JPH01129667A - Picture forming device - Google Patents

Abstract

PURPOSE:To obtain a picture without uneven density and to improve a yield by correcting the output density dispersion of a multi-head electrically due to the dispersion in manufacture process and material. CONSTITUTION:A picture data reading a vector pattern is written at every element to a RAM 255 via a buffer 256. Moreover, the address of the RAM 255 is generated by a counter 253 generating an address corresponding to the picture data and given to the RAM 255 via the selector 254. The picture data having density dispersion stored in the RAM 255 is read by a CPU 258 via the selector 254 and a buffer 257 to apply coefficient calculation to correct the uneven density. The obtained coefficient is written in an address corresponding to each recording element in the correction RAM 251 via the selector 250 and the bidirectional buffer 252.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field to which the invention pertains] The present invention relates to an apparatus that digitally processes an image and forms an image using a multi-head or the like, such as a copier, a printer, etc. that uses a multi-head.

[Description of prior art]

Conventionally, for example, in a digital color copying machine using a multi-head, data for each color R, G, and B is read.
After converting the read image data into digital signals, the data is processed and an image is formed using a multi-head.

In addition, such multi-heads have the disadvantage that density unevenness occurs in the output image due to variations in characteristics due to the manufacturing process and variations in the characteristics of the materials forming the multi-head, making it difficult to manufacture uniform multi-heads. The problem was that there was no.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned problems, and provides an image forming apparatus using a multi-head that electrically corrects density unevenness caused by the multi-head manufacturing process, and can obtain images without density unevenness. The purpose is to provide.

〔Example〕

Hereinafter, the present invention will be explained in detail based on Examples.

(Explanation of External Shape) FIG. 1 shows an external view of a digital color copying machine to which the present invention is applied.

The whole can be divided into two parts.

The upper part of Figure 1 shows the color image scanner section 1 (which reads the original image and outputs digital color image data).
The controller section 2 includes a scanner section 1 (hereinafter abbreviated as a scanner section 1), and a controller section 2, which is built into the scanner section 1 and performs various image processing of digital color image data, and has processing functions such as an interface with external devices.

The scanner section 1 reads a three-dimensional object placed downward under the document presser 11, a sheet document, and also has a built-in mechanism for reading a large-sized sheet document.

Further, the operation section 10 is connected to the controller section 2, and is used to input various information regarding the copying machine. The controller section 2 instructs the scanner section 1 and the printer section 3 regarding operations according to the input information. Further, when it is necessary to perform complicated editing processing, a digitizer or the like is attached in place of the document presser 11, and this is connected to the controller section 2, thereby making it possible to perform sophisticated processing.

At the bottom of FIG. 1 is a printer section 3 that records the color digital image signal output from the controller section 2 onto recording paper. In this embodiment, the printer section 3 is a full color ink jet printer using an ink jet recording head described in Japanese Patent Laid-Open No. 54-59936.

The two parts described above can be separated, and can be installed at separate locations by extending the connecting cable.

(Printer Section) FIG. 2 is a sectional view from the side of the digital color copying machine shown in FIG. 1.

First, an exposure lamp 14, a lens 15, and an image sensor 16 that can read line images in full color.
(in this embodiment, a CCD), the document table glass 17'
2, an image projected by a projector, or a sheet original image by the sheet feeding mechanism 12. Next, various image processing is performed by the scanner section 1 and the controller section 2, and the image is recorded on recording paper by the printer section 3.

In FIG. 2, recording paper is stored in a paper feed cassette 20 that stores cut paper of small standard sizes (A4 to A3 size in this embodiment) and large size (A2 to AI size in this embodiment). It is supplied from a roll paper 29 for carrying out the process.

Further, paper feeding from outside the apparatus (manual paper feeding) is also possible by inserting recording paper one sheet at a time through the manual feed port 22 shown in FIG. 1 along the paper feeding section cover 21.

The pick-up roller 24 is a roller for feeding cut sheets one by one from the paper feed cassette 20, and the fed cut sheets are conveyed to the 10th feed roller 26 by the cut paper feed roller 25. be done.

The roll paper 29 is sent out by a roll paper feed roller 30, cut into a standard length by a cutter 31, and then transferred to the paper feed number 10.
- It is conveyed to La 26.

Similarly, the recording paper inserted through the manual feed slot 22 is conveyed to the paper feed roller 26 by the manual feed roller 32.

