Abstract: The digital synthesizer comprises a system control unit, a read control unit, and a write drive control unit, and based on a magnification fine adjustment value set using a magnification fine adjustment panel, in the copy mode, a magnification of an image in the main scanning direction is finely adjusted by controlling a write reference clock frequency for modulating a laser beam for image formation so that a desired pixel density is obtained and also a magnification of the image in the auxiliary scanning direction is finely adjusted by controlling a scan speed when reading an image from a document, while in the printer mode, a magnification of an image in the main scanning direction is finely adjusted by controlling a write reference clock frequency and also a magnification of the image in the auxiliary scanning direction is finely adjusted by controlling a rotational speed of a polygon mirror for scanning a photosensitive mirror with a write beam.

Abstract: Reflected light from a surface not associated with an image is efficiently cut while maintaining rays in a portion associated with formation of an image in a polygon mirror. Among light guided to the polygon mirror by an incidence optical system, a beam indicated by hatching is incident to an f&thgr; lens, is reflected by an unrepresented cylindrical mirror, and forms a spot on the image plane to scan the surface with rotation of the polygon mirror. Since the beam incident to the polygon mirror is greater than the width of polygon facets, there exists a beam reflected by an adjacent facet. In order to intercept this beam, a shield member is placed in a certain determined range between the f&thgr; lens and the facet of the polygon mirror, so as to cut unwanted flare.

Abstract: Scan systems include at least one radiation source for directing at least one beam toward a scan-device system. The scan device system includes at least one scan device that reflects these beams as rotating scan beams which point to the optical aperture of a rotating optical system. The rotating optical system has at least one optical component selected from a group of reflectors and lenses, focuses the scan beams into radiation spots, and projects them onto a scanned surface as moving scan spots. Linear relative movement between the scanned surface and the rotating optical system produces an area scan of inner drum or planar surface.

Abstract: A method of activating an electrophotographic machine includes determining at least one condition of the electrophotographic machine. Power is applied to a polygon mirror. A time period required for the polygon mirror to accelerate from a stationary condition to a target rotational velocity is measured. The measured time period and data associated with the at least one condition are stored in a memory device. The polygon mirror is decelerated back to the stationary condition. Power is reapplied to the polygon mirror at a point in time. The measured time period and the data are used to determine when to begin at least one process in the electrophotographic machine relative to the point in time.

Abstract: An optical deflection device having a rotary body that is fixed on a bearing and is structured rotatably by a magnet arranged to face a coil provided on a base side, wherein the rotary body is made of a magnet and a polygon mirror is fixed on the rotary body.

Abstract: In a deflection scanning apparatus used for a laser beam printer or the like, a rotating body is provided with a deflector which has a plurality of recesses arranged in a concentric manner with the center at the rotation axis of the rotating body. Balance weights are set in the recesses so as to remove rotation unbalance in rotation of the rotating body.

Abstract: When a printer receives print data in the form of PDL, commands are analyzed and intermediate data is stored in a page buffer (102). Rotation of a polygon mirror is started at this time by a scanner pre-rotation command unit (107), after which bitmap data is expanded by a bitmap expanding processing unit (103) and printed. When printing starts, the polygon mirror is already rotating. This makes it possible to shorten first-page discharge time.

Abstract: An optical scanning system of a printer includes an optical scanning unit including a light source, a rotating polygonal mirror having a plurality of mirror surfaces for deflecting light emitted from the light source toward a photoreceptor web, and a driving source for driving the rotating polygonal mirror.

Abstract: An image forming apparatus for forming an image on a photoconductor by scanning light on the photoconductor includes a printer engine having a polygon motor that can be controlled to revolve at an arbitrary rate of revolution, a deflector driven by the polygon motor to be rotated to deflect the light, and a motor controller to control the revolution of the polygon motor. The apparatus further includes a controller to control the apparatus. The apparatus is connected with a host computer, and the polygon motor is controlled to stop revolving when the apparatus is in a waiting status. When the apparatus is set to form the image with a single picture element resolution, the controller outputs to the printer engine a request to revolve the polygon motor immediately after receiving a printing instruction to form the image from the host computer and a printing request to form the image after completing image processing for forming the image.

