JP5229168B2 - Image processing apparatus, image processing method, and image forming apparatus - Google Patents

Description

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

  2. Description of the Related Art Conventionally, as functions of an image forming apparatus improve, an image forming speed (PPM: Prints Per Minutes) per unit time of the image forming apparatus has also increased. There is an image forming apparatus that performs multi-beam exposure using a surface emitting laser (hereinafter, referred to as “VCSEL”) in order to perform high-speed and high-definition image formation.

  In an image forming apparatus that performs automatic double-sided printing, the time from the first side recording to the second side recording of paper is shortened as the image forming speed increases. The image forming apparatus itself is also downsized. For this reason, the conveyance distance from the heat fixing corresponding to the first recording surface of the paper to the recording on the second surface is shortened, the time for removing the paper from the high temperature portion is small, and it is placed in an environment that is thermally affected. It becomes difficult to get cold.

  When double-sided recording is performed in such a state, the magnification difference between the images printed on the first and second surfaces respectively corresponding to the front and back sides of the paper is, for example, when high-quality paper having a thickness of 80 μm is used as printing paper. May be 0.2-0.4% due to heat and temperature fluctuations.

  Therefore, the sub-scanning magnification changing function performs reduction by thinning out image data in the sub-scanning direction or correction by adding image data in the sub-scanning direction. Thereby, the magnification difference can be eliminated. However, when the image to be formed becomes high-definition, for example, with respect to an image having periodicity that forms one line line every 5 lines, the line is thinned out or line is adjusted for magnification adjustment to eliminate the magnification difference. In some cases, global image defects such as density unevenness and moire are remarkably generated.

  Therefore, for example, the invention such as the image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 2005-117615 (Patent Document 1) adds or deletes when changing the size of a binary image expressed in gradation by a screen pattern. A predetermined period is provided at the position of the pixel to be processed, and the angle at which the pixels are arranged is defined.

  Further, for example, Japanese Patent Laying-Open No. 2009-83472 (Patent Document 2) discloses an invention that realizes correction of a writing position in an image forming apparatus that performs multi-beam latent image formation by image scaling processing. In multi-beam latent image formation, writing with higher resolution than the resolution of input image data is possible. In view of this, the image forming apparatus described in Patent Document 2 determines pixels to be added or deleted in the scaling process based on the writing resolution, not the resolution of the input image data.

  However, in the invention such as the image forming apparatus disclosed in Patent Document 2 described above, pixel positions to be added or deleted at the time of scaling processing are determined in units of one pixel, so that a dot may be lost.

  The present invention has been invented in order to solve these problems in view of the above points, and is an image that prevents deterioration of an image due to a scaling process when writing at a higher resolution than an input image. It is an object of the present invention to provide a processing device, an image processing method, and an image forming apparatus.

  In order to achieve the above object, the image forming apparatus of the present invention employs the following configuration.

  The image forming apparatus of the present invention is composed of a plurality of pixels continuous in the main scanning direction or the sub-scanning direction with respect to the high-resolution image converted into the writing resolution that is higher than the input image resolution of the input image, and Correction means for performing zooming correction by adding or deleting a pixel group equal to or less than the number of pixels corresponding to one pixel of the input image resolution in the writing resolution at a position across a boundary of pixels in the input image; Image writing means for writing the high-resolution image corrected for scaling.

  Accordingly, it is possible to provide an image processing apparatus that prevents image degradation due to scaling processing when writing with a resolution higher than that of an input image.

  In order to solve the above problem, the present invention may be an image processing method in the image processing apparatus or an image forming apparatus having the same function as the image processing apparatus.

  According to the image processing apparatus, the image processing method, and the image forming apparatus of the present invention, the image processing apparatus and the image processing method for preventing the deterioration of the image due to the scaling process when writing with higher resolution than the input image is performed. And an image forming apparatus can be provided.