Pick up roller 24, cut paper feed roller 25
, the roll paper feed roller 30, the 10th paper feed roller 26, and the manual feed roller 32 are connected to a paper feed motor (not shown in the drawings, D
It is driven by a C servo motor (using a C servo motor), and can be turned on and off at any time by electromagnetic clutches attached to each roller.

When the printing operation is started in accordance with an instruction from the controller section 2, recording paper selectively fed from one of the above-mentioned paper feeding paths is conveyed to the paper feeding path 26. In order to eliminate the skew of the recording paper, after a predetermined amount of paper loops have been made, the 10th paper feeder 26 is turned on and the recording paper is conveyed to the 20th paper feeder 27.

Between the 10th paper feed roller 26 and the 20th paper feed roller 27, a predetermined amount of paper is applied to the recording paper in order to perform an accurate paper feeding operation between the paper feed roller 28 and the 20th paper feed roller 27. Create a buffer. The buffer amount detection sensor 33 is a sensor for detecting the buffer amount. By creating a buffer in the middle of paper transport, it is possible to reduce the load on the paper feed roller 28 and paper feed roller 27, especially when transporting large-sized recording paper, allowing accurate paper feeding operation. become.

When printing with the recording head 37, the recording head 3
A scanning carriage 34 on which a device 7 or the like is attached performs reciprocating scanning on a carriage rail 36 by a scanning motor 35.

Then, in the outward scan, the image is printed on recording paper,
In the backward scan, the paper feed roller 28 performs an operation to feed the recording paper by a predetermined amount.

At this time, while the drive system is detected by the buffer amount detection sensor 33 using the paper feed motor, control is performed so that the buffer amount is always a predetermined amount.

The printed recording paper is discharged to the paper discharge tray 23, and the printing operation is completed.

Next, a detailed explanation of the scanning carriage 3 and the invention will be given using FIG.

In FIG. 3, a paper feed motor 40 is a drive source for intermittently feeding recording paper, and a paper feed motor 40 is a driving source for intermittently feeding the recording paper.
The 20th paper feeder 27 is driven via the 0-ra clutch 43.

The scanning motor 35 moves the scanning carriage 34 to the scanning belt 34.
This is a drive source for scanning in the directions of arrows A and B. In this embodiment, since accurate paper feeding control is required, a pulse motor is used for the paper feeding motor 401 and the scanning motor 35.

When the recording paper reaches paper feed number 20-27, paper feed number 20
-La clutch 43 and paper feed motor 40 are turned on, and the recording paper is conveyed over the platen 39 to the paper feed roller 28.

The recording paper is detected by a paper detection sensor 44 provided on the platen 39.
The sensor information is used for position control, jam control, etc.

When the recording paper reaches the paper feed roller 28, the paper feed number 20-
The clutch 43 and the paper feed motor 40 are turned off, and a suction operation (not shown) is performed from inside the platen 39 to bring the recording paper into close contact with the platen 39.

Prior to the image recording operation on recording paper, the scanning carriage 34 is moved to the position of the home position sensor 41,
Next, forward scanning is performed in the direction of arrow A, and cyan, magenta, yellow, and black inks are ejected from the recording head 37 from predetermined positions to record an image. After recording the image for a predetermined length, the scanning carriage 34 is stopped, and conversely, backward scanning is started in the direction of arrow B, and the scanning carriage 34 is returned to the position of the home position sensor 41.

During the backward scan, the paper is fed by the length recorded by the recording head 37 in the direction of arrow C by driving the paper feed roller 28 by the paper feed motor 40.

In this embodiment, the recording head 37 is an ink jet nozzle that uses heat to form air bubbles and uses the resulting pressure to eject ink droplets, and uses four ink jet nozzles with 256 nozzles each assembled. ing.

When the scanning carriage 34 is homed, the position sensor 41
When it stops at the home position detected by , the recording head 37 performs a recovery operation. This is a process for stable printing operation, and in order to prevent unevenness at the start of ejection caused by changes in the viscosity of the ink remaining in the nozzles of the print head 37, paper feeding time, internal temperature of the device, etc. This is a process in which pressure is applied to the recording head 37, ink is idly ejected, etc. according to preprogrammed conditions such as ejection time and the like.

By repeating the operations described above, an image is recorded on the entire surface of the recording paper.

