JP2016064653A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To process an edge part of an area with a predetermined attribute with high resolution without increasing a data transfer amount.SOLUTION: An image forming apparatus forms an image according to light emitted from a light source, and is provided with: an image processing part which generates image data with first resolution and tag information representing attributes for every pixel; a modulation part; and a light source driving part, in which the modulation part has: a pattern matching part which matches the image data with the first resolution and the tag information with a predetermined pattern to detect an object area which is an edge part with the predetermined attribute; an image pattern generation part which generates image data with second resolution of an object area determined for the matched pattern; and a light volume pattern generation part which generates light volume pattern data with the second resolution of the object area determined for the matched pattern, and the light source driving part lights the light source by a modulation signal according to the image data with the second resolution, and controls light volume of the light source according to the light volume pattern data.SELECTED DRAWING: Figure 12

Description

  The present invention relates to an image forming apparatus.

  In recent years, digital printing machines using an electrophotographic process have been actively used in the field of production printing. For this reason, digital printers using an electrophotographic process are required to have high image quality and high reliability. In particular, digital printing machines using the electrophotographic process have improved fine line reproducibility, improved character reproducibility (for example, improved reproducibility of small-sized characters corresponding to 2 to 3 points), and characters derived from the electrophotographic process. There is a demand for suppression of fatness and improvement of color misregistration accuracy.

  For the purpose of realizing high image quality, a digital printing machine using an electrophotographic process includes an image processing unit that corrects image data by image processing. For example, the image processing unit executes image processing with high resolution and multi-bit data of 1200 dpi (dots per inch) or 2400 dpi.

  In addition, a digital printing machine using an electrophotographic process includes a photosensitive drum whose surface functions as a scanned surface having photosensitivity, a light source that emits laser light, a polygon mirror that deflects laser light from the light source, and a polygon A scanning optical system for guiding the laser beam deflected by the mirror to the surface (scanned surface) of the photosensitive drum is provided. A digital printing machine using an electrophotographic process modulates a light beam emitted from a light source according to image data, irradiates the light beam from the light source onto the surface to be scanned, and scans the surface to be scanned with the light beam. Then, an electrostatic latent image corresponding to the image data is formed on the photosensitive drum.

  The digital printer using the electrophotographic process having such a configuration uses, as a light source, an element having a plurality of light emitting points such as an LDA (Laser Diode Array) or a VCSEL (Vertical Cavity Surface Emitting Laser). As a result, the digital printing machine using the electrophotographic process can form an electrostatic latent image having a resolution higher than that of image data of 1200 dpi, for example, 2400 dpi or 4800 dpi.

  In patent document 1 and patent document 2, by detecting a white portion in an image and expanding a white line or correcting a pixel around a white character by processing in the image processing unit, A technique for preventing crushing of reversed characters and improving character reproducibility is described.

  By the way, when high-density image processing is executed, a problem occurs in data transfer from the image processing unit to the downstream light source drive circuit. When the resolution handled by the image processing unit is, for example, 2400 dpi or 4800 dpi multi-bit data, the degree of freedom of image processing is increased, and the reproducibility can be improved for 1200 dpi minute characters and lines. However, when high-density image processing is executed, the amount of data that must be transferred from the image processing unit to the light source driving circuit on the downstream side becomes enormous, which is rate-limiting for productivity.

  Moreover, if all the processing for improving the reproducibility of minute characters or the like is executed by the upstream image processing unit, the processing becomes complicated and the burden on the image processing unit becomes large. Furthermore, in addition to correcting the outline portion, various processes such as character thinning and smoothing processing must be executed by the upstream image processing unit, which further increases the processing load on the image processing unit.

  The present invention has been made in view of the above, and an image forming apparatus that processes the edge portion of a predetermined attribute area with high resolution without increasing the data transfer amount of image data, thereby realizing high image quality The purpose is to provide.

  In order to solve the above-described problems and achieve the object, the present invention is an image forming apparatus that forms an image according to light emitted from a light source, and which has first resolution image data based on input image data. And an image processing unit for generating tag information representing an attribute for each pixel of the first resolution image data, and converting the first resolution image data into second resolution image data higher than the first resolution. A modulation unit that generates a modulation signal according to the image data of the second resolution, and a light source driving unit that drives the light source by the modulation signal, the modulation unit including the image data of the first resolution And a pattern matching unit that matches the tag information with a predetermined pattern to detect a target region that is an edge portion of a predetermined attribute, and is determined corresponding to the matched pattern An image pattern generator for generating the second resolution image data of the target area, and a light quantity pattern generation for generating the second resolution light pattern data of the target area, which is determined in correspondence with the matched pattern And the light source drive unit turns on the light source by the modulation signal corresponding to the image data of the second resolution and controls the light amount of the light source according to the light amount pattern data. To do.

  According to the present invention, it is possible to achieve high image quality by processing the edge portion of a predetermined attribute region with high resolution without increasing the data transfer amount of image data.

FIG. 1 is a diagram illustrating a schematic configuration of a color printer 2000 according to the embodiment. FIG. 2 is a diagram illustrating an example of the arrangement of the optical sensors 2245a, 2245b, and 2245c. FIG. 3 is a diagram illustrating the configuration of the optical sensors 2245a, 2245b, and 2245c. FIG. 4 is a diagram illustrating a configuration of an optical system of the optical scanning device 2010. FIG. 5 is a diagram illustrating an example of an optical path from the light source 2200 a to the polygon mirror 2104 and an optical path from the light source 2200 b to the polygon mirror 2104. FIG. 6 is a diagram illustrating an example of an optical path from the light source 2200c to the polygon mirror 2104 and an optical path from the light source 2200d to the polygon mirror 2104. FIG. 7 is a diagram illustrating an example of an optical path from the polygon mirror 2104 to each photosensitive drum 2030. FIG. 8 is a diagram showing the configuration of the electrical system of the optical scanning device 2010. FIG. 9 is a diagram showing the configuration of the interface unit 3101. FIG. 10 is a diagram illustrating a configuration of the image processing unit 3102. FIG. 11 is a diagram illustrating a configuration of the drive control unit 3103. FIG. 12 is a diagram illustrating a configuration of the modulation unit 3233. FIG. 13 is a diagram illustrating the configuration of the light source driving unit 3234 together with the light source 2200. FIG. 14 is a diagram illustrating an example of a target area detected by pattern matching. FIG. 15 is a diagram illustrating an example of resolution conversion processing for each pixel by the pixel conversion unit 3254. FIG. 16 is a diagram illustrating an example of second-resolution image data and light amount pattern data of the target region. FIG. 17 is a diagram illustrating an example of second-resolution image data. FIG. 18 is a diagram illustrating an example of the light quantity pattern data of the second resolution. FIG. 19 is a diagram illustrating a conversion example when the resolution of 2400 dpi image data representing a rectangular black region is increased to 4800 dpi image data. FIG. 20A is a diagram illustrating an example of a waveform set to the reference light amount. FIG. 20B is a diagram illustrating an example of the developing electric field formed with the light intensity waveform of FIG. FIG. 21A is a diagram illustrating an example of a waveform in which the edge portion is set to a high light amount and the other portion is set to a reference light amount. FIG. 21B is a diagram showing an example of the developing electric field formed with the light intensity waveform of FIG. FIG. 22 is a diagram comparing the waveform before the area to be exposed is thinned with the waveform after the area is thinned and the amount of light at the edge portion is further increased. FIG. 23 is a diagram showing edge regions that can be detected at 1200 dpi. FIG. 24 is a diagram showing edge regions that can be detected at 4800 dpi.

