JP5574727B2 - Image forming apparatus and control method thereof - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine or a color printer.

  In an image forming apparatus using an electrophotographic method, a technique (heat fixing method) is known in which an unfixed toner image transferred onto a recording material is heated, melted, and fixed. As the heat fixing method, a planar heater method, an infrared lamp method, a fixing roller method, an IH fixing method, and the like that are currently most popular are known. In an image forming apparatus that uses a heat fixing method to fix a toner image, moisture contained in the recording material is evaporated by heat, and thus the recording material contracts after fixing. This shrinkage rate varies depending on the type and thickness of the recording material. It is empirically known that it takes about 15 to 20 minutes for the recording material once shrunk by heat fixing to absorb moisture in the air and return to its original size.

  By the way, in general, when images are formed on both sides of a recording material, a toner image is transferred to one side (front surface) of the recording material, heated and fixed, and then conveyed to an inversion path to reverse the front and back of the recording material, By transporting the recording material again to the image forming unit, the toner image is transferred to the other surface (back surface) of the recording material, and is again heat-fixed. Therefore, when the toner image is transferred to the back surface, an image is formed on the back surface without a long time elapses after the toner image is fixed on the front surface. Therefore, the toner image is transferred to the back surface of the recording material in a state where the recording material is contracted, which causes a problem that the image sizes of the front surface and the back surface are different.

  In order to solve such a problem, Japanese Patent Application Laid-Open No. H10-228561 discloses a recording in which the vertical and horizontal sizes of the recording material are detected by the same sensor immediately before the toner image is transferred to the recording material and immediately after the toner image is fixed. A technique for switching the scanning speed of the optical system based on the expansion / contraction ratio of the material has been proposed. Further, in Patent Document 2, the vertical size is detected before and after fixing the first recording material in order to reduce the control load of the technique described in Patent Document 1, and the vertical expansion ratio of the first recording material is detected. Describes a technique for switching the scanning speed of the first and second and subsequent optical systems based on the above. Patent Document 3 proposes a technique for controlling the length between image data by adding an image clock for transferring the image data at an arbitrary point and correcting the size of the image to be printed.

Japanese Patent Laid-Open No. 04-288560 Japanese Patent Laid-Open No. 10-149057 JP 2000-238342 A

  However, the above prior art examples have the following problems. For example, when the problem that the image sizes of the front and back surfaces are different occurs, the problem that the positional accuracy of the front and back images cannot be obtained also occurs. To solve this problem, it is also conceivable to determine the area of the image data and extract white information from the white data area in the white data area in the sub-scanning direction (area where no toner image is formed). For example, white information is extracted from the data of the margin area (the margin area corresponds to white data). However, if there is a black frame or the like, or if there is continuous black information, partially extracting the white information results in poor print quality. In particular, when an image in which no blank area exists is formed, there is a case where white information does not exist in the line data, and in this case, extraction cannot be performed.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an image forming apparatus that suppresses deterioration in print quality and productivity and appropriately corrects the sub-scanning magnification.

The present invention includes, for example, a photoconductor and an exposure unit that scans light emitted from a light source in accordance with image data of an image to be formed and exposes the photoconductor with the scanned light to form a latent image; Development means for developing the latent image formed on the photosensitive member with a developer, transfer means for transferring the developer image developed by the development means to a recording material, and the developer image transferred to the recording material as a recording material It can be realized as an image forming apparatus including a fixing unit for fixing. The image forming apparatus compares the number of pixel data having the same number of bits in the sub-scanning direction for each combination of two continuous line data with respect to line data for scanning the photosensitive member by light emitted from a light source. When the number of pixel data of the first combination of line data is larger than the number of pixel data of the second combination in the comparison result by the means and the comparison means, when reducing the magnification of the image in the sub-scanning direction, A magnification correction unit that prohibits emission of light from the light source based on one of the two line data in the first combination , and the magnification correction unit enlarges the magnification of the image in the sub-scanning direction. In this case, the average value of the pixels arranged in the sub-scanning direction in the two line data of the first combination is calculated to calculate Generates Ndeta, insert the generated line data between two line data of the first combination, characterized in Rukoto. The present invention also includes a photoconductor and an exposure unit that scans light emitted from a light source in accordance with image data of an image to be formed and exposes the photoconductor with the scanned light to form a latent image; Development means for developing the latent image formed on the photosensitive member with a developer, transfer means for transferring the developer image developed by the development means to a recording material, and the developer image transferred to the recording material as a recording material An image forming apparatus having a fixing unit for fixing, wherein the number of bits in the sub-scanning direction is the same for each combination of two consecutive line data with respect to line data for scanning the photosensitive member by light emitted from a light source. In the comparison means for comparing the number of pixel data to be compared and the comparison result by the comparison means, the number of pixel data in the first combination of line data is the number of pixel data in the second combination. A magnification correction unit that prohibits emission of light from the light source based on one of the two line data in the first combination when reducing the magnification of the image in the sub-scanning direction. The attribute data indicating whether each pixel is character data or photo data is added to the image data together with the number of bits of each pixel, and the comparing means includes the number of bits and the attribute of each pixel. And counting means for counting the number of white data having 0 value for each line, the number of black data having 1 value, and the number of photographic data based on the data, and the magnification correction means has the same number of bits When there are multiple line combinations with the largest number of pixel data, the line combination with the largest number of white data is determined as the line combination subject to magnification correction. It is characterized in.

