of the sheet. As a function of the signal the print controller causes the image to be exposed and developed on the photoreceptor in alignment with the sheet position. The aligned image is then transferred to the sheet.

Abstract: An apparatus for forming an image comprises a plurality of light emitting elements each emitting light having substanitially the same peak wavelength as those of others; a conveyor to convey a recording medium to receive light emitted from the plurality of light emitting elements relative to the plurality of light emitting elements; and a controller to control the plurality of light emitting elements such that a single pixel on the recording medium is formed by light emitted from at least two pieces of light emitting elements.

Abstract: An optical scanning system includes a light source for emitting light beams, a beam deflection unit for deflecting the light beams to sequentially land the light beams along a predetermined scan line, and a light source driving unit. The light source driving unit drives the light source so as to land the light beams on pixel points set at equal intervals along the scan line according to image information by controlling the emission intervals between the light beams and the exposure periods of the respective light beams. The light source driving unit also adjusts the size of spots formed on the pixel points by the light beams according to gray scale values included in the image information. Therefore, in the optical scanning system, gray scale information is expressed by forming the light beam spots of an adjusted size on the pixel points set at equal intervals along the scan line.

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: A color image forming apparatus and method avoid a problem of color image shifting due to respective line start times that are largely shifted in a sub-scanning direction. The method and apparatus include compensation mechanisms configured to adjust the start position of writing images of respective color components in the sub-scanning direction and thereby compensating the color shift, by changing over the light beam by first writing the images of the respective colors on the photosensitive body among the plural light beams in accordance with a phase relationship between the phase of the intermediate transfer standard signal and that of the line synchronization signal.

Abstract: An apparatus and method for controlling an image recording device. The apparatus includes an acousto-optic deflector that deflects a beam of light so as to write a sub-scan comprising a predetermined number of picture elements. The image recording device is arranged to write a plurality of sub-scans side by side in a substantially contiguous manner. The apparatus also includes a component that commences sub-scans, a start of sub-scan detector that detects when the light beam is directed towards a start of sub-scan position, and an end of sub-scan detector that detects when the beam of light is directed towards an end of sub-scan position. A timing logic controller generates a start reference signal representing a desired position for the start of a sub-scan. A controller compares an output of the start of sub-scan detector with respect to the start reference signal.

Abstract: A light source is used in which at least one row of light emitting elements, formed from a plurality of light emitting elements arranged along a predetermined direction, is provided. A plurality of scanning lines is recorded synchronously at one main scan operation and at least one scanning line is formed overlapping with each other in each main scan operation. In order that at least one scanning line is recorded in an overlapping region with the scanning lines overlapping each other by a combination of dots recorded by a preceding main scan operation and dots recorded by a succeeding main scan operation, emission of light from the light emitting elements is controlled based on image data. As a result, even if an error in an amount of movement in a sub-scan direction occurs, linear uneven density does not occur, and therefore, an image of high quality can be obtained.

Abstract: An image forming apparatus for forming an image on a recording material. The position of the recording material is detected when the recording material is underway from a registration roller for correcting a skew of the recording material to an image forming position for the recording material, and the image is written based on the detected position signal. The image is thus formed at a proper position on the recording material.

Abstract: An electrophotographic imaging system including a combination erase and belt position detection system which may be employed for belt registration or image registration. In one embodiment, the system includes an erase bar having a pattern of light extending longitudinally across a photoconductor belt being moved in a first direction forming a transport path, wherein the erase bar is substantially perpendicular to the first direction. A photodetector is disposed adjacent the photoconductor belt, wherein the photodetector is responsive to light from the erase bar and provides a belt position signal representative of the position of the photoconductor belt relative to the continuous transport path, in a direction substantially perpendicular to the first direction. The belt position signal may be employed for belt steering or modulation of a laser beam representative of latent images to be scanned on the photoconductor belt.

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: Printing apparatus for radiation thermal transfer of colorant from a donor to a receiver, including a flash tube for emitting high intensity radiation; a polarizer for receiving high intensity radiation from the flash tube and polarizing such radiation; and liquid crystal cells disposed to receive polarized radiation from the polarizer. Electrodes modulate the liquid crystal cells so that they change the polarization of the radiation passing through them. A second polarizer receives radiation from the liquid crystal cells and is arranged to pass different intensities of radiation depending on their polarization. The colorant donor and the receiver are positioned in colorant transfer relationship with the second polarizer at a colorant transfer position so that radiation which passes through the second polarizer illuminates the colorant donor so that colorant is transferred to the receiver.

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 system for controlling color plane image alignment in a multi-color, single pass laser printer achieves such alignment by imprinting of alignment marks directly on a belt which carries and/or drives media sheets past plural developer modules in a process direction. A pair of sensors are positioned adjacent the belt to enable a sensing of the alignment marks. A controller causes each of a plurality of developers to print a set of alignment marks on the belt, each set including plural marks that are positioned transverse to a print process direction. The controller, in response to the sensors' detecting the printed marks on the belt, determines times at which the marks pass beneath the sensors and, from such determined times, derives variations from expected sense times of the marks of each set. Thereafter, the controller adjusts data feed from color plane sub-images to one or more laser scanners in such a manner as to reduce color plane image misalignments.

