JP3144676B2 - Image forming control device and image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for forming an image using a multi-head and an image forming control device.

[Conventional technology]

Conventionally, as an example of this type of device, there is a device that converts a read image into a digital signal, performs data processing, and then forms an image using a multi-recording head. However, there is still a problem that the density unevenness occurs in the output image due to the characteristic variation due to the above and the characteristic variation of the material of the multi-recording head.

Therefore, a storage means for storing data corresponding to the output characteristics of each head of the multi-recording head array and a means for correcting the input image data based on the stored data are provided, and the density unevenness is prevented by the two means. Devices have been proposed.

<Problems to be Solved by the Invention> However, in the above-described conventional example, correction data of input image data is stored in a memory (RO) in accordance with an output characteristic unique to a recording head (recording element) of a multi-recording head array.
For example, if the output characteristics of the print head have changed due to long-term use or changes in environmental conditions, the correction using the data stored in this memory (ROM) However, the output characteristic of the recording head (recording element) cannot be sufficiently corrected even if the addition is performed, and as a result, there is a problem that the density unevenness occurs in the recorded image.

SUMMARY OF THE INVENTION It is an object of the present invention to solve such a problem and to provide an image forming apparatus capable of easily performing correction even if output characteristics of a recording element change.

<Means for Solving the Problems> In order to achieve the above object, the image forming apparatus of the present invention corrects recording conditions so that the recording states of a plurality of recording elements constituting a multi-head for image formation do not vary. Correction means (for example, 262 in FIG. 8 of the embodiment); display means for displaying a correction state of the correction means (also a
(Display unit shown in FIGS. 10 and 14) Input means (also each key shown in FIGS. 10 and 14) for changing the correction state of the correction means, and storage means (for storing the corrected state after the change) A backup RAM 272 in FIG. 8), means for causing the multi-head to record a recording pattern having a constant recording density according to the correction state stored in the storage means (also a copy start key 312), A determination means (also a registration key 315) for determining the stored correction state is provided.

Further, the image forming control device of the present invention corrects recording conditions so that the recording states of a plurality of recording elements constituting the image forming multi-head do not vary, and displays the correction state of the correcting unit. Display control means, input means for changing the correction state of the correction means, storage control means for storing the changed correction state in the storage means, constant recording on the multi-head according to the correction state stored by the storage means The image forming apparatus further includes means for recording a density recording pattern, and determining means for determining the correction state stored by the storage means.

〔Example〕

Hereinafter, the present invention will be described in detail based on examples. In the following embodiments, an image forming apparatus using an ink jet recording method will be described. In such an ink jet recording, a head having a multi-nozzle provided with a plurality of nozzles for discharging ink will be described as an example of a multi-head recording element.

FIG. 1 is a sectional 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 FIG. 1 is a color image scanner 1 for reading a document image and outputting digital color image data.
(Hereinafter, abbreviated as a scanner unit 1) and a controller unit 2 built in the scanner unit 1 and performing various image processing of digital color image data and having a processing function such as an interface with an external device. You.

The scanner unit 1 reads a three-dimensional object and a sheet document placed below the document holder 11 and also has a built-in mechanism for reading a large-size sheet document.

The operation unit 10 is connected to the control unit 2 and is used to input various information as a copier. The controller unit 2 issues an instruction regarding the operation of the scanner unit 1 and the printer unit 3 according to the input information.
Further, when a complicated editing process needs to be performed, a digitizer or the like is attached in place of the document presser 11, and this is connected to the controller unit 2, thereby enabling advanced processing.

The lower part of FIG. 1 shows a printer unit 3 for recording a color digital image signal output from the controller unit 2 on recording paper. In this embodiment, the printer unit 3 is a full-color ink jet printer using an ink jet type recording head described in Japanese Patent Application Laid-Open No. 54-59936.

The two parts described above are separable and can be installed at remote locations by extending the connecting cable.

(Printer) First, an exposure lamp 14, a lens 15, and an image sensor 16 capable of reading a line image in full color
The original image placed on the original platen glass 17 and the sheet original image by the sheet feed mechanism 12 are read by the CCD (in this embodiment, CCD). Next, various types of image processing are performed by the scanner unit 1 and the controller unit 2 and are recorded on recording paper by the printer unit 3.

In FIG. 1, the recording paper is a sheet cassette 20 for storing cut sheets of a small fixed size (A4 to A3 size in this embodiment) and a large size (A2 to A1 size in this embodiment). It is supplied from a roll paper 29 for performing.

