Abstract: An imaging apparatus forming an image by performing scanning by deflecting a light beam includes a data conversion part that converts multi-bit input image data into data specifying a pulse width or intensity of the light beam. The image data is input to the data conversion part a given number of times in succession, and the data conversion part performs a different data conversion for each of scanning lines of the given number based on the input image data.

Abstract: A method for forming a pixel (20) having a predetermined density onto a sensitized recording medium moving in a length direction energizes a pixel exposure source (14) to begin exposure at the leading edge (34) of a pixel (20) and for a first predetermined time interval. The pixel exposure source (14) is de-energized for a period depending on the predetermined density and on media transport speed, then re-energized at the termination of the period. The pixel exposure source (14) is then de-energized at the end of a second predetermined time interval to terminate exposure at the trailing edge (36) of the pixel (20), whereby spatial dimensions of each pixel (20) are maintained at variable transport speed or density of pixel (20).

Abstract: An image forming apparatus includes a modulation data storage, a pulse width modulator, and an optical writing mechanism. The modulation data storage stores different gray-scale pulse sets. Each set includes gray-scale pulses having pulse widths different from each other in steps of a predetermined value corresponding to gray-scale information possibly contained in image data to be input. Each gray-scale pulse includes at least two pulses including at least one of left-positioned and right-positioned pulses. The pulse width modulator selects a gray-scale pulse set from among the different gray-scale sets in accordance with gray-scale information and performs a pulse width modulation to control a light beam on and off at a density twice or more than twice a density of the input image data by using the gray-scale pulse set selected. The optical writing mechanism causes the light beam to scan a photosensitive member to form a latent image thereon.

Abstract: An image signal with an overshoot is generated on a positive-going edge of an input image signal with an overshoot producing unit. Then, a light signal with an overshoot is outputted from a recording light source in response to the image signal with the overshoot supplied from the overshoot producing unit. The light signal outputted from the recording light source is applied to scan a photosensitive medium to record an area gradation image on the photosensitive medium.

Abstract: An image forming apparatus which is capable of eliminating density irregularities of an image formed caused by potential irregularities of the photosensitive member when the drum is irradiated by a beam of constant luminous intensity. A laser driver irradiates a beam modulated based on an image signal onto a photosensitive member. A current controller variably controls a driving current for driving the laser driver. A PWM pulse width converter modulates a pulse width of the beam based on the image signal. A potential sensor measures the potential of the photosensitive member after the photosensitive member is irradiated by a beam having a predetermined luminous intensity. A selector causes the current controller to correct the driving current based on low frequency components of irregularities of the potential and changes a modulation coefficient used for modulating the pulse width based on high frequency components of the irregularities of the potential.

Abstract: A collimation assembly for a multi-beamed laser scanner including a collimation housing mounted to a printhead housing of the laser scanner, and at least two adjustment brackets supported on the collimation housing and located adjacent to each other in a cross-scan direction. Each of the adjustment brackets includes a mount member and a laser light source is supported within each of the mount members, each of the light sources defining a respective light beam axis. At least two collimation lenses are also provided supported on the collimation housing and intersected by one of the light beam axes. Each of the adjustment brackets is movable relative to the collimation housing in a scan direction and in the cross-scan direction to locate each of the light beam axes at a predetermined position relative to a respective collimation lens.

Abstract: An image forming apparatus is disclosed that includes a data buffer unit that buffers input binary data, the resolution of which is 2/n (n: an odd integer greater than or equal to 3) times a print resolution, a data transform unit that transforms the input binary data into output multi-level data of the print resolution, and a light beam modulation unit that modulates radiant energy of a light beam in accordance with the output multi-level data. Accordingly, an image of the print resolution printed by the image forming apparatus based on the input binary data looks as if the resolution of the image is that of the input binary data.

Abstract: A method for scaling an image includes determining a plurality of lineweight values for a plurality of virtual scan lines. In addition, the method includes determining a normalization value using the plurality of lineweight values. The method further includes determining a pulse code value for a pixel in an actual scan line using the plurality of lineweight values, the normalization value, and pulse code values for pixels in the plurality of virtual scan lines.

