JP2001113763A - Image processing apparatus, image processing method and recording medium having image processing control program recorded thereon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately perform the correspondence of a density irragularity correcting table and a printing head element even if the attaching error of a printing head is changed by the replacement or vibration of the printing head, and to eliminate the necessity for again performing the measurement/ calculation of a head shading table. SOLUTION: A printing head attaching error correction value at a time of the measurement/calculation of a head shading correction value is stored. At the usual output time of an image, a pixel to which head shading correction is applied by the shift quantity of the printing head is shifted (S105) from the difference between the newest printing head attaching error correction value at a time of the setting of a head shading table (S103) and the printing head attaching error correction value stored at a time of the measurement of the previous head shading correction value (S104). By this constitution, proper head shading correction can be applied to each printing element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus, an image processing method, and a recording medium on which an image processing control program is recorded, and more particularly, to a method for correcting density unevenness of a binary printer in a copying machine or a facsimile machine. About technology.

[0002]

2. Description of the Related Art Conventionally, a binary printer of an ink jet type or an electrophotographic type using an LED (light emitting diode) head has been developed.

First, in the output characteristics of an ink jet printer, density unevenness occurs due to a difference in the amount of ink ejected from a nozzle. To correct this, a technique called head shading is used, and a pixel signal corresponding to each nozzle is corrected by multi-value density data conversion.

[0004] Similarly, in the output characteristics of a printer using an LED head which is a binary printer, density unevenness occurs due to uneven light emission of the LED pixels. For this, head shading is used similarly to the ink jet, and correction is performed by multi-level density conversion corresponding to each light emitting pixel.

In this correction, print data is sequentially corrected for each pixel by multiple values in accordance with the print density characteristics of the print elements of a binary printer. As a method, first, a pattern having a predetermined density is printed, read, a density corresponding to each pixel of the pattern is read, and density correction is performed on the print pixels.

[0006]

The above-mentioned head shading in the above-mentioned prior art is to correct each print element. Therefore, for example, taking the LED head as an example, if there is an attachment error in the LED head, it is necessary to correct the error before measuring and calculating the density correction table for head shading.

However, when the mounting error of the LED head changes due to vibration or the like, it is necessary to change the value of the mounting error correction so as to prevent color shift during printing. At this time, if the mounting error correction value at the time of output of the normal image is different from the mounting error correction value at the time of calculating the density correction table of the head shading, appropriate density correction is not performed on each LED of the LED head. There is a problem. To solve the problem,
If you change the LED head mounting error correction value,
The measurement and calculation of the head shading correction value must be repeated.

In view of the foregoing, it is an object of the present invention to accurately determine the correspondence between the density unevenness correction table and the printhead elements even if the printhead mounting error is changed due to printhead replacement or vibration. It is an object of the present invention to provide an image processing apparatus and an image processing method capable of performing appropriate density unevenness correction, and a recording medium storing an image processing control program.

It is a further object of the present invention to provide an image processing apparatus and an image processing apparatus which eliminates the need to repeat the measurement and calculation of the head shading table when the mounting error of the print head changes, thereby simplifying the operation of the user. An object of the present invention is to provide a processing method and a recording medium on which an image processing control program is recorded.

[0010]

According to an aspect of the present invention, there is provided an image processing apparatus comprising: a document reading means for reading a document and outputting the data as multi-valued data; Correction means for correcting the density unevenness by making the correction table correspond to each pixel according to the pixel address of the print head corresponding to the multi-value data, and correcting the multi-value data according to the corresponding correction table; Printing means for printing the multi-valued data corrected by the correction means on recording paper; first storage means for storing a printhead attachment error correction value corresponding to a pixel of the printhead when the printhead is attached; A second storage means for storing a printhead installation error correction value corresponding to the latest pixel of the printhead after the installation of the printhead; And a print head attachment error correction value stored in the first storage means and a print head attachment error correction value stored in the second storage means, and when both correction values are different, Is characterized by having a correction control means for shifting the correction table by a shift amount which is a difference value between the two.

In this case, there is provided a mounting error correction value obtaining means for obtaining the print head mounting error correction value, and the mounting error correction value obtaining means outputs a pattern having a predetermined density as a test pattern as multi-valued data. Data generating means, and printing the test pattern data generated by the pattern data generating means on recording paper via the printing means, and reading the test pattern data printed on the recording paper via the document reading means. Test pattern reading control means for controlling the print pattern, print area determining means for determining a printed area from the read test pattern data, and printing on the recording paper according to the area determined by the print area determining means. Pixels corresponding to the print head and the test pattern It can be characterized by having a calculating means for calculating the print head attachment error correction value for each pixel at the time of printing.

The second storage means outputs the test head attachment error correction value calculated by the calculation means in correspondence with the pixels of the test pattern printed on the recording paper. The print head installation error correction value when the correction is performed is stored together with the correction table.

