JP2011164621A - Image forming apparatus and method of adjusting image point - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus for adjusting an image point by reading an adjustment pattern printed on a recording medium (paper or transfer belt). <P>SOLUTION: The image forming apparatus includes: a printer including a photoreceptor scanned by a laser beam from a laser exposure device for forming an image on the recording medium; an image processing part for processing an input image data and outputting the data to the printer; a printing part for controlling the printer and printing an image point adjustment pattern on the recording medium; an image reading part for reading the image point adjustment pattern printed on the recording medium; and an image point adjustment part for detecting the image point of the image based on the density of the image read at the image reading part and for controlling the laser intensity of a pixel constituting the image point according to the size of the detected image point. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  Embodiments described herein relate generally to an image forming apparatus having an image dot adjustment function and an image dot adjustment method.

  2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, the image quality may deteriorate due to a change in the environment in which the image forming apparatus is installed or a change with time. For this reason, an image quality adjustment function for automatically adjusting image quality when a preset number of sheets is printed is provided, and density adjustment, edge enhancement (sharpness adjustment), and the like are performed.

  For example, density adjustment is an example of an image quality adjustment function. An image printed on a sheet is read by a density sensor, and laser power and contrast potential are adjusted based on the value read by the sensor to stabilize the image density. Yes. However, the size of the image dots formed on the photosensitive drum and paper may change depending on humidity, temperature, laser power, and contrast potential. When the size of the image point changes, stable control of reproduction of isolated points, fine lines, and fine characters cannot be performed, and image quality maintenance control may become insufficient. Some low-cost models do not have an image quality maintenance control function.

JP 2007-336555 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus and an image point adjusting method capable of forming an image while stabilizing the size of an image dot.

  An image forming apparatus according to an embodiment includes a photoconductor that is scanned by a laser beam from a laser exposure apparatus, a printer unit that forms an image on a recording medium, and processes input image data and outputs the processed image data to the printer unit An image processing unit that controls the printer unit to print an image dot adjustment pattern on a recording medium; an image reading unit that reads the image dot adjustment pattern printed on the recording medium; An image point adjustment unit that detects an image dot of the image based on the density of the image read by the image reading unit, and controls a laser intensity of a pixel constituting the image point according to the detected size of the image point; Are provided.

1 is a configuration diagram illustrating a configuration of an image forming apparatus according to an embodiment. FIG. 2 is an enlarged configuration diagram illustrating an image forming unit according to an embodiment. Explanatory drawing which shows the example of a printing of the image point adjustment pattern in one Embodiment. 1 is a block diagram showing a configuration of a control system of an image forming apparatus according to an embodiment. The block diagram which shows the structure of the image point adjustment part which is the principal part of one Embodiment. Explanatory drawing which shows an example of the image read by the image reading part in one Embodiment. Explanatory drawing which shows operation | movement of the image point formation information generation part in one Embodiment. Explanatory drawing which shows an example of the screen pattern in one Embodiment. Explanatory drawing which shows the other example of the screen pattern in one Embodiment. Explanatory drawing which shows an example of the tint block printing in one Embodiment. Explanatory drawing which shows an example of the some tint block pattern in one Embodiment. Explanatory drawing which shows an example of the tint block pattern output in one Embodiment.

  Embodiments for carrying out the invention will be described below with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected about the same location.

(First embodiment)
FIG. 1 is a configuration diagram illustrating an image forming apparatus according to an embodiment. In FIG. 1, an image forming apparatus 100 is, for example, an MFP (Multi-Function Peripherals), a printer, a copier, or the like, which is a multifunction peripheral. In the following description, an MFP will be described as an example. An upper part of the main body 11 of the MFP 100 has a document table, and an automatic document feeder (ADF) 12 is provided on the document table so as to be opened and closed. Further, an operation panel 13 constituting an operation unit is provided on the upper portion of the main body 11. The operation panel 13 includes an operation unit 14 composed of various keys and a touch panel type display unit 15.

  A scanner unit 16 is provided below the ADF 12 in the main body 11. The scanner unit 16 reads a document sent by the ADF 12 or a document placed on a document table and generates image data. Further, a printer unit 17 is provided at the center of the main body 11, and a plurality of cassettes 18 for storing various sizes of paper are provided at the bottom of the main body 11.