Abstract: A scanning unit of a laser printer in which a cover is provided on a scanning motor so that the scanning motor is isolated from an outside and an inner portion of the cover is maintained in a vacuum state, and in which the scanning motor is provided with a magnetic bearing having a repulsive force in thrust and radial directions, and a magnetic bearing apparatus used in the scanning unit, whereby the noise is lowered and the structure of the scanning unit can be simplified.

Abstract: A scanning optical device to be used for an image forming apparatus such as a laser beam printer or a digital copying machine comprises a light source, an optical deflector, a first optical system for leading the light beam emitted from the light source to the optical deflector, and a second optical system for focussing the deflected light beam on a surface to be scanned, typically a photosensitive drum surface. The second optical system has a diffraction optical element and forms a light spot on the surface by selectively using the light beam of a predetermined order of diffraction. The sum of the light quantities of the light beams of the orders of diffraction on the positive side, relative to the predetermined order of diffraction, is smaller than that of the light beams of the orders of diffraction on the negative side, for the diffracted light beams located remotest from the optical axis or any of the light beams located within the scope of scanning.

Abstract: A scanning unit of a laser printer in which a cover is provided on a scanning motor so that the scanning motor is isolated from an outside and an inner portion of the cover is maintained in a vacuum state and in which the scanning motor is provided with a magnetic bearing having a repulsive force in thrust and radial directions, and a magnetic bearing apparatus using in the scanning unit, whereby the noise is lowered and the structure of the scanning unit can be simplified.

Abstract: In an optical system, the scanning center axis of a scanning lens, the principal ray of a laser beam applied to the scanning lens, and the rotational axis of a polygon mirror are in one plane. By forming a thin film layer on the deflecting facets, the exposure quantity of a photo conductor, which decreases as the incident angle to the deflecting facet increases, is corrected. The thin film layer has the increasing ratio of the reflectance that increases as the incident angle, which principal ray of the laser beam forms with the normal line to the deflecting facet of the polygon mirror, increases.

Abstract: There is provided a dustproof structure of an optical box in which intrusion of dust into the optical box can be prevented. Laser beams deflected by a polygon mirror of an optical box are transmitted through an optical system and exit from an opening outside the optical box, and reach a photographic printing paper. In this case, when dust and the like adhere to the polygon mirror or the optical box, the function of such an optical element deteriorates. Therefore, a dustproofing effect is required by the optical box. Accordingly, by supplying air into the optical box using a fan to thereby pressurize an interior of the optical box, the intrusion of dust from outside of the optical box into the optical box can be prevented, thereby making it possible to prevent dust or the like from adhering to the polygon mirror or the optical system.

Abstract: A light scanning apparatus includes a deflector for deflecting a light beam emitted from a laser. A rotating reflector is provided in the deflector, and a reflecting surface is formed on the rotating reflector by cutting away a portion of the rotating reflector diagonally with respect to a plane perpendicular to the axis thereof. The light scanning apparatus further includes a control device for controlling a stopping position of the rotating reflector such that the rotating reflector stops rotating in a state in which the reflecting surface faces a predetermined direction. A magnet, an electromagnet, or a gear mechanism may be used as the control device.

Abstract: Laser beams LK and LY are respectively emitted from laser diodes 51K and 51Y and incident on a mirror face of a polygon mirror 55 via collimator lenses 52K, 52Y and first cylindrical lenses 53K, 53Y. The laser beams LK and LY are reflected off the polygon mirror 55 and deflected. Incidence angles of the laser beams LK and LY are set so that the laser beams LK and LY intersect with each other at a position P which is located before the polygon mirror 55.