[0013] The print head may be an LED print head of an LED printer.

In order to achieve the above object, an image processing method according to a fifth aspect of the present invention corresponds to a document reading step of reading a document and outputting the same as multi-value data, and the multi-value data output in the document reading step. A correction table corresponding to each pixel according to the pixel address of the print head to be corrected, and correcting the multi-valued data according to the corresponding correction table to correct density unevenness. A printing step of printing the multi-valued data on recording paper, and a first storage means for storing a printhead attachment error correction value corresponding to a pixel of the printhead when the printhead is attached in the first storage means.
And a second storage step of storing a printhead attachment error correction value corresponding to the latest pixel of the printhead after the printhead is attached to the second storage means, and the first storage means. Comparing the printhead attachment error correction value stored in the second storage means with the printhead attachment error correction value stored in the second storage means,
And a correction control step of shifting the correction table by an amount of shift that is a difference value between the two when the two correction values are different from each other.

Here, there is provided a mounting error correction value obtaining step of obtaining the print head mounting error correction value,
The attaching error correction value acquiring step includes a pattern data generating step of outputting a pattern of a predetermined density as a test pattern as multi-valued data, and recording the test pattern data generated in the pattern data generating step via the printing step. A test pattern reading control step of performing control to cause the test pattern data printed on the recording paper to be read through the document reading step, and a print for determining a printed area from the read test pattern data An area determining step, and correcting the printhead mounting error for each pixel when the test pattern is printed by associating pixels printed on the recording paper with the printhead according to the area determined by the print area determining step. Calculate the value To have a calculation step can be characterized.

The second storage step may include outputting the printhead attachment error correction value calculated in the calculation step corresponding to a pixel of the test pattern printed on the recording paper. The printhead mounting error correction value at the time of the correction may be stored in the second storage means together with the correction table.

According to another aspect of the present invention, there is provided a recording medium storing an image processing control program for an image processing apparatus that performs image processing using a computer, wherein the control program is a computer. Against
A document is read and output as multi-valued data, the output multi-valued data is associated with a correction table for each pixel according to a pixel address of a corresponding print head, and the multi-valued data is output according to the corresponding correction table. The corrected multi-value data is printed on recording paper, and a print head attachment error correction value corresponding to the pixel of the print head when the print head is attached is stored in the first storage means. A print head mounting error correction value corresponding to the latest print head pixel after the head is mounted is stored in the second storage means, and the print head mounting error correction value stored in the first storage means and the (2) Compare the printhead attachment error correction values stored in the storage means, and if both correction values are different, Can be characterized by causing offset both of the correction table shifted amount is a difference value.

Further, the control program causes the computer to output a pattern of a predetermined density as a test pattern as multi-value data when acquiring the print head attachment error correction value, and to generate the test pattern data on a recording paper. The test pattern data printed on the recording paper is read, the printed area is determined from the read test pattern data, and the pixels printed on the recording paper are determined according to the determined area. The printhead attachment error correction value may be calculated for each pixel when the test pattern is printed, in correspondence with a printhead.

In addition, the control program outputs to the computer the calculated print head attachment error correction value corresponding to the pixels of the test pattern printed on the recording paper when the test pattern is output. The printhead mounting error correction value may be stored together with the correction table in the second storage means.

(Operation) In the present invention, the print head attachment error correction value at the time of measurement and calculation of the head shading correction value is stored, and at the time of setting the head shading table at the time of normal image output, the print head attachment error correction value at that time is set. The pixels to be subjected to head shading correction are shifted by the amount of shift of the print head from the difference between the correction value and the print head attachment error correction value stored at the time of measuring the head shading correction value. This makes it possible to perform appropriate head shading correction on each print element.

[0021]

Embodiments of the present invention will be described below in detail with reference to the drawings.

First Embodiment [Configuration of Apparatus] First, an internal structure of an image processing apparatus according to an embodiment of the present invention will be described with reference to FIG.

(Configuration of Reader Unit) First, the configuration of the color scanner unit (reader) shown in the broken line 380 will be described.

(Components of the apparatus) 101 is a CCD (Charge Coupled Device) image sensor (hereinafter referred to as CCD),
Reference numeral 311 denotes a CCD board on which the CCD 101 is mounted;
A scanner CPU (Central Processing Unit) 312 controls the entire reader, and an image processing (IP) base 312 includes an image processing unit that performs digital image processing after digitizing an analog image signal sent from the CCD base 311. .