In addition, by feeding recording paper one sheet at a time from the manual feed slot 22 in FIG. 1 along the paper feed unit cover 21, paper feeding from outside the apparatus = manual feeding is also possible.

The pick-up roller 24 is a roller for feeding cut sheets one by one from the sheet feed cassette 20. The fed cut sheet is conveyed to the first sheet feed roller 26 by the cut sheet feed roller 25. You.

The roll paper 29 is sent out by a roll paper feed roller 30, cut into a fixed length by a cutter 31, and conveyed to a first feed roller 26.

Similarly, the recording paper inserted from the manual feed port 22 is conveyed to the first 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 first feed roller 26, and the manual feed roller 32 are provided with a not-shown paper feed motor (in this embodiment, a DC servo motor).
(Using a motor), and an on / off control can be performed at any time by an electromagnetic clutch attached to each roller.

When the printing operation is started by an instruction from the controller unit 2, the recording paper selected and fed from any of the above-described paper feeding paths is transported to the first paper feeding roller 26. In order to remove the skew of the recording paper, a first paper feed roller 26 is turned on after a predetermined amount of paper loop is formed, and the recording paper is conveyed to a second paper feed roller 27.

When printing with the recording head 37, the recording head 37
The scanning carriage 34 on which the etc. are mounted is the carriage rail
A reciprocating scan is performed on the scan 36 by a scan motor 35. And
In the forward scan, an image is printed on the recording paper, and in the backward scan, an operation of feeding the recording paper by a predetermined amount by the paper feed roller 28 is performed.

The printed recording paper is discharged to the paper discharge tray 23 to complete the printing operation.

Next, a detailed description around the scanning carriage 34 will be given with reference to FIG.

The paper feed motor 40 is a drive source for intermittently feeding the recording paper, and includes a paper feed roller 28, a paper feed second roller clutch 43, and the like.
The second paper feed roller 27 is driven via the.

The scanning motor 35 is a drive source for causing the scanning carriage 34 to scan in the directions of arrows A and B via the scanning belt 42. In this embodiment, a pulse motor is used for the paper feed motor 40 and the scanning motor 35 because accurate paper feed control is required.

When the recording paper reaches the second paper feed roller 27, the second paper feed roller clutch 43 and the paper feed motor 40 are turned on, and the recording paper is conveyed on 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, and the sensor information is used for position control, jam control, and the like.

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

Prior to the image recording operation on the recording paper, the scanning carriage 34 is moved to the position of the home position sensor 41, and then the outward scanning is performed in the direction of arrow A, and cyan, magenta, yellow, Black ink is ejected from the recording head 37 to record an image. When the image recording for the predetermined length is completed, the scanning carriage 34 is stopped, and conversely, the 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 scanning, the paper feed for the length recorded by the recording head 37 is fed to the paper feed motor 40, and the paper feed roller 28 is driven.
In the direction of.

In this embodiment, the recording head 37 is an ink jet nozzle of a type in which bubbles are formed by heat and ink droplets are ejected at the pressure, and four recording nozzles each having 256 nozzles are used. ing.

When the scanning carriage 34 stops at the home position detected by the home position sensor 41, the recovery operation of the recording head 37 is performed. This is a process for performing a stable printing operation, and in order to prevent unevenness at the start of ejection due to a change in viscosity of ink remaining in the nozzles of the printing head 37, the feeding time, the internal temperature of the apparatus, and the like. Recording head 37 according to pre-programmed conditions such as
This is a process of performing a pressurizing operation, an idle discharge operation of ink, and the like.

By repeating the operation described above, image recording is performed on the entire surface of the recording paper.

(Scanner Unit) Next, the operation of the scanner unit 1 will be described with reference to FIGS.

FIG. 3 is a view for explaining a mechanical mechanism inside the scanner unit 1. FIG.

The CCD unit 18 is a unit composed of a CCD 16, a lens 15, etc., and has a main scanning motor 5 fixed on a rail 54.
The image forming apparatus moves on the rails 54 by a driving system including a pulley 51, a pulley 52, a pulley 52, and a wire 53 in the main scanning direction, and reads an image on the platen glass 17 in the main scanning direction. The light-shielding plate 55 and the home position sensor 56 are used for position control when the CCD unit 18 is moved to the main scanning home position in the correction area 68 shown in the figure.

