JP6724705B2 - Image forming apparatus and image forming method - Google Patents

Description

The present invention relates to an image forming apparatus and an image forming method.

In recent years, a digital printing machine using an electrophotographic process has been actively used in the production printing field. Therefore, a digital printing machine using an electrophotographic process is required to have high image quality and high reliability. In particular, a digital printing machine using an electrophotographic process is required to improve the reproducibility of fine lines, improve the reproducibility of characters, and suppress the thickening of characters due to the electrophotographic process.

Therefore, the image forming apparatus implements high resolution and thinning/whitening and thickening based on the image data and tag information indicating whether or not each pixel forms a character or a line portion, and transfers the image. The quality of characters and lines is improved without increasing the amount of data.

The image processing device described in Patent Document 1 generates a raster image, increases the resolution, and then executes the thinning process a plurality of times. Then, the image processing apparatus described in Patent Document 1 switches the data obtained by performing the thinning once or the data obtained twice based on the tag information set according to the original line width in the selection unit. ing.

However, the image processing apparatus described in Patent Document 1 has a problem in that processing such as anti-jaggies for improving the quality of halftone characters or halftone lines is not performed.

The present invention has been made in view of the above, and an image capable of improving the quality of halftone characters or halftone lines while maintaining high resolution of solid or white letters or lines. An object is to provide a forming apparatus.

In order to solve the above-mentioned problems and to achieve the object, the present invention is an image forming apparatus for forming an image according to light emitted from a light source, wherein the image data of the first resolution is based on the input image data. And tag information indicating whether or not each pixel of the image data of the first resolution is a pixel forming a character or a line, and using the tag information as a character in the image data of the first resolution. Alternatively, an image processing unit that allocates information indicating the character or the line to pixels that form an edge portion of a line, and a conversion target pixel is sequentially selected from target pixels included in the image data of the first resolution, A resolution conversion unit that converts the image data of the first resolution into image data of a second resolution higher than the first resolution for each pixel to be converted, and the light source by a modulation signal according to the image data of the second resolution. And a light source driving section for driving the light source driving section, wherein the resolution conversion section obtains image data of the first resolution and an image matrix which is the tag information in an area including the target pixel and pixels around the target pixel. an image matrix acquiring unit, based on the arrangement of the first resolution image data and the tag information of the said image in a matrix, the target pixel is a pixel constituting the edge portion, and the character or the line The type is solid, in the case of any one of white or halftone, the pattern matching unit that determines that the target pixel is the conversion target pixel, the conversion target pixel , based on the tag information, A first conversion unit for converting the image data of the second resolution having a first arrangement pattern determined according to the arrangement and the type.

According to the present invention, it is possible to improve the quality of halftone characters or halftone lines while maintaining high resolution of solid or white letters or lines.

FIG. 1 is a diagram showing a schematic configuration of a color printer according to an embodiment. FIG. 2 is a diagram showing an example of the arrangement of optical sensors. FIG. 3 is a diagram showing the configuration of the optical sensor. FIG. 4 is a diagram showing a configuration of an optical system of the optical scanning device. FIG. 5 is a diagram showing an example of an optical path from the first light source to the polygon mirror and an optical path from the second light source to the polygon mirror. FIG. 6 is a diagram showing an example of the optical path from the third light source to the polygon mirror and the optical path from the fourth light source to the polygon mirror. FIG. 7 is a diagram showing an example of optical paths from the polygon mirror to the respective photosensitive drums. FIG. 8 is a block diagram exemplifying a configuration of an optical scanning device that controls a light source. FIG. 9 is a block diagram schematically showing the configuration of the light source modulation signal generation unit. FIG. 10 is a diagram showing the configuration of the high resolution image processing unit. FIG. 11 is a diagram showing the arrangement of bits before and after the resolution conversion of image data and tag information. FIG. 12 is a diagram showing the configuration of the resolution conversion unit. FIG. 13 is a diagram showing target pixels of the first resolution, image data of the second resolution after conversion into the normal pattern, and tag information. FIG. 14 is a diagram showing an example of an edge portion of a halftone character/line. FIG. 15 is a diagram showing an example of an edge portion of a solid character/line. FIG. 16 is a diagram showing an example of an edge portion of an outline character/line. FIG. 17 is a diagram showing an example of the image matrix. FIG. 18 is a diagram for explaining a first example of conversion target pixels. FIG. 19 is a diagram for explaining a first conversion example of conversion target pixels. FIG. 20 is a diagram showing characters before and after conversion when the first conversion example shown in FIG. 19 is applied. FIG. 21 is a diagram for explaining the second conversion example of the conversion target pixel. 22 is a diagram showing characters before and after conversion when the second conversion example shown in FIG. 21 is applied. FIG. 23 is a diagram for explaining a second example of conversion target pixels. FIG. 24 is a diagram for explaining a third conversion example of conversion target pixels. FIG. 25 is a diagram showing characters before and after conversion when the third conversion example shown in FIG. 24 is applied. FIG. 26 is a diagram for explaining a third example of conversion target pixels. FIG. 27 is a diagram for explaining a fourth conversion example of conversion target pixels. FIG. 28 is a diagram showing characters before and after conversion when the fourth conversion example shown in FIG. 27 is applied. FIG. 29 is a diagram for explaining the fifth conversion example of conversion target pixels. FIG. 30 is a diagram showing a high resolution conversion example for halftone characters having a low area ratio. FIG. 31 is a diagram for explaining the edge portion emphasis process for a halftone character having a high area ratio. FIG. 32 is a diagram showing an example of high resolution conversion for halftone characters having a high area ratio.

Embodiments of an image forming apparatus and an image forming method will be described in detail below with reference to the accompanying drawings. In this embodiment, a color printer 2000, which is an example of an image forming apparatus, will be described.

(Embodiment)
FIG. 1 is a diagram showing a schematic configuration of a color printer according to an embodiment. A color printer 2000, which is an example of an image forming apparatus, produces a printed matter 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 photoconductor drums 2030a, 2030b, 2030c, and 2030d (the four photoconductor drums 2030 are collectively referred to), and four cleaning units 2031a, 2031b, and 2031c. , 2031d (four are collectively referred to as a cleaning unit 2031) and four charging devices 2032a, 2032b, 2032c, 2032d (four are collectively referred to as a charging device 2032). Further, the color printer 2000 includes four developing rollers 2033a, 2033b, 2033c, and 2033d (when the four are collectively referred to as developing roller 2033), four toner cartridges 2034a, 2034b, 2034c, and 2034d (four When collectively referred to, it is 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 ejection roller 2058, a paper feed tray 2060, and a paper ejection tray 2070. A communication control device 2080, a density detector 2245, four home position sensors 2246a, 2246b, 2246c, 2246d (when the four are collectively referred to as home position sensor 2246), a printer control device 2090. Prepare

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

The printer control device 2090 centrally controls each unit included in the color printer 2000. The printer control device 2090 includes a CPU (Central Processing Unit), a ROM (Read Only Memory) that stores a program described by a code executed by the CPU and various data used when the program is executed, and a work memory. It has a RAM (Random Access Memory) that is a memory, an AD conversion circuit that converts analog data into digital data, and the like. Then, the printer control device 2090 controls each unit according to a request from the host device and sends image data from the host device to the optical scanning device 2010.

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

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

The photoconductor drum 2030c, the charging device 2032c, the developing roller 2033c, the toner cartridge 2034c, and the cleaning unit 2031c are used as one set. These form an image forming station (sometimes called an M station) that forms a magenta image.

The photoconductor drum 2030d, the charging device 2032d, the developing roller 2033d, the toner cartridge 2034d, and the cleaning unit 2031d are used as one set. These form an image forming station (sometimes referred to as a Y station) that forms a yellow image.