  The printer unit 17 includes a photosensitive drum, a laser, and the like. The printer unit 17 processes image data read by the scanner unit 16 or image data created by a PC (Personal Computer) or the like to fix an image on a sheet as a recording medium. . The paper on which the image is fixed by the printer unit 17 is discharged to the paper discharge unit 41.

  The printer unit 17 is, for example, a tandem color laser printer, which scans a photosensitive member with a laser beam from a laser exposure device 19 to generate an image. The printer unit 17 generates black (K), yellow (Y), magenta (M ) And cyan (C) image forming units 20K, 20Y, 20M, and 20C. The image forming units 20K, 20Y, 20M, and 20C are arranged below the transfer belt 21 in parallel from upstream to downstream. Since the image forming units 20K, 20Y, 20M, and 20C have the same configuration, the configuration will be described with the image forming unit 20C as a representative.

  FIG. 2 is an enlarged configuration diagram illustrating the image forming unit 20C. The image forming unit 20C includes a photosensitive drum 22C that is an image carrier. A charging charger 23C, a developing device 24C, a primary transfer roller 25C, a cleaner 26C, a blade 27C, and the like are arranged around the photosensitive drum 22C along the rotation direction t. The exposure position of the photosensitive drum 22C is irradiated with a cyan laser beam from the laser exposure device 19 to form an electrostatic latent image on the photosensitive drum 22C.

  The charging charger 23C uniformly charges the entire surface of the photosensitive drum 22C. The developing device 24C includes a mixer that stirs the developer and a developing roller to which a developing bias is applied. The developing roller 24C supplies toner of a two-component developer including toner and a carrier to the photosensitive drum 22C. The cleaner 26C removes residual toner on the surface of the photosensitive drum 22C using the blade 27C.

  As shown in FIG. 1, a developer cartridge 28 that supplies developer to the developing devices 24K, 24Y, 24M, and 24C is provided above the image forming units 20K, 20Y, 20M, and 20C. The developer cartridge 28 is adjacent to black (K), yellow (Y), magenta (M), cyan (C) developer cartridges 28K, 28Y, 28M, and 28C.

  The transfer belt 21 moves cyclically, and for example, semiconductive polyimide is used from the viewpoint of heat resistance and wear resistance. The transfer belt 21 is stretched around a driving roller 31 and driven rollers 32 and 33, and the transfer belt 21 is in contact with and faces the photosensitive drums 22K, 22Y, 22M, and 22C. As shown in FIG. 2, a primary transfer voltage is applied by a primary transfer roller 25C to a position of the transfer belt 21 facing the photosensitive drum 22C, and a toner image (developer image) on the photosensitive drum 22C is transferred. Primary transfer is performed on the transfer belt 21.

  A secondary transfer roller 34 is disposed facing the drive roller 31 that stretches the transfer belt 21. When the sheet S passes between the driving roller 31 and the secondary transfer roller 34, a secondary transfer voltage is applied by the secondary transfer roller 34, and the toner image on the transfer belt 21 is secondarily transferred to the sheet S. A belt cleaner 35 is provided near the driven roller 33 of the transfer belt 21.

  On the other hand, the laser exposure device 19 includes a polygon mirror 19a, an imaging lens system 19b, a mirror 19c, and the like, and scans the laser beam emitted from the semiconductor laser element in the axial direction of the photosensitive drums 22K to 22C.

  Further, a separation roller 36 for taking out the paper S in the paper feed cassette 18, a transport roller 37, and a registration roller 38 are provided between the paper feed cassette 18 and the secondary transfer roller 34. A fixing device 39 is provided downstream.

  A paper discharge roller 40 is provided downstream of the fixing device 39 to discharge the paper S to the paper discharge unit 41. Further, a reverse conveyance path 42 is provided. The reverse conveyance path 42 includes rollers 43, 44, and 45, and reverses the paper S and guides it in the direction of the secondary transfer roller 34, and is used when performing double-sided printing. The paper S that has passed through the fixing device 39 is guided to the paper discharge unit 41 or the reverse conveyance path 42 by the sorting gate 46.