Reference numeral 301 denotes a document table glass; and 302, a document feeder (DF: document feeder). In addition,
A pressure plate (not shown) in place of the document feeder 302
Is also available. Reference numerals 303 and 304 denote light sources (eg, halogen lamps or fluorescent lamps) for illuminating the original, reference numerals 305 and 306 denote reflectors for condensing the light from the light sources 303 and 304 on the original, and reference numerals 307 to 309 denote the original set on the platen A mirror 310 for guiding the light to the CCD 101, and a lens 310 for condensing the projection light of the mirror 309 on the CCD 101. Reference numeral 314 denotes a first mirror base (carriage) that houses the halogen lamps 303 and 304, reflectors 305 and 306, and the mirror 307. Reference numeral 315 denotes a second mirror base that houses the mirrors 308 and 309. Reference numeral 316 denotes a first mirror base 314 and the first mirror base. 2
The mirror base 315 is moved in the sub-scanning direction (the horizontal direction in the figure).
Is a stepping motor driving unit for driving the motor.

Reference numeral 313 denotes an external interface with another device. This external interface 313 includes:
Although not shown in the present embodiment, a LAN (local area network) interface device for connecting to a network, a SCSI (small computer system interface) device for connecting to a personal computer (personal computer), etc., FAX It is possible to connect a device that is required to use this scanner image, such as a facsimile machine that operates as a (facsimile), and the scanner CPU 300 and the CPU of the external device (not shown) via the external interface 313. ) Can communicate with each other, and predetermined image data can be output from the external interface 313 at predetermined timing.

Reference numeral 353 denotes a dedicated printer interface for exchanging images and commands with a printer in charge of image output when the scanner is used as an image copying apparatus.

(Document Reading Operation) A document placed on the document feeder 302 or on the platen glass 301 by the user scans the document in response to a document reading event such as pressing of a copy button (not shown) by the user. CPU
300 gives an instruction to perform image reading to each component. More specifically, the scanner CPU 300
3, 304 is turned on to make the CCD board 311 operable, and image processing parameters are set in the image processing board 312.

When each preparation is completed, the scanner CPU 300
Operates the stepping motor drive unit 316, and the first
The mirror table 314 is driven at a constant speed in the sub-scanning direction, and the entire surface of the document is sequentially irradiated. At this time, the second mirror base 315 is mechanically and optically designed to be driven to a half of the first mirror base 314, and accurately irradiates the CCD 101 with the original. The CCD 101 has light receiving sensors arranged in the main scanning direction (front-rear direction in the figure), and a register corresponding to the light receiving sensor can take in analog voltages proportional to the light amount one by one at regular intervals. is there. By repeating the continuous scanning in the main scanning direction and the movement for driving in the sub-scanning direction, it is possible to capture the entire surface of the document as a two-dimensional image. The two-dimensional image data has a one-dimensional array on the time axis.

The image data is transferred from the CCD board 311 to the image processing board 312, and is subjected to appropriate image processing by the image processing board 312, after which the external interface 31 is processed.
3 or outputs an image outside the scanner via the printer interface 353.

(Configuration of Printer Unit) Next, the configuration of the printer unit (printer) indicated by a broken line 381 in FIG. 3 will be described.

(Components of the printer section) 383 is a reader interface, which is an interface for connecting a scanner device when using a printer as an image copying apparatus. 382 is an external interface. Although not shown in this embodiment, the external interface 382 has a LAN interface device for connecting to a network, and an SCS for connecting to a personal computer or the like.
A device that is required to output an image to the printer, such as an I interface device, can be connected.
U384 communicates with the CPU of the external device, and predetermined image data can be input from the external interface 382 at predetermined timing.

Reference numeral 317 denotes a Y image forming unit for forming a yellow (Y) image, 318 denotes an M image forming unit for forming a magenta (M) image, and 319 denotes a C image for forming a cyan (C) image. An image forming unit 320 is a K image forming unit that forms a black (K) color image. Since the configurations of the image forming units 317 to 320 are all the same, the Y image forming unit 317 will be described in detail below, and the description of the other image forming units will be omitted.

In the Y image forming section 317, reference numeral 342 denotes a photosensitive drum on which a latent image is formed by light from the LED array 210. A primary charger 321 charges the surface of the photosensitive drum 342 to a predetermined potential to prepare for forming a latent image. Reference numeral 322 denotes a developing device,
The upper latent image is developed to form a toner image. Note that the developing device 322 includes a sleeve 345 for applying a developing bias to perform development. A transfer charger 323 discharges from the back of the transfer belt 333 to transfer the toner image on the photosensitive drum 342 to recording paper on the transfer belt 333. This embodiment has good transfer efficiency,
The cleaner is not located. It goes without saying that there is no problem even if the cleaner is attached.

(Operation of Image Processing) FIG. 4 shows a flow of image data of the image processing apparatus shown in FIG. In FIG.
400 is the entire reader corresponding to 380 in FIG.
Is a CCD image sensor corresponding to 101 in FIG.
000 pixel line sensor. 402 is amplification / AD
(Analog / digital) conversion circuit, 403 is a shading circuit, 404 is a gamma conversion circuit, 405 is a head shading circuit, 406 is a binarization circuit, 407 is a program ROM (read only memory), 408 is a program RAM (random access memory) 409, a reader CPU; 410, a head shading data storage RAM for storing tables 502 and 503; 411, a communication IC (integrated circuit); and 412, a pattern generation circuit.