Each of the photoconductor drums 2030 is an example of a latent image carrier, and each has a photosensitive layer formed on its surface. That is, the surface of each photoconductor drum 2030 is a surface to be scanned. The photosensitive drums 2030a, 2030b, 2030c, and 2030d are arranged such that their rotation axes are parallel to each other, and 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, the direction parallel to the central axis of each photoconductor drum 2030 is the Y-axis direction, and the direction along the arrangement direction of each photoconductor drum 2030 is the X-axis direction. ..

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

By the way, in each photoconductor drum 2030, the area in which the image data is written is called an “effective scanning area”, an “image forming area”, an “effective image area”, or the like.

Black toner is stored in the toner cartridge 2034a. The black toner is supplied to the developing roller 2033a. Cyan toner is stored in the toner cartridge 2034b. The cyan toner is supplied to the developing roller 2033b. Magenta toner is stored in the toner cartridge 2034c. The magenta toner is supplied to the developing roller 2033c. Yellow toner is stored in the toner cartridge 2034d. The yellow toner is supplied to the developing roller 2033d.

The toner from the corresponding toner cartridge 2034 is thinly and uniformly applied to the surface of each developing roller 2033 as the developing roller 2033 rotates. Then, when the toner on the surface of each developing roller 2033 comes into contact with the surface of the corresponding photoconductor drum 2030, the toner moves to only the light-irradiated portion of this surface and adheres thereto. That is, each developing roller 2033 attaches toner to the latent image formed on the surface of the corresponding photoconductor drum 2030 to visualize the latent image.

The transfer belt 2040 is stretched around a belt rotating mechanism and rotates in a fixed direction. The outer surface of the transfer belt 2040 contacts the surface of each of the photoconductor drums 2030a, 2030b, 2030c, and 2030d at a position opposite to the optical scanning device 2010. The outer surface of the transfer belt 2040 contacts the transfer roller 2042.

Here, the image (toner image) to which the toner is attached on the surface of each photoconductor drum 2030 moves toward the transfer belt 2040 as the photoconductor drum 2030 rotates. Then, the toner images of yellow, magenta, cyan, and black are sequentially transferred onto the transfer belt 2040 at a predetermined timing, and are overlaid to form a color image. The color image formed on the transfer belt 2040 moves toward the transfer roller 2042 as the transfer belt 2040 moves.

Recording paper is stored in the paper feed tray 2060. A paper feed roller 2054 is arranged near the paper feed tray 2060. The paper feed roller 2054 takes out the recording paper one by one from the paper feed tray 2060 and conveys it to the pair of registration rollers 2056.

The pair of registration rollers 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 paper transferred here is sent to the fixing roller 2050.

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

Each cleaning unit 2031 removes the toner (residual toner) remaining on the surface of the corresponding photoconductor drum 2030. The surface of the photoconductor 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 arranged 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 photoconductor drums 2030). .. As an example, the concentration detector 2245 has three optical sensors 2245a, 2245b, 2245c as shown in FIG. FIG. 2 is a diagram showing an example of the arrangement of optical sensors.

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

FIG. 3 is a diagram showing the configuration of the optical sensor. As shown in FIG. 3, each of the optical sensors 2245a, 2245b, and 2245c emits light (hereinafter, also referred to as detection light) toward the transfer belt 2040, the transfer belt 2040, or the transfer belt 2040. A specular reflection light receiving element 12 for receiving specular reflection light from the toner pad on the belt 2040 and a diffuse reflection light receiving element 13 for receiving diffuse reflection light from the transfer belt 2040 or the toner pad on the transfer belt 2040 are provided. There is. Each of the light receiving elements outputs a signal (photoelectric conversion signal) according to the amount of received light.

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

FIG. 4 is a diagram showing a configuration of an optical system of the optical scanning device. FIG. 5 is a diagram showing an example of an optical path from the first light source to the polygon mirror and an optical path from the second light source to the polygon mirror. FIG. 6 is a diagram showing an example of the optical path from the third light source to the polygon mirror and the optical path from the fourth light source to the polygon mirror. FIG. 7 is a diagram showing an example of optical paths from the polygon mirror to the respective photosensitive drums.

Next, the configuration of the optical system of the optical scanning device 2010 will be described. The optical scanning device 2010 has, as an optical system, four light sources 2200a, 2200b, 2200c, 2200d that are first to fourth light sources, four coupling lenses 2201a, 2201b, 2201c, 2201d, and four aperture plates 2202a. , 2202b, 2202c, 2202d and four cylindrical lenses 2204a, 2204b, 2204c, 2204d. Further, the optical scanning device 2010 has a polygon mirror 2104, four scanning lenses 2105a, 2105b, 2105c, 2105d, and six folding mirrors 2106a, 2106b, 2106c, 2106d, 2108b, 2108c as an optical system. These are assembled in a predetermined position of the optical housing.

The optical scanning device 2010 also has an electric circuit, but the electric circuit will be described with reference to FIG. 8 and subsequent figures.

Each of the light sources 2200a, 2200b, 2200c, 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 such that the intervals between the light emitting units are equal when all the light emitting units are orthographically projected on a virtual line extending in the sub-scanning corresponding direction. Each of the light sources 2200a, 2200b, 2200c, 2200d is, for example, a vertical cavity surface emitting laser (VCSEL).

The coupling lens 2201a is arranged on the optical path of the light beam emitted from the light source 2200a that is the first light source, and makes the passing light beam a substantially parallel light beam. The coupling lens 2201b is arranged on the optical path of the light flux emitted from the light source 2200b which is the second light source, and makes the light flux passing therethrough into a substantially parallel light flux. The coupling lens 2201c is arranged on the optical path of the light beam emitted from the light source 2200c that is the third light source, and makes the passing light beam a substantially parallel light beam. The coupling lens 2201d is arranged on the optical path of the light beam emitted from the light source 2200d that is the fourth light source, and makes the passing light beam a substantially parallel light beam.

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

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

The 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. The 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. The 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. The 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-sided mirror having a two-stage structure that rotates around an axis parallel to the Z axis, and each mirror serves as a deflective reflection surface. The light flux from the cylindrical lens 2204b and the light flux from the cylindrical lens 2204c are respectively deflected by the first (lower) four-sided mirror, and the light flux from the cylindrical lens 2204a and the light flux from the cylindrical lens 2204c are deflected by the second (upper) four-sided mirror. The light beams from the cylindrical lens 2204d are arranged to be deflected.

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

The respective scanning lenses 2105a, 2105b, 2105c, 2105d are arranged on the surface of the corresponding photoconductor drum 2030 in accordance with the optical power for condensing the light flux near the corresponding photoconductor drum 2030 and the rotation of the polygon mirror 2104. It has optical power such that the light spot moves in the main scanning direction at a constant speed.

The scanning lens 2105a and the scanning lens 2105b are arranged on the −X side of the polygon mirror 2104. The scanning lens 2105c and the scanning lens 2105d are arranged 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 flux from the cylindrical lens 2204a deflected by the polygon mirror 2104 is irradiated onto the photosensitive drum 2030a via the scanning lens 2105a and the folding mirror 2106a, and a light spot is formed. This light spot moves in the longitudinal direction of the photoconductor drum 2030a as the polygon mirror 2104 rotates. That is, this light spot scans 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 rotating direction of the photosensitive drum 2030a is the “sub scanning direction” on the photosensitive drum 2030a.

Further, the light flux from the cylindrical lens 2204b deflected by the polygon mirror 2104 is irradiated on the photoconductor drum 2030b via the scanning lens 2105b, the folding mirror 2106b and the folding mirror 2108b, and a light spot is formed. This light spot moves in the longitudinal direction of the photosensitive drum 2030b as the polygon mirror 2104 rotates. That is, this light spot scans the photosensitive drum 2030b. The movement direction of the light spot at this time is the “main scanning direction” on the photoconductor drum 2030b, and the rotation direction of the photoconductor drum 2030b is the “sub-scanning direction” on the photoconductor drum 2030b.