  The present invention can provide, for example, an image forming apparatus that suppresses deterioration in print quality and productivity and appropriately corrects the sub-scanning magnification.

1 is a diagram illustrating a configuration of an image forming apparatus 100 according to a first embodiment. It is a figure which shows the specific structural example of the image output device 30 which concerns on 1st Embodiment. It is a figure which shows the specific structural example of the image process part 310 which concerns on 1st Embodiment. It is a figure which shows an example of the attribute map which concerns on 1st Embodiment. It is a figure which shows an example of the format at the time of hold | maintaining the image data and attribute data which concern on 1st Embodiment. It is a figure which shows the specific structural example of the exposure control part 31 which concerns on 1st Embodiment. It is a figure which shows the specific structural example of the image processing circuit 61 which concerns on 1st Embodiment. It is a flowchart which shows the process sequence of the magnification correction which concerns on 1st Embodiment. It is a figure which shows the example of an image after the magnification correction which concerns on 1st Embodiment. It is a figure which shows the modification of the specific structural example of the image process part 310 which concerns on 1st Embodiment. It is a flowchart which shows the process sequence of the magnification correction which concerns on 2nd Embodiment. It is a flowchart which shows the process sequence of the magnification correction which concerns on 3rd Embodiment. It is a flowchart which shows the process sequence of the magnification correction which concerns on 4th Embodiment.

  An embodiment of the present invention is shown below. The individual embodiments described below will help to understand various concepts, such as superordinate concepts, intermediate concepts and subordinate concepts of the present invention. Further, the technical scope of the present invention is determined by the scope of the claims, and is not limited by the following individual embodiments.

<First Embodiment>
<Configuration of image forming apparatus>
Hereinafter, the first embodiment will be described with reference to FIGS. 1 to 10. First, the configuration of the image forming apparatus 100 according to the first embodiment of the present invention will be described with reference to FIG. The image processing system according to this embodiment includes a host computer 10 and an image forming apparatus 100, and each apparatus is connected via a cable 1. Further, the image forming apparatus 100 includes a controller 20 and an image output apparatus 30, and each apparatus is connected via the cable 2. The controller 20 includes a CPU 21, ROM 22, HDD controller 23, built-in HD 24, external interface 25, and RAM 26. The RAM 26 includes a frame memory 26a and a PDL buffer 26b. The image output device 30 includes an image reading unit 300, an image processing unit 310, an image forming unit 320, an operation unit 330, and a control unit 340.

  The host computer 10 functions as a supply source of print data (for example, PDL data). The controller 20 temporarily holds the print data supplied from the host computer 10 via the cable 1 and the external interface 25 in the built-in HD 24 via the HDD controller 23. The print data held in the built-in HD is temporarily held in the PDL buffer 26b via the CPU bus 3. The controller 20 develops the PDL data held in the PDL buffer 26b in the frame memory 26a to generate image data. The image data developed in the frame memory 26a is transferred to the image output device 30 via the cable 2 and printed on a recording material. Here, the cables 1 and 2 may be general-purpose cables such as parallel cables, SCSI cables, serial cables, network cables, or dedicated cables.

  The image output device 30 functions as a printer that outputs print data generated by the host computer 10 and also functions as a copier or a scanner that copies a document. Further, the controller 20 can acquire status information and the like of the image output device 30 via the cable 2 and transmit the status information to the host computer 10 and controls the image output device 30 based on the status information.

  The CPU 21 operates based on a control program stored in the ROM 22 and controls the function of the controller 20. The built-in hard disk (HD) 24 has areas for temporarily storing printed PDL data, image data generated by expanding the PDL data, areas for storing font data, and the like. The built-in HD 24 is connected to the CPU bus 3 via the HDD controller 23. The PDL buffer 26 b is a buffer that temporarily holds PDL data received from the host computer 10. The frame memory 26a expands the PDL data and temporarily stores the expanded image data. The controller 20 generates full-color or gray-scale image data according to the PDL data supplied from the host computer 10.

  The ROM 22 may be configured by, for example, a programmable memory (for example, EEPROM) so that the control program can be installed from the host computer 10 or the like. The ROM 22 may be configured by a memory medium such as a floppy (registered trademark) disk or CD-ROM and a controller (driver) thereof.

  Transmission of image data to the image output device 30 is performed via the cable 2. In the image output device 30, the image processing unit 310 generates CMYK data (K data in the case of gray scale) based on the image data supplied from the controller 20, and supplies this to the image forming unit 320 for recording material. Output the image above. Further, the image data read by the image reading unit 300 is supplied to the image forming unit 320 to output an image on a recording material. The image forming unit 320 has a function of outputting a color or gray scale image having a resolution of 400 dpi, for example. The control unit 340 controls the operation of the image output device 30 based on a command from the controller 20 or the operation unit 330.