FIG. 1 is a diagram for explaining an image before enlargement processing. FIG. 2 is a diagram illustrating mapping of 1 pixel of 1200 dpi 2 bits to 16 pixels of 4800 dpi 4 × 4. FIG. 3 is a diagram illustrating an example in which enlargement processing is performed by adding pixels. FIG. 4 is a diagram illustrating a mechanical configuration of the image forming apparatus 100 according to the present embodiment. FIG. 5 is a diagram for explaining the configuration of the VCSEL 200. FIG. 6 is a schematic perspective view when the VCSEL 200 and the optical device 130 expose the photosensitive drum 108. FIG. 7 is a block diagram illustrating a functional configuration of the control unit 300 of the image forming apparatus 100 according to the present embodiment. FIG. 8 is a block diagram showing a detailed functional configuration of the GAVD 310. FIG. 9 is a block diagram illustrating a detailed functional configuration of the image processing unit 342. FIG. 10 is a diagram (part 1) for explaining the operation of the image path selector 354 and the shift holding memory 355. FIG. 11 is a diagram (part 2) for explaining the operation of the image path selector 354 and the shift holding memory 355. FIG. 12 is a diagram showing the relationship between the R address value and the F address value of the image data. FIG. 13 is a diagram showing a laser spot irradiated to the pixel region 706. FIG. 14 is a diagram for explaining a pixel position to be added in the sub-scanning direction. FIG. 15 is a diagram showing diagonal lines including three pixels of input image data. FIG. 16 is a diagram illustrating an image shifted in the sub-scanning direction when a pixel group is added. FIG. 17 is a diagram showing that pixel groups are added at three locations. FIG. 18 is a diagram illustrating an example in which two pixels are included in the pixel group to be added. FIG. 19 is a diagram (No. 1) for explaining the processing in the case where the position of the pixel group to be added or deleted matches the intersection of the pixels at the data resolution. FIG. 20 is a diagram (No. 2) for explaining the processing when the position of the pixel group to be added or deleted coincides with the intersection of the pixels at the data resolution. FIG. 21 is a diagram illustrating a filter that detects an intersection of pixels in the sub-scanning direction. FIG. 22 is a diagram (part 1) for explaining the addition of pixels in the main scanning direction. FIG. 23 is a diagram (part 2) for explaining the addition of pixels in the main scanning direction. FIG. 24 is a diagram illustrating a filter that detects an intersection of pixels in the main scanning direction. FIG. 25 is a diagram illustrating a pixel position to which a pixel group is added. FIG. 26 is a diagram showing the relationship between the scanning of the light beam L and the F address. FIG. 27 is a flowchart for explaining the image forming method according to the present embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

Embodiment of the present invention
FIG. 1 to FIG. 3 are diagrams for explaining an example in which pixels are added when enlarging a high-resolution image. FIG. 1 is a diagram for explaining an image before enlargement processing. FIG. 1 shows an example of hatched hatching. The resolution of input image data (hereinafter referred to as “data resolution”) is 1200 dpi, and the resolution of writing (hereinafter referred to as “writing resolution”) is 4800 dpi.

  Image data rendering is not necessarily limited to writing resolution. For example, in a configuration having a rendering unit (hereinafter referred to as “controller unit”) and an electrophotographic engine unit (hereinafter referred to as “engine unit”), the controller unit may be an option. In this case, the controller unit and the engine unit are connected by a predetermined interface.

  Such an optional controller unit has the effect of maintaining compatibility with conventional models and reducing the cost of the system.

  In the configuration in which the optional controller unit is connected to the engine unit, the image rendering resolution, that is, the data resolution, does not always match the writing resolution of the engine unit. For example, the resolution may be different, for example, the data resolution at which image rendering is performed is 1200 dpi, and the writing resolution of the engine unit is 4800 dpi.

  Therefore, in the engine unit, one pixel of 1200 dpi is mapped to 4 × 4 pixels of 4800 dpi so as to correspond to a writing system of 4800 dpi. FIG. 2 is a diagram illustrating mapping of 1 pixel of 1200 dpi 2 bits to 16 pixels of 4800 dpi 4 × 4. In FIG. 2, the resolution of the rendered image is expressed as “data resolution”, and the writing resolution of the engine unit is expressed as “writing resolution”. In the example of FIG. 2, the engine unit can perform a quadruple density process of data resolution.

  Returning to FIG. 1, the hatched hatching shown is a set of pixels arranged diagonally for each pixel of the data resolution. Here, the writing resolution is four times the data resolution. Therefore, one pixel of data resolution is 16 pixels in writing resolution.

  FIG. 3 is a diagram illustrating an example in which enlargement processing is performed by adding pixels to the hatched hatching in FIG. 1. In FIG. 3, the pixel p1 and the pixel p2 are additional pixels. By adding the pixel p1, the pixel column including the pixel p1 is shifted by one pixel below the pixel p1 in the vertical direction in the drawing. As a result, a gap is formed in the hatched diagonal line at the position s1.

  As shown in FIG. 3, the collapse of the halftone dot particularly causes a situation in which the diagonal connection is disconnected. Due to the disconnection, the formation of the hatched image becomes unstable. As a result, in the uniform image, shading unevenness tends to occur, and the image quality deteriorates.

  Note that the period of the pixel to be added or deleted does not necessarily match the structure of the halftone dots. Therefore, when the disconnection occurs at a conspicuous period, the deterioration of the image quality is more easily recognized.

  FIG. 4 is a diagram illustrating a mechanical configuration of the image forming apparatus 100 according to the present embodiment. The image forming apparatus 100 creates a latent image by writing on the photoreceptor using a VCSEL (Vertical Cavity Surface Emitting LASER), develops the latent image, and transfers it to a recording medium.

  The image forming apparatus 100 forms an image by an intermediate transfer method using a tandem structure. In the reference numerals in the figure, capital letters “K”, “Y”, “C”, and “M” are “black (K)”, “yellow (Y)”, “cyan (C)”, and “magenta”, respectively. (M) ”represents a portion related to image formation of each color. In the following embodiment, when each part having the same function and configuration between the respective colors is described, description will be made with reference numerals in which “K”, “Y”, “C”, and “M” are omitted.