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

Further, the light flux from the cylindrical lens 2204d deflected by the polygon mirror 2104 is irradiated onto the photosensitive drum 2030d via the scanning lens 2105d and the folding mirror 2106d, and a light spot is formed. This light spot moves in the longitudinal direction of the photoconductor drum 2030d as the polygon mirror 2104 rotates. That is, this light spot scans the photosensitive drum 2030d. The movement direction of the light spot at this time is the “main scanning direction” on the photoconductor drum 2030d, and the rotation direction of the photoconductor drum 2030d is the “sub-scanning direction” on the photoconductor drum 2030d.

The respective folding mirrors 2106a, 2106b, 2106c, 2106d, 2108b, 2108c have the same optical path length from the polygon mirror 2104 to the corresponding photoconductor drum 2030, and the incident position of the light flux on the corresponding photoconductor drum 2030. And the respective incident angles are equal to each other.

The optical system arranged on the optical path between the polygon mirror 2104 and each photoconductor drum 2030 is also called a scanning optical system. Here, the scanning optical system of the K station is configured by the scanning lens 2105a and the folding mirror 2106a. Further, 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 the scanning optical system of the M station. Further, the scanning lens 2105d and the folding mirror 2106d constitute a scanning optical system of the Y station. In each scanning optical system, the scanning lens 2105 may be composed of a plurality of lenses.

The color printer 2000 of the present embodiment detects an edge portion of a character or a line using pattern matching and tag information. Then, when the resolution of the edge portion of a character or a line is increased, the color printer 2000 adds the conventional thinning of a solid character and thickening of an outline character to the edge portion of a halftone character and a halftone line. Is emphasized. As a result, the color printer 2000 improves the quality of halftone characters and lines while thinning solid characters and thickening white characters. Note that the edge portion in the present embodiment may be within a region that forms a character or line, or may be a boundary region between a region that forms a character or line and a region that does not. In other words, the edge portion in the present embodiment may or may not include a region that does not form a character or a line in a part thereof.

FIG. 8 is a block diagram exemplifying a configuration of an optical scanning device that controls a light source. An optical scanning device 2010, which is a light source control system, includes an interface unit 3022, an image processing unit (IPU) 3023, and a light source drive control device 3024.

The interface unit 3022 is connected to the printer control device 2090 and sends image data and the like from the printer control device 2090 to the image processing unit 3023. The image processing unit 3023 executes various kinds of image processing on the image data, and sends the area gradation data and tag information which are the execution results to the light source drive control device 3024. The light source drive control device 3024 controls each of the light sources 2200a to 2200d based on the area gradation data and the tag information.

The image processing unit 3023 functions as an image processing unit that performs various image processes (first image process) on input image data that is high resolution and multi-bit data of, for example, 2400 dpi (dots per inch).

The interface unit 3022 has a CPU 3210, a flash memory 3211, a RAM 3212, and an IF (interface) circuit 3214. It should be noted that the arrows in FIG. 8 show typical signal and information flows, and do not show all the connection relationships of the blocks.

The IF circuit 3214 is a communication interface that controls bidirectional communication with the printer control device 2090. The image data from the host device is supplied to the image processing unit 3023 and the like via the IF circuit 3214.

The flash memory 3211 stores various programs described by codes that can be read by the CPU 3210 and various data necessary for executing the programs. The RAM 3212 is a working memory.

The CPU 3210 operates according to a program stored in the flash memory 3211 and controls the entire optical scanning device 2010.

The image processing unit 3023 includes an attribute separation unit 3215, a color conversion unit 3216, a black generation unit 3217, a γ correction unit 3218, a pseudo halftone processing unit 3219, and a tag generation unit 3226.

The attribute separation unit 3215 is connected to the interface unit 3022 and receives image data from the interface unit 3022. The attribute separation unit 3215 performs appropriate processing set for each attribute, such as text of pixels forming a character portion, line of pixels forming a line drawing, and image of bitmap data. The image data is separated for each attribute so that can be executed. The attribute separation unit 3215 sends the separated image data to the color conversion unit 3216 and the tag generation unit 3226.

The color conversion unit 3216 converts the RGB (Red, Green, Blue) image data into CMY (Cyan, Magenta, Yellow) data which is a color reproduction color in the color printer 2000. The color conversion unit 3216 sends the image data converted into CMY data to the black generation unit 3217.

The black generation unit 3217 extracts a black component from the image data converted into CMY, determines a CMY color after that, and finally converts it into CMYK (Cyan, Magenta, Yellow, Key Plate) data. The black generation unit 3217 sends the image data converted into CMYK data to the γ correction unit 3218.

The γ correction unit 3218 performs gradation correction according to the output characteristics of the color printer 2000 for each CMYK. The γ correction unit 3218 uses a binary or multi-valued dither matrix for each CMYK to change the number of pixels and the value in a certain area so as to have a continuous gradation of a halftone dot or line structure. .. The γ correction unit 3218 sends the CMYK data that has undergone the gradation correction to the pseudo halftone processing unit 3219.

The tag generation unit 3226 generates tag information (tag bit) indicating whether or not each pixel of the 1200 dpi image data is a pixel forming a character or a line. The tag generation unit 3226, as an example, generates tag information based on the attribute information. In this example, the tag generation unit 3226 assigns tag information indicating a character or a line to a pixel to which attribute information indicating a character or a line is added. The tag generation unit 3226 sends the generated tag information to the pseudo halftone processing unit 3219.

The pseudo halftone processing unit 3219 receives, for example, 1200 dpi, 8-bit CMYK format image data from the γ correction unit 3218. The pseudo halftone processing unit 3219 generates 2400 dpi, 1-bit area gradation data from 1200 dpi, 8-bit image data by performing pseudo-halftone processing such as dither processing or error diffusion processing. Further, in the present embodiment, the pseudo halftone processing unit 3219 also increases the resolution of the tag information from 1200 dpi to 2400 dpi, and the edge portion of the character or line of 5 dots of each pixel after the resolution is increased by the gradation processing. Only assign tag information. The pseudo halftone processing unit 3219 sends the area gradation data and the tag information for 5 dots to the light source drive control device 3024 (light source modulation signal generation unit 3222).

The light source drive control device 3024 includes a light source modulation signal generation unit 3222, a pixel clock generation unit 3223, and a light source drive unit 3224.

The pixel clock generation unit 3223 generates a pixel clock signal and sends it to the light source modulation signal generation unit 3222.

The light source modulation signal generation unit 3222 generates a signal for driving each of the light sources 2200a, 2200b, 2200c, 2200d. More specifically, the light source modulation signal generation unit 3222 divides the data transferred at the N resolution into the main scanning direction and the sub scanning direction, and increases the resolution to M (M>N). Further, the light source modulation signal generation unit 3222 obtains the writing start timing for each image forming station based on the output signal of the synchronization detection sensor.

Then, the light source modulation signal generation unit 3222 superimposes the dot data of each light emitting unit of each light source 2200a to 2200d on the pixel clock signal from the pixel clock generation unit 3223 at the same time as the writing start timing, and at the same time, the image processing unit. Based on information from 3023 and the like, independent modulation data is generated for each light emitting unit. Further, the light source modulation signal generation unit 3222 thins or thickens the image by lighting control, as will be described later. The light source modulation signal generation unit 3222 sends each modulation data to the light source driving unit 3224.

The light source drive unit 3224 is connected to each of the light sources 2200a to 2200d. The light source drive unit 3224 outputs a drive signal for each light emitting unit to each of the light sources 2200a to 2200d according to each modulation data from the light source modulation signal generation unit 3222.