  Next, a specific configuration example of the image output apparatus 30 will be described with reference to FIG. Here, an image output apparatus 30 having a function as a copier and a function as a printer in an electrophotographic image forming apparatus capable of outputting a full-color image will be described as an example. A DF (Document Feeder) 40 is a document feeder, and sequentially conveys a plurality of documents stacked at a predetermined position to a document reading position one by one. The document placed at the document reading position by the DF 40 or manually is read by the image reading unit 300 including, for example, an optical system, a color CCD, and the like, whereby RGB data corresponding to the document image is generated and sent to the image processing unit 310. Sent.

  The image processing unit 310 selects either image data sent from the controller or image data sent from the image reading unit 300 based on control by the control unit 340 and transmits the selected image data to the image forming unit 320 and the controller 20. To do. That is, the control unit 340 selects the image data supplied from the controller 20 when the image output apparatus 30 is used as a printer, and the image data supplied from the image reading unit 300 when used as a copying machine. Select and execute print processing. The image processing unit 310 converts the input RGB data into YMCK data, and supplies C, M, Y, and K image data to the exposure control unit 31 of the image forming unit 320.

  The exposure control unit 31 has a light source that emits light, converts the supplied C, M, Y, and K image data into laser light, and irradiates the photosensitive drum 32 that is a photosensitive member with the laser light. To form a latent image. A recording material on which an image is output is selected and fed from the upper cassette 36 or the lower cassette 37 and is conveyed to the photosensitive drum 32 via the conveyance path 6. The latent image on the photosensitive drum 32 is developed with a developer by a developing device (not shown), whereby a visible image (developer image) is formed and transferred to a recording material. The latent image formation, development, and transfer operations are performed for C, M, Y, and K colors, and a color image is synthesized on the recording material. The recording material onto which the toner image has been transferred is conveyed to a fixing device 33 where the toner image is fixed on the recording material. Thereafter, the recording material is discharged to the paper discharge tray 50 in a mode in which an image is formed on one side. On the other hand, in the mode in which images are formed on both sides, when the transfer of the toner image to one side of the recording material is completed, the toner image is reversed by the reversing unit 34 via the conveyance path 4, via the conveyance path 5 and the double-sided tray 35, It is again conveyed to the conveyance path 6. Thereafter, after the toner image is transferred to the back surface, the toner image is fixed by the fixing device 33 and discharged to the paper discharge tray 50.

<Image processing unit>
Next, a detailed configuration of the image processing unit 310 will be described with reference to FIG. In FIG. 3, image signals Y, M, C, and K output from an external device 101 such as a computer pass through a density / luminance conversion unit 102, a luminance / density conversion unit 103, a smoothing circuit 104, and a γ conversion unit 105. The data is sequentially transferred for each scanning plane in the printer unit 106. The density / luminance conversion unit 102 converts Y, M, C, and K density signals into R, G, and B brightness signals for each color using a lookup table ROM. The luminance density conversion unit 103 converts the RGB three primary color signals transferred from the CCD 210 or an external device into Y, M, C, and K density signals, and outputs them in a predetermined bit width (8 bits) in frame order.

  Next, the smoothing circuit 104 generates data having a resolution twice as high as the reading resolution in accordance with the result of the image area separation unit 107 and the area signal from the operation unit 330 or the external device 101. Then, the γ conversion unit 105 converts the density data of each resolution using the γ table according to the gradation reproduction of the printer. The MCYK image signal and the attribute data processed in this way are sent to the laser driver, and the printer unit 106 performs density recording by PWM processing.

  The image area separation unit 107 includes an edge detection unit 108, a saturation determination unit 109, a thickness determination circuit 110, and a lookup table (LUT) 111. The edge detection unit 108 generates an edge signal edge from the MCYK image signal output from the density luminance conversion unit 102 and outputs the edge signal edge to the LUT 111. The saturation determination unit 109 generates a saturation signal col from the MCYK image signal output from the density luminance conversion unit 102 and outputs it to the LUT 111. The thickness discriminating circuit 110 generates a thickness signal zone from the MCYK image signal output from the density luminance conversion unit 102 and outputs it to the LUT 111. Further, the LUT 111 outputs attribute data of the image area determination signal.

  Further, the image area separation unit 107 performs feature extraction such as edge detection / thickness determination on the basis of information from the surrounding pixels for each pixel, and is a character / graphic area or a photographic area with the extracted features. Determine whether. When the character / graphic area is determined, smoothing processing is performed by the smoothing circuit 104 to smooth the edges, and a good image can be obtained by the printer unit 106.

  The smoothing circuit 104 switches between 400 lines / 800 lines for each pixel according to the image area separation result of the image area separation unit 107, and generates data having double the resolution of the input image. The γ conversion unit 105 converts the density data of each resolution according to the gradation reproduction of the printer. The YMCK image signal and image area separation attribute data processed in this way are sent to the laser driver, and density recording is performed by the printer unit 106.

<Data format>
Next, the format of the YMCK image signal and attribute data sent to the printer unit 106 will be described with reference to FIG. 401 shows an example of an attribute map associated with each pixel of this embodiment. Reference numeral 401 represents an image in which C, which is a character pixel, is included in a bitmap image. Assuming that the attribute map generated by the image area separation unit 107 represents a character pixel as 1 and a character margin as 0, an attribute map is a two-dimensional arrangement of 0 and 1 corresponding to each color, as shown at 402. Is generated. Similarly, attribute data is also given to a photographic pixel, and an attribute map in which character part attribute data and picture part attribute data are integrated is given and generated. That is, the attribute data includes information indicating whether each pixel is character data or photo data.