The rail 54 is mounted on the rails 65 and 69, and includes the sub-scanning motor 60, pulleys 67, 68, 71, 76, shafts 72, 73, and wires 66, 69.
It is moved by the drive system 70 in the sub-scanning direction. The light-shielding plate 57 and the home position sensors 58 and 59 are used in the book mode for reading a document such as a book placed on the platen glass 17 and in the sheet mode for reading a sheet, respectively. Is used for position control when the rail 54 is moved.

This mechanism is a mechanism for feeding a sheet document placed on the document table glass 17 downward and by a predetermined amount by a sheet feed roller (not shown).

FIG. 4 is an explanatory diagram of a reading operation in the book mode and the sheet mode.

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

Prior to scanning of the document, data necessary for processes such as shading correction, black level correction, and color correction are set in the correction area 68. Thereafter, the main scanning motor 50 starts scanning in the main scanning direction in the direction of the arrow shown in the figure. When the reading operation of the area indicated by is completed, the main scanning motor 50 is rotated in the reverse direction, and the sub-scanning motor 60 is driven to move the correction area 68 of the area in the sub-scanning direction. continue,
Similarly to the main scanning of the area, processing such as shading correction, black level correction, and color correction is performed as necessary.
The reading operation of the area is performed.

By repeating the above scanning, the reading operation of the entire area is performed. After the reading operation of the area is completed, the CCD unit 18 is again set to the book mode home mode.
Return to position.

In the present embodiment, the platen glass 17 can actually read a document having a maximum size of A2.In practice, however, it is necessary to perform a larger number of scans.However, in the present description, the operation is simplified for easy understanding of the operation. .

In the sheet mode, the CCD unit 18 is moved to the illustrated sheet mode home position (sheet mode HP).
Move to the area of the sheet original and feed the sheet feed motor
Scanning is repeated while the 61 is intermittently operated, and the entire sheet document is scanned.

Prior to the scanning of 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 reading operation on the forward path in the area is completed, the main scanning motor 50 is rotated in the reverse direction, and the sheet feed motor 61 is driven during the scanning on the backward path to move the sheet document by a predetermined amount in the sub-scanning direction. Subsequently, the same operation is repeated to read the entire surface of the sheet document.

Assuming that the above-described reading operation is the same-size reading operation, the area that can be read by the CCD unit 18 is actually a large area as shown in FIG. This is because the digital color copying machine of the present embodiment has a 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 described above, for example, when a 50% reduction operation is performed, the image information of the area of 512 bits at least twice as large is required. Is necessary. Therefore, the scanner unit 1 has a function of reading and outputting image information of an arbitrary image area by one main scanning reading.

(Explanation of Entire Function Block) Next, the function block of the digital color copying machine of this embodiment will be described with reference to FIG.

The control units 102, 111, and 121 are control circuits that control the scanner unit 1, the controller unit 2, and the printer unit 3, respectively, and include a micro computer, a program ROM, a data memory, a communication circuit, and the like. Control units 102-111
The control units 111 and 121 are connected to each other by a communication line, and employ a so-called master-slave control mode in which the control units 102 and 121 operate according to instructions from the control unit 111.

When operating as a color copier, the control unit 111 performs a control operation in accordance with input instructions from the operation unit 10 and the digitizer 114.

The digitizer 114 is for inputting position information necessary for trimming, masking processing and the like, and is connected as an option when complicated editing processing is required.

The control unit 102 controls the mechanical drive unit 105 that controls driving of the mechanism of the scanner unit 1 described above, and controls the exposure control unit 103 that controls exposure of the lamp when reading a reflected original. Further, the control unit 102 also controls the analog signal processing unit 100 and the input image processing unit 101 that perform various kinds of processing related to images.

The control unit 121 controls the mechanical drive unit 122 that controls the mechanism of the printer unit 3 described above, and absorbs the time variation of the mechanical operation of the printer unit 3 and corrects the delay due to the arrangement of the recording heads 117 to 120 on the mechanism. The synchronization delay memory 115 is controlled.

Next, the image processing block of FIG. 5 will be described in detail along the flow of images.

The image formed on the CCD 16 is converted into an analog electric signal by the CCD 16. The converted image information is red → green →
Analog signal processing unit 100 processed serially like blue
Is input to In the analog signal processing unit 100, red, green,
After performing sample & hold, dark level correction, dynamic range control, etc. for each blue color, analog-to-digital conversion (A / D conversion) is performed, and serial multivalued (8-bit length for each color in this embodiment) ), And outputs the digital image signal to the input image processing unit 101.

