JPH08289149A - Image recording device and method thereof - Google Patents

Abstract

PURPOSE: To obtain an excellent image by adjusting an image formation parameter by taking the fluctuation of an image formation condition into account. CONSTITUTION: The luminance information on the original image outputted from a CCD 105 is converted into area sequential density information by an image processing part 108. This density information is the image data to be corrected according to the gamma characteristic of a printer at the time of an initialization. An LUT 25 converts the density characteristic of the image data inputted from the image processing part 108 so as to match the density of an original image and the density of the outputted image. The image data outputted from the LUT 25 is inputted in a PWM 26. The CPU 214 of a reader part A and the CPU 28 of a printer part B execute an image adjusting processing by coorporating with each other. At first, the gradation characteristic of the printer is adjusted, next, the color reproducing characteristic of the printer is adjusted, and the image adjusting processing is terminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording apparatus and method thereof, for example, an image recording apparatus and method for forming a color image on a recording medium.

[0002]

2. Description of the Related Art N sets of input signals A known to an image forming apparatus are known.
N (print signal) is given to form N sets of patterns of a specific color on the recording medium, the brightness Bn of the formed pattern is read, and the output signal value Cn of the N sets of printers is calculated from the brightness Bn by masking calculation. obtain. Then, there is a technique for improving the stability of image quality by adjusting image forming parameters such as a masking coefficient so that N sets of input signals An and output signals Cn are substantially equal.

[0003]

However, the above-mentioned technique has the following problems. That is, when the image formation is repeated, the toner is crushed, the crushed toner is attached around the developer carrier, and the maximum density of the copy image is reduced.
This decrease in maximum density narrows the color reproduction range,
Even if an image forming parameter such as a masking coefficient is adjusted in this state, a good image quality cannot be obtained. The deterioration of the image quality due to the deterioration of the durability of the developer can be improved by replacing the developer. However, it is not realistic to regularly replace the developer in consideration of the deterioration of durability because it causes an increase in copy cost.

The present invention is for solving the above-mentioned problems, and an image recording apparatus capable of obtaining a good image quality by adjusting image forming parameters in consideration of a change in image forming conditions. And to provide a method thereof.

[0005]

[Means for Solving the Problems] and

The present invention has the following structure as one means for achieving the above object.

An image recording apparatus according to the present invention is an image recording apparatus for recording an image on a recording medium, which comprises a first feedback adjusting means for adjusting gradation characteristics and an image after adjustment by the first feedback adjusting means. , And second feedback adjusting means for adjusting the color reproduction characteristic.

The image recording method according to the present invention is an image recording method for recording an image on a recording medium, wherein the gradation characteristics are adjusted by the first feedback system and then the color reproduction characteristics are adjusted by the second feedback system. It is characterized by adjusting.

Further, a first pattern forming step of forming a first test pattern on the recording medium, and a first reading step of reading the first test pattern formed on the recording medium in the first pattern forming step. A first adjusting step of adjusting gradation characteristics based on information of the first test pattern read in the first reading step, and a second pattern forming step of forming a second test pattern on a recording medium And a second reading step of reading the second test pattern formed on the recording medium in the second pattern forming step, and color reproduction based on the information of the second test pattern read in the second reading step. And a second adjusting step for adjusting the characteristic.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image recording apparatus according to an embodiment of the present invention will be described in detail below with reference to the drawings.

[0010]

First Embodiment First, an outline of a full-color image forming method will be described.

FIG. 1 is a view showing the arrangement of an image recording apparatus according to the first embodiment of the present invention, which is composed of a reader section A and a printer section B.

The original 101 placed on the original table glass 102 of the reader unit A is illuminated by a light source 103. The reflected light from the original 101 is imaged on the CCD sensor 105 via the optical system 104. The CCD sensor 105 uses the red, green, and blue CCD line sensor groups arranged in three rows to generate red, green, and blue color component signals for each line sensor. These reading optical system units scan the document in the direction indicated by the arrow in the figure to convert the document image into an electric signal data string in line units.

Further, the white level of the CCD sensor 105 and the positioning member 107 for preventing the original 101 from being obliquely placed by abutting the sides of the original 101 on the original table glass 102, determine the white level of the CCD sensor. A reference white plate 106 for performing shading correction in the thrust (array) direction of 105 is arranged.

The image signal output from the CCD sensor 105 is
After being subjected to image processing by the image processing unit 108, it is input to the printer control unit 109 of the printer unit B.

FIG. 2 is a block diagram showing a configuration example of the image processing unit 108.

In the figure, a CPU 214 controls the entire reader unit A including the following components according to a program stored in advance in a ROM 216 or the like. The RAM 215 is used as a work area by the CPU 214, and the ROM 216 stores image processing parameters and the like in addition to the control program. The operation unit 217 has a display unit 218 such as a keyboard, a touch panel, and an LCD, and transmits an instruction from an operator to the CPU 214, and displays the operating condition and state of the device by the CPU 214.