  The attribute map may be configured in any way as long as attribute data is stored in association with each pixel. For example, the image data (image signal) and the attribute map may be stored separately as an attribute map plane 402. In this case, as indicated by reference numeral 501 in FIG. 5, five planes obtained by adding attribute map planes to CMYK planes are held as one page images (Planner). Further, as indicated by 502 in FIG. 5, information of several bits may be stored in one pixel and one surface may be held as an image of one page. In this case, for example, as shown at 503 in FIG. 5, the attribute data may be embedded in the information of the CMYK data of each pixel (Chunky). In order to reduce the data amount, the attribute map may be embedded in the lower bits for each pixel of any one plane or a plurality of planes among the CMYK planes. Reference numeral 503 denotes an example in which attribute data is held for each color of CMYK. 2-bit attribute data is added to 8 bits of image data of each color of CMYK. As described above, data indicating a character pixel, a character margin portion, a photographic pixel, or a photographic margin portion is set in the 2-bit attribute data.

<Exposure control unit>
Next, a specific configuration example of the exposure control unit 31 will be described with reference to FIG. The exposure control unit 31 includes an image processing circuit 61 and a laser driving device 62. The image processing circuit 61 performs sub-scanning magnification correction based on Y, M, C, and K image signals, attribute data, and magnification correction data input from the image processing unit 310, and is pixel-division modulated. The main scanning magnification is corrected in synchronization with the image clock and output. The laser driving device 62 drives the semiconductor laser 63 based on the pixel division modulated image signal output from the image processing circuit 61.

  Inside the semiconductor laser 63, a photodiode sensor (PD sensor) for detecting a part of the laser light is provided. The laser driving device 62 performs APC (Auto Power Control) control of the semiconductor laser 63 using the detection signal of the PD sensor. Laser light emitted from the semiconductor laser 63 becomes substantially parallel light via an optical system having a collimator lens and a diaphragm, and is incident on a polygon mirror (rotating polygonal mirror) 33 with a predetermined beam diameter. The polygon mirror 65 rotates at a constant angular velocity in a predetermined direction. With this rotation, the laser light incident on the polygon mirror 65 is reflected as a deflected beam that continuously changes its angle. The laser beam reflected as a deflected beam is focused by the f-θ lens 64. At the same time, the f-θ lens 64 corrects distortion so as to guarantee the temporal linearity of scanning. Therefore, the laser light that has passed through the f-θ lens 64 is combined and scanned on the photosensitive drum 32 at a constant speed in a predetermined direction. Near one end of the photosensitive drum 32, a beam detect sensor for detecting the laser beam reflected from the polygon mirror 65 is provided. The detection signal of this sensor is used as a synchronization signal for synchronizing the rotation of the polygon mirror 65 and the data writing. In such a laser driving device 62, in order to keep the amount of laser light during one scanning constant, the output of the laser light is detected in the light detection section during one scanning, and the driving current of the semiconductor laser 63 is set to 1. A drive system is used in which the image is held during scanning.

<Image processing circuit>
Next, a specific configuration example of the image processing circuit 61 will be described with reference to FIG. The image processing circuit 61 includes a magnification correction circuit 131, a FIFO 132, a PS conversion circuit 133, an SP conversion circuit 134, a timing adjustment circuit 135, a delay time generation circuit 136, a line counter 137, a control signal generation circuit 138, a FIFO clock generation circuit 139, A PS clock generation circuit 140 and an SP clock generation circuit 141 are provided.

  The magnification correction circuit 131 performs magnification correction using the image data, attribute data, and magnification correction data sent from the image processing unit 310. The control signal generation circuit 138 includes a FIFO control signal 161 for a FIFO (First In-First Out Memory) clock generation circuit 139, a PS conversion control signal 162 for a parallel-serial (hereinafter referred to as PS) clock generation circuit 140, and a serial-parallel. An SP conversion control signal 163 for the generation circuit 141 (hereinafter abbreviated as SP) is generated. The FIFO clock generation circuit 139 generates a read clock 164 for the FIFO 132 based on the reference clock 159 and the FIFO control signal 161. The PS clock generation circuit 140 generates a conversion clock 165 for the PS conversion circuit 133 based on the reference clock 159 and the PS conversion control signal 162. The SP clock generation circuit 141 generates an SP conversion clock 166 for the SP conversion circuit 134 based on the reference clock 159 and the SP conversion control signal 163. The SP conversion clock 166 is output as an image clock.

  A FIFO write address reset signal 156 and a write clock 157 are supplied to the FIFO 132 from the main body control unit, and an image signal is input pixel by pixel from an external image generation unit. That is, 16-bit write pixel data 151 is input to the FIFO 132. From the FIFO 132, 16-bit read pixel data 152 is output by a read clock 164 from the FIFO clock generation circuit 139 and a read address reset signal 158 input from the main body control unit.