  A sensor 63 for reading an adjustment pattern (described later) printed on the paper S is provided downstream of the paper discharge roller 40. Alternatively, as shown in FIG. 2, a sensor 64 that reads the adjustment pattern printed on the transfer belt 21 may be provided downstream of the photosensitive drum 22C.

  Next, the operation of the image forming apparatus 100 of FIGS. 1 and 2 will be described. When image data is input from the scanner 16 or a PC, images are sequentially formed in the image forming units 20K to 20C. Taking the image forming unit 20C as an example, the photosensitive drum 22C is irradiated with a laser beam corresponding to cyan (C) image data to form an electrostatic latent image. Further, the electrostatic latent image on the photosensitive drum 22C is developed by the developing device 24C to form a cyan (C) toner image (developer image).

  The photosensitive drum 22C comes into contact with the rotating transfer belt 21 and primarily transfers a cyan (C) toner image onto the transfer belt 21 by the primary transfer roller 25C. After the toner image is primarily transferred to the transfer belt 21 on the photosensitive drum 22C, the residual toner is removed by the cleaner 26C and the blade 27C, so that the next image can be formed.

  In the same manner as the cyan (K) toner image forming process, black (K), yellow (Y), and magenta (M) toner images are formed by the previous image forming units 20K, 20Y, and 20M, and the toners of the respective colors. Images are sequentially transferred to the same position on the transfer belt 21. Accordingly, a black (K), yellow (Y), magenta (M), and cyan (C) toner image can be multiplex-transferred onto the transfer belt 21 to obtain a full-color toner image.

  The transfer belt 21 performs secondary transfer of the full-color toner image onto the sheet S at once by the transfer bias of the secondary transfer roller 34. In synchronization with the full-color toner image on the transfer belt 21 reaching the secondary transfer roller 34, the paper S is fed from the paper feed cassette 18 to the secondary transfer roller 34. The sheet S on which the toner image is secondarily transferred reaches the fixing device 39 and fixes the toner image. The paper S on which the toner image is fixed is discharged to the paper discharge unit 41. On the other hand, the transfer belt 21 is cleaned of residual toner by a belt cleaner 35 after the completion of the secondary transfer.

  Further, the image forming apparatus (MFP) 100 has an image point adjustment function (details will be described later), and prints an adjustment pattern on the paper S or the transfer belt 21 during image point adjustment. FIG. 3 shows a state in which the adjustment pattern P is printed on the paper S. The adjustment pattern P printed on the paper S is read by the sensor 63 (FIG. 1). Further, the adjustment pattern P printed on the transfer belt 21 may be read by the sensor 64 (FIGS. 1 and 2). For the sensors 63 and 64, for example, a high resolution sensor such as a CCD sensor or a CMOS sensor used in a digital camera is used.

  FIG. 4 is a block diagram illustrating a configuration of a control system of the image forming apparatus (MFP) 100 according to the embodiment. In FIG. 4, the MFP 100 includes a main control unit 50, an operation panel 13, a scanner unit 16, and a printer unit 17. The control system of the MFP 100 includes a plurality of CPUs including a main CPU 500 in the main control unit 50, a panel CPU 130 of the operation panel 13, a scanner CPU 160 of the scanner unit 16, and a printer CPU 170 of the printer unit 17.

  The main control unit 50 includes a main CPU 500, ROM 501, RAM 502, NVRAM 503, shared RAM 504, page memory control unit 505, page memory 506, HDD 507 as a storage device, network controller 508, and image processing unit 60. Reference numeral 101 denotes an image data bus.

  The main CPU 500 controls the overall operation of the MFP 100 and controls the ADF 12. The ROM 501 stores a control program and the like. The RAM 502 temporarily stores data. The NVRAM 503 is a non-volatile memory and retains stored data even when the power is turned off. The shared RAM 504 is used for bidirectional communication between the main CPU 500 and the printer CPU 170.

  The image processing unit 60 controls the page memory control unit 505 to control storage and reading of image data in the page memory 506. Thereby, image conversion processing such as enlargement / reduction of image information is performed. The page memory 506 has an area capable of storing image information for a plurality of pages, and can store image information from the scanner unit 16 for each page. The network controller 508 is connected to a network, and the MFP 100 can be connected to an external device such as a server or a PC (Personal Computer) via the network controller 508.