  A color printer 2000 as an example of an image forming apparatus according to an embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

  FIG. 1 is a diagram illustrating a schematic configuration of a color printer 2000 according to the embodiment. The color printer 2000 manufactures a printed material by transferring toner onto a recording paper (object). The color printer 2000 is a tandem multicolor printer that forms a full-color image by superimposing four colors (black, cyan, magenta, and yellow).

  The color printer 2000 includes an optical scanning device 2010, four photosensitive drums 2030a, 2030b, 2030c, and 2030d (referred to as the photosensitive drum 2030 when four are collectively referred to), and four cleaning units 2031a, 2031b, and 2031c and 2031d (when four are collectively referred to as cleaning unit 2031) and four charging devices 2032a, 2032b, 2032c and 2032d (when four are collectively referred to as charging device 2032). Prepare. Further, the color printer 2000 includes four developing rollers 2033a, 2033b, 2033c, and 2033d (collectively referred to as developing roller 2033) and four toner cartridges 2034a, 2034b, 2034c, and 2034d (four). Are collectively referred to as a toner cartridge 2034). Further, the color printer 2000 includes a transfer belt 2040, a transfer roller 2042, a fixing roller 2050, a paper feed roller 2054, a registration roller pair 2056, a paper discharge roller 2058, a paper feed tray 2060, and a paper discharge tray 2070. A communication control device 2080, a density detector 2245, four home position sensors 2246a, 2246b, 2246c, and 2246d (four are collectively referred to as home position sensors 2246), and a printer control device 2090. Is provided.

  The communication control device 2080 controls bidirectional communication with a host device (for example, a computer) via a network or the like.

  The printer control device 2090 comprehensively controls each unit provided in the color printer 2000. The printer control device 2090 includes a CPU (Central Processing Unit), a program described by codes executed by the CPU, and a ROM that stores various data used when executing the program, a RAM that is a working memory, An AD conversion circuit that converts analog data into digital data is included. The printer control device 2090 controls each unit in response to a request from the host device, and sends image data from the host device to the optical scanning device 2010.

  The photosensitive drum 2030a, the charging device 2032a, the developing roller 2033a, the toner cartridge 2034a, and the cleaning unit 2031a are used as a set. These constitute an image forming station (also referred to as a K station) that forms a black image.

  The photosensitive drum 2030b, the charging device 2032b, the developing roller 2033b, the toner cartridge 2034b, and the cleaning unit 2031b are used as a set. These constitute an image forming station (also referred to as C station) for forming a cyan image.

  The photosensitive drum 2030c, the charging device 2032c, the developing roller 2033c, the toner cartridge 2034c, and the cleaning unit 2031c are used as a set. These constitute an image forming station (also referred to as an M station) for forming a magenta image.

  The photosensitive drum 2030d, the charging device 2032d, the developing roller 2033d, the toner cartridge 2034d, and the cleaning unit 2031d are used as a set. These constitute an image forming station (also referred to as a Y station) for forming a yellow image.

  Each of the photosensitive drums 2030 is an example of a latent image carrier, and each has a photosensitive layer formed on the surface thereof. That is, the surface of each photoconductor drum 2030 is a scanned surface. Note that the photosensitive drums 2030a, 2030b, 2030c, and 2030d are arranged so that their rotation axes are arranged in parallel, and, for example, all rotate in the same direction (for example, the arrow direction in the plane in FIG. 1).

  Here, in the XYZ three-dimensional orthogonal coordinate system, a direction parallel to the central axis of each photoconductor drum 2030 is defined as a Y-axis direction, and a direction along the arrangement direction of each photoconductor drum 2030 is described as an X-axis direction. .

  Each charging device 2032 uniformly charges the surface of the corresponding photosensitive drum 2030. The optical scanning device 2010 applies a light beam modulated for each color based on image data (black image data, cyan image data, magenta image data, yellow image data) to the surface of the corresponding charged photosensitive drum 2030. Irradiate each. As a result, on the surface of each photoconductive drum 2030, the charge disappears only in the portion irradiated with light, and a latent image corresponding to the image data is formed on the surface of each photoconductive drum 2030. The latent image formed here moves in the direction of the corresponding developing roller 2033 as the photosensitive drum 2030 rotates. Details of the configuration of the optical scanning device 2010 will be described later.

  By the way, in each photoconductor drum 2030, areas where image data is written are called “effective scanning area”, “image forming area”, “effective image area”, and the like.

  The toner cartridge 2034a stores black toner. The black toner is supplied to the developing roller 2033a. The toner cartridge 2034b stores cyan toner. The cyan toner is supplied to the developing roller 2033b. The toner cartridge 2034c stores magenta toner. The magenta toner is supplied to the developing roller 2033c. The toner cartridge 2034d stores yellow toner. The yellow toner is supplied to the developing roller 2033d.

  As each developing roller 2033 rotates, the toner from the corresponding toner cartridge 2034 is thinly and uniformly applied to the surface thereof. Then, when the toner on the surface of each developing roller 2033 comes into contact with the surface of the corresponding photosensitive drum 2030, the toner moves only to the portion irradiated with light on the surface and adheres to the surface. That is, each developing roller 2033 causes toner to adhere to the latent image formed on the surface of the corresponding photoconductor drum 2030 to be visualized.

  The transfer belt 2040 is wound around a belt rotation mechanism and rotates in a certain direction. The outer surface of the transfer belt 2040 is in contact with the surface of each of the photoconductive drums 2030a, 2030b, 2030c, and 2030d at a position opposite to the optical scanning device 2010. Further, the outer surface of the transfer belt 2040 comes into contact with the transfer roller 2042.

  Here, an image (toner image) to which toner adheres on the surface of each photosensitive drum 2030 moves in the direction of the transfer belt 2040 as the photosensitive drum 2030 rotates. The yellow, magenta, cyan, and black toner images are sequentially transferred onto the transfer belt 2040 at a predetermined timing, and are superimposed to form a color image. The color image formed on the transfer belt 2040 moves in the direction of the transfer roller 2042 as the transfer belt 2040 moves.

  The paper feed tray 2060 stores recording paper. In the vicinity of the paper feed tray 2060, a paper feed roller 2054 is disposed. The paper supply roller 2054 takes out the recording paper one by one from the paper supply tray 2060 and conveys it to the registration roller pair 2056.

  The registration roller pair 2056 sends the recording paper toward the gap between the transfer belt 2040 and the transfer roller 2042 at a predetermined timing. As a result, the color image on the transfer belt 2040 is transferred to the recording paper. The recording sheet transferred here is sent to the fixing roller 2050.

  The fixing roller 2050 applies heat and pressure to the recording paper. Thereby, the fixing roller 2050 can fix the toner on the recording paper. The recording paper on which the toner is fixed is sent to a paper discharge tray 2070 via a paper discharge roller 2058 and is sequentially stacked on the paper discharge tray 2070.

  Each cleaning unit 2031 removes toner (residual toner) remaining on the surface of the corresponding photosensitive drum 2030. The surface of the photosensitive drum 2030 from which the residual toner has been removed returns to the position facing the corresponding charging device 2032 again.

  The density detector 2245 is disposed on the −X side of the transfer belt 2040 (a position upstream of the fixing roller 2050 in the traveling direction of the transfer belt 2040 and downstream of the four photosensitive drums 2030). . As an example, the density detector 2245 includes three optical sensors 2245a, 2245b, and 2245c, as shown in FIG.