  The read pixel data 152 output from the FIFO 132 is input to the PS conversion circuit 133. The PS conversion circuit 133 converts the input 16-bit read pixel data 152 into a serial pixel signal 153 using the PS conversion clock 165 and outputs the serial pixel signal 153. The output serial pixel signal 153 is input to the SP conversion circuit 134. The SP conversion circuit 134 converts the input serial pixel signal 153 into a 16-bit parallel signal 154 according to the SP conversion clock 166 and outputs it. A BD signal 167 output from a BD sensor (not shown) is counted by a line counter 137, and a line select signal 168 circulated, for example, in units of 4 lines is output. In response to the line select signal 168, the delay time generation circuit 136 generates four types of delay times 169 synchronized with the SP variation conversion clock 166. The timing adjustment circuit 135 delays the parallel signal 154 for each line in accordance with the delay time 169, and outputs it as image data 155.

<Procedure for magnification correction>
Next, with reference to FIG. 8, a processing procedure for front / back magnification correction will be described. First, in step S <b> 1001, the controller 20 causes the image output apparatus 30 to start printing using image data input from the host computer 10 or the image reading unit 300. In step S <b> 1002, the control unit 340 determines whether it is a front surface print (first surface print). If it is determined that the print is front side printing, the process advances to step S1003, and the control unit 340 causes the image forming unit 320 to perform an image forming operation, further executes a fixing operation in step S1004, and outputs a printed matter in step S1005.

  On the other hand, if it is determined in step S1002 that the print is not the front print, the process advances to step S1006, and the control unit 340 determines whether the print is the back print (second print). If it is determined in S1006 that the print is the back side, the process proceeds to S1007 to start the magnification correction operation. On the other hand, if it is determined that the print is not back side printing, the process returns to S1002. When the magnification correction operation is started, in step S1008, the control unit 340 sets an N value and reads data for N lines. Here, N is a natural number and is a unit for dividing the image data. In the magnification correction operation, insertion processing or thinning-out processing for one line is performed for each divided N lines of data. Therefore, the image processing circuit 61 secures a memory area for N lines necessary for processing in the magnification correction circuit 131 and reads data (usually multi-value data including image area information). Note that this memory area may be freely configured according to the processing method, whether it is a FIFO or a normal RAM.

  In the magnification correction, when 2% reduction correction is performed on image data having an A4 horizontal size of 210 mm, assuming that the pixel size is 600 dpi and 42.3u, 99 lines corresponding to 2% of 4964 lines are corrected. become. Therefore, in order to correct 99 lines equally over the entire image, it is sufficient to correct 1 line in about 50 (N) lines. In this case, N is 50. Actually, the N is subjected to a fixing experiment using standard paper in advance, the reduction / enlargement ratio of the paper immediately after copying the surface (that is, the expansion / contraction ratio of the size of the storage material before and after fixing), and environmental conditions. A map with (humidity and temperature) is created and determined by comparison with actual copy conditions. Alternatively, it is also possible to measure the reduction / enlargement ratio of the paper when actually copying the front surface with a sensor and determine the value based on the measured value. Furthermore, it is also possible to set and determine the reduction / enlargement ratio with a copying apparatus or a printer.

  In step S <b> 1009, the control unit 340 sets the first two continuous lines of data that are read out to be compared. Subsequently, in S1010, the control unit 340 compares the data of the two lines for each pixel, and determines whether or not the data (number of bits) of each pixel match. If all the bit numbers match, the process proceeds to S1011 and the control unit 340 stores the line number of the line in the register. In the case of reducing correction, in step S1012, the control unit 340 reads the line number of the first coincidence data from the register and deletes any line (decimation process). Alternatively, the circuit may be configured such that the exposure control unit 31 ignores the image data. That is, the control unit 340 prohibits light emission related to the image data. Further, in the case of enlarging correction, in S1012, the control unit 340 adds the same line data between the data (insertion process). Thereafter, in step S1013, the control unit 340 sends data for N lines to the image forming unit, and the process advances to step S1014. In other words, in the present embodiment, when a comparison result in which the number of bits of all pixel data matches in a combination of two consecutive lines is obtained, the comparison processing of other combinations in S1010 is interrupted and becomes a magnification correction target. The combination of lines is determined as the combination of lines as a result of the comparison. In step S1014, the control unit 340 determines whether or not the above processing has been performed for all the sub-scanning lines. If all sub-scan lines have been performed, the process proceeds to S1003. If not, the process proceeds to S1015. The control unit 340 reads data for the next N lines and proceeds to S1010. Further, while performing the above-described processing for each N lines, the data for N lines in S1013 may be sent to the FIFO 132, and the operation of S1003 may be started simultaneously. When the processing of S1003 is completed, the fixing operation is performed in S1004, the printing operation is completed in S1005, and the printed matter is output.

  On the other hand, if there is a mismatch in the number of bits of any of the pixel data in the two lines of data in S1010, the process proceeds to S1016, where the control unit 340 counts the number of mismatches or the number of matches, and the number of matches is N lines up to that point. It is determined whether or not the maximum value is shown in the comparison (that is, the number of mismatches is minimum). If the maximum value is indicated here, the process proceeds to S1017, and the control unit 340 stores the line number of the line in the register, and the process proceeds to S1018. On the other hand, if the maximum value is not indicated, the process proceeds to S1018. In step S1018, the control unit 340 determines whether data comparison has been completed for all combinations of the two lines in the N line (including the first combination and the second combination). If completed, the process proceeds to S1012. If not completed, the process proceeds to S1019. The control unit 340 sets data of two lines to be compared next, and proceeds to S1010. Here, in S1012, the MAX line number written in the register in S1017 is read, the above-described line thinning processing or insertion processing is performed, and the processing from S1013 onward is performed. In the case where the processing of S1016 to S1018 is executed and the insertion processing is performed in S1012, line data is generated by calculating the average value of the data of each pixel of the two lines, and the line is Inserted.