  The image forming apparatus 100 includes an optical device 130, an image forming unit 112, a primary transfer unit 150, a secondary transfer unit 160, and a fixing unit 170. The optical device 130 is a post-object type that does not use an fθ lens. The optical device 130 includes a polygon mirror 131, a reflection mirror 132K, a reflection mirror 132Y, a reflection mirror 132C, a reflection mirror 132M, a second cylindrical lens 133K, a second cylindrical lens 133Y, a second cylindrical lens 133C, and And a second cylindrical lens 133M.

  A light beam L emitted from the VCSEL and collected by a first cylindrical lens (not shown) is input to the polygon mirror 131. A number of light beams L corresponding to each color are generated. The polygon mirror 131 deflects these light beams L to the reflection mirror 132 corresponding to each color.

  FIG. 5 is a diagram for explaining the configuration of the VCSEL 200. The VCSEL is a surface emitting semiconductor laser in which a plurality of light sources are arranged in a lattice pattern on the same chip. The VCSEL 200 in FIG. 5 is a semiconductor laser array in which a plurality of light sources 1001 are arranged. The plurality of light sources 1001 are provided to be inclined at a predetermined angle θ with respect to the rotation axis of the polygon mirror 131.

  In FIG. 5, the vertical arrangement of the light sources is a, b, c, the horizontal arrangement is 1, 2, 3, 4, the upper left light source is a1, and the right adjacent light source is a2. And Since the light source 1001 is arranged at an angle θ, the light source a1 and the light source a2 expose different scanning positions. Thus, the center distance between the two light sources is equivalent to 4800 dpi, and high-precision image formation can be realized.

  Returning to FIG. 4, the light beam L is deflected by the polygon mirror 131, reflected by the reflecting mirror 132, and condensed again by the second cylindrical lens 133, and then the photosensitive drum 108 is exposed.

  Since the irradiation of the light beam L is performed using a plurality of optical elements, timing synchronization is performed in the main scanning direction and the sub-scanning direction. The main scanning direction is the light beam scanning direction, and the sub-scanning direction is a direction orthogonal to the main scanning direction.

  The image forming unit 112 includes a photosensitive drum 108K, a photosensitive drum 108Y, a photosensitive drum 108C, a photosensitive drum 108M, a charger 104K, a charger 104Y, a charger 104C, a charger 104M, a developer 106K, a developer 106Y, A developing unit 106C and a developing unit 106M are provided.

  The photosensitive drum 108 has a photoconductive layer having a charge generation layer and a charge transport layer on a conductive drum such as aluminum. The charger 104 includes a corotron, a scorotron, a charging roller, or the like, and applies a surface charge to the photoconductive layer of the photosensitive drum 108. Thereby, the photosensitive drum 108 holds an electrostatic charge.

  An electrostatic latent image is formed by exposing the electrostatic charge applied to the photosensitive drum 108 on the image with the light beam L. The developing device 106 develops the electrostatic latent image formed on the photosensitive drum 108. The developing device 106 includes, for example, a developing sleeve, a developer supply roller, and a regulating blade.

  The primary transfer unit 150 includes an intermediate transfer belt 151, a conveyance roller 152a, a conveyance roller 152b, a conveyance roller 152c, a primary transfer roller 110K, a primary transfer roller 110Y, a primary transfer roller 110C, a primary transfer roller 110M, and A cleaning unit 116 is included.

  The electrostatic latent image developed on the photosensitive drum 108 is transferred to an intermediate transfer belt 151 sandwiched between the photosensitive drum 108 and the primary transfer roller 110. The intermediate transfer belt 151 is moved in the direction of arrow A by the transport rollers 152a to 152c. Accordingly, the electrostatic latent image is transferred to the intermediate transfer belt 151 in the order of K, Y, C, and M.

  The primary transfer roller 110 applies a transfer bias to the intermediate transfer belt 151 to transfer the electrostatic latent image developed on the photosensitive drum 108 to the intermediate transfer belt 151. The cleaning unit 116 cleans the untransferred developer from the transfer belt 151 after the color developed image is transferred by the secondary transfer unit 160 and supplies it to the next image forming process.

  The secondary transfer unit 160 includes a secondary transfer belt 161, a transport roller 162 a, a transport roller 162 b, a paper feed cassette 165, and a transport roller 166. The secondary transfer belt 161 is conveyed by the conveyance roller 162a and the conveyance roller 162b and moves in the direction of arrow B. A recording medium 168 supplied from a paper feed cassette 165 is supplied to the secondary transfer belt 161 by a conveying roller 166 and the like. The recording medium 168 is conveyed while being held by suction on the secondary transfer belt 161. The recording medium is, for example, fine paper, a plastic film or the like. A recording medium on which an image is formed is also referred to as “image receiving material”.

  The multicolor developed image transferred and carried on the intermediate transfer belt 151 is transferred to the recording medium 168 conveyed on the secondary transfer belt 161 by applying a secondary transfer bias. The recording medium 168 carrying the multicolor developed image as an unfixed image is supplied to the fixing unit 170 by the conveyance of the secondary transfer belt 161.