Reference numeral 420 denotes the entire printer, and reference numeral 421 denotes an LED.
The head driver 422 is an LE corresponding to 210 in FIG.
D head, 423 is a communication IC, 424 is a printer CP
U, 425 is the program RAM, 426 is the program R
OM and 427 are binary page memories.

The image data read from the CCD 401 is processed in each of the processing blocks described above, and finally becomes a light emission pattern of each LED of the LED head 422.

FIG. 5 shows the configuration of the head shading circuit 405 of FIG. 4 for performing density unevenness correction. In FIG.
503, a head shading gamma table for converting multi-valued image data according to the table number; 502, a head shading gamma table number designation table for designating the table number; 501, a counter for designating the table; It counts up in synchronization and is cleared by HSYNC (horizontal synchronization signal) synchronized with main scanning. A sampling circuit 504 averages a predetermined number of pixels in the main scanning direction and stores the result as a sub-scanning pixel in a sampling memory. The capacity of the sampling memory is an integer multiple (5 times in this embodiment) of the print LED pixel.

Referring to the flowchart of FIG. 1 and FIG. 5, the image processing and the image processing control procedure when the image read by the reader 400 in FIG. 4 is printed out by the printer 420 will be described below.

First, when the power of the reader 400 and the printer 420 is turned on (S101), the CPU 40 of the reader
Numeral 9 reads out the correction data for the head shading which is the density correction processing of each pixel of the LED from the RAM 410 in which the correction data is stored, and reads the data.
It is set in the head shading gamma table number designation table 502 in the middle (S102). This correction data indicates a gamma table number for density correction for each pixel of the LED of the LED head 422, and is a density correction value different for each device.

Next, the CPU 409 on the reader side stores the data of the head shading gamma table in the RAM 4 as well.
10 and write it to the head shading gamma table 503 (S103). The data to be written is table data common to the same type of printer.

Thereafter, when a copy start is instructed from an operation panel (not shown) (S106), the scanner reading unit starts scanning the document on the document table 301, and the document image is read by the CCD image sensor 401 (S10).
7). At this time, the data read in the main scanning direction by the line sensor 401 is printed in the main scanning direction by the printer 420 through the following image processing.

That is, when a document is read,
The output of the CCD image sensor 401 is amplified and A / D converted by an amplifying / AD converting circuit 402 and output as 8-bit image data. Next, the shading circuit 40
In step 3, the read image data is subjected to shading correction.
Further, the read image data is gamma-corrected by the gamma conversion circuit 404 (S108), and the density is corrected by the head shading circuit 405 described in detail below (S10).
9). The density-corrected image data is subjected to a binarization process such as error diffusion by a binarization circuit 406 (S11).
0).

Next, the operation of the head shading circuit 405 will be described.

In the head shading gamma conversion table 503, the upper 6 bits of the address input are table number selection bits, and the lower 8 bits are an image signal. That is, the head shading gamma conversion table 503 stores 32 (5 bit address) head shading gamma tables (for 8-bit data conversion).

The head shading gamma table number designation table 502 converts an LED address into a head shading gamma table number (5 bits).
That is, what address of the LED indicates which table of the head shading gamma table 503 is to be used. This gamma table number designation table 5
02 designates the number of the 32 gamma tables 503 to which the pixel address of the LED is assigned. The instruction data is created by a head shading creation operation described below. This instruction data is stored in the head shading storage RAM 410, and is transferred from the RAM 410 by the CPU 409 when the power is turned on.

The counter 501 is a counter for designating the head shading gamma table number designation table 502. The output of the counter 501 is 13 bits and counts up by VCLK (vertical synchronization signal) and is cleared by HSYNC (horizontal synchronization signal) to count main scanning pixels. This counter 50
The output of 1 indicates the address of the LED. The counter 501 can set a load value when cleared by the HSYNC from the CPU 409, thereby moving the designated LED address in the main scanning direction.

As described above, the image data is subjected to multi-level density conversion by the head shading circuit 405, then binarized by the binarization circuit 406, and output from the reader 400.

The image data output from the reader 400 is input to the printer 420 and written to the binary page memory 427. The driver 42 from the page memory 427
1, the image data is read out in the order written
It is converted into a light emission signal of each LED of the LED head 422. At this time, in the LED head driver 421, LE
A signal is output in consideration of a mechanical mounting error of the D head 422 (S111, S112).