  The optical sensor 2245a is disposed at a position facing the vicinity of the −Y side end in the effective image area of the transfer belt 2040 (one end side in the width direction of the transfer belt 2040). The optical sensor 2245c is disposed at a position facing the vicinity of the + Y side end in the effective image area of the transfer belt 2040 (the other end in the width direction of the transfer belt 2040). The optical sensor 2245b is disposed at a substantially central position between the optical sensor 2245a and the optical sensor 2245c (a central position in the width direction of the transfer belt 2040) in the main scanning direction. Here, regarding the main scanning direction (Y-axis direction), the center position of the optical sensor 2245a is Y1, the center position of the optical sensor 2245b is Y2, and the center position of the optical sensor 2245c is Y3.

  Each of the optical sensors 2245a, 2245b, 2245c, as an example, as shown in FIG. 3, emits light (hereinafter also referred to as detection light) toward the transfer belt 2040, the transfer belt 2040, or the transfer. A specular reflection light receiving element 12 that receives specular reflection light from the toner pad on the belt 2040; and a diffuse reflection light receiving element 13 that receives diffuse reflection light from the transfer belt 2040 or the toner pad on the transfer belt 2040. Yes. Each light receiving element outputs a signal (photoelectric conversion signal) corresponding to the amount of received light.

  The home position sensor 2246a detects a rotation home position in the photosensitive drum 2030a. The home position sensor 2246b detects the home position of rotation in the photosensitive drum 2030b. The home position sensor 2246c detects the home position of rotation in the photosensitive drum 2030c. The home position sensor 2246d detects the rotation home position in the photosensitive drum 2030d.

  FIG. 4 is a diagram illustrating a configuration of an optical system of the optical scanning device 2010. FIG. 5 is a diagram illustrating an example of an optical path from the light source 2200 a to the polygon mirror 2104 and an optical path from the light source 2200 b to the polygon mirror 2104. FIG. 6 is a diagram illustrating an example of an optical path from the light source 2200c to the polygon mirror 2104 and an optical path from the light source 2200d to the polygon mirror 2104. FIG. 7 is a diagram illustrating an example of an optical path from the polygon mirror 2104 to each photosensitive drum 2030.

  Next, the configuration of the optical system of the optical scanning device 2010 will be described. The optical scanning device 2010 includes four light sources 2200a, 2200b, 2200c, and 2200d (referred to as a light source 2200 when four are collectively referred to), four coupling lenses 2201a, 2201b, 2201c, and 2201d as an optical system. There are four aperture plates 2202a, 2202b, 2202c, 2202d and four cylindrical lenses 2204a, 2204b, 2204c, 2204d. Further, the optical scanning device 2010 includes a polygon mirror 2104, four scanning lenses 2105a, 2105b, 2105c, and 2105d as optical systems, and six folding mirrors 2106a, 2106b, 2106c, 2106d, 2108b, and 2108c. These are assembled at predetermined positions of the optical housing.

  The optical scanning device 2010 also has an electric circuit, which will be described in FIG.

  Each of the light sources 2200a, 2200b, 2200c, and 2200d includes a surface emitting laser array in which a plurality of light emitting units are two-dimensionally arranged. The plurality of light emitting units of the surface emitting laser array are arranged so that the intervals between the light emitting units are equal when all the light emitting units are orthogonally projected onto a virtual line extending in the sub-scanning corresponding direction. Each of the light sources 2200a, 2200b, 2200c, and 2200d is, for example, a vertical cavity surface emitting laser (VCSEL).

  The coupling lens 2201a is disposed on the optical path of the light beam emitted from the light source 2200a, and the light beam passing through the coupling lens 2201a is a substantially parallel light beam. The coupling lens 2201b is disposed on the optical path of the light beam emitted from the light source 2200b, and the light beam passing through the coupling lens 2201b is a substantially parallel light beam. The coupling lens 2201c is disposed on the optical path of the light beam emitted from the light source 2200c, and the light beam passing through the coupling lens 2201c is a substantially parallel light beam. The coupling lens 2201d is disposed on the optical path of the light beam emitted from the light source 2200d, and makes the passing light beam a substantially parallel light beam.

  The aperture plate 2202a has an aperture and shapes the light beam that has passed through the coupling lens 2201a. The aperture plate 2202b has an aperture and shapes the light beam that has passed through the coupling lens 2201b. The aperture plate 2202c has an aperture and shapes the light beam that has passed through the coupling lens 2201c. The aperture plate 2202d has an aperture and shapes the light beam that has passed through the coupling lens 2201d.

  The cylindrical lens 2204 a forms an image of the light beam that has passed through the opening of the aperture plate 2202 a in the vicinity of the deflection reflection surface of the polygon mirror 2104 in the Z-axis direction. The cylindrical lens 2204b forms an image of the light beam that has passed through the opening of the aperture plate 2202b in the vicinity of the deflection reflection surface of the polygon mirror 2104 in the Z-axis direction. The cylindrical lens 2204 c forms an image of the light beam that has passed through the opening of the aperture plate 2202 c in the vicinity of the deflection reflection surface of the polygon mirror 2104 in the Z-axis direction. The cylindrical lens 2204d forms an image of the light flux that has passed through the opening of the aperture plate 2202d in the vicinity of the deflection reflection surface of the polygon mirror 2104 in the Z-axis direction.

  An optical system including the coupling lens 2201a, the aperture plate 2202a, and the cylindrical lens 2204a is a pre-deflector optical system of the K station. An optical system including the coupling lens 2201b, the aperture plate 2202b, and the cylindrical lens 2204b is a pre-deflector optical system of the C station. An optical system including the coupling lens 2201c, the aperture plate 2202c, and the cylindrical lens 2204c is a pre-deflector optical system of the M station. An optical system including the coupling lens 2201d, the aperture plate 2202d, and the cylindrical lens 2204d is a pre-deflector optical system of the Y station.

  The polygon mirror 2104 has a four-stage mirror having a two-stage structure that rotates around an axis parallel to the Z axis, and each mirror serves as a deflecting reflection surface. In the first-stage (lower) tetrahedral mirror, the light beam from the cylindrical lens 2204b and the light beam from the cylindrical lens 2204c are respectively deflected. In the second-stage (upper) tetrahedral mirror, the light beam from the cylindrical lens 2204a and The light beams from the cylindrical lens 2204d are arranged so as to be deflected.

  Further, the light beams from the cylindrical lens 2204a and the cylindrical lens 2204b are deflected to the −X side of the polygon mirror 2104, and the light beams from the cylindrical lens 2204c and the cylindrical lens 2204d are deflected to the + X side of the polygon mirror 2104. .

  Each scanning lens 2105 a, 2105 b, 2105 c, 2105 d has an optical power for condensing the light beam in the vicinity of the corresponding photosensitive drum 2030, and the surface of the corresponding photosensitive drum 2030 as the polygon mirror 2104 rotates. The optical spot has an optical power that moves at a constant speed in the main scanning direction.

  The scanning lens 2105 a and the scanning lens 2105 b are disposed on the −X side of the polygon mirror 2104. The scanning lens 2105c and the scanning lens 2105d are disposed on the + X side of the polygon mirror 2104.

  The scanning lens 2105a and the scanning lens 2105b are stacked in the Z-axis direction. The scanning lens 2105b faces the first-stage four-sided mirror. The scanning lens 2105a faces the second-stage four-sided mirror.

  The scanning lens 2105c and the scanning lens 2105d are stacked in the Z-axis direction. The scanning lens 2105c faces the first-stage four-sided mirror. The scanning lens 2105d faces the second-stage four-sided mirror.