FIG. 9 is a block diagram schematically showing the configuration of the light source modulation signal generation unit. The light source modulation signal generation unit 3222 includes a high resolution image processing unit 101, a pulse generation unit 102, and an applied current setting unit 103. The light source modulation signal generation unit 3222 (the high resolution image processing unit 101, the pulse generation unit 102, the applied current setting unit 103) and the light source drive unit 3224 are integrated as a light source drive control device 3024 in a single integrated device. There is.

The high resolution image processing unit 101 sequentially selects target pixels from the image data (first resolution image data) based on the image data (first resolution image data) output from the image processing unit 3023. The high-resolution image processing unit 101 sets the image data of the first resolution higher than the first resolution when the sequentially selected target pixels are pixels forming the edge portion (end portion, contour portion) of the halftone character. The image data of the resolution (image data of the second resolution) is converted and processed (second image processing). The high resolution image processing unit 101 sends the image data of the second resolution to the pulse generation unit 102. In this way, the high resolution image processing unit 101 receives the image data of the first resolution, and the high resolution image processing unit 101 outputs the image data of the second resolution. In other words, in the high resolution image processing unit 101, the image data of the first resolution is the input data and the image data of the second resolution is the output data.

The pulse generation unit 102 serially converts the image data (image information) of the second resolution and outputs it as a light source modulation pulse signal (on/off modulation signal) to the light source drive unit 3224. Here, the light source modulation pulse signal is a serial signal, and the H period and the L period indicate on/off and switching timing as they are. In this way, the pulse generation unit 102 generates the modulated pulse signal by modulating the image data of the second resolution into a clock signal and converting the level into a level according to the characteristics of the light sources 2200a to 2200d. The pulse generator 102 outputs the light source modulation pulse signal to the light source driver 3224.

The applied current setting unit 103 outputs a current setting value (light source applied current data) to be supplied to the light sources 2200a to 2200d to the light source driving unit 3224. The light source driving unit 3224 drives each of the light sources 2200a to 2200d according to the light source applied current data (current setting value) and the light source modulation pulse signal (ON/OFF modulation signal) from the pulse generation unit 102.

The light source modulation signal generation unit 3222 may be realized using a program and a processor such as a CPU. In this case, the CPU executes the process of the light source modulation signal generation unit 3222 using the program stored in the ROM.

FIG. 10 is a diagram showing the configuration of the high resolution image processing unit. The high resolution image processing unit 101 includes a buffer memory 3251 and a resolution conversion unit 3252, and generates a modulation signal.

The buffer memory 3251 stores 2-bit data (upper bits are image data (CMYK)) and lower bits are tag information of the first resolution (2400 dpi) sent from the image processing unit 3023. The buffer memory 3251 passes the accumulated image data and tag information to the resolution conversion unit 3252 according to the reading from the resolution conversion unit 3252 at the subsequent stage.

The resolution conversion unit 3252 converts the image data of the first resolution and the tag information stored in the buffer memory 3251 into the image data and the tag information of the second resolution (4800 dpi/1 bit equivalent) higher than the first resolution. In the present embodiment, the resolution conversion unit 3252 converts the data in the main scanning direction to 2400 dpi/4 bits (the upper bits are image data (CMYK), the lower bits are tag information) and the sub scanning direction is 4800 dpi/1 bit. To do.

The resolution conversion unit 3252 sequentially selects target pixels from the image data of the first resolution, and executes resolution conversion processing for each target pixel. The resolution conversion unit 3252 sends the converted second resolution image data to the pulse generation unit 102.

FIG. 11 is a diagram showing the arrangement of bits before and after the resolution conversion of image data and tag information. FIG. 11 shows the bit arrangement of the image data and the tag information of the first resolution (2400 dpi) before the resolution conversion and the arrangement of the image data of the second resolution (4800 dpi) and the bit of the tag information after the resolution conversion. ..

The image data of the first resolution which is the input image data is, for example, 2400 dpi/2 bits in the main scanning direction and 2400 dpi in the sub scanning direction. Here, the image data of the first resolution is indicated by "bit1", and the tag information of the first resolution is indicated by "bit0".

The high resolution image processing unit 101 performs a process of converting the image data of the first resolution into the image data of the second resolution which is higher than the first resolution. In the present embodiment, the second resolution is twice the resolution of the first resolution, and the high resolution image processing unit 101 converts, for example, image data from 2400 dpi to 4800 dpi.

The image data of the second resolution which is the output image data is, for example, 2400 dpi/4 bits in the main scanning direction and 4800 dpi in the sub scanning direction. Here, the image data of the second resolution is shown by "bit2" and "bit3", and the tag information of the first resolution is shown by "bit0" and "bit1".

FIG. 12 is a diagram showing the configuration of the resolution conversion unit. The resolution conversion unit 3252 includes an image matrix acquisition unit 3261, a pattern matching unit 3262, a first conversion unit 3263, a second conversion unit 3264, and a selector 3265.

The image matrix acquisition unit 3261 detects the image matrix from the buffer memory 3251. The image matrix is image data of the first resolution and tag information in a region including the target pixel and pixels around the target pixel. For example, the image matrix is image data of the first resolution and tag information in a rectangular area centered on the target pixel. In the present embodiment, the image matrix is image data of the first resolution and tag information in a 9×9 pixel area centered on the target pixel. The image matrix acquisition unit 3261 sends the image matrix to the pattern matching unit 3262, and sends the target pixel to the second conversion unit 3264.

The pattern matching unit 3262 determines whether or not the target pixel is a pixel forming an edge portion of a character or a line based on the arrangement of the image data and the tag information in the image matrix. Pixels forming the edge portion are pixels near the boundary between the black pixel and the white pixel. For example, the pixels forming the edge portion are pixels within a certain range from the boundary between the black pixel and the white pixel.

For example, the pattern matching unit 3262 determines that the target pixel is the conversion target pixel if the arrangement of the image data and the tag information in the image matrix matches any of a plurality of patterns registered in advance. To do. The conversion target pixel here is a solid character/line (solid character, solid line), a white character/line (white character, white line), a halftone character/line (halftone character, halftone line). Is a pixel that constitutes one of the edge portions. That is, the conversion target pixel is a pixel (a pixel included in any) that constitutes any of the following (a) to (f). In other words, the conversion target pixels are some of the following pixels (a) to (f).
(A) Edge part of solid character (b) Edge part of solid line (c) Edge part of white character (d) Edge part of white line (e) Edge part of halftone character (f) ) Edge part of halftone line As described above, in the pattern matching part 3262, the target pixel is a pixel forming the edge part of a character or line, and the type of character or line is solid, white or intermediate. If it is one of the tones, the target pixel is determined as the conversion target pixel and is extracted.

On the other hand, the pattern matching unit 3262 determines that the target pixel is not the conversion target pixel if the arrangement of the image data and the tag information in the image matrix does not match any of the plurality of patterns registered in advance. ..

When the pattern matching unit 3262 determines that the target pixel is the conversion target pixel, the pattern matching unit 3262 passes the matching signal for identifying the arrangement of the image data and the tag information in the image matrix to the first conversion unit 3263. In addition, when the pattern matching unit 3262 determines that the target pixel is not the conversion target pixel, the pattern matching unit 3262 does not pass the matching signal to the first conversion unit 3263.

When the target pixel is a conversion target pixel, the first conversion unit 3263 converts the image data and the tag information of the target pixel into the image data and the tag information of the second resolution of the pattern determined corresponding to the arrangement in the image matrix. Convert to. As described above, when the target pixel is a conversion target pixel, the first conversion unit 3263 converts the image data and tag information of the target pixel into image data and tag information having a predetermined pattern. In the present embodiment, the first conversion unit 3263 outputs data of 2400 dpi/4 bits in the main scanning direction and 4800 dips/1 bit in the sub scanning direction as the second resolution image data and tag information. In this case, the upper bits are the image data and the lower bits are the tag information.