Abstract: An image forming apparatus is provided that is capable of forming an image with excellent gradation quality without affected by variations in the sensitivity characteristic of the photoreceptor and the light quantity characteristic of the LED print head among individual products. A highest gradation appropriate exposure amount appropriate for the highest gradation is calculated from the sensitivity characteristic of the photoreceptor and the light quantity characteristic of the LED print head. Then, based on the highest gradation appropriate exposure amount, an appropriate lighting time of the LEDs that is appropriate for each gradation is calculated so that the increment of the exposure amount between the gradations including the first gradation, and the lighting times of the gradations are set based on the appropriate lighting times. Then, the LEDs are lit for the lighting time set in accordance with the gradation of the inputted image data.

Abstract: A laser imaging device is described. The laser imaging device includes a laser driver, and a pulse width modulator system. The pulse width modulator system includes a first pulse width modulator having a first operating frequency and a second pulse width modulator having a second operating frequency, which provides to the laser driver a pulse width modulated output signal having a desired modulation frequency greater than the first and second operating frequencies.

Abstract: Provided is a display device having a storing circuit 21 section for storing image signals for controlling display and an active device section 22 for performing display control on the basis of the image signals stored by the storing circuit section 21, provided in each dot as a minimum unit of display, thereby achieving space saving.

Abstract: An image processing apparatus for a laser printer, wherein a halftone control through laser pulse modulation (PWM) is used in combination with distributed clustered-dot halftone processing which distributes a tone level over four clustered-dots, and the value represented by higher bits of a threshold are used to switch a PWM pulse pattern in a highlight area to a discontinuous pattern, thereby implementing the high density halftone processing, which provides a high highlight tone density and stability, only with a small scale memory and circuit.

Abstract: There is described a duplex image-forming apparatus having a function of forming images onto both sides of a transfer material. The apparatus includes an image-forming section to respectively form an obverse-side image and a reverse-side image on a photoreceptor element by scanning a light beam, modulated with image signals based on pixel-clock signals and reflected from a polygon mirror rotating at an operating velocity based on polygon-clock signals; a transferring section to transfer said obverse-side image and said reverse-side image onto both surfaces of said recording sheet; a fixing section to fix the images onto both surfaces of said recording sheet; and a clock-frequency changing section to change a pixel-clock frequency, and a polygon-clock frequency, corresponding to a degree of shrinkage of said recording sheet caused by a fixing operation performed in said fixing section, at a transition time of an image-forming operation from one side to another side.

Abstract: A photosensitive body has a photosensitive layer. An optical scanning device has a deflector deflecting a light flux emitted from a light source, and scans the surface of the photosensitive body by the thus-deflected light flux. A dot is formed at a center between adjacent light fluxes as a result of the adjacent light fluxes being overlapped with one another in a sub-scan direction. A ratio of a static beam-spot diameter Ws in the sub-scan direction on the surface of the photosensitive body defined by 1/e2 of the maximum value in the exposure distribution of the beam spot to an interval L between adjacent scan lines satisfies the following formula: 1.2<Ws/L<4.5.

Abstract: An input bit sequence with predetermined bit periods T is converted into a corresponding light-emission waveform; and a beam with the thus-obtained light-emission waveform is applied onto a phase-change optical disk so as to record the input bit sequence thereon. The light-emission waveform comprises a heating pulse for heating the recording medium occurring for an interval tw and a cooling pulse for cooling the recording medium occurring for an interval tc, and the intervals tw and tc on the heating/cooling pulses satisfy the following requirement in case the heating/cooling pulses occur alternately with repetition: 1.5T≦tw+tc≦3T.

Abstract: A high-quality image forming apparatus that is capable of accurately adjusting the size and position of an image during image formation on a second surface of a transfer material, even when there has been expansion/contraction of the transfer material due to thermal fixing after image formation on a first surface thereof, to thereby avoid image displacement during two-sided image formation and multiple image formation.

Abstract: A laser print apparatus includes a memory for storing a multi-bit image including a plurality of pixels. Each pixel is represented by an N-bit value, wherein N is greater than one. A modulation code generator analyzes three adjacent pixels. The three adjacent pixels include a left pixel, a center pixel, and a right pixel. The modulation code generator is configured to generate a pulse width value based on the value of the center pixel, and a justification value based on the values of the left pixel and the right pixel. A laser print engine forms an output pixel on media based on the pulse width value and the justification value.