  The fixing unit 170 includes a fixing member 171. The fixing member 171 includes a fixing roller and the like. The fixing roller includes, for example, silicone rubber, fluorine rubber, or the like. The fixing unit 170 pressurizes and heats the recording medium 168 and the multicolor developed image, and outputs the printed material 180 to the outside of the image forming apparatus 100.

  FIG. 6 is a schematic perspective view for one color when the VCSEL 200 and the optical device 130 expose the photosensitive drum 108. In FIG. 6, the light beam L emitted from the VCSEL 200 is collected by the first cylindrical lens 202 that shapes the light beam bundle, passes through the reflection mirror 204 and the imaging lens 206, and is then deflected by the polygon mirror 131. The

  The polygon mirror 131 is rotationally driven by a spindle motor or the like that rotates several thousand to several tens of thousands. The light beam L reflected by the polygon mirror 131 is reflected by the reflection mirror 132 and then reshaped by the second cylindrical lens 133 to expose the photosensitive drum 108.

  The reflection mirror 208 is provided to synchronize the scanning start timing of the light beam L in the sub-scanning direction. The reflection mirror 208 reflects the light beam L to the synchronization detection device 210 before starting scanning in the sub-scanning direction. The synchronization detection device 210 includes a photodiode or the like. When detecting the light beam, the synchronization detection device 210 generates a synchronization signal to start sub-scanning, and synchronizes processing such as generation of a drive control signal to the VCSEL 200.

  The VCSEL 200 is driven by a pulse signal sent from a GAVD 310 described later. As a result, the light beam L is exposed at a position on the photosensitive drum 108 corresponding to a predetermined image bit of the image data, and an electrostatic latent image is formed.

  FIG. 7 is a block diagram illustrating a functional configuration of the control unit 300 of the image forming apparatus 100 according to the present embodiment. The control unit 300 includes a scanner unit 302, a printer unit 308, and a main control unit 330.

  The scanner unit 302 has a function of reading an image formed on a medium, and sends the acquired read image to the printer unit 308 as digital data. The scanner unit 302 includes a VPU 304 and an IPU 306. The VPU 304 performs A / D conversion on the optically read image signal to perform black offset correction and shading correction. The IPU 306 performs image processing for converting the acquired image data from RGB color system image data to CMYK color system image data.

  The printer unit 308 includes a GAVD 310, an LD driver 312, and the VCSEL 200. The GAVD 310 performs drive control of the VCSEL 200. The GAVD 310 divides the image data sent from the scanner unit 302 so as to correspond to the spatial size of the semiconductor laser element emitted by the VCSEL 200, and executes a resolution enhancement process.

  The LD driver 312 supplies a current for driving the semiconductor laser element to the semiconductor laser element by the drive control signal generated by the GAVD 310. The VCSEL 200 includes two-dimensionally arranged semiconductor laser elements.

  The scanner unit 302 and the printer unit 308 are connected to the main control unit 330 via the system bus 316. The main control unit 330 outputs instructions to the scanner unit 302 and the printer unit 308, and controls image reading and image formation.

  The main control unit 330 includes a CPU 320, a RAM 322, a ROM 324, an image storage 326, and an interface 328. The CPU 320 receives a command from the user via the interface 328, calls a program module for executing processing corresponding to the command, and executes processing such as copying, facsimile, scanner, and image storage.

  The RAM 322 provides a processing space used when the CPU 320 performs processing. The ROM 324 stores initial setting data, control data, programs, and the like of the CPU 320 so that the CPU 320 can use them. The image storage 326 is configured as a fixed or detachable memory device such as a hard disk device, an SD card, or a USB memory, and stores image data acquired by the image forming apparatus 100 and can be provided to various processes. The interface 328 receives an instruction from the operator to the main control unit 330.

  When the image data acquired by the scanner unit 302 is input to the printer unit 308, the GAVD 310 processes the image data and causes the photosensitive drum 108 to output an image as an electrostatic latent image. At this time, the CPU 320 performs main scanning direction control and sub-scanning position control of an image receiving material for forming an image.

  The CPU 320 outputs a start signal to the GAVD 310 when starting scanning in the sub-scanning direction. When the GAVD 310 receives the start signal, the IPU 306 scan process is started. Thereafter, the GAVD 310 receives image data stored in a buffer memory or the like (not shown), processes the image data, and outputs it to the LD driver 312.

  The LD driver 312 generates a drive control signal for the VCSEL 200 based on the image data received from the GAVD 310. The LD driver 312 lights up the VCSEL 200 by sending this drive control signal to the VCSEL 200. The LD driver 312 drives the semiconductor laser element by PWM control or the like.

  Although VCSEL 200 in the present embodiment has 8 channels of semiconductor laser elements, the number of channels of the semiconductor laser elements is not limited.

  FIG. 8 is a block diagram showing a detailed functional configuration of the GAVD 310. The GAVD 310 receives the image data from the IPU 306 and outputs the processed image data to the LD driver 312. The GAVD 310 includes a memory 340, an image processing unit 342, and an output data control unit 344. The GAVD 310 is connected to the PLL 346 and the synchronization detection device 210.