As an example, the first conversion unit 3263 thins the target pixel by thinning a solid character/line, thickening a white character/line, and thickening a halftone dot at an edge portion of a halftone character/line. The image data to be emphasized and converted into the image data of the second resolution having the pattern (first arrangement pattern) and the tag information. Then, when the conversion is performed, the first conversion unit 3263 sends the pattern subjected to the image processing (image processing pattern) and the enable signal to the selector 3265.

When the target pixel is not the conversion target pixel, the second conversion unit 3264 converts the image data and tag information of the second resolution having a pattern (second arrangement pattern) according to the value (pixel value) of the target pixel. To do. Specifically, the second conversion unit 3264 converts the target pixel into image data of the second resolution and tag information having a pattern (normal pattern) in which image processing is not performed. In the present embodiment, the second conversion unit 3264 outputs data of 2400 dpi/4 bits in the main scanning direction and 4800 dpi/1 bit in the sub scanning direction as the second resolution image data and tag information. In this case, the upper bits are the image data and the lower bits are the tag information. The second conversion unit 3264 sends the normal pattern to the selector 3265.

The selector 3265 receives the image processing pattern and the enable signal from the first conversion unit 3263. Further, the selector 3265 receives the normal pattern from the second conversion unit 3264. The selector 3265 outputs the image processing pattern to the pulse generation unit 102 when the enable signal is received (that is, when the target pixel is a pixel forming an edge portion of a character or a line). Further, when the selector 3265 does not receive the enable signal (that is, the target pixel is not the conversion target pixel), it outputs the normal pattern to the pulse generation unit 102.

The resolution conversion unit 3252 having such a configuration can convert the image data of the first resolution into the image data of the second resolution and can perform the image processing on the edge portion of the character/line. For example, the resolution conversion unit 3252 can thicken and emphasize the halftone dots of the edge portion of the halftone character.

FIG. 13 is a diagram showing target pixels of the first resolution, image data of the second resolution after conversion into the normal pattern, and tag information. FIG. 13 shows target pixels of the first resolution of 2400 dpi, image data of the second resolution of 4800 dpi after conversion to the normal pattern, and tag information of 4800 dpi.

The second conversion unit 3264 converts the target pixel into image data of the second resolution having a pattern corresponding to the value of the target pixel and tag information. For example, when the image data of the target pixel is “0” and the tag information is “0”, the second conversion unit 3264 is a portion of the image data in the main scanning direction, as shown in (A) of FIG. Data in which (higher 2 bits) is "0" and tag information portion (lower 2 bits) is "0" is output.

Further, as shown in FIG. 13B, when the image data of the target pixel is “1” and the tag information is “0”, the second conversion unit 3264 is the portion of the image data in the main scanning direction. Data in which (higher 2 bits) is "1" and tag information portion (lower 2 bits) is "0" is output.

In addition, as shown in (C) of FIG. 13, when the image data of the target pixel is “0” and the tag information is “1”, the second conversion unit 3264 is the portion of the image data in the main scanning direction. Data in which (higher 2 bits) is "0" and tag information portion (lower 2 bits) is "1" is output.

In addition, as shown in (D) of FIG. 13, when the image data of the target pixel is “1” and the tag information is “1”, the second conversion unit 3264 is the portion of the image data in the main scanning direction. Data in which (upper 2 bits) is "1" and the tag information portion (lower 2 bits) is "1" is output.

FIG. 14 is a diagram showing an example of an edge portion of a halftone character/line. FIG. 15 is a diagram showing an example of an edge portion of a solid character/line. FIG. 16 is a diagram showing an example of an edge portion of an outline character/line.

14 to 16 show edge portions of 2400 dpi characters or lines. The image shown in FIG. 14 is an edge portion of a halftone character or an edge portion of a halftone line. Further, the image shown in FIG. 15 is an edge portion of an outline character or an edge portion of an outline line. The image shown in FIG. 16 is an edge portion of a solid character or an edge portion of a white line.

In FIGS. 14 to 16, a black pixel to which tag information is added (black pixel with tag) is indicated by a pixel 200Bt, and a black pixel to which tag information is not added (black pixel without tag) is indicated by a pixel 200Bx. ing. 14 to 16, a white pixel to which tag information is added (white pixel with tag) is shown by a pixel 200Wt, and a white pixel without tag information (white pixel without tag) is shown to a pixel 200Wx. It shows with.

Tag information is added to each pixel in the input image data. For example, in the example of FIG. 14, tag information (Tag bit) indicating that it is the edge portion of a character or a line drawing (line) is added to the pixels of the edge portion 5 dots inside the halftone character (halftone line). ing. In other words, the pixel area corresponding to 5 dots of the edge portion inside the halftone character is the tag information allocation area.

Further, in the example of FIG. 15, tag information (Tag bit) indicating that it is an edge portion of a character or a line drawing (line) is added to pixels corresponding to 5 dots of an edge portion inside a solid character (solid line). In other words, the pixel area corresponding to 5 dots of the edge portion inside the solid character is the tag information allocation area.

In addition, in the example of FIG. 16, tag information (Tag bit) indicating that it is the edge portion of a character or a line drawing (line) is added to the pixels of 5 dots in the edge portion inside the outline character (white line). ing. In other words, the pixel area corresponding to 5 dots of the edge portion inside the outline character is the tag information allocation area.

FIG. 17 is a diagram showing an example of the image matrix. In the present embodiment, as shown in FIG. 17, the image matrix acquisition unit 3261 acquires an image matrix composed of an area of 9×9 pixels (main scanning direction×sub scanning direction) centered on the target pixel. To do.

FIG. 18 is a diagram for explaining a first example of conversion target pixels. Comparing the edge portions of each character (each line) in FIGS. 14 to 16, only the edge portion of the halftone character (halftone line) shown in FIG. 14 has a white pixel (pixel 200Wt) to which tag information is assigned. It is adjacent to the black pixel (pixel 200Bt) to which the tag information is assigned.

Therefore, in the pattern matching unit 3262, as shown in FIG. 18, a white pixel (pixel 200Wt) to which tag information is assigned by pattern matching and a black pixel (pixel 200Bt) to which tag information is assigned are adjacent to each other. White pixels in the area are detected as conversion target pixels 1 and 2.

The conversion target pixel 2 is a white pixel adjacent to the black pixel B1 to which the tag information is assigned, and the conversion target pixel 1 is a white pixel adjacent to the conversion target pixel 2. In this way, the conversion target pixel 2 is arranged between the conversion target pixel 1 and the black pixel B1 to which the tag information is assigned. The first conversion unit 3263 performs conversion as shown in FIG. 19 when converting the detected conversion target pixels 1 and 2 into high resolution.

FIG. 19 is a diagram for explaining a first conversion example of conversion target pixels. When the conversion target pixels 1 and 2 and the black pixel B1 to which the tag information is assigned are lined up in the main scanning direction (horizontal direction), as shown in (a) and (b) of FIG. One pixel is converted into a black pixel (pixel 200Bt) to which tag information is assigned with high resolution.

Further, when the conversion target pixels 1 and 2 and the black pixel B1 to which the tag information is assigned are arranged in the sub-scanning direction (vertical direction), as shown in (c) and (d) of FIG. The three pixels of (3) are converted into black pixels (pixels 200Bt) to which tag information is assigned with high resolution.

Therefore, when the conversion target pixels 1 and 2 and the black pixel B1 shown in (a) to (d) of FIG. 19 are extracted, the first conversion unit 3263 corresponding to the conversion target pixels 1 and 2 of FIG. High resolution conversion as shown in (e) and (f) is executed. Specifically, as illustrated in (e) of FIG. 19, the first conversion unit 3263 converts the conversion target pixel 1 into high resolution conversion into a black pixel (pixel 200Bt) to which tag information is assigned. In addition, the first conversion unit 3263 converts the conversion target pixel 2 into a high resolution black pixel (pixel 200Bt) to which tag information is assigned, as illustrated in (f) of FIG.