Abstract: The invention relates to an apparatus for printing a multibit per pixel image (10) from a halftone binary digital bitmap having pixels having a multibit per pixel image memory for receiving the multibit per pixel image; a lookup table (16) external to the memory disposed in a programmable gate array (18) for converting the multibit per pixel image to a base duty cycle (20) wherein the base duty cycle is disposed in the programmable gate array and is adapted for creating a modulated drive signal (22) from the base duty cycle to modulate an exposure (24) for each pixel in the multibit per pixel image; and a printer (28) adapted for using the modulated exposure to print an image, having a dpi greater than 1400, further comprising a drum (32) capable of spinning, and an encoder (34) disposed on the drum for providing a home signal (36) and a pixel rate (38).

Abstract: A laser imaging device is described. The laser imaging device includes a laser driver, and a pulse width modulator system. The pulse width modulator system includes a first pulse width modulator having a first operating frequency and a second pulse width modulator having a second operating frequency, which provides to the laser driver a pulse width modulated output signal having a desired modulation frequency greater than the first and second operating frequencies.

Abstract: An optical recording method in which an effective recording sensitivity in the recording of image information on a photosensitive material is raised, whereby a productivity is enhanced owing to lowered energy (laser power) required for the recording or a heightened recording speed. An image is recorded by projecting a light beam onto the photosensitive material formed on a base material backing. The optical recording method includes the steps of: (a) successively outputting pulse light whose duty factor is at most 50%, from a light source; (b) modulating the pulse light output from the light source, in accordance with an image signal, and then projecting the modulated pulse light onto the photosensitive material; and (c) recording the image by causing the pulse light to scan the photosensitive material.

Abstract: A method for optically recording information on an optically re-writable information medium is described. A mark is formed on a recording medium by radiating a laser light having the strength of the short recording pulse signal followed by the off-pulse signal. The recording film is heated to form the mark and the mark is extended by thermal diffusion while the off-pulse signal is provided. Therefore, the length of the recorded mark ML is longer than the recording pulse width at a predetermined linear velocity. The erasing pulse signal follows the off-pulse signal and the extended recorded mark is erased by the erasing pulse signal. The recording method according to the present invention can form a mark on the recording medium by radiating the laser light having a shorter recording pulse width than a recording pulse width used in the conventional method to form a mark having the same length.

Abstract: In an image forming apparatus having an LED print head according to the present invention, the cycle period of a lighting reference clock signal is variably set according to the tone level of image data so as to variably set the lighting period of an LED according to the tone level of the image data. This makes it possible to provide a linear characteristic relationship between the image data and the tone level of a formed toner image for improvement of an image quality.

Abstract: A method is provided of modifying pulsed image data signals for controlling an acousto-optic modulator in an image setter system. The method comprises modifying the pulse widths of the image data signals in accordance with predetermined parameters so as to improve the correspondence between the data representing the image and the data recorded on the record medium. Following modification the data signals are supplied to the acousto-optic modulator.

Abstract: A method for printing on a material is disclosed. The method includes providing a printing system having a laser source for producing a printing beam and directing the printing beam to a plurality of locations on a material. The method also includes adjusting a dwell time of the printing beam at the one or more locations so as to form a spot at each location.

Abstract: There is described a duplex image-forming apparatus having a function of forming images onto both sides of a transfer material. The apparatus includes an image-forming section to respectively form an obverse-side image and a reverse-side image on a photoreceptor element by scanning a light beam, modulated with image signals based on pixel-clock signals and reflected from a polygon mirror rotating at an operating velocity based on polygon-clock signals; a transferring section to transfer said obverse-side image and said reverse-side image onto both surfaces of said recording sheet; a fixing section to fix the images onto both surfaces of said recording sheet; and a clock-frequency changing section to change a pixel-clock frequency, and a polygon-clock frequency, corresponding to a degree of shrinkage of said recording sheet caused by a fixing operation performed in said fixing section, at a transition time of an image-forming operation from one side to another side.