(Scanner Section) Next, the operation of the scanner section 1 will be explained using FIGS. 4 and 5.

FIG. 4 is a diagram for explaining the mechanical mechanism inside the scanner section 1. As shown in FIG.

The CCD unit 18 is a unit composed of a CCD 16, a lens 15, etc., and includes a main scanning motor 50 fixed on a rail 54, a pulley 51, a pulley 52, and a wire 5.
It moves on the rail 54 by a drive system in the main scanning direction consisting of 3, and reads the image on the document platen glass 17 in the main scanning direction. Light shielding plate 55, home position sensor 56
is used for position control when moving the CCD unit 18 to the main scanning home position in the correction area 68 in the figure.

The rail 54 rests on rails 65 and 69, and includes a sub-scanning motor 60, pulleys 67, 68, 71, and 76, and a shaft 72.
73, is moved by a drive system in the sub-scanning direction consisting of wires 66 and 70. Light shielding plate 57, home position
Sensors 58 and 59 are used to move the rail 54 to the home position for sub-scanning in the book mode for reading a document such as a book placed on the document table glass J7, and in the sheet mode for sheet reading. Used for position control.

Sheet feed motor 61, sheet feed rollers 74 and 75,
The pulleys 62 and 64 and the wire 63 are mechanisms for feeding the sheet original. This mechanism is located on the document table glass 17, and transports the sheet document placed face down to the sheet feed roller 7.
This is a mechanism for feeding a predetermined amount at a time of 4.75.

FIG. 5 is an explanatory diagram of the reading operation in book mode and sheet mode.

In the book mode, the CCD unit 18 is moved to the book mode home position (book mode HP) shown in the correction area 68 in FIG. Start reading the entire surface.

Prior to scanning the original, data settings necessary for processing such as shading correction, black level correction, and color correction are performed in the correction area 68. Thereafter, scanning in the main scanning direction is started by the main scanning motor 50 in the direction of the illustrated arrow. When the reading operation in the area indicated by ■ is completed, the main scanning motor 50
and drive the sub-scanning motor 60,
The correction area 68 of the area is moved in the sub-scanning direction.

Subsequently, similarly to the main scanning of the area (2), processing such as shading correction, black level correction, color correction, etc. is performed as necessary, and the reading operation of the area (2) is performed.

By repeating the above scanning, the entire areas ① to ② are read, and after completing the reading operation in the area ②, the CCD unit 18 is returned to the book mode home position.

In this embodiment, the document platen glass 17 can read a maximum A2 size document, so in reality it must be scanned more times, but in this explanation, the operation is simplified to make it easier to understand. .

In the sheet mode, move the CCD unit I-18 to the sheet mode home position (sheet mode HP) shown in the figure, read the sheet document in the area marked ■ repeatedly while operating the sheet feed motor 61 intermittently, and then Read the entire manuscript.

Prior to scanning the document, processing such as shading correction, black level correction, and color correction is performed in the correction area 68, and then scanning in the main scanning direction is started by the main scanning motor 50 in the direction of the arrow shown in the figure. When the forward scanning operation of the area (3) is completed, the main scanning motor 50 is reversed, and during this backward scanning, the sheet feed motor 61 is driven to move the sheet original by a predetermined amount in the sub-scanning direction. Subsequently, the same operation is repeated to read the entire sheet document.

Assuming that the reading operation described above is a reading operation at the same magnification, the area that can be read by the CCD unit 18 is actually a wide area as shown in FIG. this is,
This is because the digital color copying machine of this embodiment has a built-in magnification/reduction function. That is, since the area that can be recorded by the recording head 37 is fixed at 256 bits at a time as explained above, when performing a 50% reduction operation, for example, the image information of an area of at least twice as much as 512 bits is This is because it is necessary. Therefore, the scanner section 1 has a built-in function of reading and outputting image information of an arbitrary image area by one main scanning reading.

(Film Projection System) The scanner section 1 of this embodiment can be equipped with a projection exposure means for film projection.

FIG. 6 is a perspective view when a projector unit 81 serving as projection exposure means and a reflecting mirror 80 are attached to the scanner section l.

The projector unit 81 is a projector for projecting negative film and positive film, and the film is held in a film holder 82 and attached to the projector unit 81. Projector unit 81
The image projected from is reflected by the reflection mirror 80,
Fresnel lens 83 is reached. fresnel lens 83
converts this image into parallel light and forms the image on the document table glass 17.