The input image processing unit 101 similarly performs necessary correction processing in a reading system such as CCD correction and γ correction as a serial multi-valued digital image signal.

The image processing unit 107 performs smoothing processing, edge enhancement,
This circuit performs black extraction, masking processing for color correction of recording ink used in the recording heads 117 to 120, and the like. The serial multi-valued digital image signal output is output to the binarization processing unit 10
8. Each is input to the period delay memory 115.

The binarization processing unit 108 is a circuit for binarizing a serial multi-valued digital image signal, and can select a simple binary with a fixed slice level, a pseudo halftone process with a dither method, or the like. Here, the serial multi-valued digital image signal is converted into a binary parallel image signal of four colors.

The synchronization delay memory 115 of the printer unit 3
Absorption and recording head 117-120
This is a circuit for performing delay correction based on the arrangement of the mechanisms, and internally generates timing necessary for driving the recording heads 117 to 120.

The head driver 116 is an analog drive circuit for driving the recording heads 117 to 120, and
A signal that can directly drive 20 is generated internally.

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

FIG. 6 is an explanatory diagram of the timing of an image between the circuit blocks described in FIG.

The signal BVE is a signal indicating an image effective section for each scan in the main scanning reading operation described with reference to FIG. Signal BV
By outputting E multiple times, full-screen image output is performed.

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

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

The signal HS is a signal used when the signal VE outputs one line, and is valid when the valid and invalid sections are repeated discontinuously. When the signal VE is valid continuously while the one line is output, an unnecessary signal is used. It is. This signal indicates the start of image output of one line.

Next, rough signal processing in the image processing unit will be described with reference to FIG.

In FIG. 7, image data (hereinafter, input image data) serially input to the image processing unit 107 is sent to the serial / parallel conversion unit 201, where Y (yellow), M (magenta), and C (cyan) are used. And then sent to the masking unit 202 and the selector 203.

The masking unit 202 is a circuit for correcting the color smear of the output ink, and performs the following calculation.

These nine coefficients are input to the selector unit 203 and the UCR unit 205 as serial signals after correcting the ink smearing in the masking unit 202 determined by the masking control signal from the control unit 200.

The selector 203 has input image data and a masking unit 2.
The image data output from 02 is input.

In the selector 203, input image data is selected by a selector control signal 1 sent from the normal control unit 200. When the color correction in the input system is not sufficiently performed, the image data output from the masking unit 202 is selected by the control signal 1 and output. The serial image data output from the selector 203 is input to the black extraction unit 204. In order to set the minimum value of Y, M, C in one pixel as black data, the black extracting unit 204
The minimum value of Y, M, C is detected. The detected black data is input to the UCR unit 205.

The UCR unit 205 subtracts black data extracted from the Y, M, and C signals. The coefficient is simply multiplied for the black data. The black data input to the UCR unit 205 is corrected for time lag with respect to the image data sent from the masking unit 202, and then the following equation is calculated.

Y ′ = Y−a ₁ Bk M ′ = M−a ₂ Bk C ′ = Ca− ₃ Bk Bk ′ = a ₄ Bk where Y, M, C, and Bk indicate input data of the extraction unit, and Y ′ ,
M ', C', and Bk 'indicate extraction unit output data. The coefficients (a ₁ , a ₂ , a ₃ , a ₄ ) are determined by the UCR control signal sent from the control unit 200.

Then, the data output from the UCR unit 205 is γ,
It is input to the offset unit 206.

In the .gamma., offset section 206, the following tone correction is performed.

Y ′ = b ₁ (Y−C ₁ ) M ′ = b ₂ (M−C ₂ ) C ′ = b ₃ (C−C ₃ ) Bk ′ = b ₄ (Bk−C ₄ ) where Y, M , C, Bk are γ, offset part input data, and Y ′, M ′, C ′, Bk ′ are γ, offset part output data.

Further, the coefficients (b _{1 to} b ₄ , C _{1 to} C ₄ ) in the above equation are determined by the γ and offset control signals sent from the control unit 200.

The signal whose tone has been corrected by the .gamma., offset unit 206 is used as a line buffer 207 for storing image data for the next N lines.
Is input to In this line buffer 207, the control unit 200
According to the memory control signal sent from the controller, five lines of data necessary for the subsequent smoothing and edge emphasis unit 208 are output in five lines in parallel. The signals for these five lines are sent to the control unit 20.
A filter control signal from 0 is input to a spatial filter with a variable filter size, where smoothing is performed and then edge enhancement is performed.