FIG. 6 schematically shows yellow, magenta, cyan, and black LED heads 210 to 213 (see FIG. 3). In FIG. 6, the cyan head 212 is mounted one pixel to the left of the black head 213, and the magenta head 211 is mounted two pixels to the right of the black head 213 with a shift. These mounting errors are LED
It is measured when the heads 210 to 213 are mounted, and can be read by the printer CPU 424. The read LED head mounting error value is stored in the program RAM 4
25. Since the program RAM 425 is backed up by a battery, the value of the attachment error is retained even when the power of the printer is turned off.

FIG. 7 shows the storage state of the LED head mounting error in the program RAM 425. In FIG. 7, the mounting error of the yellow head 210 is stored in the address 701, and the mounting error of the magenta head 211 is stored in the address 702.
3 stores the mounting error of the cyan head 212. Each mounting error value is black head 213
Is shown in pixel units, and is a value centered on 100H (hexadecimal).

Therefore, when the respective LED heads are attached as shown in FIG. 6, 100H is stored in the address 701 because the yellow head 210 is not shifted with respect to the black head 213.
Since the magenta head 211 is shifted two pixels to the right with respect to the black head 213, the address 702 has 102
H is stored. Since the cyan head 212 is shifted one pixel to the left with respect to the black head 213, the address 7
03 stores FFH.

The printer CPU 424 has a program RAM
The setting of the LED head driver 421 is performed according to the LED head attachment error values stored in the LED head 425. The state of light emission of the LED heads 210 to 213 at this time will be described. In FIG. 6, image data 601 is obtained by schematically extracting one main scanning line of image data, and data starts from the 128th pixel. For the image data of the 128th pixel, the yellow head 210 and the black head
The LED 421 is driven by the driver 421 so as to emit light. On the other hand, the magenta head 211 is driven by the driver 421 such that the 126th LED emits light for the image data of the 128th pixel, and the cyan head 212 is driven by the driver 421 such that the 129th LED emits light. In this manner, printing is performed so that color shift does not occur even if there is an installation error.

As described above, the density unevenness of the print head is corrected, and the read image is printed on paper.

The pattern generation circuit 412 of FIG.
According to an instruction from the PU 409, an arbitrary image signal can be generated and output. The binarizing circuit 406 selects and inputs the image signal from the pattern generating circuit 412, binarizes the image signal and outputs the binarized signal from the reader 400, so that the printer 420 can print an arbitrary pattern on output paper.

(Preparation of Head Shading Table)
Next, a procedure for creating a head shading table will be described with reference to the flowchart in FIG.

First, a test pattern is printed.
This test pattern is transmitted from the pattern generation circuit 412 to FIG.
(S204). That is, each of the print areas of C (cyan), M (magenta), Y (yellow), and K (black) is a single color signal having a density of 80H (8 bits), and the density outside the print area is 0, that is, white. . Each print area starts from the 128th pixel in the main scanning direction.
It is up to the pixel. This test pattern signal generated from the pattern generation circuit 412 is binarized by the binarization circuit 406 as in the case of a normal read image and output to the printer 420 (S205).

The printer outputs the received test pattern signal to the LED head 422 in the same procedure as that for a normal read image, and prints it on output paper. At this time, the mounting error correction is also performed on the LED head driver 421 in the same manner as the normal read image (S206).
Therefore, for example, in the case as shown in FIG. 6, 12 ends which are the leading ends in the main scanning direction of the Y print area and the K print area.
The test pattern signal of the eighth pixel is a light emission signal of the 128th LED of the LED head 210 and the LED head 213. The 128th pixel of the M print area corresponds to the 126th LED, and the 128th pixel of the C print area. Corresponds to the 129th LED.

The operation at this time will be described in detail. When a head shading table creation instruction is input from an operation panel (not shown) (S201), the printer CPU
424 is the LED head 42 from the program RAM 425
2 is read, and the read mounting error correction value is transmitted to the reader 400 via the communication IC 423 (S202). Upon receiving the attachment error correction value transmitted via the communication IC 411, the reader CPU 409 stores it in the program RAM 408 (S203). Thus, the program RAM 4
The value stored in 08 is used at the time of reading the test pattern as a mounting error correction value at the time of outputting the test pattern.

The reading of the test pattern is performed as follows. That is, as shown in FIG. 9, the pattern is read by sub-scanning in a direction perpendicular to the print main scanning (S20).
7). The main scanning 128 pixels of the pattern are averaged for each sub-scanning pixel, and the result is written to a sampling memory (not shown) (S208). This sampling memory has an average value storage capacity for 8000 pixels, and is incorporated in the sampling circuit 504 of FIG.

FIG. 10 shows the state of the sampling memory when the average value is read according to FIG. FIG. 11 shows an example of graphing data of one color (here, C) taken into the sampling memory of the sampling circuit 504 by the sub-scanning.