  The memory 340 receives the synchronization signal, and stores and stores image data sent from the IPU 306. The memory 340 is a memory such as a FIFO buffer, and outputs the image data transmitted from the IPU 306 to the image processing unit 342 by a first-in / first-out method.

  The image processing unit 342 reads image data from the memory 340, and performs resolution conversion of the image data, channel assignment of the semiconductor laser element, and addition or deletion of image bits. This process is a process for correcting the size of the image data. The image bit to be added or deleted is a correction pixel for scaling the image data.

  In the image data to be processed, a position at which the photosensitive drum 108 is exposed is defined by a main scanning line address value defined in the main scanning direction and a sub scanning line address value defined in the sub scanning direction.

  In the address coordinates in this embodiment, image data is designated by a main scanning line address value (hereinafter referred to as “R address value”) and a sub scanning line address value (hereinafter referred to as “F address value”). In this case, each address value corresponding to a specific image bit is set. The address coordinates are determined for each pixel (that is, “pixel column”) arranged on the line in the main scanning direction and the line in the sub-scanning direction.

  The output data control unit 344 generates a drive control signal for the VCSEL 200 corresponding to the image data generated by the image processing unit 342. The output data control unit 344 converts the image data into time-series drive pulses from the F address value and the sub-scanning speed. The output data control unit 344 further generates a drive control signal by generating a synchronization control signal for giving a synchronization signal to the synchronization detection device 210 and adding it to the drive pulse.

  The drive control signal generated by the output data control unit 344 is transmitted to the LD driver 312 to drive the VCSEL 200. The output data control unit 344 also receives the synchronization signal from the synchronization detection device 210 and synchronizes the transmission of the drive control signal to the LD driver 312.

  Note that the processing of the memory 340, the image processing unit 342, and the output data control unit 344 is synchronized with the operation clock by the PLL 346.

  FIG. 9 is a block diagram illustrating a detailed functional configuration of the image processing unit 342. The image processing unit 342 includes a resolution conversion unit 350, a sub-scanning scaling unit 352, and an address generation unit 356.

  The resolution conversion unit 350 assigns laser element channels of the VCSEL 200 to the image data acquired from the memory 340 in association with the writing pixel. The channel assignment is based on the number of channels of the VCSEL 200 and the size of the writing pixel. Thereby, the input image data can be handled with the writing resolution.

  When forming image data of 1200 dpi with a writing resolution of 4800 dpi, the resolution conversion unit 350 performs vertical / horizontal quadruple density processing to determine drive assignment of laser element channels.

  The address generation unit 356 generates an R address value and an F address value for each pixel of input image data. These address values are values corresponding to the writing resolution. The generated address is output to the sub-scan scaling unit 352.

  The sub-scanning scaling unit 352 performs scaling correction in the sub-scanning direction on the high-resolution image data input from the resolution conversion unit 350. The sub-scanning scaling unit 352 includes a scaling signal generation unit 353, an image path selector 354, and a shift holding memory 355.

  The scaling signal generation unit 353 receives the R address value and F address value used when forming an image from the address generation unit 356. The scaling signal generation unit 353 determines whether or not the received address value is an address value of an address to which an image bit is added or deleted. In the case of an address for adding or deleting an image bit, a scaling signal such as an addition flag or a deletion flag is generated and output to the image path selector 354 and the shift holding memory 355.

  The shift holding memory 355 holds the shift amount for shifting the image bits, and further counts and holds the magnification signal input from the magnification signal generation unit 353. As a result, for example, after adding a pixel to the channel above any one of the 8ch in the first scan of the main scan, the position where the pixel is added in the 8ch in the second scan can be determined.

  The image path selector 354 performs enlargement or reduction processing on the image data of the writing resolution input from the resolution conversion unit 350. More specifically, a pixel is inserted into or deleted from the pixel located at the coordinate address designated by the R address value and the F address value for each pixel row arranged in the main scanning direction and sub scanning direction lines. Perform correction processing.

  For example, when the magnification signal is input from the magnification signal generation unit 353 to the image path selector 354 at the time of enlargement, the value of the image bit corresponding to the magnification signal is set to a value corresponding to “white”. Thereafter, the address of the pixel in the input image data is shifted by one pixel.

  The image path selector 354 selects and outputs a pixel of input image data based on the shift amount input from the shift holding memory 355 for a pixel to which no scaling signal is input.

  When the 8-channel VCSEL 200 is used as the semiconductor laser, a scaling signal indicating the position of the pixel to be added or deleted generated by the scaling signal generation unit 353 and a signal indicating the shift amount held by the shift holding memory 355. Requires 8ch. These signals are used for driving the VCSEL 200.

  In the above example, the scaling signal generation unit 353 is provided as an independent module in the sub-scanning scaling unit 352. However, the scaling signal generation unit 353 is a function unit that is the same as a unit that realizes other functions in the image processing unit 342. It may be provided.