  The HDD 507 compresses and stores image data read by the scanner unit 16 and image data (document data, drawing image data, etc.) from the PC. The image data stored in the HDD 507 is input to the image processing unit 60, subjected to various image processing, and printed on paper by the printer unit 17. The image processing unit 60 has an image point adjustment function, which will be described later.

  The operation panel 13 includes a panel CPU 130 connected to the main CPU 500, a display unit 15 including various operation keys 14 and liquid crystal, and the operation key 14 includes a numeric keypad for instructing the number of copies to be printed. The display unit 15 has a touch panel function, and can input various instructions such as paper size and printing magnification, and can perform various settings such as image point adjustment by operating the display 15.

  The scanner unit 16 includes a scanner CPU 160, an image correction unit 161, a CCD driver 162 that drives an image sensor, and the like. The CCD driver 162 drives the image sensor to read an image of the document and converts it into image data. The image correction unit 161 converts the R, G, and B analog signals output from the image sensor into digital signals, the shading correction circuit, and the corrected digital signal from the shading correction circuit, respectively. It is composed of a line memory and the like for storing once.

  The printer unit 17 includes a printer CPU 170, a laser driver 171 that drives the laser of the laser exposure device 19, a transport control unit 172 that controls transport of the paper P, and a control unit 173 that controls the charger, the developing device, the transfer device, and the like. Have.

  The main CPU 500 performs bidirectional communication with the printer CPU 170 via a shared RAM (random access memory) 504, the main CPU 500 issues an operation instruction, and the printer CPU 170 returns a status status. The printer CPU 170 and the scanner CPU 160 perform serial communication, the printer CPU 170 issues an operation instruction, and the scanner CPU 160 returns a status status. Note that the image processing unit 60, the page memory 506, the network controller 508, the image correction unit 161, and the laser driver 171 are connected by the image data bus 101.

  FIG. 5 is a block diagram illustrating a configuration of the image processing unit 60 and the image point adjustment unit 70 which are main parts of the embodiment. Image data read by the scanner unit 16 is input to the image processing unit 60, and image data whose image quality has been adjusted by the image processing unit 60 is output to the printer unit 17. The image processing unit 60 includes, for example, a color conversion unit, a spatial filter, a density conversion unit, and the like.

  The color conversion unit converts the R, G, and B image data from the scanner unit 16 into yellow (Y), magenta (M), and cyan (C) data. The spatial filter performs processing such as background removal, noise removal, and edge enhancement on the Y, M, and C image data output from the color conversion unit. The density conversion unit adjusts the density of each color of C, M, and Y. After the density conversion, each of the C, M, and Y image data is subjected to black correction processing (inking), and Y, M, C, and K (black) image data is obtained.

  The image point adjustment unit 70 forms part of the density conversion unit, and is configured in the image processing unit 60. The image point detection unit 71, the image point formation information calculation unit 72, and the image point control information. A generation unit 73 and an image point control unit 74 are included.

  The printer unit 17 is connected to an image reading unit 64 including first and second sensors 63 and 64. The sensors 63 and 64 selectively read the adjustment pattern P printed on the paper S that has passed through the transfer belt 21 or the fixing device 39 of the printer unit 17, and send the read result to the image point detection unit 71.

  The data of the adjustment pattern P is stored in the memory 61. The printer unit 17 is controlled by the printer CPU 170. The printer CPU 170 reads the adjustment pattern data stored in the memory 61 in the image point adjustment mode, and the printer unit 17 prints the adjustment pattern P on the transfer belt 21 or the paper S. The printer CPU 170 and the memory 61 constitute a printing unit that controls the printer unit 17 to print the adjustment pattern P on the transfer belt 21 and the paper S.

  Hereinafter, the operation of the image point adjustment unit 70 will be described. First, the adjustment pattern P formed on the recording medium such as the transfer belt 21 or the paper S is read as a two-dimensional image by the sensor 63 or 64 of the image reading unit 62. FIG. 6 shows an image P1 read by the image reading unit 62. The read image P1 is fed back to the image point detector 71.