The data of the print pattern (test pattern) read as described above is written into the sampling memory at address 8000. In this example, a print area of 7000 pixels is written, and white image data as a blank is written in the remaining addresses. In FIG. 10, a data area having a density of 50 or more is determined as a print area for this data.
In the figure, addresses 101 to 70 of the sampling memory are used.
Assume that up to 99 are determined to be pattern print areas.
This means that data for 6999 pixels has been read. Since the number of printed pixels is 7000 pixels,
This means that one pixel has been reduced during the printing operation. This is due to the fact that toner is transferred to paper by electrophotography,
The fact that the paper shrinks when passing through the heating roll and the LED head 210 for forming a latent image on the photosensitive drum 342
It is conceivable that the placement accuracy of .about.213 was not obtained.

In any case, since an LED correction table for 7,000 pixels cannot be created based on data for 6,999 pixels, interpolation is performed to correct the sampling data for 7,000 pixels. Alternatively, correction data may be created by changing the sub-scanning speed and performing sub-scanning again to obtain print data for 7000 pixels. The sub-scanning speed at this time is 69
The speed may be 99/7000 times (99.99%).

Using the sampling data thus obtained, each LED head 2 for each color is used.
A γ table (not shown) to be used for 10 to 213 (LED head 422) is determined (S209). γ
32 types of tables are prepared according to the expected characteristics of the LED heads 210 to 213 (LED head 422).

First, address 10 of the sampling memory
An average value m of the density is obtained from 1 to the address 7099 of the sampling memory.

Next, from address 101 to address 7
With respect to the densities x stored one by one in the sampling memory until 099, a change amount v with respect to the average density m is calculated. The formula for calculating the change amount v is as follows.

[0067]

V = ((x−m) / m) ^* 100 + 16 (1) where v is the amount of change to be obtained, x is the density stored in the target sampling memory, and m is the average density. The change amount v obtained here is used as a gamma table number. However, if v becomes a negative value, the gamma table of No. 0 is used, and if v becomes larger than 32, the gamma table of No. 32 is used. By performing this calculation for each pixel,
A head shading table is created.

At this time, the LED head attachment error correction value at the time of outputting the test pattern, which is obtained at the time of outputting the test pattern, is stored in another area on the program RAM 408 (S210).

The program RAM 408 is backed up by a battery or the like, and is retained even after the power is turned off. The mounting error correction value stored in the other area is used at the time of normal image printing as an LED head mounting error correction value when calculating the head shading table.

(Setting of Head Shading Table)
The head shading table created by the above-described procedure is set in the head shading gamma table number designation table 502 in the head shading circuit 405 in FIG. 5 for density correction at the time of output (S211).
At this time, the gamma table designation number to be set is shifted and stored so that the address of 80H in the table 502 becomes the correction value corresponding to the 0th pixel. this is,
This is because the head shading gamma table number designation table 502 can be moved in the main scanning direction at the time of output. By designating the load value of the counter 501 to 80H, appropriate correction can be performed from the 0th pixel.

At the time of normal image output, the mounting error of the LED head 422 may be changed due to the LED head replacement, vibration, or the like. At this time, the LED head attachment error correction value stored in the program RAM 425 of the printer 420 is changed to prevent color misregistration.

Therefore, during normal image output, the reader CPU 409 sends the current L level to the printer CPU 424 via the communication IC 411 as shown in the flowchart of FIG.
Requests acquisition of ED head attachment error, printer CPU
Reference numeral 424 denotes an LED head attachment error correction value stored in the program RAM 425 to the reader 400 via the communication IC 423.
(S103).

The reader CPU 409, which has acquired the current LED head attachment error correction value, sets the program RAM 408
The value is compared with the LED head attachment error correction value at the time of calculation of the correction table held above (S104), and when both values are different, the difference is reflected in the load value of the counter 501 (S105). For example, when the correction value of the LED head mounting error at the time of calculating the correction table is 102H, while the current mounting error correction value is 108H, 86H is set as the load value of the counter 501. If the LED head mounting error correction value at the time of calculation of the correction table is 102H and the current mounting error correction value is FEH, 7CH is set to the load value of the counter 501.

In this way, appropriate density correction is applied to each pixel.

(Other Embodiments) In the above-described embodiment of the present invention, the case where the present invention is applied to an LED printer has been described as an example. However, the present invention is not limited to this. The same can be applied to.

The present invention can be applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, and a printer).
The present invention may be applied to a device including two devices (for example, a copying machine, a facsimile device, etc.).

Another object of the present invention is to provide a recording medium (storage medium) recording software program codes for realizing the functions of the above-described embodiments to a system or an apparatus, and to provide a computer for the system or the apparatus. Needless to say, the present invention is also achieved when the CPU (or the CPU or the MPU) reads out and executes the program code stored in the recording medium.

In this case, the program code itself read from the recording medium realizes the function of the above-described embodiment, and the recording medium on which the program code is recorded constitutes the present invention.