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 and system for compensating for scanner facet height error in a laser imaging application including a rotating polygon for directing a laser beam across a dimension of a photographic element. The present invention compensates for facet height error by measuring a scan interval for each facet of the rotating polygon and modifies the pixel clock for a subset of pixels of each scan line as a function of variations in scan intervals for the respective facets of the rotating polygon.Several advantages of the present invention have been illustrated including the low cost of such a compensation system and technique. Furthermore, the present invention is not limited in accuracy by the pixel clock as are conventional techniques. Furthermore, the modified pixels are evenly distributed over the entire length of the facet's corresponding scan line.

Abstract: A tandem type color printer, having optical beam scanning units and corresponding photosensitive drums, which detects a positional shift of a scanning locus occurring on a corresponding one of the plurality of photosensitive drums, and automatically corrects the detected positional shift of the scanning locus. A detecting window, in which a beam transmission time varies with a change in the beam scanning position, is provided at each of the start end side and the terminal end side of each of a plurality of beam scanning loci in a mask plate. The mask plate is arranged between the optical beam scanning units and the photosensitive drums, to provide output of a detection signal corresponding to the incident time of the transmission beam resulting from beam scanning by a light source, and thus determines and corrects the direction and the amount of positional shift of the scanning locus.

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: A method for forming an integral image on an image receiving medium which image is aligned or alignable with an integral lens sheet having a back side and a plurality of separate lens elements on a front side, and apparatus which can perform such a method. The method includes: directly sensing the location of each of a plurality of reference elements on the lens sheet which reference elements are separated in a same direction the lens elements are separated; and writing portions of the lenticular image on the image receiving medium each of which is associated with a corresponding lens element, in accordance with the sensed positions of the reference elements; wherein each of a plurality of image portions is written at a position which is a function of the directly sensed location of at least one selected reference element, the functions for at least some of the plurality of image portions being based on at least one different reference element.

Abstract: An image forming method includes the steps of compressing input image data and coding the input image data in block units, each block unit corresponding to a plurality of pixels. The method also includes storing the image data coded in the coding step in block units in a storing means, forming an image according to image data from the storing step, and correcting positional deviations of the image formed in the image forming step in units smaller than the block units.

Abstract: An ink sheet having an ink layer, containing ink to be molten by heat generated by its absorption of received light, includes a magnetic layer being magnetized to have a preset magnetic pattern. The direction of polarization of the reflecting light varies depending on a state of the magnetization on the magnetic layer when part of the received light is incident on and reflected from the magnetic layer. The ink sheet is combined with a printer in which a recording medium and the ink sheet are coupled together, and ink is transferred to the recording medium when the ink sheet receives light. The printer includes optical heads for projecting a light beam upon the ink sheet while moving in the width direction of the ink sheet, sensors for sensing a state of polarization of the light beam reflected from the ink sheet, and actuators for adjusting an irradiating position of the light beam on the ink sheet on the basis of a state of polarization of the reflecting light that is sensed by the sensor.

Abstract: A color image forming device that can certainly correct uniform velocity error associated with the characteristic of each optical system and can realize high-quality color image printing by performing a fine laser beam irradiating position control, in consideration of an error in surface accuracy of each mirror surface of a rotary polygon mirror. The color image forming device includes a storage unit for holding uniform velocity correction data previously created for each mirror surface of a rotary polygon mirror to correct a distortion in expansion or contraction of the electrostatic latent image in the main scanning direction due to the characteristic of an optical system, and an image clock generating unit for reading uniform velocity correction data on each mirror surface used in the rotary polygon mirror at a scanning time out of the storage unit and then generating image clock pulses for image signal creation with a period corresponding to the uniform velocity correction data.

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: A beam position detector output processor converts an output from a beam position detector into beam position information. A main control unit detects a total offset value of a plurality of operational amplifiers constituting the processor. The detected offset value is used to compensate a determination reference value used to control the sub-scanning position of a beam, or the beam position information obtained from the beam position detector output processor. As a result, the offsets of the operational amplifiers constituting the beam position detector output processor are compensated.

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 image forming apparatus includes an image bearing member; a scanning device for scanning the image bearing member in accordance with image data; driving source for driving the image bearing member; and a gear for transmitting power to the image bearing member from the driving source.The movement pitch of the image bearing member corresponding to a gear pitch of the gear, and a line pitch of a basic matrix for tone gradation printing are sufficiently different to prevent interference fringe of the image.

Abstract: The present invention is a method and apparatus for compensating for position error inherent in a raster output scanning printing system by adjusting the intensity of image exposure to effect a correction in the output image. The invention is particularly well suited to compensate for position errors arising from a plurality of sources by first summing the errors and then applying a single compensating adjustment to the intensity of individual scan rasters based upon the position error thereof.