FIG. 20 is a diagram showing characters before and after conversion when the first conversion example shown in FIG. 19 is applied. When the first conversion unit 3263 performs high resolution conversion on the halftone character (10 pt, Mincho type) by applying the first conversion example shown in FIG. 19, the character 301A is converted to the character 301B. In this way, the first conversion unit 3263 thickens the halftone dots of the edge portion (where tag information is assigned) of the halftone character. As a result, since the edge portion of the halftone character is emphasized, jaggies at the edge portion can be suppressed and the quality can be improved.

The first conversion unit 3263 may change the processing intensity of the edge enhancement processing between the main scanning direction and the sub scanning direction. In other words, when rearranging the pixel of interest of the first resolution with the pixel of the second resolution, the first conversion unit 3263 determines the processing intensity in the vertical direction (sub-scanning direction) and the horizontal direction (main scanning direction). You can change it.

In addition, the first conversion unit 3263 may switch conversion of the conversion target pixels 1 and 2 (setting of the first arrangement pattern) according to the strength setting of the edge portion emphasis processing. In other words, the first conversion unit 3263 may change how to rearrange the target pixel of the first resolution with the pixel of the second resolution based on the processing intensity switching signal of the edge enhancement processing. .. For example, in the case of suppressing the emphasis of the edge portion more than the conversion shown in FIG. 19, the first conversion unit 3263 performs the high resolution conversion as shown in FIG.

FIG. 21 is a diagram for explaining the second conversion example of the conversion target pixel. When the conversion target pixels 1 and 2 and the black pixel B1 to which the tag information is assigned are lined up in the main scanning direction (horizontal direction), as shown in (a) and (b) of FIG. Two pixels of 1 (pixels that are not adjacent to the conversion target pixel 2) are subjected to high resolution conversion into white pixels to which tag information is not added. Then, the remaining two pixels of the conversion target pixel 1 (pixels adjacent to the conversion target pixel 2), the conversion target pixel 2, and the black pixel B1 to which the tag information is allocated are assigned the tag information. The converted black pixels are converted into high resolution.

Further, when the conversion target pixels 1 and 2 and the black pixel B1 to which the tag information is assigned are arranged in the sub-scanning direction (vertical direction), as shown in (c) and (d) of FIG. Two pixels of the target pixel 1 (pixels that are not adjacent to the conversion target pixel 2) are high-resolution converted into white pixels to which tag information is not added. Then, the remaining two pixels of the conversion target pixel 1 (pixels adjacent to the conversion target pixel 2), the conversion target pixel 2, and the black pixel B1 to which the tag information is allocated are assigned the tag information. The converted black pixels are converted into high resolution.

Therefore, when the conversion target pixels 1 and 2 and the black pixel B1 shown in (a) to (d) of FIG. 21 are extracted, the first conversion unit 3263 corresponding to the conversion target pixels 1 and 2 of FIG. High resolution conversion as shown in (e) and (f) is executed. Specifically, as shown in (e) of FIG. 21, the first conversion unit 3263 performs high resolution conversion on two pixels of the conversion target pixel 1 into white pixels to which tag information is not added, The remaining two pixels of the conversion target pixel 1 are high resolution converted into black pixels to which tag information is assigned. Further, the first conversion unit 3263 performs high resolution conversion of the conversion target pixel 2 into a black pixel to which tag information is assigned, as shown in (f) of FIG.

22 is a diagram showing characters before and after conversion when the second conversion example shown in FIG. 21 is applied. When the first conversion unit 3263 converts the halftone character (10 pt, Mincho type) into high resolution by applying the second conversion example shown in FIG. 21, the character 302A is converted to the character 302B. As a result, the degree of emphasis of the edge portion can be reduced as compared with the example of FIG. In this way, the color printer 2000 can change the settings according to the image forming conditions and preferences.

FIG. 23 is a diagram for explaining a second example of conversion target pixels. Comparing the edge portions of each character (line) in FIGS. 14 to 16, the edge portion of the solid character (solid line) shown in FIG. Are adjacent to the black pixel (pixel 200Bt) to which is assigned.

Therefore, in the pattern matching unit 3262, as shown in FIG. 23, a white pixel (pixel 200Wx) to which tag information is not assigned by pattern matching and a black pixel (pixel 200Bt) to which tag information is assigned are adjacent to each other. The black pixels in the existing area are detected as the conversion target pixels 3 and 4. In this case, the pattern matching unit 3262 sets the black pixels that are continuous to some extent (the black pixels are continuous for a predetermined number or more) as the detection targets of the conversion target pixels 3 and 4. The reason why the black pixels that are continuous to some extent are targeted for detection is to prevent a fine black region from being erased by thinning.

The conversion target pixel 3 is a black pixel adjacent to the white pixel W1 to which no tag information is assigned, and the conversion target pixel 4 is a black pixel adjacent to the conversion target pixel 3. In this way, the conversion target pixel 3 is arranged between the conversion target pixel 4 and the white pixel W1 to which the tag information is not assigned. The first conversion unit 3263 performs conversion as shown in FIG. 24 when performing high resolution conversion on the detected conversion target pixels 3 and 4.

FIG. 24 is a diagram for explaining a third conversion example of conversion target pixels. When the conversion target pixels 3 and 4 and the white pixel W1 to which the tag information is not assigned are lined up in the main scanning direction (horizontal direction), as shown in (a) and (b) of FIG. Two pixels of the pixels 3 (pixels that are not adjacent to the conversion target pixel 4) and the white pixel W1 to which the tag information is not assigned are high-resolution converted to the white pixel to which the tag information is not attached. .. Then, the remaining two pixels of the conversion target pixel 3 (pixels adjacent to the conversion target pixel 4) and the conversion target pixel 4 are high-resolution converted into black pixels to which tag information is assigned.

Further, when the conversion target pixels 3 and 4 and the black pixel B1 to which the tag information is assigned are arranged in the sub-scanning direction (vertical direction), as shown in (c) and (d) of FIG. Two pixels of the target pixels 3 (pixels that are not adjacent to the conversion target pixel 4) and the white pixel W1 to which the tag information is not assigned are high-resolution converted into white pixels to which the tag information is not assigned. It Then, the remaining two pixels of the conversion target pixel 3 (pixels adjacent to the conversion target pixel 4) and the conversion target pixel 4 are high-resolution converted into black pixels to which tag information is assigned.

Therefore, when the conversion target pixels 3 and 4 and the white pixel W1 shown in (a) to (d) of FIG. 24 are extracted, the first conversion section 3263 of the conversion target pixels 3 and 4 of FIG. High resolution conversion as shown in (e) and (f) is executed. Specifically, as shown in (e) of FIG. 24, the first conversion unit 3263 performs high resolution conversion of two pixels of the conversion target pixel 3 into white pixels to which tag information is not added, The remaining two pixels of the conversion target pixel 3 are converted into black pixels to which tag information is assigned with high resolution. Further, the first conversion unit 3263 converts the conversion target pixel 4 into high resolution conversion into a black pixel to which tag information is assigned, as shown in (f) of FIG.

FIG. 25 is a diagram showing characters before and after conversion when the third conversion example shown in FIG. 24 is applied. When the first conversion unit 3263 converts the solid characters (10 pt, Mincho type) into high resolution by applying the third conversion example illustrated in FIG. 24, the characters 303A are converted to the characters 303B. As a result, the edge portion of the solid character is scraped and thinned, so that it is possible to suppress the thickening of the solid character derived from the electrophotography and improve the quality. It should be noted that since there is no edge portion emphasizing pattern implemented for halftone characters in solid characters, only the thinning is performed without being affected by the edge portion emphasizing processing.