The image data output from the smoothing / edge enhancement unit 208 is input to a color conversion unit 209, and color conversion is performed by a color conversion control signal from the control unit 200. The color to be converted, the color to be converted, and the area where the signal is valid are input from the digitizer device 114 in FIG. 5 in advance, and the image data is replaced by the color conversion unit 209 based on the data. In this embodiment, a detailed description of the color conversion unit 209 is omitted. The image signal output from the smoothing / edge enhancement unit 208 and the image signal after the 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 designating a valid area input from the digitizer 114. The image signal selected by the selector 210 is input to the head correction unit 211.

Next, the head correction unit 211 will be described with reference to FIG.

FIG. 8 is a block diagram of the head correction unit 211 shown in FIG. 7. A counter 250 is an address counter for generating an address of a correction amount selection table RAM 260 (hereinafter, selection RAM).
In this embodiment, the head of 256 nozzles is for four colors, that is, one head in total.
This is a 10-bit counter that counts values corresponding to 024 nozzles, and is controlled by signals HS and VE.

The ROMs 265 to 268 are characteristic ROMs in which characteristic information of density unevenness of 256 nozzles provided in each of the heads of C, M, Y, and Bk is written. In 268, data for correcting head unevenness in density corresponding to the number of nozzles is written. In VDin, color component image data for each pixel is sequentially input in a dot-sequential manner such that digital image data is C, M, Y, K, C, M, Y, K. Select RAM 260 according to the order of input image data
Data is retrieved from 65-268 and stored. 263 is RO
This is a bidirectional buffer for writing data taken out of M265 to 268 to the RAM 260.

259 is the lower 10 bits of the address of the 16-bit address bus output from the CPU 258 or 10 of the counter 250.
This is a selector for selecting one of the bit outputs. RAM2
The selector 259 selects the output of the CPU 258 when writing data to 60, and selects the output of the counter 250 when reading data from the RAM 260.

The data output from RAM 260 is flip-flop 252
Is input to an address of a correction table ROM (hereinafter, correction ROM) 262 together with the image data VDin.

Correction tables such as 1-n to + n in FIG. 9 are written in the correction ROM 262 in advance. Fig. 9 shows 2n
Although +1 kinds of correction tables are shown, the actual correction table is sufficient for a total of about 61 kinds with a correction amount of ± 30% in increments of 1%. The table written in the correction ROM 262 is written so as to output the correction data △ A corresponding to the input A, and the correction data △ A is selected according to the image signal VDin input to the address of the ROM 262 and the selection data. Are latched once by the flip-flop 254, added to the input image data A by the adder 256, and output as corrected data A + ΔA via the flip-flop 257.

RAM271 selects characteristic data from characteristic ROMs 265 to 268
Work RAM used when writing to 260. The backup RAM 272 is a RAM for holding data written in the selection RAM 260, and is always backed up by the battery 273. Both RAM 271 and backup RAM 272 allow the operator to control the characteristics of each head from the operation unit 10.
It is used when the characteristic is changed to a characteristic different from the contents of the characteristic ROMs 265 to 268. Hereinafter, the characteristic change will be described.

FIG. 10 is an operation screen in the case of changing the characteristics of the liquid crystal touch panel in the operation unit 10 employed in this embodiment.

When a characteristic mode is entered by a service mode switch (not shown) in the operation unit 10, the screen shown in FIG. 10 is displayed on the liquid crystal touch panel in the operation unit 10. Reference numeral 316 denotes the type of head color whose characteristics are to be changed, 301 denotes the nozzle number of the head, and 302 denotes the current correction data. First
In FIG. 0, ΔA of the first nozzle of C (cyan) head is +3.
% Correction is performed. 10th in one screen
As shown in the figure, correction data for 30 nozzles is displayed for one color. To change correction data for nozzles that are not displayed, select the nozzle to be corrected using the next screen key 303 and the previous screen key 305. The head can be selected every 30 nozzles, or the head of the color to be displayed can be selected by the color selection key 317. The control is performed by the control unit 111.
To change the correction data 302 displayed as shown in FIG. 10 according to the characteristics, use the next screen key 303 and the previous screen key 30.
4. Use the color selection key 317 to select a screen, and use the cursor keys 308 to 311 to move the cursor 318 to a position where the correction data corresponding to the head nozzle to be changed is displayed. Next, by turning on the up-down keys 307 to 308, the correction data corresponding to the cursor 318 increases or decreases. In the case of the present embodiment, the correction data can be changed up to ± 30% in increments of 1%.