In this way, negative film and positive film images are imaged on the document platen glass 17'' by the projector unit 81, the reflective mirror 80, and the Fresnel lens 83. 1
8, image reading becomes possible.

FIG. 7 is a diagram for explaining the film projection system in more detail.

The projector unit 81 includes a halogen lamp 90
, reflection plate 89, condensing lens 91, film holder 8
2. Consists of a projection lens 92.

The direct light emitted by the halogen lamp 90 and the light reflected by the reflection plate 89 are condensed by a condenser lens 91 and reach the window of the film holder 82 . The film holder 82 has a window slightly larger than one frame of negative film or positive film, so that the film can be loaded inside with plenty of room.

The projection light reaching the window of the film holder 82 passes through the film mounted therein, thereby obtaining a projected image of the film. The projected image thus obtained is optically magnified by the projection lens 92, changed in direction by the reflecting mirror 80, and then converted into a parallel light image by the Fresnel lens 83.

The CCD unit 18 inside the scanner 1 reads this image in the book mode described above and converts it into a video signal.

FIG. 8 is a diagram showing an example of the relationship between the film and the projected image formed on the document table glass.

22 x 34. The film image of mm is shown magnified eight times and focused on the original platen glass 17.

(Overall Functional Block Description) Next, the functional blocks of the digital color copying machine of this embodiment will be described using FIG. 9.

The control units 102, 11.1, and 121 are control circuits that control the scanner unit 1, controller unit 2, and printer unit 3, respectively, and are controlled by a microcomputer and program R.
Consists of OM, data memory, communication circuit, etc. The control units 102 to 111 and the control units 111 to 121 are connected by a communication line, and the control units 102 , ], 2 ] operate according to instructions from the control unit 111.
Adopts master-slave control format.

When operating as a color copying machine, the control section 111 operates according to input instructions from the operation section 10 and the digitizer 114.

As shown in FIG. 6, the operation section 10 uses, for example, a liquid crystal (LCD display section 84) as a display section, and is equipped with a touch panel 85 made of transparent electrodes on its surface, so that color-related information can be displayed. Selection instructions such as specification and editing operation can be made. In addition, there are keys related to operations, such as a start key 87 for instructing to start a copying operation, a stop key 88 for instructing to stop a copying operation, a reset key 89 for returning the operation mode to the standard state, and a projector key for selecting a projector. Frequently used keys such as 86 are provided separately.

The digitizer 114 is used to input position information necessary for trimming, masking processing, etc., and is connected as an option when complex editing processing is required.

The control unit 111 also controls a control circuit-I/F control unit 112 of a general-purpose parallel interface such as IEEE-488, so-called GP-IB interface, and inputs and outputs image data between external devices. , remote control by external devices can be performed via this interface.

Furthermore, the control unit 111 includes a multi-value synthesis unit 106, an image processing unit 107, and a binarization processing unit 1, which perform various processes related to images.
08. Also controls the binary synthesis unit 109 and buffer memory 110.

The control unit 102 controls a mechanical drive unit 105 that controls the drive of the mechanism of the scanner unit l described above, an exposure control unit 103 that controls the exposure of a lamp when reading a reflective original, and a halogen lamp when using a projector. The exposure controller 104 controls the exposure control section 90. In addition, the control unit 1
02 also controls the analog signal processing section 100 and the input image processing section 101, which perform various processes related to images.

The control unit 121 includes a mechanical drive unit 105 that controls the drive of the mechanism of the printer unit 3 described above, and absorbs time variations in the mechanical operation of the printer unit 3 and delays due to the mechanical arrangement of the recording heads 117 to 120. Synchronous delay memory 11 for correction
5 control is performed.

Next, the image processing block in FIG. 9 will be explained along the flow of the image.

The image formed on the CCD 16 is converted into an analog electrical signal by the CCD 16. The converted image information is
The signals are serially processed in the order of red → green → blue and input to the analog signal processing section 100. The analog signal processing section 100 performs sample and hold, dark level correction, dynamic range control, etc. for each color of red, green, and blue, and then performs analog-to-digital conversion (A/D conversion) and serial multi-color signal processing. The digital image signal is converted into a digital image signal with a value (in this embodiment, each color has a length of 8 bits) and is output to the input image processing unit 101.