Abstract: An optical deflection device includes: a fixed supporting member; a coil supporting member fixed on the fixed supporting member; a coil fixed on the coil supporting member; a rotary body having a rotary polygon mirror, a magnet facing and apart from the coil and a rotary supporting member for supporting the rotary polygon mirror and the magnet; a bearing unit supported on the fixed supporting member for rotatably supporting the rotary body; and a buffer member interposed between the fixed supporting member and the coil supporting member.

Abstract: A first polygonal motor correction value and a first drum motor correction value are provided to the polygonal motor and the photosensitive drum motor so that an image formed by a printer unit has a 100% magnification on the basis of data provided from a reference pattern generating unit which generates an ideal pattern data having no magnification error. Next, a document, on which a predetermined pattern is printed, is scanned by a scanner unit, and then, a second polygonal motor correction value and a carriage motor correction value are provided to the polygonal motor and the carriage motor so that an image printed using the printer unit has a 100% magnification.

Abstract: A color copying machine includes four image forming sections that are arranged side by side. A conveyor mechanism for conveying a recording sheet is provided under the image forming sections. Located on the downstream side of the conveyor mechanism is a fixing unit for heating the recording sheet, having a transferred toner image thereon, thereby fixing the toner image. A driving roller of the conveyor mechanism, which is located close to the fixing unit, is formed of Nobinite with a low thermal expansion coefficient. Thus, although the driving roller is subjected to thermal expansion by heat from the fixing unit, the traveling speed of a conveyor belt of the conveyor mechanism cannot be changed, so that an output image can be prevented from suffering shifts.

Abstract: An improved raster scanner, and electrostatographic printing machines which use such scanners, in which facet tracking is achieved by incorporating a semiconductor laser having an electronically tunable wavelength and a wavelength dispersive element which directs the laser beam onto the facets of a rotating polygon. The wavelength dispersive element is positioned, and the wavelength output from the laser is adjusted, such that as the polygon rotates the laser beam produces a spot on a facet which tracks the facet.

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: A light scanning apparatus includes a deflector for deflecting a light beam emitted from a laser. A rotating reflector is provided in the deflector, and a reflecting surface is formed on the rotating reflector by cutting away a portion of the rotating reflector diagonally with respect to a plane perpendicular to the axis thereof. The light scanning apparatus further includes a control device for controlling a stopping position of the rotating reflector such that the rotating reflector stops rotating in a state in which the reflecting surface faces a predetermined direction. A magnet, an electromagnet, or a gear mechanism may be used as the control device.

Abstract: A laser beam emitted by a semiconductor laser is applied through a beam shaper optical system to a recording film to produce the image of a near field pattern of the laser beam which is of a narrow width in a main scanning direction of the recording film and which has a wide, substantially rectangular intensity distribution in an auxiliary scanning direction. The image recorded on the recording film is free of image density irregularities in the auxiliary scanning direction.

Abstract: In an image forming apparatus in which an exposure is conducted by scanning of a laser beam, the apparatus includes a photoreceptor for forming a latent image thereon; an exposure device having a rotary polygonal mirror for exposing the photoreceptor, wherein the laser beam is deflected and scanned onto the photoreceptor by rotating the rotary polygonal mirror; a controller for controlling a linear speed of the photoreceptor; and a braking device for decreasing forcibly a speed of rotation of the polygonal mirror. When the controller decreases the linear speed of the photoreceptor according to an image formation mode, the braking device decreases the speed of rotation of the polygonal mirror.

Abstract: An optical scanner comprises a light source, a polygon mirror having plural light deflection faces for deflecting a light flux emitted from the light source, a first optical system for introducing the light flux emitted from the light source to the polygon mirror in which the light flux introduced to the polygon mirror has a breadth in a main scanning direction larger than a breadth of one of the light deflection faces in the main scanning direction, and a second optical system for condensing the light flux deflected by the polygon mirror onto a scanned face, wherein the second optical system has at least one reflection member for reflecting and introducing the light flux onto the scanned face, and each of the reflection members has a reflectivity varying from a center toward a periphery in the main scanning direction to uniformize substantially a light quantity distribution in the main scanning direction of the light flux on the scanned face.