<Image example after magnification correction>
Next, an image after magnification correction will be described with reference to FIG. Here, an example in which a black frame exists in an image will be described. Reference numeral 901 denotes an image before reduction correction. Reference numeral 902 denotes an image after reduction correction. In 901 and 902, a katakana portion indicates a character portion, a hatched portion indicates a photograph portion, and a white portion indicates a blank portion. As shown in FIG. 9, it can be seen that the black line existing at the center of the image is reduced by thinning out.

  Reference numeral 903 denotes an image before enlargement correction. Reference numeral 904 denotes an image after enlargement correction. In 903 and 904, as in 901 and 902, the katakana portion indicates a character portion, the hatched portion indicates a photograph portion, and the white portion indicates a blank portion. As shown in FIG. 9, at the time of enlargement correction, it can be seen that a line is inserted into the black frame portion to enlarge the image.

<Modification>
In the present embodiment, the magnification correction processing is performed in the exposure control unit 31 of the image forming unit 320. However, the present invention is not intended to be limited to this configuration, and the magnification correction processing is performed on the image. You may implement by the process part 310. FIG. In this case, it can be realized by providing a magnification correction circuit 131 in the image processing block as shown in FIG. In the case of such a configuration, the image processing circuit 61 in the exposure control unit 31 is not necessary. Therefore, the exposure control unit 31 receives the image data from the image processing unit 310 and can perform image writing by performing predetermined processing with the laser driving device 62.

  As described above, the image forming apparatus according to the present embodiment compares the number of bits of pixel data for each combination of two consecutive lines for each N lines in the image data, A combination of lines having a large number is determined as a magnification correction target. Further, in the determined line combination, each pixel has an average value of corresponding pixels in the two lines when one of the lines is deleted when the magnification is reduced and when the magnification is enlarged. A line is inserted between the two lines. In the present embodiment, when the image data is divided into N lines, the image data is divided in a direction corresponding to the sub-scanning direction of the exposure unit. However, the present invention is not limited to this, and the exposure unit may be divided in a direction corresponding to the main scanning direction. Thereby, the image forming apparatus can appropriately correct the sub-scanning magnification (or main-scanning magnification) while suppressing a decrease in print quality and productivity.

<Second Embodiment>
Next, a second embodiment will be described with reference to FIG. FIG. 11 shows a modification of the flowchart of FIG. In the present embodiment, in the comparison process of two lines, when the whole line does not match and there are a plurality of comparison results having mismatched (or matched) data with the same number of pixels, which line is selected. To control whether to perform insertion / decimation processing. Specifically, steps S1020 and S1021 are added to the flowchart described in the first embodiment. Therefore, the other processes are the same as those in the first embodiment, and thus description thereof is omitted.

  If there is a mismatch portion in the comparison of two lines (Yes in S1010) and there are a plurality of comparison results having mismatch data with the same number of pixels, in S1017, the control unit 340 sets the numbers of the plurality of lines respectively. Store in multiple registers. At that time, the control unit 340 further counts the number of matched white data information (for example, 0 value), black data information (for example, 1 value), and photo information, and stores them in the register. Specifically, the control unit 340 determines whether each pixel is white data information, black data information, or photographic information using the value (number of bits) of each pixel and the attribute data described above, The above counting is performed.

  If it is determined in step S1018 that the comparison of N lines has been completed, in step S1020, the control unit 340 determines whether there are a plurality of matching comparison results. If it does not exist, the process proceeds to S1012 as in the first embodiment. If it exists, the process advances to step S1021, and the control unit 340 determines a thinning line or insertion line target based on the white data information, black data information, and photo information stored in the register, and thins only the determined line information. Or set to the register used for insertion. As the determination method, there are a plurality of methods as described below.

In particular,
1: Insertion / decimation processing is performed on the first line set in the register among the ones with the most white information 2: Insertion / decimation is performed on the line with the least amount of photo information among the ones with the most white information Process.
3: Insertion / decimation processing is performed on the line with the least amount of photographic information and the line with the least amount of black information in the photographic information among the ones with the largest amount of white information.
4: Insertion / decimation processing is performed on one of the longest continuous lines among the lines having continuous matching data.

<Third Embodiment>
Next, a third embodiment will be described with reference to FIG. FIG. 12 shows a modification of the flowchart of FIG. In the present embodiment, in the comparison process of two lines, when a plurality of comparison results that match the entire line are generated, which line is selected and the insertion / decimation process is controlled. Specifically, steps S1022 to S1024 are added to the flowchart described in the second embodiment. Accordingly, the other processes are the same as those in the second embodiment, and thus description thereof is omitted.