The input image processing unit 101 similarly performs correction processing necessary in the reading system, such as CCD correction and γ correction, on the serial multivalued digital image signal.

The multi-value synthesis section 106 of the controller section 2 is connected to the scanner section 1.
This is a circuit block that performs selection and compositing processing between a serial multi-value digital image signal sent from a serial multi-value digital image signal and a serial multi-value digital image signal sent via a parallel I/F. The selectively combined image data is sent to the image processing unit 107 as a serial multi-level digital image signal.

The image processing unit 107 performs smoothing processing, edge enhancement,
This circuit performs masking processing for extracting fish oil and correcting the color of recording ink used in the recording heads 117 to 120. The serial multilevel digital image signal output is input to the binarization processing unit 108 and the buffer memory 110, respectively.

The binarization processing unit 108 is a circuit for binarizing a serial multilevel digital image signal, and can select simple binary processing using a fixed slice level, pseudo halftone processing using a dither method, etc. Here, the serial multi-value digital image signal is converted into a four-color binary parallel image signal.

Image data of four colors is sent to the binary synthesis unit 109, and image data of three colors is sent to the buffer memory 110.

The binary synthesis section 109 combines the three-color binary parallel image signals sent from the buffer memory 110 and the binarization processing section 1.
This is a circuit for selecting and combining four-color binary parallel image signals sent from 08 to produce four-color binary parallel image signals.

The buffer memory 110 is a buffer memory for inputting and outputting multivalued images and binary images via a parallel I/F, and has memory for three colors.

The synchronization delay memory 115 of the printer section 3
Absorption of time variations in mechanical operation and recording head 117~
This is a circuit for correcting the delay due to the mechanical arrangement of the recording heads 117 to 120, and internally also generates the timing necessary for driving the recording heads 117 to 120.

The head driver 116 drives the recording heads 117 to 120.
This is an analog drive circuit for driving the recording heads 117 to 120, and internally generates signals that can directly drive the recording heads 117 to 120.

The recording heads 117 to 120 eject cyan, magenta, yellow, and black ink, respectively, to record an image on recording paper.

FIG. 10 is an explanatory diagram of the timing of images between the circuit blocks described in FIG. 9.

Signal BVE is a signal indicating the image effective section for each scan in the main scanning reading operation explained in FIG. Signal B
Full-screen image output is performed by outputting VE multiple times.

The signal VE is a signal indicating the valid section of the image read by the CCD 16 for every l line. Only the signal VE is valid when the signal BVE is valid.

Signal VCK is a clock signal for sending out image data VD. Signal BVE and signal VE also change in synchronization with this signal VCK.

The signal H3 is a signal used when the valid and invalid sections are repeated discontinuously while the signal VE outputs one line.
If the signal VE is continuously valid while outputting one line, it is an unnecessary signal. ■This signal indicates the start of line image output.

Next, the rough signal processing in the image processing section will be explained using FIG. 11.

In FIG. 9, a serial number (for example, 1
．． The image data (hereinafter referred to as input image data) that is input (in this order) is sent to the serial-to-parallel converter 201, where it is converted into parallel signals of Y (yellow), 2M (magenta), and C (cyan), and then sent to the masking unit 202. and selector 2
Sent to 03.

The masking unit 202 is a circuit for correcting cloudiness in the color of output ink, and performs calculations as shown in the following equation.

Therefore, the A/D converter 110 has B, G, R, B, G, R.
Outputs digital data in the order of...

The obtained digital data is converted into complementary color data Y, M, C by the complementary color conversion circuit 120, and Y, M, C, Y, M, C.
... are output in order.

The obtained color sequential color image data is sent to the time axis conversion unit 20.
Sent to 0a. Since the input image data and the subsequent image data have different frequencies, the time axis conversion unit 200a performs frequency conversion according to the time axis conversion control signal sent from the control unit 200 and outputs the result. . The output image data (hereinafter referred to as input image data) is sent to the serial/parallel converter 201, and is converted into Y (yellow).
, M (magenta), and C (cyan) parallel signals, and then sent to the masking unit 202 and the selector 203.

The masking unit 202 is a circuit for correcting cloudiness in the output ink color, and performs calculations as shown in the following equation.