  The light beam from the cylindrical lens 2204a deflected by the polygon mirror 2104 is irradiated onto the photosensitive drum 2030a through the scanning lens 2105a and the folding mirror 2106a, thereby forming a light spot. This light spot moves in the longitudinal direction of the photosensitive drum 2030a as the polygon mirror 2104 rotates. That is, the light spot scans on the photosensitive drum 2030a. The moving direction of the light spot at this time is the “main scanning direction” on the photosensitive drum 2030a, and the rotational direction of the photosensitive drum 2030a is the “sub-scanning direction” on the photosensitive drum 2030a.

  The light beam from the cylindrical lens 2204b deflected by the polygon mirror 2104 is irradiated onto the photosensitive drum 2030b through the scanning lens 2105b, the folding mirror 2106b, and the folding mirror 2108b, thereby forming a light spot. This light spot moves in the longitudinal direction of the photosensitive drum 2030b as the polygon mirror 2104 rotates. That is, the light spot scans on the photosensitive drum 2030b. The moving direction of the light spot at this time is the “main scanning direction” on the photosensitive drum 2030b, and the rotational direction of the photosensitive drum 2030b is the “sub-scanning direction” on the photosensitive drum 2030b.

  The light beam from the cylindrical lens 2204c deflected by the polygon mirror 2104 is irradiated onto the photosensitive drum 2030c through the scanning lens 2105c, the folding mirror 2106c, and the folding mirror 2108c, thereby forming a light spot. This light spot moves in the longitudinal direction of the photosensitive drum 2030c as the polygon mirror 2104 rotates. That is, the light spot scans on the photosensitive drum 2030c. The moving direction of the light spot at this time is the “main scanning direction” on the photosensitive drum 2030c, and the rotational direction of the photosensitive drum 2030c is the “sub-scanning direction” on the photosensitive drum 2030c.

  The light beam from the cylindrical lens 2204d deflected by the polygon mirror 2104 is irradiated onto the photosensitive drum 2030d through the scanning lens 2105d and the folding mirror 2106d, thereby forming a light spot. This light spot moves in the longitudinal direction of the photosensitive drum 2030d as the polygon mirror 2104 rotates. That is, this light spot scans on the photosensitive drum 2030d. The moving direction of the light spot at this time is the “main scanning direction” on the photosensitive drum 2030d, and the rotational direction of the photosensitive drum 2030d is the “sub-scanning direction” on the photosensitive drum 2030d.

  Each of the folding mirrors 2106a, 2106b, 2106c, 2106d, 2108b, and 2108c has the same optical path length from the polygon mirror 2104 to the corresponding photosensitive drum 2030, and the incident position of the light beam on the corresponding photosensitive drum 2030. And the incident angles are arranged to be equal to each other.

  An optical system disposed on the optical path between the polygon mirror 2104 and each photosensitive drum 2030 is also called a scanning optical system. Here, the scanning optical system of the K station is composed of the scanning lens 2105a and the folding mirror 2106a. The scanning optical system of the C station is composed of the scanning lens 2105b and the two folding mirrors 2106b and 2108b. The scanning lens 2105c and the two folding mirrors 2106c and 2108c constitute a scanning optical system for the M station. Further, the scanning optical system of the Y station is composed of the scanning lens 2105d and the folding mirror 2106d. In each scanning optical system, the scanning lens 2105 may be composed of a plurality of lenses.

  FIG. 8 is a diagram showing the configuration of the electrical system of the optical scanning device 2010. The optical scanning device 2010 includes an interface unit 3101, an image processing unit 3102, and a drive control unit 3103 as an electric system configuration.

  The interface unit 3101 acquires image data transferred from a higher-level device (for example, a computer) from the printer control device 2090. The interface unit 3101 passes the acquired image data to the subsequent image processing unit 3102.

  In this example, the interface unit 3101 acquires image data in the RGB format, the resolution is 1200 dpi, and the number of bits is 8 bits, and passes it to the image processing unit 3102.

  The image processing unit 3102 functions as an image processing unit. The image processing unit 3102 acquires image data from the interface unit 3101 and converts it into color image data corresponding to the printing method. As an example, the image processing unit 3102 converts RGB format image data into tandem format (CMYK format) image data. Further, the image processing unit 3102 executes various types of image processing in addition to data format conversion.

  In this example, the image processing unit 3102 outputs image data in the CMYK format, the resolution is 2400 dpi, and the number of bits is 1 bit. Note that the resolution of the image data output from the image processing unit 3102 is not limited to 2400 dpi. The resolution of the image data output from the image processing unit 3102 is referred to as the first resolution.

  Further, the image processing unit 3102 generates tag information indicating whether each pixel of the image data of the first resolution (2400 dpi) is a pixel constituting a character or a line. The image processing unit 3102 then passes the generated first resolution image data and tag information to the drive control unit 3103.

  The drive control unit 3103 acquires the first resolution image data and the tag information from the image processing unit 3102 and converts them into color image data of the second resolution corresponding to the light source drive. Note that the second resolution is higher than the first resolution. In this example, the drive control unit 3103 converts the image data into CMYK format, resolution is 4800 dpi, and the number of bits is 1 bit.

  The drive control unit 3103 modulates the second resolution image data into a clock signal indicating the light emission timing of the pixel, and generates an independent modulation signal for each color. Then, the drive control unit 3103 drives the light sources 2200a, 2200b, 2200c, and 2200d according to the modulation signals corresponding to the respective colors to emit light. Note that the drive control unit 3103 may integrally perform the resolution conversion process and the modulation process.

  Further, the drive control unit 3103 is, for example, a single integrated device formed into a single chip provided in the vicinity of the light sources 2200a, 2200b, 2200c, and 2200d. The image processing unit 3102 and the interface unit 3101 are arranged farther from the light sources 2200a, 2200b, 2200c, and 2200d than the drive control unit 3103. The image processing unit 3102 and the drive control unit 3103 are connected by a cable 3104.

  The optical scanning device 2010 having such a configuration can form a latent image by emitting light corresponding to image data from the light sources 2200a, 2200b, 2200c, and 2200d.

  FIG. 9 is a diagram showing the configuration of the interface unit 3101. As an example, the interface unit 3101 includes a flash memory 3211, a RAM 3212, an IF circuit 3213, and a CPU 3214. Flash memory 3211, RAM 3212, IF circuit 3213, and CPU 3214 are each connected by a bus.

  The flash memory 3211 stores a program executed by the CPU 3214 and various data necessary for executing the program by the CPU 3214. The RAM 3212 is a working storage area when the CPU 3214 executes a program. The IF circuit 3213 performs bidirectional communication with the printer control device 2090.

  The CPU 3214 operates according to a program stored in the flash memory 3211 and controls the entire optical scanning device 2010. The interface unit 3101 having such a configuration passes the input image data (RGB format, 1200 dpi, 8 bits) transmitted from the printer control apparatus 2090 to the image processing unit 3102.

  FIG. 10 is a diagram illustrating a configuration of the image processing unit 3102. The image processing unit 3102 includes an attribute separation unit 3220, a color conversion unit 3221, a black generation unit 3222, a gamma correction unit 3223, a position correction unit 3224, a gradation processing unit 3225, and a tag generation unit 3226. .

  The attribute separation unit 3220 receives input image data (RGB format, 1200 dpi, 8 bits) from the interface unit 3101. Here, attribute information is added to each pixel of the input image data. The attribute information indicates the type of object that is the source of the area (pixel). For example, if the pixel is a part of a character, the attribute information indicates an attribute indicating “character”. For example, if the pixel is a part of a line, the attribute information indicates an attribute indicating “line”. If the pixel is a part of a graphic, the attribute information indicates an attribute indicating “graphic”. If the pixel is a part of a photograph, the attribute information indicates an attribute indicating “photo”.