Abstract: A beam scanning apparatus of an electrophotographic color printer having first and second light sources, and a deflecting unit including a driving source and first and second beam deflectors. The driving source has a rotation shaft and the first and second beam deflectors are coaxially installed on the rotation shaft and respectively deflect and scan beams of light emitted from the first and second light sources. First and second beam correcting units are arranged along the path of light between the deflecting unit and a photoreceptor and respectively correct the beams deflected by the first and second beam deflectors.

Abstract: In a laser scanning apparatus having a polygonal mirror, the laser light reflected from the multiple reflecting surfaces of polygonal mirror is detected with a photosensor. The respective detection outputs are stored in associated storage media (sample and hold circuits). When a certain reflecting surface has been rotated to the next laser light scan position, the detection output for the previous laser light scan is read out of the storage medium. A correction voltage is generated on the basis of the thus read detection output and the reference voltage is corrected with the generated correction voltage. Since the emission output of laser diode is controlled on the basis of the corrected reference voltage, the photoreceptor can be scanned with laser light of constant optical intensity despite the variation in the reflectance of laser light among the multiple reflecting surfaces of the polygonal mirror.

Abstract: A polygonal mirror assembly is provided with a vibration absorption. The polygonal mirror assembly includes a motor and a polygonal mirror rotatably installed around the rotation shaft of the motor. The polygonal mirror is provided with a plurality of reflective facets. The vibration absorption device is provided for absorbing rotational vibration due to the eccentric mass of the polygonal mirror, by elastically moving in the radial direction of the polygonal mirror. Therefore, the linearity of a scan line scanned from the laser scanning unit to the photoreceptor medium can be maintained.

Abstract: A latent image of a medical image is recorded on a heat development photosensitive material. Development is carried out on the photosensitive material, on which the latent image has been recorded, and the medical image having multiple gradation levels is thereby obtained. The development is carried out at a heating temperature falling within the range of 120.+-.10.degree. C., at a width-direction temperature accuracy falling within the range of .+-.3.degree. C., and for a development time falling within the range of 5 seconds to 30 seconds. In the heat development technique, the processing time is thus set to be a practically acceptable short time, noise is reduced, and a medical image having good image quality is obtained.

Abstract: The present invention discloses an image forming apparatus capable of preventing generation of color shade and moire fringes and forming an image exhibiting excellent image quality by setting recording intervals, which are different for each of a plurality of color signals, and by forming a color image having the number of screen lines and screen angles different for respective color signals in accordance with the set recording intervals.

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: A laser beam that is emitted from a light source is reflected by a first mirror, and then incident on each facet of a polygon mirror. The laser beam is moved for scanning in the fast scan direction by the facet, and reflected again by the first mirror. Since the laser beam is reflected two times by the first mirror, the first mirror may be located close to the polygon mirror, and hence the optical scanning device may be reduced in the size thereof. The incident angle of the incident light beam projected onto the polygon mirror and the reflecting angle of the reflecting light beam reflected by the polygon mirror, may be small. This fact leads to little curving of the scanning line.

Abstract: A laser pattern generator for semiconductor mask making or direct writing of features on a semiconductor wafer uses a pulsed laser source to achieve high power and short wavelength (e.g. 263 nm or less) radiation, for writing very small-sized features. The laser pulse frequency is either synchronous or asynchronous to the writing grid of the features being written, in various embodiments.