Y, M, C: Input data Y', M', C': Output data These nine coefficients are determined by a masking control signal from the control unit 200. After correcting ink cloudiness in the masking unit 202, they are converted into serial signals. The data is input to the selector section 203 and the UCR section 205 as a.

Input image data and image data output from the masking unit 202 are input to the selector 203 .

The selector 203 normally selects input image data based on a selector control signal l sent from the control section 200. If the color correction in the input system is not sufficiently performed, the image data output from the masking section 202 is selected and output by control signal 1. Serial image data output from the selector 203 is input to the heavy oil pile section 204. Y, M in one pixel.

In order to use the minimum value of C as black data, in the heavy oil mountain area 204, Y
, M, and C are detected. The detected black data is input to the UCR section 205.

The UCR unit 205 subtracts the extracted black data from each of the Y, M, and C signals. Also, regarding black data,
It is simply multiplied by a coefficient. After correcting the time difference between the black data input to the UCR unit 205 and the image data sent from the masking unit 202, the following calculation is performed.

Y'=Y-alEk M'=M-a2Bk C'=C-a3Bk Bk'=a4Bk Here, Y, M, C, and Bk indicate the extraction unit input data,
Y', M', C', and Bk' indicate output data.

The coefficient (aI +a2 +a3 +a4) is determined by the UCR control signal sent from the control unit 200.

The data output from the UCR unit 205 is then input to the γ, offset 206.

γ, the offset unit 206 performs gradation correction as shown in the following equation.

y' -S, (y-c,) M' = b2 (M-02) C' = b3 (C-03) Bk' = b4 (Bk-C4) Here, Y, M, C, Bk are γ, There is large input data to the offset section, and Y', M', C', and Bk' are γ and offset section output data.

Further, the coefficients (b+ to b4.c, to C, S) in the above equation are determined by the γ and offset control signals sent from the control section 200.

γ, the tone-corrected signal by the offset unit 206 is then sent to the line buffer 20 which stores N942 worth of image data.
7 is input. This line buffer 207 outputs 5 lines of data necessary for the subsequent smoothing and edge emphasis section 208 in 5 lines in parallel according to the memory control signal sent from the control section 200. These 5 lines worth of signals are input to a spatial filter whose filter size is variable according to a filter control signal from the control unit 200, and smoothed.
Edge enhancement is then performed. In smoothing, as shown in FIG. 12, image noise is removed by setting the average value of the pixel of interest and surrounding pixels as the density value of the pixel of interest.

Further, edge enhancement is performed by using the difference between the pixel data of interest and the smoothed signal as an edge signal, and adding this to the pixel data of interest. A detailed explanation of the smoothed edge enhancement unit 208 will be omitted.

The image data output from the smoothing and edge enhancement unit 208 is input to a color conversion unit 209, and color conversion is performed in response to a color conversion control signal from the control unit 200.

The color to be converted, the color to be converted, and the area in which the signal is valid are input in advance from the digitizer device 114 in FIG. 9, and the color conversion unit 209 replaces the image data based on the data.

In this embodiment, a detailed explanation of the color conversion unit 209 will be omitted. The image signal output from the smoothing and edge emphasis section 208 and the image signal after color conversion are input to the selector 210, and the selector control signal 2 selects the image data to be output. Which image data to select is determined by specifying a valid area input from the digitizer device 114. The image signal selected by the selector 210 is input to the buffer memory 110 and the binarization processing section 108 in FIG.

A description of the system input to the buffer memory 110 will be omitted here.

The binarization processing unit 108 will be explained. The image data input to the binarization processing section 108 is input to the head correction section 211 shown in FIG. The head correction section 211 will be explained later. The image signal whose density has been corrected by the head correction section is then sent to a dither section 212 for Y and M signals.

C and Bk are input serially in 8 bits.

The dither section 212 uses 6 bits in the main scanning direction for each color.
.

It has a memory space of 6 bits in the sub-scanning direction or 4 bits in the main scanning direction and 8 bits in the sub-scanning direction, and the control unit 200
A dither control signal from the matrix sets the dither matrix size and the dither threshold within the matrix. When the dither circuit operates, the mechanical main scanning direction counts the image reading period signal of one line of the CCD, and the sub-scanning direction counts the image video clock, and reads out the set dither threshold value in the memory space. Also, serial dither threshold values can be obtained by serially switching this memory space to Y, M, C, and Bk.

Next, this threshold value is input to a comparator (not shown) and compared in size with image data input from the selector 210.