  The attribute separation unit 3220 separates attribute information and image data from the input image data. The attribute separation unit 3220 passes the separated attribute information and image data to the tag generation unit 3226. The attribute separation unit 3220 passes the image data to the color conversion unit 3221. The image data output from the attribute separation unit 3220 is, for example, RGB, 1200 dpi / 8 bits. Further, the attribute information output from the attribute separation unit 3220 is, for example, data having the same resolution (1200 dpi) as the image data and a bit number of 2 bits.

  The color conversion unit 3221 converts 8-bit RGB image data into 8-bit CMY image data. The black generating unit 3222 generates black components from the CMY format image data generated by the color conversion unit 3221 to generate CMYK format image data. The gamma correction unit 3223 linearly converts the level of each color of the CMYK format image data generated by the black generation unit 3222 using a table or the like.

  The position correction unit 3224 receives the image data from the gamma correction unit 3223 and removes noise or distortion. Further, the position correction unit 3224 performs image position correction by scaling or shifting. At this time, the position correction unit 3224 converts the resolution of 1200 dpi to 2400 dpi. Then, the position correction unit 3224 outputs 2400 dpi (first resolution) CMYK format image data in which one pixel is represented by a plurality of bits (8 bits in this example).

  The gradation processing unit 3225 receives 2400 dpi, 8-bit CMYK format image data from the position correction unit 3224. The gradation processing unit 3225 generates 1-bit area gradation data from 8-bit image data by performing pseudo-halftone processing by, for example, dither processing or error diffusion processing.

  The tag generation unit 3226 generates tag information representing pixel attributes for each pixel of 1200 dpi image data. In this example, the tag generation unit 3226 generates tag information indicating whether or not the pixel constitutes a character or a line.

  As an example, the tag generation unit 3226 generates tag information based on the attribute information. In this example, the tag generation unit 3226 assigns tag information indicating a character or line to a pixel to which attribute information indicating a character or line is added.

  Tag information generated by the tag generation unit 3226 is passed to the drive control unit 3103 via the position correction unit 3224 and the gradation processing unit 3225. Here, the position correction unit 3224 performs the same process on the tag information as the process of increasing the resolution of image data from 1200 dpi to 2400 dpi and the process of correcting the position of the image data. Accordingly, the position correction unit 3224 can increase the resolution of the tag information from 1200 dpi to 2400 dpi, and assign the tag information to each pixel after the resolution is increased.

  The gradation processing unit 3225 transmits the 1-bit image data with the first resolution (2400 dpi) and the 1-bit tag information with the first resolution (2400 dpi) to the drive control unit 3103, respectively. Note that the gradation processing unit 3225 may transmit, to the drive control unit 3103, 2-bit data having a first resolution (2400 dpi) in which the upper bits represent image data (CMYK) and the lower bits represent tag information.

  As described above, the image processing unit 3102 can generate tag information associated with each pixel of image data of the first resolution (2400 dpi) and transmit the tag information to the drive control unit 3103. The image processing unit 3102 may be partly or entirely realized by hardware, or may be realized by a CPU executing a software program.

  FIG. 11 is a diagram illustrating a configuration of the drive control unit 3103. The drive control unit 3103 includes a clock generation unit 3232, a modulation unit 3233, and a light source drive unit 3234.

  The clock generation unit 3232 generates a clock signal indicating the light emission timing of the pixel. The clock signal is a signal that can modulate image data with a resolution corresponding to the second resolution (4800 dpi).

  The modulation unit 3233 obtains first resolution image data and tag information from the image processing unit 3102. Then, the modulation unit 3233 converts the first resolution image data into the second resolution image data higher than the first resolution based on the first resolution image data and the tag information. In this example, the modulation unit 3233 generates CMYK format, 4800 dpi, 1-bit image data based on the CMYK format, 2400 dpi, 1-bit image data and tag information. Then, the modulation unit 3233 modulates such second resolution image data into a clock signal, and generates a modulation signal for forming a 4800 dpi image. Further, the modulation unit 3233 generates light amount data representing the amount of light emitted from the light source 2200 for each pixel of the second resolution based on the image data of the first resolution and the tag information.

  The light source driving unit 3234 receives a modulation signal and light amount data corresponding to the second resolution image data. The light source driving unit 3234 drives the corresponding light sources 2200a, 2200b, 2200c, and 2200d in accordance with the modulation signals independent from each other for each color output from the modulation unit 3233. Furthermore, the light source driving unit 3234 changes the amount of current for causing the corresponding light sources 2200a, 2200b, 2200c, and 2200d to emit light in accordance with each independent light amount data output from the modulation unit 3233. As a result, the light source driving unit 3234 can cause each of the light sources 2200a, 2200b, 2200c, and 2200d to emit light with the light amount indicated in the light amount data at the timing according to the modulation signal.

  FIG. 12 is a diagram illustrating a configuration of the modulation unit 3233. The modulation unit 3233 includes a resolution conversion unit 3241, a pulse generation unit 3242, an applied current setting unit 3243, and a mode setting unit 3244. The modulation unit 3233 (resolution conversion unit 3241, pulse generation unit 3242, applied current setting unit 3243, and mode setting unit 3244) and the light source driving unit 3234 are integrated in a single integrated device.

  Based on the first resolution image data and tag information output from the image processing unit 3102, the resolution conversion unit 3241 generates second resolution image data and light amount pattern data from the first resolution image data. The pulse generation unit 3242 generates a modulation signal which is an on / off modulation signal corresponding to the image data, based on the second resolution image data generated by the resolution conversion unit 3241. Further, the pulse generation unit 3242 generates a power modulation control signal based on the light amount pattern data generated by the resolution conversion unit 3241. Based on the power modulation control signal, the applied current setting unit 3243 generates light amount data representing the amount of current that flows to each light source (2200a, 2200b, 2200c, 2200d).

  The resolution conversion unit 3241 includes a buffer memory unit 3251, a pattern matching unit 3252, an image / light quantity pattern generation unit 3253, a pixel conversion unit 3254, and a first switching unit 3255.

  The buffer memory unit 3251 receives 2400 dpi / 1-bit image data and tag information sent from the image processing unit 3102 and accumulates image data and tag information for a plurality of main scanning lines. The buffer memory unit 3251 passes the accumulated image data and tag information to the downstream side in response to reading from the downstream data processing unit (here, the pattern matching unit 3252 and the pixel conversion unit 3254). At this stage, the image data has the first resolution (2400 dpi / 1 bit). The image data and tag information output from the buffer memory unit 3251 are input to the pattern matching unit 3252 and the pixel conversion unit 3254.

  The pattern matching unit 3252 pattern-matches image data and tag information corresponding to 2400 dpi / 1-bit image dots with image processing target pixels using an image matrix. In this case, the pattern matching unit 3252 performs pattern matching by specifying a necessary image area from the image attributes indicated in the tag information, and whether the characteristic image area matches each preset pattern. Is detected. Here, the attribute of the image is, for example, a character, a photograph, or a figure. Thereafter, the pattern matching unit 3252 outputs a matching signal indicating which pattern is matched to the image / light quantity pattern generation unit 3253. Further, the pattern matching unit 3252 outputs an enable signal that is asserted when matching with any pattern to the first switching unit 3255.

  The image / light quantity pattern generation unit 3253 outputs the second resolution image data specified based on the matching signal from the pattern matching unit 3252 to the first switching unit 3255. Further, the image / light quantity pattern generation unit 3253 outputs the light quantity pattern data specified based on the matching signal from the pattern matching unit 3252 to the pulse generation unit 3242. The light quantity pattern data is data indicating a pixel that modulates the light quantity at the second resolution.