As a recording medium for recording the program code and for recording variable data such as a table, for example, a floppy disk (FD), hard disk, optical disk, magneto-optical disk, CD-ROM, CD-R, magnetic tape, A nonvolatile memory card (IC memory card), a ROM, or the like can be used.

Further, when the computer executes the readout program code, not only the functions of the above-described embodiment are realized, but also the OS (Operating System) running on the computer based on the instruction of the program code. It goes without saying that an operating system) may perform some or all of the actual processing, and the processing may realize the functions of the above-described embodiments.

[0081]

As described above, according to the present invention,
The print head attachment error correction value at the time of measurement and calculation of the head shading correction value is stored, and is stored at the time of setting the head shading table at the time of normal image output and at the time of measuring the print head attachment error correction value and the head shading correction value at that time. Since pixels to be subjected to head shading correction are shifted by the amount of shift of the print head based on the difference from the print head attachment error correction value, appropriate head shading correction can be performed on each print element.

Therefore, according to the present invention, even if the mounting error of the print head is changed due to the change of the print head or the vibration, etc., the correspondence between the density unevenness correction table and the print head element can be accurately performed. It is possible to improve density unevenness correction.

Further, according to the present invention, when the mounting error of the print head changes, it is not necessary to repeat the measurement and calculation of the head shading table, so that the effect that the operation of the user is simplified can be obtained.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an operation at the time of normal image output according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a processing procedure of density unevenness correction processing according to an embodiment of the present invention.

FIG. 3 is a longitudinal sectional view illustrating the entire internal structure of the image processing apparatus according to the embodiment of the present invention.

FIG. 4 is a block diagram illustrating an overall circuit configuration of the image processing apparatus of FIG. 3;

5 is a block diagram illustrating a configuration of a head shading circuit 405 in FIG. 4 that performs density unevenness correction.

FIG. 6 shows LEs for yellow, magenta, cyan, and black.
It is a schematic diagram which shows a D head typically.

FIG. 7 is an explanatory diagram showing a storage state of LED head attachment error values (attachment position correction values) in a program RAM 425 of FIG. 4;

8 is a schematic diagram illustrating an example of a print sample for generating unevenness correction data generated from a pattern generation circuit 412 in FIG. 4;

FIG. 9 is a schematic diagram illustrating a method of reading a print pattern for unevenness correction.

FIG. 10 is a schematic diagram showing a state of writing data to a sampling memory at the time of reading an average value according to FIG. 9;

FIG. 11 shows the sampling circuit 50 of FIG.
4 is a graph showing an example of graphing data of one color taken into a sampling memory of No. 4;

[Explanation of symbols]

101 CCD image sensor (CCD) 210-213 LED array (print head) 300 Scanner CPU 301 Platen glass 302 Document feeder (DF) 303, 304 Light source (halogen lamp) 305, 306 Reflector 307-309 Mirror 310 Lens 311 CCD board 312 Image processing (IP) board 313 External interface 314 First mirror base (carriage) 315 Second mirror base 316 Stepping motor drive section 317 Y image formation section 318 M image formation section 319 C image formation section 320 K image formation Unit 321 Primary charger 322 Developing unit 323 Transfer charger 333 Transfer head 342 Photosensitive drum 353 Printer interface 380 Color scanner unit (leader) 381 Printer unit (printer) 382 External unit Interface 383 reader interface 400 whole reader 401 CCD image sensor 402 amplification / AD conversion circuit 403 shading circuit 404 gamma conversion circuit 405 head shading circuit 406 binarization circuit 407 program ROM 408 program RAM 409 reader CPU 410 head shading data storage RAM 411 Communication IC 412 Pattern generation circuit 420 Overall printer 421 LED head driver 422 LED head 423 Communication IC 424 Printer CPU 425 Program RAM 426 Program ROM 427 Binary page memory 501 Counter for specifying table 502 Head shading gamma table Number designation table 503 Head shading gun Table 504 sampling circuit 601 image data 701 to 703 printhead mounting error correction value

Continued on the front page F term (reference) 2C087 AA16 AC07 BB10 BC05 BC07 BD24 BD53 CA02 CB04 2H027 DA21 EC03 EC06 EE08 FD01 FD06 FD08 5C077 LL04 MM03 MP08 PP09 PP39 PP54 PP58 PQ17 PQ24 TT02 TT05 9A001 KK04 CC02

Claims (10)