Necessary changes are completed and the operator starts copy start key 312
Is turned on, a pattern signal is generated from the pattern generator 130 shown in FIG. 5, and the pattern signal is recorded by one of the recording heads 117 to 120, for example, as shown in FIG. The operator determines whether further changes are necessary. If a change is necessary, the above operation is repeated to change the correction data to an appropriate value. When the change is no longer necessary, the registration key 315 is pressed. In response to such an operation, the CPU 258 registers the correction data in the backup RAM 272.

The above-described correction data change is internally performed as follows. First, when the power is turned on, the CPU 258 transfers the data for four colors of 256 nozzles of C, M, Y, K backed up from the backup RAM 272 to the work RAM 271. Back-up RAM272
When the data is empty, that is, at the time of shipment from the factory, the data in the characteristic ROMs 265 to 268 is loaded into the work RAM 271 and the backup RAM 272 by the characteristic reset key 314. Next, the correction data increased or decreased by the up-down keys 306 to 307 is reflected only in the work RAM 271.
The data in 71 is transferred to the selection RAM 260, and the above-described correction is performed by this data. When the registration key 315 is depressed without the need for change, the data in the work RAM 271 is transferred to the backup RAM 272 and used as correction data until the next change. Recall key 313 is
It is used when returning to the registered correction data when the correction data is not properly changed, and the data in the backup RAM 272 is transferred to the work RAM 271. When all the changing operations are completed, the EXIT key 304 is pressed to cancel the characteristic changing mode. Thereafter, when the copy start key is pressed, a normal copying operation is started.

Next, the copy start key 312 will be described with reference to FIGS. 11 and 12.
Will be described. That is, when the copy start key 312 is selected, a level L digitized pattern signal is generated by the pattern generator 130 shown in FIG. 5, and this pattern signal is input to the input image processing unit 101. The recording pattern is sent to the recording heads 117, 118, 119, and 120 via the image processing unit 107 and the binarization processing unit 108, and records a recording pattern of a constant recording density _DH corresponding to the image input signal L as shown in FIG. Record on paper. In the case of the display screen shown in FIG. 10, the color of cyan (C) is selected. In this case, when the copy start key 312 is selected, a recording pattern based on cyan head is recorded.

Further, in this embodiment, the print pattern generated by the print pattern generator 130 is such that print printing for three scan scans by the print head is performed as shown in FIG. In other words, by performing print recording for the number of scans of the recording head by the recording head in this manner, variations in output characteristics of the recording head and density unevenness due to a change can be easily visually determined.

Also, here, the digitized pattern signal of level L generated by the pattern generator 130 is input to the image processing unit 107, and then normally, as shown in FIG. 7, black extraction, masking, UCR, Signal processing such as .gamma.-offset, smoothing, edge emphasis, etc. is performed, and as a result, the signal level given to the recording head of each color is not always the same signal level. In this embodiment, when the copy start key 312 is selected and the recording pattern is recorded by the recording head, the above-described masking, UCR, γ, offset, This is given to each recording head by sending it to the binarization processing unit 108 without performing image processing such as smoothing and edge enhancement. Turn signal recording density level of the recording pattern to be recorded by each recording head becomes constant control unit 200 to be the same in each recording head is UCR205, controls the masking 202, and the like.

In this embodiment, a limiter is provided for the correction data ΔA on the screen shown in FIG. That is, as shown in FIG. 9, the number of correction data written in the correction table ROM is finite, the upper and lower limits of the correction amount are fixed, and the correction data corresponding to each nozzle of each recording head is If the variable width of the correction data ΔA is too large while looking at the screen shown in FIG. 10 of the present embodiment, the total correction data for each nozzle of the recording head will not exceed the upper limit or In some cases, the saturation may be saturated to the lower limit, and the recording density unevenness of the recording head may not be completely corrected. Therefore, in this embodiment, the correction data ΔA of the screen shown in FIG.
By setting the upper and lower limits of the variable width of ± α%, the above-described problem can be avoided as much as possible.
The present inventors have experimentally verified that the upper and lower limits ± α% of the correction data ΔA are approximately ±
It was found that within 20%, the recording head density unevenness could be sufficiently solved.