FIG. 26 is a diagram for explaining a third example of conversion target pixels. Comparing the edge portions of each character (line) in FIGS. 14 to 16, the edge portion of the white character (white line) shown in FIG. 16 is a white pixel (pixel 200Wt) to which tag information is assigned. It is adjacent to a black pixel (pixel 200Bx) to which tag information is not assigned.

Therefore, in the pattern matching unit 3262, as shown in FIG. 26, a white pixel (pixel 200Wt) to which tag information is assigned by pattern matching and a black pixel (pixel 200Bx) to which tag information is not assigned are adjacent to each other. The black pixels in the existing area are detected as the conversion target pixels 5 and 6.

The conversion target pixel 5 is a black pixel adjacent to the white pixel W1 to which no tag information is assigned, and the conversion target pixel 6 is a black pixel adjacent to the conversion target pixel 5. In this way, the conversion target pixel 5 is arranged between the conversion target pixel 6 and the white pixel W1 to which the tag information is not assigned. The first conversion unit 3263 performs conversion as shown in FIG. 27 when converting the detected conversion target pixels 5 and 6 into high resolution.

FIG. 27 is a diagram for explaining a fourth conversion example of conversion target pixels. When the conversion target pixels 5 and 6 and the white pixel W1 to which the tag information is assigned are lined up in the main scanning direction (horizontal direction), as shown in (a) and (b) of FIG. 5 and the white pixel W1 to which the tag information is assigned are converted by high resolution to the white pixel to which the tag information is assigned. In addition, the conversion target pixel 6 is converted into a black pixel to which no tag information is assigned with high resolution.

Further, when the conversion target pixels 5 and 6 and the white pixel W1 to which the tag information is assigned are arranged in the sub-scanning direction (vertical direction), as shown in (c) and (d) of FIG. The target pixel 5 and the white pixel W1 to which the tag information is assigned are converted into the white pixel to which the tag information is assigned with high resolution. In addition, the conversion target pixel 6 is converted into a black pixel to which no tag information is assigned with high resolution.

Therefore, when the conversion target pixels 5 and 6 and the white pixel W1 shown in (a) to (d) of FIG. 27 are extracted, the first conversion unit 3263 corresponding to the conversion target pixels 5 and 6 of FIG. High resolution conversion as shown in (e) and (f) is executed. Specifically, as shown in (e) of FIG. 27, the first conversion unit 3263 performs high resolution conversion of the conversion target pixel 6 into a black pixel to which tag information is added. Further, the first conversion unit 3263 converts the conversion target pixel 5 into high resolution conversion into white pixels to which tag information is assigned, as shown in (f) of FIG. 27.

Further, as shown in (e) of FIG. 27, the single conversion target pixel 6 is subjected to high resolution conversion into a black pixel to which tag information is not assigned, and the single conversion target pixel 5 is converted to the black pixel of FIG. 27(f). As shown in, the high resolution conversion is performed on the white pixels to which the tag information is assigned.

FIG. 28 is a diagram showing characters before and after conversion when the fourth conversion example shown in FIG. 27 is applied. When the first conversion unit 3263 applies high resolution conversion to white characters (10 pt, Mincho type) by applying the fourth conversion example shown in FIG. 27, the characters 304A are converted to the characters 304B. In this way, the first conversion unit 3263 can improve the quality by expanding the edge portion of the blank character and making it thicker so as to suppress the crushing of the blank character derived from the electrophotography. It should be noted that the outline character does not have a pattern for emphasizing the edge portion performed for the halftone character, and thus is not affected by the edge portion emphasizing processing, and only thickening is performed.

By the way, as shown in FIG. 29, the first conversion unit 3263 simultaneously converts the conversion target pixels 1 and 2 for the halftone character edge portion emphasis processing and the conversion target pixels 3 and 4 for thinning into high resolution. May be.

FIG. 29 is a diagram for explaining the fifth conversion example of conversion target pixels. For example, the first conversion unit 3263 performs high resolution conversion on the pixels by performing edge enhancement processing on the halftone characters of the conversion target pixels 1 and 2 and thinning the conversion target pixels 3 and 4.

For example, when the conversion target pixels 1 and 2 and the black pixel B1 to which tag information is assigned are arranged in the main scanning direction (horizontal direction), as shown in (a) and (b) of FIG. The three pixels of (3) are converted into black pixels (pixels 200Bt) to which tag information is assigned with high resolution.

When the conversion target pixels 1 and 2 and the black pixel B1 to which the tag information is assigned are arranged in the sub-scanning direction (vertical direction), as shown in (c) and (d) of FIG. The three pixels of (3) are converted into black pixels (pixels 200Bt) to which tag information is assigned with high resolution.

Therefore, when the conversion target pixels 1 and 2 and the black pixel B1 shown in (a) to (d) of FIG. 29 are extracted, the first conversion unit 3263 corresponding to the conversion target pixels 1 and 2 of FIG. High resolution conversion as shown in (e) and (f) is executed. Specifically, as shown in (e) of FIG. 29, the first conversion unit 3263 performs high resolution conversion of the conversion target pixel 1 into a black pixel (pixel 200Bt) to which tag information is assigned. Further, the first conversion unit 3263 converts the conversion target pixel 2 into high resolution conversion into a black pixel (pixel 200Bt) to which tag information is assigned, as shown in (f) of FIG.

Further, when the conversion target pixels 3 and 4 and the white pixel W1 to which the tag information is not assigned are lined up in the main scanning direction (horizontal direction), as shown in (g) and (h) of FIG. The conversion target pixel 3 and the white pixel W1 to which the tag information is not assigned are converted to high resolution by conversion to the white pixel to which the tag information is not assigned.

When the conversion target pixels 3 and 4 and the black pixel B1 to which the tag information is assigned are arranged in the sub-scanning direction (vertical direction), conversion is performed as shown in (i) and (j) of FIG. The target pixel 3 and the white pixel W1 to which the tag information is not assigned are converted into high-resolution conversion into the white pixel to which the tag information is not attached.

Therefore, when the conversion target pixels 3 and 4 and the white pixel W1 shown in ((g) to (j) of FIG. 24 are extracted, the first conversion unit 3263 corresponds to the conversion target pixels 3 and 4 and FIG. (K) and (l) of FIG. 29. Specifically, the first conversion unit 3263 converts the conversion target pixel 3 into the tag information as shown in (k) of FIG. The high-resolution conversion is performed on the white pixels to which the tag information is not added, and the first conversion unit 3263 converts the conversion target pixel 4 to the black pixel to which the tag information is assigned with the high resolution as illustrated in (l) of FIG. Convert.

As a result, it is possible to simultaneously perform high resolution conversion on the conversion target pixels 1 and 2 for the edge enhancement processing of halftone characters and the conversion target pixels 3 and 4 for thinning.

FIG. 30 is a diagram showing a high resolution conversion example for halftone characters having a low area ratio. A character 305A shown in FIG. 30 is obtained by performing only the edge portion emphasis process on a halftone character (10 pt, Mincho typeface) having a low halftone dot area ratio. Further, the character 305B shown in FIG. 30 is obtained by performing the edge enhancement processing and the thinning processing on the halftone character (10 pt, Mincho type) having a low halftone dot area ratio. In the present embodiment, the resolution conversion unit 3252 executes the edge enhancement processing and the thinning processing on the halftone character having a low halftone dot area ratio like the character 305B.

When the area ratio of halftone dots is low, it is desired to improve the quality of halftone characters by emphasizing the contour by edge emphasizing processing. On the other hand, in the case of a character having a low area ratio of halftone dots, shaving the edge portion more than necessary in the thinning process lowers the readability. Since the resolution conversion unit 3252 of the present embodiment detects black pixels that are continuous to some extent as a target of thinning processing, edge enhancement is performed while reducing the influence of thinning on halftone characters having a low area ratio. The effect of can be increased.