  When all the data match in the comparison of the two lines (No in S1010), in S1011, the control unit 340 stores the numbers of the plurality of lines in the plurality of registers. At that time, the control unit 340 further counts the number of matched white data information, black data information, and photo information and stores them in the register. Thereafter, in S1022, the control unit 340 determines whether or not the comparison of N lines has been completed. If not completed, the process advances to step S1023, and the control unit 340 sets data of two lines to be compared next, and the process advances to step S1010. On the other hand, if completed, the process advances to step S1024, and the control unit 340 determines a thinning line or insertion line target based on the white data information, black data information, and photo information stored in the register. Further, the control unit 340 sets only the determined line information in a register used for thinning out or inserting lines. As the determination method, there are a plurality of methods as described below.

In particular,
1: Insertion / decimation processing is performed on the first line set in the register among the ones with the most white information 2: Insertion / decimation is performed on the line with the least amount of photo information among the ones with the most white information Process.
3: Insertion / decimation processing is performed on the line with the least amount of photographic information and the line with the least amount of black information in the photographic information among the ones with the largest amount of white information.
4: Insertion / decimation processing is performed on one of the longest continuous lines among the lines having continuous matching data.

  If it is a normal document, there is no problem with the determination method 1 described above, but the determination method 4 is preferable for photographic information or the like. As described above, the determination methods 1 to 4 may be selected for the processing of S1024 according to the information to be printed.

<Fourth Embodiment>
Next, a fourth embodiment will be described with reference to FIG. FIG. 13 shows a modification of the flowchart of FIG. In the present embodiment, reduction and enlargement are performed based on the enlargement ratio set in the printer or the copying apparatus from the configuration of the third embodiment. Specifically, S1002 and S1006 are deleted from the flowchart of FIG. 12, and S4001 and S4002 are added. Therefore, the other processes are the same as those in the third embodiment, and a description thereof will be omitted.

  In step S <b> 4001, the control unit 340 sets an enlargement / reduction ratio for the image forming unit 320. This enlargement / reduction ratio is set by an operator via the operation unit 330, for example. Thereafter, when printing is started in S1001, in S4002, the control unit 340 determines whether or not the minute enlargement possible range is reached. If it is not in the minute enlargement possible range, the process proceeds to S1003 and subsequent steps, and is processed in the normal copy mode. On the other hand, when it is determined that the range can be minutely enlarged, the process proceeds to S1007 and subsequent steps. In S4002, it is determined whether or not it is within a minute enlargement possible range, but it may be judged whether or not it is within a minute reduction possible range.

  In the above-described processing, the enlargement / reduction ratio may be set in a minute enlargement / reduction mode in which a fixed magnification of 1 to 2% is set. Alternatively, in the case of normal enlargement / reduction setting, the configuration is such that enlargement / reduction can be executed by inserting / decimating lines in the sub-scanning direction up to the prepared FIFO (register) range for N lines. May be.

  For example, in the magnification correction, when 2% enlargement correction is performed on image data of A4 horizontal size 210 mm, assuming that the pixel size is 600 dpi and 42.3u, 98 lines corresponding to 2% of 4964 lines are inserted. It will be corrected. Therefore, to correct 98 lines equally over the entire image, it is sufficient to correct 1 line in about 50 lines. In this case, N is 50. This process is performed in S1007.

  The description of the subsequent processing is the same as in the third embodiment, and will be omitted. For the sake of simplicity, the enlargement / reduction in the main scanning direction has not been described. Of course, if it is necessary to perform the enlargement / reduction in the sub scanning direction together with the enlargement / reduction in the sub scanning direction, the data in the main scanning direction immediately before the image formation in S1003. Is divided into N equal parts, and a pixel piece (white or black data) is inserted into each divided one area, so that enlargement / reduction at the same time in main scanning and sub-scanning can be realized. This is the same in the first to third embodiments. With this configuration, even in the normal copy mode, in the case of minute enlargement / reduction, enlargement / reduction in the main / sub-scanning direction can be realized with a simple procedure.

Claims (10)