Abstract: Exposure of a medium is controlled by changing an emission level of a radiation source from a first power to a second power. The second power emits for less time than required by an irradiance profile to traverse a full-width at half maximum of the irradiance profile projected onto the medium along a direction of relative motion between the irradiance profile and the medium. The emission level changes to the first power emits for less time than required by the irradiance profile to traverse the full-width at half maximum of the irradiance profile projected onto the medium along the direction of relative motion between the irradiance profile and the medium. Then the emission level changes to the second power. Brief pulsing of a single binary source can transfer intermediate amounts of thermally transferable colorant from a donor exhibiting a continuous-tone transfer response.

Abstract: An image forming apparatus includes a semiconductor laser that irradiates a laser beam modulated based on an image modulation signal, a scanning device that scans an image carrier with the semiconductor laser beam, and a pixel clock generating device that generates a pixel clock that controls the laser beam. The pixel clock includes a plurality of pulses having a prescribed normal width constituted by a prescribed number of fractions (N), and substantially periodically includes one or more pulses having a greater width constituted by a number of fractions of (N) plus (M).

Abstract: An optical scanning device for optically scanning a surface of a photoconductor to form an electrostatic latent image thereupon. The scanning device includes a light source to emit a light flux and pulse modulate the light flux. A deflector deflects the light flux from the light source. A scanning image formation element condenses the light flux deflected by the deflector to form a scanning beam spot on the scanned surface. The scanning beam spot scans the scanned surface to form the electrostatic latent image on the scanned surface. A stationary beam spot, formed by stationary light flux on the scanned surface, has a stationary beam spot diameter &ohgr;m in a main scanning direction that is smaller than a stationary beam spot diameter &ohgr;s in a sub-scanning direction.

Abstract: A PDL interpreter rasterizes image data, which are described in page description language, entered from a host computer, and stores the rasterized image data in an image memory. A CPU discriminates the type of image, pixel by pixel, by referring to the image data stored in the image memory, and stores a discrimination code, which indicates the result of discrimination, in a code memory. The CPU reads out image data that have been stored in the image memory and reads the discrimination code corresponding to these image data out of the code memory. The image data read out of the image memory are subjected to different binarizing processing by two binarizing circuits. Depending upon the discrimination code read out of the code memory, a selector selects the output of one of the two binarizing circuits and sends the selected image data to a printer.

Abstract: An object of the present invention is to solve a problem in which in an image forming apparatus which performs pulse width modulation, when the maximum pulse width is changed to change the maximum density, the exposure amount in patch formation also changes to make it difficult to accurately control the patch and maintain gradation characteristics. To achieve this object, the maximum pulse width of pulse width modulation can be changed. It is determined whether a patch is to be formed. For normal image formation, the maximum pulse width is set to a changed value. For patch formation, the maximum pulse width is set at a predetermined value, and an image is formed.

Abstract: A method for optically recording information on an optically re-writable information medium is described. A mark is formed on a recording medium by radiating a laser light having the strength of the short recording pulse signal followed by the off-pulse signal. The recording film is heated to form the mark and the mark is extended by thermal diffusion while the off-pulse signal is provided. Therefore, the length of the recorded mark ML is longer than the recording pulse width at a predetermined linear velocity. The erasing pulse signal follows the off-pulse signal and the extended recorded mark is erased by the erasing pulse signal. The recording method according to the present invention can form a mark on the recording medium by radiating the laser light having a shorter recording pulse width than a recording pulse width used in the conventional method to form a mark having the same length.

Abstract: When maximum density of an output image is lowered by a gamma correction, the number of tones is reduced and the tonality of the output image declines. In order to solve this problem, a pattern generator (215) is caused to generate a toned pattern and the gain of a D/A converter of a PWM circuit (212) is controlled so as to output a test pattern having a density ranging from maximum pulse width Pff(50%) to maximum pulse width Pff(100%) for each color component (step S1). Image information that has been read (step S2) from the test pattern is converted to density information (step S3), and Pff is set (step S4) from the relationship between Pff and image density based upon coordinate information provided by the test pattern.