FIG. 31 is a diagram for explaining the edge portion emphasis process for a halftone character having a high area ratio. A character 306A shown in FIG. 31 is a halftone character (close to a solid character) having a high dot area ratio. The character 306B shown in FIG. 31 is obtained by performing only the edge emphasis processing on the halftone character (character 306A) having a high halftone dot area ratio. Since a halftone character having a high area ratio is close to a solid character, the shape of the character does not change much before and after the edge portion emphasis process, but as with the solid character, thickening of the character may cause a problem.

FIG. 32 is a diagram showing an example of high resolution conversion for halftone characters having a high area ratio. The character 306A shown in FIG. 32 is a halftone character (close to a solid character) having a high dot area ratio. A character 306C shown in FIG. 32 is obtained by performing the edge enhancement processing and the thinning processing on the halftone character (character 306A) having a low halftone dot area ratio.

For halftone characters with a high area ratio, the frequency of continuous black pixels is high, and thinning processing is strongly required. Therefore, the resolution conversion unit 3252 according to the present embodiment executes the edge enhancement processing and the thinning processing on the halftone character having a high halftone dot area ratio like the character 306C.

The image forming apparatus described in the above embodiments may be applied to a multi-function peripheral having at least two functions of a printer function, a copy function, a scanner function and a facsimile function. Further, the image forming apparatus described in the above embodiment can be applied to any image forming apparatus such as a copying machine, a scanner device, and a facsimile device.

Conventionally, with respect to halftone characters and halftone lines, no countermeasures have been taken against problems such as jaggies, and there has been a problem that image quality deteriorates. In the present embodiment, the light source modulation signal generation unit 3222 performs processing for detecting an edge portion of a solid character and thinning it, processing for detecting an edge portion of a blank character and thickening a blank character, and halftone A structure peculiar to a character or a halftone line (adjacent arrangement of white pixels to which tag information is added and black pixels to which tag information is added) is detected. Then, the light source modulation signal generation unit 3222 performs an emphasis process for thickening the halftone dots at the edge portion of the halftone character or the halftone line.

As described above, the resolution conversion unit 3252 according to the present embodiment applies the combination process of the edge enhancement process and the thinning process. As a result, the halftone character having a low area ratio is greatly emphasized in the edge portion and is not significantly affected by the thinning processing. Further, in the case of a halftone character having a high area ratio, the influence of edge enhancement is small and the influence of thinning processing is large. As a result, it is possible to improve the quality of halftone characters with various area ratios.

101 high resolution image processing unit 2000 color printer 2010 optical scanning device 2200a to 2200d light source 3023 image processing unit 3024 light source drive control device 3222 light source modulation signal generation unit 3224 light source driving unit 3226 tag generation unit 3252 resolution conversion unit 3261 image matrix acquisition unit 3262 Pattern matching unit 3263 First conversion unit 3264 Second conversion unit

JP, 2009-212146, A

Claims (11)

An image forming apparatus for forming an image according to light emitted from a light source,
Based on the input image data to generate the image data of the first resolution, and a tag information indicating whether or not each pixel is a pixel constituting a character or line image data of the first resolution, said tag An image processing unit that allocates, as the information, information indicating that the character or the line is the pixel forming the edge portion of the character or the line in the image data of the first resolution ,
Conversion target pixels are sequentially selected from target pixels included in the image data of the first resolution, and the image data of the first resolution is converted into image data of a second resolution higher than the first resolution for each of the conversion target pixels. A resolution converter to convert,
A light source drive section for driving the light source by a modulation signal according to the image data of the second resolution,
Equipped with
The resolution conversion unit,
An image matrix acquisition unit that acquires an image matrix that is the image data of the first resolution and the tag information in a region including the target pixel and pixels around the target pixel;
The image based on the arrangement of the image data and the tag information of the first resolution in the matrix, the target pixel is a pixel constituting the edge portion, and the character or type of the line, solid, A pattern matching unit that determines that the target pixel is the conversion target pixel when it is either white or halftone,
A first conversion unit that converts the conversion target pixel into image data of the second resolution having a first arrangement pattern determined according to the arrangement and the type , based on the tag information ;
An image forming apparatus comprising: The first conversion unit is
When the conversion target pixel is a pixel forming the edge part of the halftone character, the conversion target pixel is converted into the image data of the second resolution by performing image processing for emphasizing the edge part of the halftone character. Converted,
When the conversion target pixel is a pixel forming the edge part of the halftone line, the conversion target pixel is converted into the image data of the second resolution by performing image processing for emphasizing the edge part of the halftone line. Convert,
The image forming apparatus according to claim 1, wherein: The first conversion unit is
When the conversion target pixel is a pixel forming an edge portion of a solid character, the conversion target pixel is converted into image data of the second resolution by performing image processing for thinning the edge portion of the solid character. Converted,
When the conversion target pixel is a pixel forming an edge part of a solid line, the conversion target pixel is converted into image data of the second resolution by performing image processing for thinning the edge part of the solid line. Convert,
The image forming apparatus according to claim 1, wherein: The first conversion unit is
When the conversion target pixel is a pixel forming an edge portion of a blank character, the conversion target pixel is converted into image data of the second resolution by performing image processing for thickening the edge portion of the blank character. Converted to
When the conversion target pixel is a pixel forming the edge part of the outline line, the conversion target pixel is converted into image data of the second resolution by performing image processing for thickening the edge part of the outline line. Convert to,
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The pattern matching unit,
In the edge portion, when a white pixel forming the character or the line and a black pixel forming the character or the line are adjacent to each other, the type of the character or the line having the edge portion is a halftone. Judge that there is,
The image forming apparatus according to claim 1, wherein: The pattern matching unit,
In the edge portion, when the white pixels that do not form the character or the line and the black pixels that form the character or the line are adjacent to each other, the type of the character or the line having the edge portion is solid. Judge,
The image forming apparatus according to claim 1, wherein: The pattern matching unit,
In the edge portion, when a white pixel forming the character or the line and a black pixel not forming the character or the line are adjacent to each other, the type of the character or the line having the edge portion is white. Judge that there is,
The image forming apparatus according to claim 1, wherein: The resolution conversion unit,
When the target pixel does not form the edge portion of the character or the line, the conversion target pixel is converted into image data of the second resolution having a second arrangement pattern according to the value of the target pixel. 2 further includes a conversion unit,
The image forming apparatus according to any one of claims 1 to 7, characterized in that. The image processing unit,
Changing the first arrangement pattern based on the intensity setting of the edge enhancement processing,
The image forming apparatus according to any one of claims 1 to 8, characterized in that. The image processing unit,
The processing strength of the edge portion emphasis processing is changed between the main scanning direction and the sub scanning direction,
The image forming apparatus according to any one of claims 1 to 8, characterized in that. An image forming method for forming an image according to light emitted from a light source,
Based on the input image data to generate the image data of the first resolution, and a tag information indicating whether or not each pixel is a pixel constituting a character or line image data of the first resolution, said tag Assigning, as the information, information indicating the character or the line to a pixel forming an edge portion of the character or the line in the image data of the first resolution ,
Conversion target pixels are sequentially selected from target pixels included in the image data of the first resolution, and the image data of the first resolution is converted into image data of a second resolution higher than the first resolution for each of the conversion target pixels. The process of converting,
Driving the light source with a modulation signal according to the image data of the second resolution;
Including
The converting step includes
Acquiring an image matrix that is the image data of the first resolution and the tag information in a region including the target pixel and pixels around the target pixel;
The image based on the arrangement of the image data and the tag information of the first resolution in the matrix, the target pixel is a pixel constituting the edge portion, and the character or type of the line, solid, A step of determining that the target pixel is the conversion target pixel in the case of either white or halftone;
Converting the pixel to be converted into image data of the second resolution having a first arrangement pattern determined according to the arrangement and the type based on the tag information ;
An image forming method comprising:

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