Formed on the photoconductor, an exposure unit that scans light emitted from a light source according to image data of an image to be formed, and exposes the photoconductor with the scanned light to form a latent image. Developing means for developing the latent image formed with a developer, transfer means for transferring the developer image developed by the developing means to a recording material, and fixing the developer image transferred to the recording material to the recording material An image forming apparatus comprising fixing means for causing
Comparison means for comparing the number of pixel data having the same number of bits in the sub-scanning direction for each combination of two consecutive line data with respect to line data for scanning the photosensitive member by one light emitted from the light source;
When the number of the pixel data of the first combination of the line data is larger than the number of the pixel data of the second combination in the comparison result by the comparison unit, when reducing the magnification of the image in the sub-scanning direction And a magnification correction means for prohibiting emission of the light from the light source based on any one of the two line data in the first combination ,
The magnification correction unit generates line data by calculating an average value of pixels arranged in the sub-scanning direction in the two line data of the first combination when enlarging the magnification of the image in the sub-scanning direction. an image forming apparatus characterized that you insert the generated line data between two line data of the first combination. Further comprising a dividing means for dividing the image data of the image to be formed into a predetermined number of lines in a direction corresponding to a sub-scanning direction of the exposure means;
The comparison unit compares the number of pixel data having the same number of bits in the sub-scanning direction for each combination of two consecutive line data among the predetermined number of lines divided by the division unit. The image forming apparatus according to claim 1 . The comparison means interrupts the subsequent comparison process when the number of bits matches in all pixel data in the combination of the two consecutive lines,
3. The image formation according to claim 1, wherein the magnification correction unit determines a combination of lines having the same number of bits in all the pixel data as a combination of lines to be subjected to the magnification correction. apparatus. Formed on the photoconductor, an exposure unit that scans light emitted from a light source according to image data of an image to be formed, and exposes the photoconductor with the scanned light to form a latent image. Developing means for developing the latent image formed with a developer, transfer means for transferring the developer image developed by the developing means to a recording material, and fixing the developer image transferred to the recording material to the recording material An image forming apparatus comprising fixing means for causing
Comparison means for comparing the number of pixel data having the same number of bits in the sub-scanning direction for each combination of two consecutive line data with respect to line data for scanning the photosensitive member by one light emitted from the light source;
When the number of the pixel data of the first combination of the line data is larger than the number of the pixel data of the second combination in the comparison result by the comparison unit, when reducing the magnification of the image in the sub-scanning direction And magnification correction means for prohibiting emission of the light from the light source based on any one of the two line data in the first combination.
Further comprising
In addition to the number of bits of each pixel, attribute data indicating whether each pixel is character data or photo data is added to the image data,
The comparing means is a counting means for counting the number of white data having 0 value, the number of black data having 1 value, and the number of photographic data based on the number of bits of each pixel and the attribute data. With
The magnification correction means includes
When there are a plurality of combinations of lines with the largest number of pixel data having the same number of bits, a combination of lines with the largest number of white data is determined as a combination of lines to be subjected to the magnification correction. images forming device you characterized. When the magnification correction in the sub-scanning direction is completed by the magnification correction unit, the image data for which the magnification correction has been completed is divided into a predetermined number of lines in a direction corresponding to the main scanning direction of the exposure unit, comparison means and using said magnification compensation means, the image forming apparatus according to any one of claims 1 to 4, further comprising means for executing the magnification correction in the main scanning direction. 6. The image forming apparatus according to claim 5 , wherein the predetermined number is obtained from an expansion / contraction ratio between a size of the recording material before fixing by the fixing unit and a size of the recording material after fixing. A setting unit for setting an enlargement ratio or a reduction ratio in image formation;
The image forming apparatus according to claim 5 , wherein the predetermined number is obtained from an enlargement ratio or a reduction ratio set by the setting unit. The image forming apparatus can form images on both sides of a recording material,
The magnification correcting means, in the case of forming images on both sides of the recording material, according to any one of claims 1 to 7, characterized in that to perform the magnification correction in forming an image of the second surface Image forming apparatus. Formed on the photoconductor, an exposure unit that scans light emitted from a light source according to image data of an image to be formed, and exposes the photoconductor with the scanned light to form a latent image. Developing means for developing the latent image formed with a developer, transfer means for transferring the developer image developed by the developing means to a recording material, and fixing the developer image transferred to the recording material to the recording material And a fixing unit that controls the image forming apparatus.
Comparing means compares the number of pixel data having the same number of bits in the sub-scanning direction for each combination of two consecutive line data with respect to line data for scanning the photosensitive member by one light by the light emitted from the light source. A comparison step;
When the number of pixel data in the first combination of the line data is greater than the number of pixel data in the second combination in the comparison result in the comparison step, the magnification correction unit A magnification correction step for prohibiting emission of the light from the light source based on any one of the two line data in the first combination when reducing the magnification ;
The magnification correction step generates line data by calculating an average value of pixels arranged in the sub-scanning direction in the two line data of the first combination when enlarging the magnification of the image in the sub-scanning direction. , inserted to a control method of an image forming apparatus according to claim Rukoto between the generated line data of two line data of the first combination. Formed on the photoconductor, an exposure unit that scans light emitted from a light source according to image data of an image to be formed, and exposes the photoconductor with the scanned light to form a latent image. Developing means for developing the latent image formed with a developer, transfer means for transferring the developer image developed by the developing means to a recording material, and fixing the developer image transferred to the recording material to the recording material And a fixing unit that controls the image forming apparatus.
Comparing means compares the number of pixel data having the same number of bits in the sub-scanning direction for each combination of two consecutive line data with respect to line data for scanning the photosensitive member by one light by the light emitted from the light source. A comparison step;
When the number of pixel data in the first combination of the line data is greater than the number of pixel data in the second combination in the comparison result in the comparison step, the magnification correction unit A magnification correction step for prohibiting emission of the light from the light source based on any one of the two line data in the first combination when the magnification is reduced;
In addition to the number of bits of each pixel, attribute data indicating whether each pixel is character data or photo data is added to the image data,
The comparison step counts the number of white data having 0 value, the number of black data having 1 value, and the number of photographic data based on the number of bits of each pixel and the attribute data. Including
The magnification correction step includes
When there are a plurality of combinations of lines with the largest number of pixel data having the same number of bits, a combination of lines with the largest number of white data is determined as a combination of lines to be subjected to the magnification correction. And a control method for the image forming apparatus .

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