Abstract: An image forming apparatus having first and second basic cells each containing a predetermined number of cells in a main scanning direction and a sub-scanning direction and disposed adjacent to each other in the sub-scanning direction, a gradation processing portion arranged to perform a gradation expressing process for each basic cell in accordance with a density of a supplied image and a dot forming portion capable of forming dots on a recording medium to correspond to each pixel subjected to the gradation expressing process by the gradation processing portion. The gradation processing portion performs the gradation expressing process in such a manner that enlargement of dots in the first and second basic cells adjacent to each other in the sub-scanning direction is inhibited in the sub-scanning direction until the dots are enlarged and connected to each other in the main scanning direction.

Abstract: An image forming apparatus includes a modulation data storage, a pulse width modulator, and an optical writing mechanism. The modulation data storage stores different gray-scale pulse sets. Each set includes gray-scale pulses having pulse widths different from each other in steps of a predetermined value corresponding to gray-scale information possibly contained in image data to be input. Each gray-scale pulse includes at least two pulses including at least one of left-positioned and right-positioned pulses. The pulse width modulator selects a gray-scale pulse set from among the different gray-scale sets in accordance with gray-scale information and performs a pulse width modulation to control a light beam on and off at a density twice or more than twice a density of the input image data by using the gray-scale pulse set selected. The optical writing mechanism causes the light beam to scan a photosensitive member to form a latent image thereon.

Abstract: A pulse width modulation circuit is provided with a signal generating circuit generating a reference clock signal and a predetermined signal which is approximately inversely proportional to a digital data input signal, a delay quantity generating circuit delaying the reference clock signal by a desired phase delay to output a pulse signal, based on the predetermined signal from the signal generating circuit, a delay quantity controller controlling a delay quantity of the delay quantity generating circuit, and a modulated signal generator generating a modulated signal which is pulse-width-modulated based on the pulse signal from the delay quantity generating circuit and the reference clock signal.

Abstract: When a CPU begins to monitor whether delay variation characteristics of a pulse width variation circuit have varied, it selects a basic delay setting value in a basic delay value setting block from a smallest one. The CPU sets a division number in a phase select block from a given minimum desired division number for pulse width modulation. The CPU senses the level of a phase comparison result signal (PHASE) from the pulse width modulation circuit. If the phase comparison result signal is stable at “1”, the CPU 1 fixes the division number. If the phase comparison result signal is “0” and the division number is not maximum, the CPU increases the division number and goes back to the setting of the division number. If the division number is maximum, the CPU increases the basic delay and goes back to the basic delay setting.

Abstract: An optical recording method in which an effective recording sensitivity in the recording of image information on a photosensitive material is raised, whereby a productivity is enhanced owing to lowered energy (laser power) required for the recording or a heightened recording speed. An image is recorded by projecting a light beam onto the photosensitive material formed on a base material backing. The optical recording method includes the steps of: (a) successively outputting pulse light whose duty factor is at most 50%, from a light source; (b) modulating the pulse light output from the light source, in accordance with an image signal, and then projecting the modulated pulse light onto the photosensitive material; and (c) recording the image by causing the pulse light to scan the photosensitive material.

Abstract: An exposure apparatus for image formation uses power control means provided to a laser driver for controlling exposure energy and accordingly forming an image. Specifically, exposure energy is varied depending on an isolated-dot pattern and an isolated-line pattern by changing the pulse height (drive power) of a drive pulse for each dot. Both of the isolated-line and isolated-dot patterns of a high resolution can thus be reproduced with a high image quality without increase of cost due to requirements for accuracy in processing and positioning of a lens and without decrease of life of a photoreceptor due to a decreased thickness of its photosensitive layer.

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 object of the present invention is to solve a problem in which in an image forming apparatus which performs pulse width modulation, when the maximum pulse width is changed to change the maximum density, the exposure amount in patch formation also changes to make it difficult to accurately control the patch and maintain gradation characteristics. To achieve this object, the maximum pulse width of pulse width modulation can be changed. It is determined whether a patch is to be formed. For normal image formation, the maximum pulse width is set to a changed value. For patch formation, the maximum pulse width is set at a predetermined value, and an image is formed.

Abstract: There is provided an image forming apparatus such as a latent image forming apparatus, in which the density of a half tone is stable independent on a write position of a main scanning line, even if a plurality of semiconductor lasers are used. The image forming apparatus has a latent image forming unit for pulse-width-modulating a drive signal of the semiconductor laser in response to the write position of image data. The latent image forming unit has an image sorting circuit for sorting the image data into an odd line and an even line, a memory for storing a turning on position, a pulse generating position control circuit for generating a pulse generating position signal, a PWM circuit for generating a triangular wave in accordance with the pulse generating position signal, and a beam-A-circuit and a beam-B-circuit, which control beams from the semiconductor laser.