FIG. 13A shows a second embodiment of a recording pattern recording method using the copy start key 312 in the characteristic changing mode of the image forming apparatus according to the present embodiment, and the recording pattern is obtained by scanning the recording head. The control units 121 and 111 shown in FIG. 5 operate so as to perform pattern recording from the second scan without intentionally recording the first scan at the time of recording.

That is, when the recording sheet is fed by the mechanism shown in FIG. 1 in order to record the recording pattern by the recording head in the image forming apparatus of the present embodiment, the recording sheet is supplied due to curl of the recording sheet, conveyance failure, or the like. After the paper is fed, the paper feed roller 28
In some cases, the initial conveyance amount becomes unstable, and the first scan and the second scan when recording the recording pattern overlap as shown in FIG. 13 (B), causing unevenness in the density of the recording head. In some cases, visual evaluation was hindered.

Therefore, as shown in FIG. 13 (A), in this embodiment, after the recording paper is fed and the initial conveyance of the recording paper is stabilized, the recording pattern by the recording head on the recording paper is recorded. Thus, the above-described problem can be prevented beforehand.

FIG. 14 shows an operation screen of the third embodiment in the characteristic change mode of the image forming apparatus of the present embodiment, in which multi-nozzles are divided at equal intervals instead of performing correction for each nozzle of the recording head. The rewriting operation of the correction data of each nozzle of the recording head is simplified by collectively setting the correction data for every several nozzles. In other words, in the present embodiment, correction data is corrected at 0.5 mm pitch for 8 nozzles collectively for a multi-recording head having 256 nozzles at a resolution of 400 dpi and a recording capability of 16 mm width. All correction data for 256 nozzles (16 mm width) can be displayed on the screen. Further, the position of the divided area whose correction data is to be corrected is displayed as a dimension (numerical data indicated by 350 in FIG. 14) to further simplify the operation. Here, the division unit of the correction data of the recording head may be set according to the number of nozzles and the resolution of the recording head, and the present inventor collectively collects eight nozzles for a multi-recording head having a resolution of 400 dpi and 256 nozzles. 0.5mm
It has been confirmed that the method of correcting the correction data with pitch can visually correct the density unevenness of the recording head to a level that does not cause any problem.

FIG. 15 shows a fourth embodiment of the recording pattern of the text sample recorded by the copy start key 312 on the operation screen of the third embodiment, and an area which is not recorded in a part of the recording pattern by the recording head. Is provided. That is, by providing a blank portion in a part of the recording pattern as in the present embodiment, it is possible to easily understand the correspondence relationship between the region where the density unevenness of the multi-recording head occurs and the position of the nozzle of the corresponding recording head. It is. Further, in this embodiment, the blank portion of the above-described recording pattern is recorded by only the nozzle corresponding to the boundary of the divided area unit for which the correction data of the multi-recording head is to be corrected. (Scale).

That is, by providing a scale (scale) corresponding to a correction data correction unit obtained by dividing the recording head shown in the third embodiment at equal intervals in the recording pattern of the multi-recording head as in this embodiment, the density unevenness can be reduced. The nozzle area of the recording head that has occurred can be easily recognized, and the correction data changing operation using the operation screen in the characteristic changing mode can be further simplified.

As described above, in addition to the conventional means for electrically correcting variations in head output density, means for displaying correction data such as a liquid crystal touch panel in the operation unit,
By adding a means for changing this, and a means for performing recording by the multi-recording head according to the corrected data after the change, the density unevenness of the recording head is changed to the change of the head density unevenness due to the use state or the use time. It can be handled without changing the characteristic ROM or the recording head, and can always provide a stable and uniform image. Further, in this embodiment, by correcting the image data in a color sequence, it is possible to perform the processing with one circuit without providing a circuit for each color, so that a high-quality and low-cost image forming apparatus can be provided.

Further, in the above-described embodiment, since the description has been made by using the ink jet recording method, as an example of the multi-head, an apparatus for performing recording by a multi-nozzle provided with a plurality of nozzles for ejecting ink is shown. The present invention is not limited to an apparatus having a nozzle for ejecting ink, but also an apparatus using another multihead, for example, an apparatus using a multihead provided with a plurality of heating elements for applying heat to perform recording using a thermal transfer recording method. The same applies to the case.