  The pixel conversion unit 3254 divides each pixel of the image data output from the buffer memory unit 3251 into, for example, 2 × 2 pixels and increases the resolution to the second resolution (for example, 4800 dpi). The pixel conversion unit 3254 outputs the second resolution image data to the first switching unit 3255.

  The first switching unit 3255 selects either the second resolution image data output from the pixel conversion unit 3254 or the second resolution image data output from the pattern matching unit 3252. The first switching unit 3255 selects the image data of the second resolution output from the pattern matching unit 3252 when an enable signal that is asserted when matching with any pattern is input. The first switching unit 3255 selects the second resolution image data output from the pixel conversion unit 3254 when no enable signal is input.

  The pulse generation unit 3242 generates a modulation signal that is a signal for turning on / off according to the image data of the second resolution, and a power modulation control signal that is a signal for switching the applied current.

  More specifically, the pulse generation unit 3242 modulates the second resolution image data output from the resolution conversion unit 3241 into a clock signal to generate a modulation signal. In the modulation signal, for example, the on period indicates a period during which the light source 2200 emits light, and the off period indicates a period during which the light source 2200 is turned off. The pulse generation unit 3242 generates a power modulation control signal by modulating the light amount pattern data into a clock signal. The power modulation control signal is used by the applied current setting unit 3243 to select reference light amount data and high light amount data. The power modulation control signal indicates, for example, a period in which the light source 2200 emits light with a high light amount during an on period, and a period during which the light source 2200 emits light with a reference light amount.

  The applied current setting unit 3243 includes a reference light amount setting unit 3261, a power modulation current setting unit 3262, a power modulation value holding unit 3263, and a second switching unit 3264. The applied current setting unit 3243 outputs light amount data that is switched according to the power modulation control signal generated by the pulse generation unit 3242. Thereby, the applied current setting unit 3243 can perform applied current modulation (power modulation) for switching the exposure intensity.

  The reference light amount setting unit 3261 generates preset reference light amount data. The power modulation current setting unit 3262 generates high light amount data obtained by scaling the reference light amount data generated by the reference light amount setting unit 3261. The power modulation current setting unit 3262 holds the scaling factor in the power modulation current setting unit 3262. The reference light amount data generated by the reference light amount setting unit 3261 and the high light amount data generated by the power modulation current setting unit 3262 are output to the second switching unit 3264.

  The second switching unit 3264 selects one of the reference light amount data and the high light amount data based on the power modulation control signal from the pulse generation unit 3242. The second switching unit 3264 outputs the selected one of the reference light amount data or the high light amount data to the light source driving unit 3234 as the light amount data.

  Then, the light source drive unit 3234 in the subsequent stage corresponds to each light source (2200a, 2200b) according to the light amount data (current setting value) from the second switching unit 3264 and the modulation signal (on / off modulation signal) from the pulse generation unit 3242. 2200c, 2200d).

  The mode setting unit 3244 accepts the setting of the normal mode or the high quality mode from the interface unit 3101 prior to the printing operation. When the normal mode is set, the mode setting unit 3244 causes the second switching unit 3264 to fix the switching operation so that the reference light amount data output from the reference light amount setting unit 3261 is continuously selected. Thereby, in the normal mode, the second switching unit 3264 outputs light amount data indicating the reference light amount. Further, when the high-quality mode is set, the mode setting unit 3244 causes the second switching unit 3264 to perform a switching operation according to the power modulation control signal.

  Such a mode setting unit 3244 can fix the light amount emitted from the light source 2200 to the reference light amount in the normal mode. On the other hand, the mode setting unit 3244 can emit light from the light source 2200 by switching the reference light amount and the high light amount in units of pixels in the high quality mode.

  In addition, when the mode is set to the normal mode, the mode setting unit 3244 causes the first switching unit 3255 to fix the switching operation so that the second resolution image data converted by the pixel conversion unit 3254 is continuously selected. . The mode setting unit 3244 causes the first switching unit 3255 to perform a switching operation according to the enable signal when the high-quality mode is set.

  In the normal mode, the mode setting unit 3244 can cause the first switching unit 3255 to fix and output the second resolution image data having a higher resolution in units of pixels. On the other hand, in the high-definition mode, the mode setting unit 3244 causes the first switching unit 3255 to change the resolution of the second resolution image data that has been increased in pixel units and the second resolution that has been increased in resolution by replacing the pattern in units of regions. The resolution image data can be switched and output.

  The modulation unit 3233 having such a configuration can convert the image data of the first resolution into the image data of the second resolution and can perform image processing on the edge of the character or the line. For example, the modulation unit 3233 can thin a character or line, or can thicken a white character or line.

  Furthermore, the modulation unit 3233 can increase the amount of light for forming pixels at the edge portion of the character or line in units of pixels of the second resolution image data. As a result, the modulation unit 3233 can print the edge portion of the character or line with high quality.

  FIG. 13 is a diagram illustrating the configuration of the light source driving unit 3234 together with the light source 2200. The light source drive unit 3234 includes a current source 3271, a lighting switch 3272, and a DA converter 3273.

  The current source 3271 supplies the current set by the DA converter 3273 to the corresponding light source 2200. The lighting switch 3272 switches whether or not to supply current to the light source 2200 at the timing of the modulation signal received from the modulation unit 3233. Specifically, the lighting switch 3272 causes the current of the current source 3271 to flow through the light source 2200 at the generation timing of the modulation signal pulse. Accordingly, the lighting switch 3272 can cause the light source 2200 to emit light at the timing of the modulation signal pulse (timing for forming a black pixel).

  The DA converter 3273 receives light amount data from the modulation unit 3233. The DA converter 3273 DA converts the received light quantity data and provides an analog current signal to the current source 3271. The current source 3271 passes a current proportional to the amount of current supplied from the DA converter 3273 to the light source 2200. Therefore, the DA converter 3273 can control the light amount of the light source 2200 according to the light amount data.

  As described above, the light source driving unit 3234 can turn on the light source 2200 by using the modulation signal corresponding to the second resolution image data generated by the modulation unit 3233. At the same time, the light source driving unit 3234 can control the light amount of the light source 2200 according to the light amount data selected according to the light amount pattern data generated by the modulating unit 3233.

  The light source driving unit 3234 may include a second switching unit 3264 included in the modulation unit 3233 instead of the modulation unit 3233. In this case, the modulation unit 3233 receives the power modulation control signal, the reference light amount data, and the high light amount data from the modulation unit 3233 instead of the light amount data.

<Specific examples of processing contents of each part>
Hereinafter, the processing content of each unit will be described with reference to specific image data and the like.

  FIG. 14 is a diagram illustrating an example of a target area detected by pattern matching. As an example, the pattern matching unit 3252 stores pixel data representing an edge and a pattern of tag information in advance. Then, the pattern matching unit 3252 matches these patterns with the input first resolution image data and tag information.

  If the input first resolution image data and tag information match any of a plurality of patterns stored in advance, the pattern matching unit 3252 has a predetermined attribute (for example, a character or a line) in the matched area. Is determined to be included. Then, as illustrated in FIG. 14, the pattern matching unit 3252 detects a target region (an edge portion of a predetermined attribute (for example, a character or a line)) in the input first resolution image data based on the matched pattern.