  That is, when the image point adjustment is performed using the adjustment pattern fixed on the paper S, the adjustment pattern P is printed on the paper S. Then, the adjustment pattern P is read by the sensor 63. In addition, when the image point adjustment is performed using the adjustment pattern P printed on the transfer belt 21, the adjustment pattern P printed on the transfer belt 21 is read by the sensor 64.

  When the image point is adjusted using the adjustment pattern P printed on the transfer belt 21, it is not necessary to print on the paper S, so that the image point can be adjusted at high speed. In addition, when adjusting the image point using the adjustment pattern P printed on the paper S, the toner is fixed on the paper S and the adjustment pattern P is printed with high accuracy. it can. Which sensor 63, 64 output is used is arbitrary.

  The image point detection unit 71 detects an image point based on the density of the read image P1. That is, an image P2 having a high density (indicated by a black dot) contained in the image P1 is extracted to detect an image point. The image P2 is a set of a plurality of points. For example, when the resolution is 600 dpi, one point (one image point) has a size of 42 μm × 42 μm.

  Note that the image reading unit 62 needs to use a sensor having a resolution higher than the resolution of image formation in the printer unit 17 in order to detect an image point. For example, if the resolution of the printer unit 17 is 2400 dpi, the sensor resolution may be about 4800 dpi.

  The image point formation information calculation unit 72 calculates image point formation information based on the image points detected by the image point detection unit 71. That is, as shown in FIG. 7, when the size of one pixel on image formation is L1, the major axis / minor axis of the detected image point P0, its ratio (roundness), and average value (diameter). Are calculated and used as the dot formation information. Since the size of the image point P0 changes depending on the surrounding environment (temperature, humidity, laser power, contrast potential, etc.) as in P01 and P02, the image dot formation information also changes.

  The image point control information generation unit 73 generates image point control information based on the image point formation information. For example, the laser exposure device 19 is controlled according to the size of the diameter of the image point P0, and information for controlling the laser lighting time in the pixel is generated. Alternatively, information for controlling the laser power is generated. The laser lighting time can be controlled by PWM (pulse width modulation).

  The image point control unit 74 adjusts the image points based on the image point control information generated by the image point control information generation unit 73.

  (First Example of Image Point Adjustment) For example, when the diameter of the image point P0 is smaller than a preset size, the pulse width of PWM is increased to increase the laser emission energy. Or increase the laser power. On the other hand, when the diameter of the image point P0 is larger than a preset size, the pulse width of PWM is reduced to lower the laser emission energy. Or reduce the laser power.

  (Second Example of Image Point Adjustment) Further, the image point control unit 74 may switch the screen configuration in the halftone process without being limited to the laser control. For example, when image formation is performed at a high resolution (for example, 2400 dpi or 4800 dpi) by the printer unit 17 and a single dot pattern is formed by a plurality of pixels, halftone adjustment is performed according to the size of the detected dot diameter. Switch screen configuration in processing.

  In other words, in the image forming apparatus, when outputting an image including a halftone such as a photograph, the halftone portion is divided into fine areas of a certain size, and dots (halftone dots) are placed on the respective areas. Brightness and darkness can be expressed by size and density. Accordingly, the screen dots can be adjusted by preparing a plurality of screen panes having different halftone dot patterns and switching the screen patterns according to the contents to be output.

  FIG. 8 shows an example of a screen pattern, which is composed of, for example, 6 × 6 squares (36 strokes). As shown in FIGS. 8A and 8B, a plurality of screen patterns S1, S2,... Having different dot sizes in a dot pattern (represented by a collection of black dots) are prepared. When the detected image point is large, the screen pattern S1 (FIG. 8A) composed of small dots is used, and when the detected image point is small, the screen pattern S2 composed of large dots is used (FIG. 8B). .

  That is, when the detected image point is large, one image point tends to become thicker, so that the size of the image point is brought close to a specified value by using the screen pattern S1 composed of small dots in anticipation of becoming thicker. be able to. Further, when the detected image point is small, one image point tends to become thin. Therefore, the size of the image point can be brought close to a specified value by using the screen pattern S2 composed of large dots.