The output from the comparator is as follows: image data>threshold: 1 image data≦threshold: 0. This data is then transferred to the buffer memory 110 in FIG. 9 and the binary synthesis section 109 as parallel 4b'it data in the serial/parallel conversion section.
is output to.

Next, the head correction section 211 will be explained using FIG. 19.

In advance, a solid pattern of all discharges is outputted by a printer, and image data is obtained by reading the pattern with a portion of the scanner. Next, the head correction section 211 will be explained using FIG. 19.

Since the recording characteristics of the solid pattern differ for each element of each head, the image data obtained by reading the solid pattern is
Each element is written to the RAM 255 via the buffer 256. Further, the address of the RAM 255 is determined by a counter 2 that generates an address corresponding to the image data.
53 and is generated in the RAM 255 via the selector 254.
given to. The image data with uneven density stored in the RAM 255 in this way is then transferred to the selector 254. The image is read by the CPU via the buffer 257, and coefficient calculation is performed to correct density unevenness. In this embodiment, the correction coefficient for each element is determined by the following calculation.

FH Di αi: When the correction coefficient Di, the read pixel density data of the solid pattern, and the actual input pixel data DTi, the calculation of DTi Xαi is performed to obtain the output pixel data. Of course, it is also possible to perform correction by calculations other than those in this embodiment.

The coefficients obtained in this manner are written to addresses corresponding to each recording element of the correction RAM 251 via the selector 250° bidirectional buffer 252. Next, during normal image reading, the input image and the signal from the counter 253 that generates the address are selected by the selector 250 and input to the address of the correction RAM. Address assignment is to input image data to the lower 8 bits and input image data to the upper 8 bits.
Address data corresponding to each recording element of the head from the counter 253 is assigned to the bit. By inputting image data and corresponding address data from the counter 253 to the correction RAM 251, image data corrected according to the characteristics of each recording element of the head can be obtained as an output of the correction RAM 251. This output is input to the dither section 211, binarized, and output. Note that the characteristic data and correction coefficient data for each recording element are Y, M, and C.

Stored for all heads of BK.

Here, in this embodiment, the correction was performed using the RAM, but the characteristics of the multi-head may be investigated in advance and written in the ROM or the like. Alternatively, the characteristics of each head may be investigated and only the correction coefficients thereof may be written in the ROM, RAM, or the like.

Note that the present invention is applicable not only to inkjet heads but also to multi-recording heads such as thermal heads.

[Explanation of effects]

As described above, according to the present invention, by electrically correcting the output density variations of the multi-head due to variations in the manufacturing process and material properties, it is possible to increase the production yield and achieve high quality and An inexpensive image forming apparatus can be provided.

[Brief explanation of the drawing]

Fig. 1 is an external view of a digital color copying machine to which the present invention is applied, Fig. 2 is a sectional view from the side of the digital color copying machine of Fig. 1, and Fig. 3 is a detailed view of the scanning carriage 3 and the invention. 4 is a diagram for explaining the mechanical mechanism inside the scanner section 1. FIG. 5 is an explanatory diagram of the reading operation in book mode and sheet mode. FIG. 6 is a diagram showing the projection exposure on the scanner section 1. FIG. 7 is a detailed explanatory diagram of the film projection system, and FIG. 8 shows the projected image formed on the film and document table glass. FIG. 9 is an explanatory diagram of functional blocks of a digital color copying machine to which the present invention is applied. FIG. 10 is an explanatory diagram of image timing between circuit blocks. FIG. 11 is a diagram illustrating color image processing. A block diagram of the device, Fig. 12 is a timing chart of smoothing and edge enhancement processing, Fig. 13 is a detailed circuit diagram of the masking section, and Fig. 14 is a
Figure 3 is a timing chart of each part, Figure 15 is a detailed circuit diagram of the heavy oil mountain section, Figure 16 is a detailed circuit diagram of the UCR section, Figure 17 is a detailed circuit diagram of smoothing, and Figure 18 is a detailed circuit diagram of the dither processing section. Detailed circuit diagram: FIG. 19 shows a detailed circuit diagram of the head correction section.

Claims (1)

[Claims] In an image forming apparatus that forms an image using a multi-head array, a storage means for storing data corresponding to the output characteristics of each head of the multi-head array; An image forming apparatus characterized by having a correction means for correcting data.