  10 and 11 are diagrams for explaining the operations of the image path selector 354 and the shift holding memory 355. FIG.

  FIG. 10 is a diagram illustrating an example of scanning without additional bits. The input data 600 in FIG. 10 is 15 pixels read from the memory 340 and converted into the writing resolution, and the attention data 620 is 8 pixels in the sub-scanning direction of the VCSEL 200. The numbers in each frame are pixel identifiers. The attention data 620 includes eight pixels from pixel 0 to pixel 7. When there is no enlargement processing, the output data 640 corresponding to the address of the attention data 620 is the same as the attention data 620, and shiftn (n = 0 to 7) indicating the shift amount is all zero.

  FIG. 11 is a diagram illustrating processing corresponding to a variable magnification signal. The example of FIG. 11 is an example of scanning that includes additional bits. In FIG. 11, the first to third scans of the VCSEL 200 are shown for every eight addresses corresponding to 8ch of the VCSEL 200. The input data 600 is the same as in FIG.

  In the first scan of the VCSEL 200, one pixel is added at the position of the pixel 0 with respect to the data of interest 620. As a result, in the output data 660, the white pixel is associated with ch0, the pixels 0 to 6 are associated with ch1 to ch7, and the shift amounts shiftn are all the value 1. Therefore, the count value 1 is held in the shift holding memory 355.

  In the second scan of the VCSEL 200, there is no additional pixel for the new attention data 621. Therefore, the output data 661 takes over the shift amount of the first scan of the VCSEL 200, and all the shift amounts shiftn are 1, and the pixels 7 to 14 are associated with ch0 to ch7, respectively.

  In the third scan of the VCSEL 200, one pixel is added to the position of the pixel 16 with respect to the new attention data 622. As a result, shiftn becomes a value 2 that is obtained by adding a value 1 to the shift amount 1 of the first and second scans of the VCSEL 200, and the white pixel corresponds to ch0, and the pixels 15 to 21 correspond to ch1 to ch7, respectively. It is attached. The count value of the shift holding memory 355 is 2.

  FIG. 12 is a diagram showing the relationship between the R address value and the F address value of the image data. In FIG. 12, for the image data 700, an address indicating the position of the VCSEL 200 in the main scanning direction is an R address, and an address indicating the position of the VCSEL 200 in the sub scanning direction is an F address. Signals 702 and 704 are signals representing assertion and negation of the writable address range of the R address and the F address.

  The R address value and the F address value are values included in the writable range of the image receiving material. Corresponding to these address values, feed in the main scanning direction and lighting control of the semiconductor laser element are performed with respect to the VCSEL 200. As a result, the light beam L scans on the photosensitive drum 108, and an electrostatic latent image that has been subjected to zooming control is formed.

  FIG. 13 is a diagram showing a laser spot irradiated on the photoreceptor surface 706 by the VCSEL 200. The photoreceptor surface 706 includes eight laser spots 708. The laser spot 708 irradiates the photosensitive member surface 706 with a writing resolution that divides the photosensitive member surface 706 into four parts in the sub-scanning direction and four parts in the main scanning direction, for a total of 16 parts. As a result, the pitch of the light beam in the sub-scanning direction is about 5 microns, which is four times finer than the data resolution of the image to be read. Specifically, when the data resolution is 1200 dpi, the writing resolution is 4800 dpi, and a latent image is formed at this resolution.

  FIG. 14 is a diagram for explaining a pixel position to be added in the sub-scanning direction. In FIG. 14, a sub-scanning position 1004 and a sub-scanning position 1006 are main scanning lines including a pixel position to which a pixel is added. One of these sub-scanning positions is provided for every 16 main scanning lines. Therefore, the enlargement process is 6.25% in the sub-scanning direction. Actually, for example, when an enlargement process of 0.625% is performed, one line is added per 160 lines. In FIG. 14, 1004 and 1006 are linear in the main scanning direction, but the sub-scanning position may be different for each main scanning coordinate (R address value), and one additional pixel is added to 16 sub-scanning pixels. Then, 6.25% enlargement processing can be realized in the sub-scanning direction.

  FIGS. 15 to 21 are diagrams illustrating an example in which pixels are added in the sub-scanning direction. The ratio of pixels added in FIGS. 15 to 21 is several percent to several tens of percent or more, but this is an additional frequency for the sake of explanation.

  FIG. 15 is a diagram showing diagonal lines including three pixels of input image data. In FIG. 15, the position of one pixel of data resolution is indicated by a rectangle. One rectangle includes 16 pixels of writing resolution. The pixel position t10 is the position of a pixel that is scheduled to be added side by side in the main scanning direction for four pixels in the writing resolution. A cluster of pixels composed of a plurality of pixels arranged in succession is referred to as a “pixel group”.

  FIG. 16 is a diagram showing an image shifted in the sub-scanning direction after the pixel group is added at the position shown in FIG. In FIG. 16, pixel groups are added at two locations from pixel positions t10 to t11. By adding the pixel position t10, 16 pixels corresponding to the second pixel in the data resolution are shifted down by one line. As a result, a gap S1 is generated and a line is lost.