  FIG. 15 is a diagram illustrating an example of resolution conversion processing for each pixel by the pixel conversion unit 3254. The pixel conversion unit 3254 increases the resolution of the input first resolution image data for each pixel, and generates second resolution image data. As an example, the pixel conversion unit 3254 divides a pixel into two in the main scanning direction and the sub-scanning direction of 2400 dpi image data, and generates 4800 dpi image data.

  More specifically, as shown in FIG. 15A, the pixel conversion unit 3254 includes four black pixels each having the first resolution, each including two pixels in the main scanning direction and the sub-scanning direction. Conversion to black pixels of the second resolution. Note that the pixel conversion unit 3254 converts one black pixel having the first resolution to another pixel having four second resolution pixels such as a pattern having three black pixels and one white pixel. You may convert into a pattern.

  Further, as shown in FIG. 15B, the pixel conversion unit 3254 has four second resolutions each composed of two pixels in the main scanning direction and the sub-scanning direction, for each white pixel having the first resolution. Convert to white pixels. Note that the pixel conversion unit 3254 may convert one white pixel having the first resolution into another pattern including four pixels having the second resolution.

  FIG. 16 is a diagram illustrating an example of image data in the target area and light amount pattern data in the target area.

  The image / light quantity pattern generation unit 3253 generates second resolution image data in the target area detected by the pattern matching unit 3252. As an example, the image / light quantity pattern generation unit 3253 previously stores image data of the second resolution of the target area in association with each pattern. Then, the image / light quantity pattern generation unit 3253 selects and outputs the second resolution image data corresponding to the matched pattern.

  As an example, the image / light quantity pattern generation unit 3253 generates image data of the second resolution that thins the black portion in the target area, as shown in FIG. That is, the image / light quantity pattern generation unit 3253 generates second-resolution image data having a pixel arrangement that widens the white area and narrows the black area at the edge. As a result, the image / light quantity pattern generation unit 3253 can make the edge portion in the region of a predetermined attribute such as a character or a line thinner in units of pixels of the second resolution.

  The image / light quantity pattern generation unit 3253 generates second resolution light quantity pattern data in the target area detected by the pattern matching unit 3252. As an example, the image / light quantity pattern generation unit 3253 stores light quantity pattern data of the second resolution of the target region in advance corresponding to each pattern. Then, the image / light quantity pattern generation unit 3253 selects and outputs the light quantity pattern data of the second resolution corresponding to the matched pattern.

  As an example, as shown in FIG. 16B, the image / light quantity pattern generation unit 3253 generates light quantity pattern data of the second resolution so that the black portion (exposure area) in the target area has a high light quantity. That is, the image / light quantity pattern generation unit 3253 generates second resolution light quantity pattern data for increasing the light quantity of the black region adjacent to the edge after the edge is narrowed. As a result, the image / light quantity pattern generation unit 3253 can expose an edge portion in a predetermined attribute area such as a character or a line with a large light quantity in units of pixels of the second resolution.

  FIG. 17 is a diagram illustrating an example of second-resolution image data. The first switching unit 3255 selects and outputs the second resolution image data generated by the image / light quantity pattern generation unit 3253 in the target region, and the second conversion unit 3254 converted by the pixel conversion unit 3254 in the region other than the target region. Select and output resolution image data. As a result, as shown in FIG. 17, the first switching unit 3255 can generate image data of the second resolution by combining the image data of the target area and the image data of the area other than the target area. Then, the pulse generation unit 3242 modulates the clock signal with the image data of the second resolution synthesized in this way to generate a modulation signal.

  FIG. 18 is a diagram illustrating an example of the light quantity pattern data of the second resolution. The second switching unit 3264 switches and outputs the high light amount data or the reference light amount data based on the power modulation control signal corresponding to the second resolution light amount pattern data generated by the image / light amount pattern generating unit 3253 in the target region. . The second switching unit 3264 selects and outputs the reference light amount data output from the reference light amount setting unit 3261 in the region other than the target region. As a result, as shown in FIG. 18, the second switching unit 3264 uses the pattern in which the high light amount and the reference light amount are switched according to the light amount pattern data for the target region, and sets the reference light amount for regions other than the target region. The light amount data can be output by the fixed pattern.

<Effect>
FIG. 19 is a diagram illustrating a conversion example when the resolution of 2400 dpi image data representing a rectangular black region is increased to 4800 dpi image data.

  In the color printer 2000 according to this embodiment, the image processing unit 3102 generates first-resolution image data and transmits it to the drive control unit 3103 via the cable 3104. Thus, according to the color printer 2000, the amount of data transferred from the image processing unit 3102 to the drive control unit 3103 can be reduced.

  Further, the drive control unit 3103 performs printing by converting image data having a first resolution (for example, 2400 dpi) into image data having a second resolution (for example, 4800 dpi). In this case, the drive control unit 3103 matches the image data of the first resolution and the tag information with a predetermined pattern, and detects a target region that is an edge region of a predetermined attribute (for example, a character or a line). . Then, the drive control unit 3103 replaces the target area with the image data of the second resolution determined corresponding to the matched pattern.

  Accordingly, the drive control unit 3103 converts the image data of the first resolution (2400 dpi) having the shape as shown in FIG. 19A to the second resolution (4800 dpi) as shown in FIG. 19B, for example. ) Can be converted into image data of the second resolution (4800 dpi) in which the edge portion is narrowed in pixel units.

  In particular, since the drive control unit 3103 generates image data in units of detected target areas, the edge can be narrowed regardless of the main scanning direction and the sub-scanning direction, and an arbitrary number of pixels of the second resolution can be obtained. Edges can be narrowed in units.

  Furthermore, the drive control unit 3103 changes the light amount of the light source 2200 in units of the detected target area. For example, as shown in FIG. 19B, the drive control unit 3103 can cause the light source 2200 to emit light with a light amount larger than the reference light amount at the pixel at the edge portion of the predetermined attribute (character or line).

  FIG. 20 is a diagram illustrating an example of the waveform of the reference light amount and the developing electric field formed with this waveform. In the normal mode, assume that image data of a line having a width of 4 pixels at 2400 dpi is input to the drive control unit 3103. In this case, the light source driving unit 3234 causes the light source 2200 to emit light with a waveform as shown in FIG. 20A (reference light amount, for example, 4 pixels of 2400 dpi), and forms a developing electric field on the photosensitive drum 2030. .

  When the photosensitive drum 2030 is exposed with the waveform shown in FIG. 20A, the developing electric field formed on the photosensitive drum 2030 gradually changes at the edge portion as shown in FIG. For this reason, the distance Δl of the weak electric field region (region between E1 and E2) where the toner adhesion is unstable becomes long. Therefore, in the normal mode, the color printer 2000 has uneven toner adhesion and cannot print characters and lines clearly.

  FIG. 21 is a diagram showing an example of a waveform in which the edge portion has a high light amount and the other portion has a reference light amount, and a developing electric field formed with this waveform. Assume that line data having a width of 4 pixels at 2400 dpi is input to the drive control unit 3103 in the high quality mode. In this case, the light source driving unit 3234 narrows the line width as shown in FIG. 21A, and causes the light source 2200 to emit light with a waveform having a high light amount at the edge portion and a reference light amount at the other portion. Then, a developing electric field is formed on the photosensitive drum 2030.

  When the photosensitive drum 2030 is exposed to the waveform shown in FIG. 21A, the edge of the developing electric field formed on the photosensitive drum 2030 becomes steep as shown in FIG. Therefore, the distance Δl ′ of the weak electric field region (region between E1 and E2) where toner adhesion is unstable can be shortened. Accordingly, in the high-quality mode, the color printer 2000 can reduce unevenness in toner adhesion, improve density stability, and print characters and line edges clearly.