Abstract: An image forming apparatus of the present invention outputs a laser beam used for image formation in accordance with image data, and reflects said beam by a rotatably driven polygonal mirror having polygonal prism-like lateral surfaces as the reflective surfaces so as to scan a charged surface of a photoconductive member in a main scanning direction and form an electrostatic latent image on said photoconductive member, said image forming apparatus comprising a photoemitter which emits a forced laser beam unrelated to image data before outputting a laser beam for image formation so as to adjust the output timing of said beam used for image formation, photoreceptor which detects the forced laser beam at a predetermined position directly before starting a main scanning of said photoconductive member, calculator which calculates the period of one rotation of said polygonal mirror based on the detection by said photoreceptor, and a controller which controls the rotational speed of said polygonal mirror based on th

Abstract: A dual format pre-objective scanner optionally, usable as a laser printer, having an incident beam from input optics incident on a polygon tower which is comprised of a first polygon and a second polygon rotating about an axis common to both the first and second polygon, the polygon tower capable of moving in a vertical direction so that the incident light is directed in a plane approximately perpendicular to the axis rotation of the first and second polygon, at either the first polygon or the second polygon, and with the polygon tower further being capable of moving in a lateral direction approximately perpendicular to the axis of rotation of the polygon tower or moved simultaneously both vertically and laterally so that incident beams on the facets of the first polygon become incident on the facets of the second polygon at approximately the same distance from a scan lens.

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 for printing interdigitated images comprising the steps of interdigitating f images by modulating b beams of light (12) with image information. The b beams of light (12) are scanned onto an image-forming medium (50) by a polygon scanner (30) which has p sides. The relationship between the number of images f, the beams of light b, and the number of sides of the polygon p is given by f/pb=n where n is an integer. The image-forming medium is registered with a lenticular medium.

Abstract: An exposing device is composed of a photosensitive drum having a surface partitioned into a plurality of exposure areas in a main scanning direction, for carrying an image formed by exposing the surface, a laser light source for emitting a laser beam, a polygon mirror for rotating at a constant speed to scan the surface of the photosensitive drum in the main scanning direction with the laser beam from the laser light source, and an exposure control circuit for producing items of emission data for one line while the number of emission data items for one dot is varied for each exposure area, and for supplying the emission data items for one line to the laser light source in response to a print clock pulse.

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: A system and method of providing a periodic trajectory scan path for a laser beam across a photoconductive surface in a laser printer. A preferred embodiment of the periodic trajectory for a system with a two-axis deflector includes a multiple-frequency omega wave trajectory for providing a substantially rectangular grid of available dot locations for selective laser beam pulsing. As such, a plurality of generally linear rows of dots are completed in a single scan pass of the laser beam across the surface. The periodic trajectory is provided by deflecting the laser beam with an optical beam deflector, such as an electro-optic deflector, placed between the laser and the rotating polygon scanning mirror. A preferred embodiment of the beam deflector includes a folded optical path.

Abstract: A system and method of deflecting a laser beam in a laser printer for providing enhanced resolution and reduced banding effects. Specifically, to enhance resolution, the laser beam is borrowed (deflected) from a white space area adjacent an image to double resolution at the edges of the image. Similarly, banding is reduced by deflecting the beam to compensate for drum rotational and translational errors. The beam is deflected using an electro-optic modulator placed between the laser diode and the scanning mirror. Encoders detect drum rotational errors and motion between the optics unit and the drum to provide a closed loop feedback system for reducing banding.

Abstract: A rotary polygon mirror optical scanning device comprises a fixed shaft and a rotor having a shaft hole, to which the fixed shaft is inserted, and is rotatably supported against an outer perimeter of the fixed shaft. The device also includes a hydrodynamic bearing mechanism for supporting the rotor. The hydrodynamic bearing mechanism has first and second hydrodynamic pressure generating grooves which are, axially away from one another, formed on at least one of an outer surface of the fixed shaft and an inner surface of the shaft hole of the rotor. A rotary mirror is mounted on the rotor. A motor portion is arranged for rotating the rotor. The fixed shaft has a diameter bearing which is one-third or more of a diameter of a polygonal inscribed circle of the rotary polygon mirror. An area for cutting the first hydrodynamic pressure generating groove is arranged at an axially identical position with the rotary polygon mirror.