  (Third Example of Image Point Adjustment) As shown in FIG. 9, the image point control unit 74 prepares a plurality of screen patterns S3, S4,. Depending on the size, screen patterns S3, S4... May be selected. FIG. 9A shows an example of the screen pattern S3 having a large number of dots, and FIG. 9B shows an example of the screen pattern S4 having a small number of dots. When the detected image dot is small, the screen pattern S3 with a large number of dots is used, and when the detected image dot is large, the screen pattern S4 with a small number of dots is used.

  As described above, by selecting a screen pattern with a different dot size or a screen pattern with a different number of dots according to the detection result of the dot size, the total area of the dots constituting the dot pattern is made uniform. Can do. Therefore, the average image density can be made constant even when the surrounding environment changes.

  Also, when a pattern with a specific density (background pattern) is superimposed on the output image and synthesized as in background pattern printing, the visual density of the background pattern may appear different depending on the size of the image dots.

  FIG. 10 is an explanatory diagram illustrating an example of tint block printing. Background pattern printing is a technique for attaching a special background pattern to the background of an original in order to distinguish the original from a copy. For example, as shown in FIG. 10, when the character A is printed on the paper S and it is desired to make the character A rise when it is copied, the portion of the character A increases the size of the dot pattern J1 and the density. The background pattern printing is performed by reducing the size of the dot pattern J2 and the density of the portion other than the letter A. However, the visual density of the tint block pattern appears different when the size of the image point changes.

  (Fourth Example of Image Point Adjustment) Therefore, the image point control unit 74 prepares and detects a plurality of background pattern patterns having different dot pattern sizes and densities in order to keep the background pattern pattern density constant. The copy-forgery-inhibited pattern is switched according to the diameter of the image dot.

  FIG. 11 is a diagram illustrating an example of a plurality of tint block patterns having different dot sizes, and a plurality of tint block patterns such as “dark”, “intermediate”, and “light” are prepared depending on the dot size and the dot shape. ing. The copy-forgery-inhibited pattern is a type of screen pattern. For example, when the detected dot size is small, the image dot control unit 74 outputs a copy-forgery-inhibited pattern with large dots, and when the detected image dot size is large, the image dot control unit 74 Outputs a small tint block pattern.

  FIG. 12 shows an example of the output tint block pattern (screen pattern), where (a) illustrates the tint block pattern Q1 with large dots, and (b) illustrates the tint block pattern Q2 with small dots. In this way, by switching the tint block pattern according to the detected image dot size, the visual density of the tint block pattern can be stabilized.

  As described above, in the image forming apparatus according to the embodiment, the image formed on the recording medium is read by the image reading unit, the formation state of the image dots is determined, and the laser lighting time and the laser power in the pixel are determined. By adjusting, it is possible to control the dot reproduction (dot gain) to be constant. Alternatively, it is possible to control the average image density to be constant by judging the formation state of the image dots and switching the screen configuration and the background pattern pattern configuration in halftone processing.

  Note that the image point adjustment as described above is automatically performed, for example, when the power is turned on, when a preset number of prints is reached, or every preset time (for example, once a week). The user may operate the operation panel 13 to forcibly execute the image point adjustment.

(Second Embodiment)
In the first embodiment, the example in which the image point adjustment is performed by feeding back the reading result of the image reading unit 62 to the image point detection unit 71 has been described. Is to do. When performing image point adjustment by a manual instruction, an image density level item is selected from a menu screen displayed on the display unit 15 of the operation panel 13.

  Then, the image point control information generation unit 73 determines the image point control information in accordance with the manual input of the image density level, and switches the adjustment values of the laser pulse width and laser power to values designated by the user. Alternatively, a screen pattern or a tint block pattern may be selected from a plurality of patterns and switched according to a user operation. By adopting such a configuration, the size of the image dot (dot gain) can be stably formed based on the user operation.

  According to the embodiment described above, the image density can be stabilized by adjusting the image point. In addition, it is not limited to the said embodiment, A various deformation | transformation is possible. For example, the adjustment pattern on the photosensitive drum may be read by a sensor.

  As mentioned above, although several embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the invention described in the claims and equivalents thereof as well as included in the scope and gist of the invention.