[Claims] 1. A document reading means for reading a document and outputting it as multi-value data, and a correction table corresponding to each pixel according to a pixel address of a print head corresponding to the multi-value data output from the document reading means. Correction means for correcting density unevenness by correcting the multi-value data according to the corresponding correction table; printing means for printing the multi-value data corrected by the correction means on recording paper; First storage means for storing a printhead mounting error correction value corresponding to the pixel of the printhead when the printhead is mounted, and printhead mounting error correction corresponding to the latest printhead pixel after the printhead is mounted. Second storage means for storing a value, and a printhead attachment error correction value stored in the first storage means. Comparing with the print head attachment error correction value stored in the second storage means, and when both correction values are different, the correction control for shifting the correction table by an amount of deviation which is a difference value between the two. And an image processing apparatus. 2. An image forming apparatus comprising: a mounting error correction value obtaining unit configured to obtain the print head mounting error correction value; wherein the mounting error correction value obtaining unit outputs pattern data of a predetermined density as a test pattern as multi-value data. Generating means for printing the test pattern data generated by the pattern data generating means on a recording paper via the printing means, and reading the test pattern data printed on the recording paper via the manuscript reading means Test pattern reading control means for performing control; print area determining means for determining a printed area based on the read test pattern data; and printing on the recording paper according to the area determined by the print area determining means. Pixels correspond to the printheads and the test pattern The image processing apparatus according to claim 1, characterized in that it comprises a calculating means for calculating the print head attachment error correction value for each pixel at the time of cement. 3. The storage device according to claim 2, wherein the second storage unit is configured to correspond to a pixel of the test pattern printed on the recording paper,
3. The image processing apparatus according to claim 2, wherein the printhead attachment error correction value calculated by the calculation unit is stored together with the correction table as a printhead attachment error correction value when the test pattern is output. apparatus. 4. The apparatus according to claim 1, wherein said print head is an LED print head of an LED printer.
4. The image processing apparatus according to any one of claims 3 to 3. 5. A document reading step of reading a document and outputting it as multi-value data, and a correction table corresponding to each pixel according to a pixel address of a print head corresponding to the multi-value data output in the document reading step. A correction step of correcting density unevenness by correcting the multi-value data according to the corresponding correction table; a printing step of printing the multi-value data corrected in the correction step on recording paper; The printhead mounting error correction value corresponding to the pixel of the printhead when the head is mounted is set to the first value.
A first storage step of storing the print head mounting error correction value corresponding to the latest pixel of the print head after the print head is mounted in the second storage means. And comparing the printhead installation error correction value stored in the first storage means with the printhead installation error correction value stored in the second storage means, and when both correction values are different, A correction control step of shifting the correction table by a shift amount that is a difference value between the two. 6. A mounting error correction value obtaining step for obtaining the print head mounting error correction value, wherein the mounting error correction value obtaining step includes pattern data for outputting a pattern of a predetermined density as a test pattern as multi-valued data. Generating the test pattern data generated in the pattern data generating step on a recording sheet through the printing step, and reading the test pattern data printed on the recording sheet through the document reading step A test pattern reading control step of performing control; a print area determining step of determining a printed area from the read test pattern data; and a print area printed on the recording paper according to the area determined by the print area determining step. Pixel to the print head The image processing method according to claim 5, characterized in that in correspondence with a calculation step of calculating the print head attachment error correction value for each pixel at the time of printing of the test pattern. 7. The test pattern outputting the print head attachment error correction value calculated in the calculation step corresponding to a pixel of the test pattern printed on the recording paper, in the second storing step. 7. The image processing method according to claim 6, wherein a print head attachment error correction value when the correction is performed is stored in the second storage unit together with the correction table. 8. A recording medium storing an image processing control program of an image processing apparatus for performing image processing using a computer, wherein the control program causes a computer to read a document and output it as multi-valued data. The corrected multi-value data is associated with a correction table for each pixel according to a pixel address of a corresponding print head, the multi-value data is corrected according to the corresponding correction table, and the corrected multi-value data is recorded. A print head mounting error correction value corresponding to the pixel of the print head at the time of mounting the print head;
The print head mounting error correction value corresponding to the latest pixel of the print head after the print head is mounted is stored in the second storage means, and stored in the first storage means. The print head attachment error correction value is compared with the print head attachment error correction value stored in the second storage means. If the two correction values are different from each other, the difference is the difference between the two. A recording medium storing an image processing control program, wherein the correction table is shifted. 9. The control program causes the computer to output a pattern of a predetermined density as a test pattern as multi-valued data when acquiring the print head attachment error correction value, and prints the generated test pattern data on a recording paper. The test pattern data printed on the recording paper is read, the printed area is determined from the read test pattern data, and the pixels printed on the recording paper are determined according to the determined area. 9. The recording medium according to claim 8, wherein the print head attachment error correction value for each pixel when the test pattern is printed is calculated in correspondence with a print head. 10. The control program according to claim 1, wherein the calculated print head attachment error correction value is output to the computer in correspondence with the pixels of the test pattern printed on the recording paper. The recording medium according to claim 9, wherein the image processing control program according to claim 9 is stored in the second storage unit together with the correction table as the print head attachment error correction value.