  FIG. 17 is a diagram illustrating that pixel groups are added to three positions from pixel positions t21 to t22. Here, the added pixel group is disposed at a position across the boundary of the pixels in the data resolution. Thereby, the gap S1 in FIG. 16 does not occur, and the intersection of the pixels of the data resolution can be prevented from leaving.

  FIG. 18 shows an example in which two pixels are included in the pixel group to be added. In FIG. 18, a pixel group including pixels having two writing resolutions is added at pixel positions t31 to t36. Again, the added pixel group is arranged at a position across the pixel boundary in the data resolution. Thereby, the gap S1 in FIG. 16 does not occur, and the intersection of the pixels of the data resolution can be prevented from leaving.

  FIG. 19 to FIG. 21 are diagrams for explaining processing when the position of the pixel group to be added or deleted matches the intersection of the pixels at the data resolution. In FIG. 19, a pixel position t41 that is an intersection of pixels in the data resolution is the position of the pixel group to be added. As a result, at the pixel position t41, the intersection of the pixels of the data resolution is separated.

  FIG. 20 is a diagram illustrating an example in which a pixel group is added at the pixel position t42 instead of the pixel position t41. As shown in FIG. 20, when the pixel position to be added coincides with the intersection of the data resolution, it is possible to prevent the intersection of the pixels from being separated at the pixel position t41 by shifting backward in the sub-scanning direction. .

  FIG. 21 is a diagram illustrating a filter that detects intersections of pixels. The four filters shown in FIG. 21 correspond to 4 pixels of 2 × 2 pixels in the writing resolution, and the pixel value exists only in the pixel position where the mark X is provided (not a white pixel). It is determined that this is the intersection of The arrow in the figure is the F address where the pixel position to be added exists.

  22 to 24 are diagrams for explaining the addition of pixels in the main scanning direction. 22 and 23, the scanning of the light beam L by the VCSEL 200 is from the left to the right. FIG. 22 is a diagram illustrating that a pixel group is added to three pixel positions from the pixel position t51 to the pixel position t53. The rectangle in the figure represents one pixel at the data resolution.

  As shown in FIG. 22, a pixel group is added for every four pixel positions continuous in the sub-scanning direction. The pixel position to which the pixel group is added straddles the pixel boundary in the data resolution.

  FIG. 23 is a diagram for explaining processing when the position of the pixel group to be added or deleted matches the intersection of pixels at the data resolution. In FIG. 23, the pixel position t54 is an intersection of pixels of data resolution. Therefore, by changing the pixel position to be added to the pixel position t55 that is behind the pixel position t54 in the main scanning direction, it is possible to prevent the intersection of the pixels in the data resolution from leaving.

  FIG. 24 is a diagram illustrating a filter that detects intersections of pixels. The four filters shown in FIG. 24 correspond to 4 pixels of 2 × 2 pixels in the writing resolution, and when the pixel value exists only at the pixel position where the mark X is provided (not a white pixel), Judge as an intersection. In addition, the arrow in a figure is R address where the pixel position to add exists.

  FIG. 25 is a diagram illustrating a pixel position to which a pixel group is added. In FIG. 25, the numbers written in the uppermost columns are R addresses, and the numbers written in the leftmost columns are F addresses. A frame 800 shown at the bottom indicates a pixel position at the data resolution.

  Here, an example in which quadruple density processing has been performed for higher resolution will be described. The pixel group to be added is four pixels, and is arranged at a position across the pixel boundary in the data resolution. The first two R addresses of 0 and 1 are set as one pixel group, and after the R address value is 2, one pixel group is set for every four addresses.

  In the drawing, a pixel position 810 indicates that a pixel group is added to four pixel positions having an R address value of 10 to 13 in a main scanning line having an F address value of 28. Therefore, in FIG. 25, one line is added for every 16 main scanning lines.

  FIG. 26 is a diagram showing the relationship between the scanning of the light beam L and the F address. Each frame of a rectangle 705 provided on the left side of the image 700 corresponds to one scan of the VCSEL 200. By synchronizing the F address and the light beam L, it is possible to control a plurality of channels across data resolution.

  In FIG. 26, a signal 702 and a signal 704 are signals representing assertion and negation of the writable address range of the R address and the F address, respectively.

  FIG. 27 is a flowchart for explaining the image forming method according to the present embodiment. In the image forming method of FIG. 23, an R address value and an F address value depending on the resolution at the time of writing are set based on the input image data, and further, by inserting pixels based on a predetermined interval, The enlargement / reduction processing is performed.

  In step S101 in FIG. 27, the address generation unit 356 sets an R address value. Progressing to step S102 following step S101, the scaling signal generation unit 353 calculates an F address value for adding or deleting a pixel. This calculation corresponds to the scaling method used in the image path selector 354.

  Progressing to step S103 following step S102, the scaling signal generation unit 353 determines whether the address is a pixel contact at the data resolution from the R address value set in step S101 and the F address value calculated in step S102. Judge whether or not. If it is a contact, the process proceeds to step S104. If not, the process proceeds to step S105.