  FIG. 22 is a diagram comparing the waveform of the normal light amount with the waveform obtained by narrowing the edge portion and increasing the light amount of the edge portion. Since the light source driving unit 3234 increases the amount of light while reducing the line width, the total amount of exposure energy does not increase significantly. Accordingly, in the high quality mode, the color printer 2000 can print characters and lines with appropriate exposure energy.

  For example, as shown in FIG. 22, the image / light quantity pattern generation unit 3253 reduces the integral light quantity of the target region when the light source 2200 emits light with the reference light quantity without reducing the exposure part, The second resolution image data in the target area may be generated such that the integrated light amount when the light source 2200 emits light with the same light amount is the same. Thereby, the light source driving unit 3234 can print characters and lines without changing the total amount of exposure energy.

  FIG. 23 is a diagram showing an edge region when the line is thinned at 1200 dpi. FIG. 24 is a diagram showing an edge region when it is thinned at 4800 dpi.

  When the thinning is performed at 1200 dpi (FIG. 23) and the thinning is performed at 4800 dpi (FIG. 24), an image can be printed with a finer shape when the thinning is performed at the second resolution. . Furthermore, since the area | region which makes a high light quantity can also be set in the unit of 2nd resolution, exposure energy can also be adjusted appropriately and a character and a line can be printed more clearly.

  The above-described embodiment of the present invention has been presented as an example, and is not intended to limit the scope of the invention. The embodiment can be implemented in various other forms, and can be omitted, replaced, or changed as appropriate.

2000 Color Printer 2010 Optical Scanning Device 2030a, 2030b, 2030c, 2030d Photosensitive Drum 2031a, 2031b, 2031c, 2031d Cleaning Unit 2032a, 2032b, 2032c, 2032d Charging Device 2033a, 2033b, 2033c, 2033d Developing Roller 2034a, 2034b, 2034d 2034d Toner cartridge 2040 Transfer belt 2042 Transfer roller 2050 Fixing roller 2054 Paper feed roller 2056 Registration roller pair 2058 Paper discharge roller 2060 Paper feed tray 2070 Paper discharge tray 2080 Communication control device 2090 Printer control device 2104 Polygon mirrors 2105a, 2105b, 2105c, 2105d Scanning lenses 2106a, 2106b, 2106 , 2106d, 2108b, 2108c Folding mirrors 2200a, 2200b, 2200c, 2200d Light sources 2201a, 2201b, 2201c, 2201d Coupling lenses 2202a, 2202b, 2202c, 2202d 2246b, 2246c, 2246d Home position sensor 3101 Interface unit 3102 Image processing unit 3103 Drive control unit 3211 Flash memory 3212 RAM
3213 IF circuit 3214 CPU
3220 attribute separation unit 3221 color conversion unit 3222 black generation unit 3223 gamma correction unit 3224 position correction unit 3225 gradation processing unit 3226 tag generation unit 3232 clock generation unit 3233 modulation unit 3234 light source drive unit 3241 resolution conversion unit 3242 pulse generation unit 3243 application Current setting unit 3244 Mode setting unit 3251 Buffer memory 3252 Pattern matching unit 3253 Image / light quantity pattern generation unit 3254 Pixel conversion unit 3255 First switching unit 3261 Reference light quantity setting unit 3262 Power modulation current setting unit 3263 Power modulation value holding unit 3264 Second Switching unit 3271 Current source 3272 Lighting switch 3273 DA converter

Japanese Patent No. 4968902 Japanese Patent No. 4640257

Claims (12)

An image forming apparatus that forms an image according to light emitted from a light source,
An image processing unit that generates tag information representing attributes for each pixel of the first resolution image data and the first resolution image data based on the input image data;
A modulation unit that converts the image data of the first resolution into image data of a second resolution higher than the first resolution, and generates a modulation signal according to the image data of the second resolution;
A light source driving unit for driving the light source by the modulation signal;
With
The modulator is
A pattern matching unit that matches the image data of the first resolution and the tag information with a predetermined pattern to detect a target region that is an edge portion of a predetermined attribute;
An image pattern generation unit configured to generate image data of the second resolution of the target area, which is defined corresponding to a matched pattern;
A light amount pattern generating unit that generates light amount pattern data of the second resolution of the target area, which is determined corresponding to a matched pattern;
Have
The light source driving unit turns on the light source by the modulation signal corresponding to the image data of the second resolution, and controls the light amount of the light source according to the light amount pattern data. The modulator is
A pixel conversion unit that converts the image data of the first resolution into the image data of the second resolution for each pixel of the first resolution;
The second resolution image data generated by the image pattern generation unit or the second resolution image data converted by the pixel conversion unit is switched and output for each pixel of the second resolution. A switching unit;
A pulse generation unit that modulates a clock signal with the image data of the second resolution output from the first switching unit and outputs the modulation signal;
Further comprising
The first switching unit includes:
In the target area, output the second resolution image data generated by the image pattern generation unit,
The image forming apparatus according to claim 1, wherein the image data of the second resolution converted by the pixel conversion unit is output in an area that is not the target area. A reference light amount pattern output unit that outputs the light amount pattern data indicating the reference light amount;
A second switching unit that switches and outputs the light amount pattern data generated by the light amount pattern generation unit or the light amount pattern data output by the reference light amount pattern output unit for each pixel of the second resolution;
Further comprising
The second switching unit is
In the target area, output the light amount pattern data generated by the light amount pattern generation unit,
The image forming apparatus according to claim 1, wherein the light amount pattern data output by the reference light amount pattern output unit is output in a region that is not the target region. The light amount pattern data is data indicating, for each pixel of the second resolution, whether the light source emits light with the reference light amount or whether the light source emits light with a light amount higher than the reference light amount. Image forming apparatus. The modulator is
A light amount data holding unit for holding light amount data representing the reference light amount;
A multiplier for generating light amount data representing the high light amount by multiplying a light amount data representing the reference light amount by a predetermined magnification;
A selector that selects the light amount data held by the light amount data holding unit or the light amount data generated by the multiplication unit according to the light amount pattern data;
Further comprising
The selector is
At the timing when the reference light amount is indicated in the light amount pattern data, the light amount data held by the light amount data holding unit is selected and output,
At the timing when the high light amount is indicated in the light amount pattern data, the light amount data output by the multiplication unit is selected and output,
The image forming apparatus according to claim 4, wherein the light source driving unit controls a light amount of the light source according to the light amount data output from the selector. The image pattern generator generates the second resolution image data in which an exposed portion is made thinner than the first resolution image data,
The image forming apparatus according to claim 5, wherein the light quantity pattern generation unit generates the light quantity pattern data in which the exposed portion has the high light quantity. The image pattern generator emits the light source with the integrated light amount of the target area when the light source emits light with the reference light amount without thinning the exposed portion, and the high light amount with the exposed portion thinned. The image forming apparatus according to claim 6, wherein second-resolution image data is generated in the target area so that the integrated light quantity in the case is the same. The said image processing part produces | generates the said tag information which shows whether it is a pixel of the attribute which comprises a character or a line for every pixel of the image data of said 1st resolution. The image forming apparatus described in 1. The image forming apparatus according to claim 8, wherein the image pattern generation unit generates the second resolution image data in which a character or line edge is thinned. The image forming apparatus according to claim 8, wherein the image pattern generation unit generates the image data of the second resolution in which a white part of a white character or a line is thickened. The image forming apparatus according to claim 1, wherein the modulation unit and the light source driving unit are integrated in a single integrated device. The image forming apparatus according to claim 1, wherein the light source is a vertical cavity surface emitting laser.

Images