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: A system that includes multiple, elliptical writing spots produced by a single, integrated laser diode array head. The beams, generated by the array and shaped by beam shaping optics into the elliptical spots, are scanned across a thermal media writing plural lines at the same time. The elliptical writing spots have an energy profile and a concatenated, angular orientation and staggered arrangement that, due to the thermal interaction of the spots on the media, creates substantially Gaussian thermal profiles in the media.

Abstract: A web is punched with registration holes and imaged prior to cutting the web into individual imaged plates particularly for use as printing plates. The web with an imageable surface is serially punched, imaged and sheeted with the punched holes being utilized to assure registration and alignment in the imaging operation and in the subsequent use of the plates on a printing press. The punching and imaging may be performed at separate stations or at a single punching and imaging station. The web is preferably advanced under tension and tension and/or vacuum may be used to hold the web flat on the imaging platen.

Abstract: In a color image forming apparatus, a plurality of color images of component colors are combined to form a full color image. These images of the component colors are overlapped on an intermediate recording medium, and are then transferred to a transfer medium. Control circuitry reduces the amount of time required to form the component color images on the intermediate transfer medium, and to prevent an abnormality such as an out-of-phase or pull-out of a closed loop control circuit for controlling such a formation of the component color images. This may be achieved by abruptly changing a phase of a motor synchronizing signal. Further, for a period of time after the motor synchronizing signal is abruptly changed, a gain of an amplifier in the motor control circuit can be reduced, an abnormality detection in the motor control circuit can be reduced, the motor control circuit can be placed in an open loop state, or an addition or subtraction signal can be input to the closed loop motor control circuit.

Abstract: The invention provides an image forming apparatus which requires only a little standby time at the time of shifting from a standby state to a usual operation state, and accordingly can reduce the required processing time. In a copy machine 2 employed in the invention, a scanner CPU 121 generates a timing signal with a number of clocks substantially equal to the number of clocks of a horizontal synchronization signal, thereby performing shading correction of the output of a CCD line sensor 24 using a shading correction circuit 126. The scanner CPU 121 counts clocks CKS, each of which is obtained by dividing, using the divider 168, the frequency of a reference clock CK by a predetermined value, and outputs a pulse signal as the timing signal substantially in synchronism with the output of a horizontal synchronization signal when the number of counted clocks CKS reaches a predetermined value.

Abstract: An imaging system for forming multiple superimposed image exposure frames on a photoconductive member moving in a process direction including a rotating polygon having a plurality of facets. A raster output scanner forms a plurality of scanlines in a transverse direction across the photoconductive member by reflecting modulated beams from the rotating polygon. A method of providing scanning speed and phase shift control by providing a signal representing image exposure frame registration and a start of scan (SOS) signal representing the beginning of a scanline. The relative phase between the start of scan signal and the signal representing image exposure frame registration is determined and converted into a digital signal along with a speed determination signal by use of a fast clock timer. The digital signals are summed and inverted in polarity in order to change the speed of the rotating polygon to synchronize the signal representing image exposure frame registration with the SOS signal.

Abstract: An optical scanner including a light source which is turned ON and OFF in accordance with drawing data. A hologram deflector, made of a rotatable planar hologram disc, provided with a plurality of hologram facets through which light emitted from the light source passes, is rotated to scan an image surface with light emitted from the light source. An optical detector detects light passing in a scanning direction through at least a first reference point, for the commencement of the scanning, and a second reference point, for the completion of the scanning. A scanning time detector detects a scanning time period in which the light deflected by each hologram facet of the hologram disc, passes the first reference point and reaches the second reference point. Finally, a frequency varying device varies the frequency of the light source for each hologram facet in accordance with a unique scanning time period directed by the scanning time detector for each hologram facet.

Abstract: In the production of a screen printing stencil, a thin-walled hollow cylinder having a light responsive layer on the outside is rotated about its cylinder axis and exposed by means of a laser beam impinging on it. The laser beam is focused in the region of the light responsive layer. The laser beam is moved in the direction of the cylinder axis, and is switched on and off in agreement with a desired stencil pattern. A radial deviation of the actual position of the wall of the hollow cylinder from its ideal position is determined from at least one measuring position fixed relative to the laser beam for a multiplicity of circumferential positions of the hollow cylinder. A first actuating signal is then derived from at least one of the radial positional deviations obtained at the measuring positions.

Abstract: An oscillator generates a rectangular wave, based on which sawtooth waves are produced. When a synchronizing signal which is created when a laser beam from a laser diode is incident on a photosensor, is detected, a voltage of one of the sawtooth waves is sampled to hold it as a sample-hold signal. Comparators compare the sample-hold signal with the sawtooth waves, and a flip flop alternately outputs one of the compared results, to produce a pixel clock which regularly keeps a constant time relation to the synchronizing signal.