100: Image forming apparatus (MFP)
11. Image forming apparatus main body 13. Operation panel (operation unit)
16: Scanner unit 17 ... Printer unit 20K, 20Y, 20M, 20C ... Image forming unit 21 ... Transfer belts 22K, 22Y, 22M, 22C ... Photosensitive drum (image carrier)
34 ... Secondary transfer roller 39 ... Fixing device 40 ... Paper discharge roller 41 ... Paper discharge unit 42 ... Reverse conveyance path 50 ... Main control unit 60 ... Image processing unit 61 ... Memory 62 ... Image reading units 63, 64 ... First, Second sensor 70 ... image point adjustment unit 71 ... image point detection unit 72 ... image point formation information calculation unit 73 ... image point control information generation unit 74 ... image point control unit 170 ... printer CPU
500 ... Main CPU

Claims (10)

A printer unit that includes a photoreceptor that is scanned by a laser beam from a laser exposure apparatus and that forms an image on a recording medium;
An image processing unit that processes input image data and outputs the processed image data to the printer unit;
A printing unit for controlling the printer unit to print a pattern for image dot adjustment on a recording medium;
An image reading unit for reading the image dot adjustment pattern printed on the recording medium;
An image point adjusting unit that detects an image dot of the image based on the density of the image read by the image reading unit, and controls a laser intensity of a pixel constituting the image point according to the detected size of the image point; An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the image point adjusting unit controls at least one of a lighting time of the laser and a power of the laser according to a size of the detected image dot. The printer unit includes a transfer belt that transfers a developer image formed on an image carrier, and a fixing device that fixes the developer image transferred to the transfer belt to a sheet.
The image forming apparatus according to claim 1, wherein the image reading unit includes a sensor that reads the image dot adjustment pattern printed on the transfer belt or the image dot adjustment pattern fixed on the paper. A printer unit including an image forming unit;
An image processing unit that processes input image data and outputs the processed image data to the printer unit;
A printing unit for controlling the printer unit to print a pattern for image dot adjustment on a recording medium;
An image reading unit for reading the image dot adjustment pattern printed on the recording medium;
The image point of the image is detected based on the density of the image read by the image reading unit, and the halftone process of the image is performed by selectively switching the configuration of the screen pattern according to the detected size of the image point. And an image point adjusting unit.   The image dot adjustment unit includes a plurality of screen patterns having different dot sizes, and selects a screen pattern including small dots when the detected image dot is large, and selects a large dot when the detected image dot is small. The image forming apparatus according to claim 4, wherein the halftone process is performed by selecting a screen pattern.   The image dot adjustment unit includes a plurality of screen patterns with different numbers of dots, selects a screen pattern with a small number of dots when the detected image dot is large, and has a large number of dots when the detected image dot is small. The image forming apparatus according to claim 4, wherein the halftone process is performed by selecting a screen pattern.   The image point adjustment unit includes a plurality of copy-forgery-inhibited pattern patterns having different dot sizes as the screen pattern, and when the detected image dot is large, selects a copy-forgery-inhibited pattern pattern with small dots, and the detected image dot size is The image forming apparatus according to claim 4, wherein when it is small, a tint block pattern having large dots is selected and the halftone process is performed. The printer unit includes a transfer belt that transfers a developer image formed on an image carrier, and a fixing device that fixes the developer image transferred to the transfer belt to a sheet.
The image forming apparatus according to claim 4, wherein the image reading unit includes a sensor that reads the image dot adjustment pattern printed on the transfer belt or the image dot adjustment pattern fixed on the paper. Including a photoconductor that is scanned by a laser beam from a laser exposure apparatus, and a printer unit that forms an image on a recording medium;
The input image data is processed by the image processing unit and output to the printer unit,
Controlling the printer unit to print a pattern for image point adjustment on the recording medium;
Read the image point adjustment pattern printed on the recording medium with an image reading unit,
Detecting an image dot of the image based on the density of the image read by the image reading unit;
An image point adjustment method for controlling a laser intensity of a pixel constituting the image point in accordance with the detected size of the image point. A printer unit including an image forming unit;
The input image data is processed by the image processing unit and output to the printer unit,
Controlling the printer unit to print a pattern for image point adjustment on the recording medium;
Read the image point adjustment pattern printed on the recording medium with an image reading unit,
Detecting an image dot of the image based on the density of the image read by the image reading unit;
An image point adjustment method for performing halftone processing of the image by selectively switching a screen pattern configuration in accordance with the detected image point size.

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