  In step S104 following step S103, 8 is added to the F address value calculated in step S102. Progressing to step S105 following step S103 or step S104, the image path selector 354 adds or deletes a pixel at the pixel position of the address calculated up to step S104.

  Progressing to step S106 following step S105, the address value is transferred to the output data control unit 344. The output data control unit 344 generates a pulse signal and a laser drive signal for controlling the LD driver 312 based on the transferred address, and outputs the pulse signal and the laser drive signal to the LD driver 312.

  Progressing to step S107 following step S106, it is determined whether or not the processing of the sub-scanning range at the R address set in step S101 is completed. If the process is completed, the process proceeds to step S108. If the process is not completed, the process returns to step S102 and the process is repeated.

  In step S108 following step S107, it is determined whether or not the processing of the main scanning range is finished. If the processing of the main scanning range is finished, the processing is finished. If the processing of the main scanning range is not finished, the processing returns to step S101 and is repeated.

(Realization by computer etc.)
The image forming apparatus according to the embodiment of the present invention may be realized by a personal computer (PC), for example. In addition, the image forming method according to the embodiment of the present invention is executed by using, for example, a main memory such as a RAM as a work area in accordance with a program stored in a ROM or a hard disk device by a CPU.

  Although the best mode for carrying out the invention has been described above, the present invention is not limited to the embodiment described in the best mode. Modifications can be made without departing from the spirit of the present invention.

  As described above, the image processing apparatus according to the present invention is useful for image formation, and is particularly suitable for an image forming apparatus that performs multi-beam latent image formation.

100 Image forming apparatus 104, 104K, 104Y, 104C, 104M Charger 106, 106K, 106Y, 106C, 106M Developer 108, 108K, 108Y, 108C, 108M Photosensitive drum 110, 110K, 110Y, 110C, 110M Primary transfer Roller 112 Image forming unit 116 Cleaning unit 130 Optical device 131 Polygon mirrors 132, 132K, 132Y, 132C, 132M Reflective mirrors 133, 133K, 133Y, 133C, 133M Cylindrical lens 150 Primary transfer unit 151 Intermediate transfer belts 152a, 152b , 152c Conveying roller 160 Secondary transfer unit 161 Secondary transfer belts 162a and 162b Conveying roller 165 Feed cassette 166 Conveying roller 168 Recording medium 170 Fixing unit 171 Fixing member 180 Printed product 202 Cylindrical lens 204 Reflecting mirror 206 Imaging lens 208 Reflecting mirror 210 Synchronization detection device 300 Control unit 302 Scanner unit 308 Printer unit 312 LD driver 316 System bus 326 Image storage 328 Interface 330 Main control unit 340 Memory 342 Image processing Unit 344 output data control unit 350 resolution conversion unit 352 sub-scanning scaling unit 353 scaling signal generation unit 354 image path selector 355 shift holding memory 356 address generation unit

JP 2005-117615 A JP 2009-83472 A

Claims (5)

A high resolution image converted to a writing resolution that is higher than the input image resolution of the input image, and composed of a plurality of pixels that are continuous in the main scanning direction or the sub scanning direction, and the input image at the writing resolution Correction means for adding or deleting a pixel group equal to or less than the number of pixels corresponding to one pixel of resolution at a position across the boundary of the pixel in the input image, and performing zooming correction;
Image writing means for writing the high-resolution image corrected for scaling,
An image processing apparatus comprising:   When the pixel group is located at a contact point in the oblique direction of the pixel in the input image resolution, the correction unit shifts the position of the pixel group in a direction orthogonal to the direction in which the pixel group is arranged. The image processing apparatus according to claim 1.   The image writing unit performs writing of a plurality of pixel columns in the main scanning direction in one scan, and ends of the plurality of pixel columns in the sub-scanning direction are different from pixel boundaries in the input resolution. The image processing apparatus according to claim 2. A high resolution image converted to a writing resolution that is higher than the input image resolution of the input image, and composed of a plurality of pixels that are continuous in the main scanning direction or the sub scanning direction, and the input image at the writing resolution Correction means for adding or deleting a pixel group equal to or less than the number of pixels corresponding to one pixel of resolution at a position across the boundary of the pixel in the input image, and performing zooming correction;
Image writing means for irradiating the photosensitive drum with a plurality of light beams corresponding to a plurality of pixel rows in the main scanning direction by one scanning to form the high-resolution image corrected for scaling as a latent image;
Transfer means for transferring a developed image obtained by developing the latent image to a medium;
Fixing means for fixing the transferred developed image to the medium;
An image forming apparatus comprising: A high resolution image converted to a writing resolution that is higher than the input image resolution of the input image, and composed of a plurality of pixels that are continuous in the main scanning direction or the sub scanning direction, and the input image at the writing resolution A correction step of adding or deleting a pixel group equal to or less than the number of pixels corresponding to one pixel of resolution at a position across the boundary of the pixel in the input image, and performing zooming correction;
An image writing step of writing the high-resolution image corrected for scaling;
An image processing method comprising:

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