In the above-described embodiment, the image data given to each printing element is corrected when the printing condition of the printing element is corrected. However, the present invention is not limited to this, and the power energy given to each printing element is not limited to this. A change method may be used. In the case of using an ink jet system in which ink is ejected using air pressure and electrostatic force as a multi-head, for example, the printing condition of each print element is changed by correcting the air pressure and / or electrostatic force described above. You may. The method of correction can be variously modified according to the recording method of the head for image formation.

As described above, according to the present embodiment, in addition to the conventional means for electrically compensating for variations in the output density of the recording head, a means for displaying correction data, a means for changing this, and a means for changing Even if the density variation of the recording head changes due to the addition of means for performing recording using the recording head in accordance with the correction data, it is possible to respond to the variation in the density variation with a simple operation and always obtain a stable and uniform image. Can be provided.

<Effect of the Invention> As described above, according to the present invention, even if the output characteristics of the recording element for image formation change, such a change can be easily corrected. Change the correction state that is set so that the variation in the recording state of each recording element is reduced, then form a recording pattern with a constant recording density, and check whether the variation in the density of this pattern is within a predetermined range After that, the correction state stored in the storage means can be determined, so that the correction state can be reliably set so as to suppress variations in the density of the image formed by each recording element.

[Brief description of the drawings]

FIG. 1 is a sectional view of a digital color copying machine embodying the present invention, FIG. 2 is a detailed explanatory view around a scanning carriage, FIG. 3 is a view for explaining an input mechanism inside a scanner section, FIG. FIG. 5 is an explanatory diagram of a reading operation of a scanner section. FIG. 5 is a functional block diagram of a digital color copying machine to which the present invention is applied. FIG. FIG. 8 is a detailed circuit diagram of the first embodiment of the present invention, FIG. 9 is a diagram of a correction table written in the correction ROM shown in FIG. 8, and FIG. FIG. 11 is an explanatory view of a screen in the characteristic change mode of the liquid crystal touch panel in the operation unit used in the first embodiment, FIG. 11 is a diagram of a pattern signal generated from the pattern generator shown in FIG. 5, and FIG. The recording head recorded by the recording head FIG. 13A is an explanatory diagram showing a second embodiment of the recording pattern of the image forming apparatus of the present invention, and FIG. 13B is a diagram showing the recording pattern of the image forming apparatus shown in FIG. FIG. 14 is an explanatory view showing a problem that occurs in the case, FIG. 14 is an explanatory view of a screen in a characteristic change mode of a liquid crystal touch panel in an operation unit used in a third embodiment of the present invention, and FIG. FIG. 14 is an explanatory diagram showing a fourth embodiment of the recording pattern recorded from the recording head in the characteristic change mode shown. 250 ... Counter 260 ... Selection RAM 262 ... Correction ROM 256 ... Adder 258 ... CPU 10 ... Operation unit 265-268 ... Characteristic ROM 271 ... Work RAM 272 ... Back-up RAM 281 ... Correction RAM 312 ... Copy start key

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Kiyohisa Sugishima 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Yoshiki Kuboti 3-30-2 Shimomaruko, Ota-ku, Tokyo (56) References JP-A-62-108587 (JP, A) JP-A-62-229426 (JP, A) JP-A-63-264378 (JP, A) JP-A-63-131877 (JP, A) JP, A)

Claims (4)

(57) [Claims] A correcting means for correcting a recording condition of each of a plurality of recording elements constituting a multi-head for image formation so as not to vary; a display means for displaying a correction state of the correcting means; Input means for changing the correction state of the storage means, storage means for storing the corrected state after the change, means for causing the multi-head to record a recording pattern of a fixed recording density according to the correction state stored by the storage means, An image forming apparatus comprising: a determination unit that determines a correction state stored by the storage unit. 2. The image forming apparatus according to claim 1, wherein image data of each recording element is corrected as a recording condition of each recording element of the image forming multi-head. 3. The image forming apparatus according to claim 1, wherein the recording pattern having a constant recording density is a recording pattern having a constant density corresponding to a digitized pattern signal having a predetermined density. 4. A correction means for correcting recording conditions so that the recording states of a plurality of recording elements constituting the multi-head for image formation do not vary; a display control means for displaying the correction state of the correction means; Input means for changing the correction state of the means, storage control means for storing the changed correction state in the storage means, recording of a recording pattern of a fixed recording density on the multi-head in accordance with the correction state stored by the storage means And a determining means for determining the correction state stored by the storage means.