Abstract: In a deflection scanning apparatus used for a laser beam printer or the like, a rotating body is provided with a deflector which has a plurality of recesses arranged in a concentric manner with the center at the rotation axis of the rotating body. Balance weights are set in the recesses so as to remove rotation unbalance in rotation of the rotating body.

Abstract: A beam passing position controlling apparatus comprises a light source for emitting a beam, a mechanism for reflecting the beam toward an image carrier surface to scan the image carrier surface, a sensor for detecting a position where the beam passes on the image carrier surface, a circuit for calculating a correction amount from the position detected, a mechanism for correcting the passing position of the beam on the basis of the correction amount, and a circuit for controlling respective operations of the apparatus.

Abstract: A laser printer is provided having an automatic printhead identification system for use in a family of laser printers that are compatible with more than one model of printhead. For example, a single laser printer model can be made so that two different printheads can be successfully used, so long as the printer system knows which laser printhead has actually been installed. To detect which printhead has been installed, the printer operating system provides a reference clock signal having a pre-determined frequency, which dictates the rotational speed of the motor. Once the motor has achieved a "lock" operational speed, the printer measures the scan rate of the faceted mirror by detecting the time interval between pulses of the "HSYNC" signal. The HSYNC signal is sent to a "divide-by-n counter" circuit which divides the pulse frequency of the HSYNC signal, thereby increasing the time interval (by a factor of "n") that must be sensed by the system to determine which printhead is in fact installed.

Abstract: A dual format pre-objective scanner (10), for use in a laser printer, having an incident beam (22) from input optics (12) incident on a polygon tower (14) comprised of a first polygon (20) having a first diameter and first number of facets and a second polygon (30) having a second diameter and second number of facets, rotating about an axis (42) common to both first and second polygon. The polygon tower (14) is moved in a vertical direction so that the incident light is directed in a plane approximately perpendicular to the axis rotation of the first and second polygon, at either the first polygon (20) or the second polygon (30). The polygon tower (14) is also moved in a lateral direction approximately perpendicular to the axis (42) of rotation of the polygon tower (14).

Abstract: A laser scanner (10) has a light source (12), which produces a light beam (32) which is incident on a polygon tower (14) comprised of a first polygon (30) having a first diameter and first number of facets, and a second polygon (20) having a second diameter and second number of facets. The polygon tower (14) rotates about an axis common to both the first (30) and second (20) polygon and the first polygon. The point at which the light beam is incident on the polygon tower is shifted in a direction approximately parallel to the axis of the polygon tower so that the incident light is directed at either the first polygon or the second polygon. In one embodiment a reflected light beam from one of the polygons is off center from an optical axis of a scan lens (16).

Abstract: An apparatus for forming an image corresponding to an input image signal, includes a light beam generator for generating a light beam; a driver for driving the light beam generator; and an image outputting device for scanning the generated light beam which has been reflected by a rotary polygonal mirror to a recording medium in a primary direction and, for moving the recording medium in a secondary direction substantially perpendicular to the primary direction so that the image is formed. A periodical modulation signal generator changes a phase or an amplitude of a first reference signal including a fundamental frequency having a period corresponding to one rotation of the rotary polygonal mirror, and generates a plurality of periodical modulation signals having different phases or different amplitudes from each other. A multiplier multiplies a second reference signal having a predetermined frequency value by the plurality of periodical modulation signals respectively.

Abstract: A system for scanning or tracking, which includes a polygon rotatable about a rotational axis. The system further includes a fixed radiation source directing radiation at the polygon along a path whose extension would intersect the rotational axis of the polygon. The intersection of the extended path with the rotational axis of the polygon constitutes an original imaginary intersection point. The system includes a first scanned region onto which the radiation is projected, the projection being characterized in that radiation emanating from the radiation source is reflected from the polygon and is made to propagate, prior to impinging on the first scanned region, along a path which includes at least one additional path segment with the additional path segment passing through or directed at an additional intersection point, the additional intersection point being a real or imaginary image of the original intersection point.