Abstract: When a CPU begins to monitor whether delay variation characteristics of a pulse width variation circuit have varied, it selects a basic delay setting value in a basic delay value setting block from a smallest one. The CPU sets a division number in a phase select block from a given minimum desired division number for pulse width modulation. The CPU senses the level of a phase comparison result signal (PHASE) from the pulse width modulation circuit. If the phase comparison result signal is stable at “1”, the CPU 1 fixes the division number. If the phase comparison result signal is “0” and the division number is not maximum, the CPU increases the division number and goes back to the setting of the division number. If the division number is maximum, the CPU increases the basic delay and goes back to the basic delay setting.

Abstract: A device for forming an image on a printing plate includes at least one laser, and an optical system for forming an image of radiation from the laser on the printing plate, the laser radiation having ultrashort pulses with a duration of less than 1 ns; a printing unit having at least one of the imaging devices; and a printing machine with at least one of the printing units.

Abstract: When a CPU begins to monitor whether delay variation characteristics of a pulse width variation circuit have varied, it selects a basic delay setting value in a basic delay value setting block from a smallest one. The CPU sets a division number in a phase select block from a given minimum desired division number for pulse width modulation. The CPU senses the level of a phase comparison result signal (PHASE) from the pulse width modulation circuit. If the phase comparison result signal is stable at “1”, the CPU 1 fixes the division number. If the phase comparison result signal is “0” and the division number is not maximum, the CPU increases the division number and goes back to the setting of the division number. If the division number is maximum, the CPU increases the basic delay and goes back to the basic delay setting.

Abstract: An image processing apparatus for performing pulse-width modulation processing based on input image data. A maximum pulse width of a pulse signal, which can be outputted as a modulation signal obtained by the pulse width modulation, is changed in accordance with an image processing mode.

Abstract: When a multiple-color image is printed by electrophotography unwanted spaces are produces between different colors. These spaces are attributed to non-development of toner caused by the influence of an electric field at the boundary of an electrostatic latent image formed on a photosensitive drum. Accordingly, when data conversion is converted from two-bit data of a bitmap to eight-bit data that are used for modulating a light signal, a pixel of interest and the neighboring 9×9 pixels are stored and the state thereof is determined. If the pixel of interest is a white pixel and the neighboring pixels are all non-white pixels, then the pixel of interest is not left at a value corresponding to white, but is converted to a value corresponding to a potential that will not develop toner. The photosensitive drum is irradiated with a laser based upon the data resulting from the conversion.

Abstract: For pulsed marking systems, where the marking is dot by dot, a method is disclosed for finer rendition of marked edges and finer control of the size and shape of half-tone spots, whereby the position of dots at boundaries of marked areas are variable. In particular, while most dots are marked at regularly spaced grid points, boundary dots may be marked displaced by various amounts to either side of a grid point, thereby shrinking or expanding the marked area. Specific techniques for generating appropriate dot displacement, in conjunction with known half-tone screening methods, are disclosed. Apparatus for carrying out marking and screening by a pulsed marking device, with fine position control of the edge of marked areas, is also disclosed.

Abstract: A plate-making method is capable of recording a sharp image on a photosensitive plate, and is applicable to a process operation executed in a light room, while adverse influences caused by laser flares can be hardly received. Ultra-short pulse laser light emitted from a Ti:Al2O3 laser light source is modulated by an AOM (acousto-optic modulating element). The modulated laser light is focused by a collective lens onto a high-sensitive photopolymer layer of a photosensitive plate-making material. The focused ultra-short pulse laser light may cause a photopolymerization reaction in a laser-light-irradiated portion of the high-sensitive photopolymer layer by way of a multiple photon absorption phenomenon, so as to form a hardened portion.

Abstract: The present invention relates to a pulse generation apparatus for generating a pulse signal having a pulse width controlled, and a pulse signal having a pulse width controlled with high precision is generated by a circuit suitable for conversion into LSI.

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.