The address counter 212 counts the clock CLK for each pixel generated by the clock generator 211 and outputs a main scanning address signal representing a pixel address of one line. The decoder 213 decodes the main scanning address signal output from the address counter 212, and shifts the reset pulse or the reset pulse to the CCD sensor 1 for each line.
Signal 219 that drives 05 and 1 output from CCD sensor 105
A signal VE representing an effective area in the line signal, a line synchronization signal HSYNC, etc. are generated. The address counter 212
Is cleared by the signal HSYNC and starts counting the main scanning address of the next line.

The image signal output from the CCD sensor 105 is
After being input to the analog signal processing unit 201 and adjusted for gain and offset, the A / D conversion unit 202, for example,
It is converted into an 8-bit RGB digital image signal, and the shading correction unit 203 performs known shading correction using the signal obtained by reading the reference white plate 106 for each color.

The line delay unit 204 corrects the spatial deviation contained in the image signal output from the shading correction unit 203. This spatial shift is caused by the line sensors of the CCD sensor 105 being arranged at a predetermined distance from each other in the sub-scanning direction. Specifically, with the B color component signal as a reference, the R and G color component signals are line-delayed in the sub-scanning direction to synchronize the phases of the three color component signals.

The input masking unit 205 converts the color space of the image signal output from the line delay unit 204 into the NTSC standard color space by the matrix calculation of the equation (1). That is, the color space of each color component signal output from the CCD sensor 105 is determined by the spectral characteristics of the filter for each color component,
This is converted to the standard color space of NTSC. However, Ro, Go, Bo: Output image signal Ri, Gi, Bi: Input image signal

The LOG conversion unit 206 is composed of a look-up table including, for example, a ROM, and the input masking unit 20.
The RGB luminance signal output from 5 is converted to a CMY density signal. The line delay memory 207 includes a control signal UCR, FILTER,
LOG converter 20 for the period (line delay) for generating SEN, etc.
The image signal output from 6 is delayed.

The masking / UCR unit 208 generates the black component signal K from the minimum value min (M, C, Y) of the image signal output from the line delay memory 207, and further, the spectral distribution of the color toner and the reading optics. The masking process that optimizes the matching between the spectral characteristics of the CCD used in the system and the spectral characteristics of the color separation filter is performed by the matrix calculation of the following equation, and the reader unit A
For example, an 8-bit color component image signal is output in the order of M, C, Y, and K for each reading operation. The matrix coefficients b11 to b44 used in the matrix calculation are set by the CPU 214. However, Mo, Co, Yo, Ko: Output image signal Mi, Ci, Yi: Input image signal Ki = min (Mi, Ci, Yi)

The gamma correction unit 209 performs density correction on the image signal output from the masking / UCR unit 208 in order to match the image signal with the ideal gradation characteristic of the printer unit B.
The output filter (spatial filter processing unit) 210 applies edge enhancement or smoothing processing to the image signal output from the gamma correction unit 209 according to the control signal from the CPU 214.

The density converting section 220 converts the RGB image signal output from the line delay section 204 into an optical density, which will be described in detail later.

The MCYK frame-sequential color component image signal processed in this way is sent to the printer section B, and density recording by PWM is performed.

FIG. 3 is an example of a timing chart of each control signal in the image processing unit 108.

In the figure, a signal VSYNC is an image effective section signal in the sub-scanning direction, and image reading (scanning) is performed in the section where the signal is "1", and M, C, Y and K are sequentially read. An image signal is formed. Further, the signal VE is an image effective section signal in the main scanning direction, and the start timing of main scanning (that is, the timing when the signal HSYNC falls from "1" to "0") in the section where the signal is "1". Besides, it is mainly used for line counting control of line delay. Signal CLK
Is a pixel synchronization signal, and the image data is transferred at the timing when the signal rises from “0” to “1”.

FIG. 4 is a block diagram showing a configuration example of the printer control unit 109. The printer unit B will be described with reference to FIGS. 4 and 1.

The image data input from the reader unit A to the printer control unit 109 is converted by the pulse width modulator (PWM) 26 into a pulse signal corresponding to the image data, and the laser light source is used.
It is input to the laser driver 27 that drives 110. The laser light output from the laser light source 110 is scanned by the polygon mirror 1 in the main scanning direction, and then irradiates the photosensitive drum 4 uniformly charged by the primary charger 8 via the mirror 2. An electrostatic latent image is formed on the photosensitive drum 4.

The photosensitive drum 4 is rotating in the direction of the arrow shown in the figure, and the latent images formed on the photosensitive drum 4 are sequentially developed with toner by the developing device 3 for each formed color. In this embodiment, a two-component system is used as a developing system, and developing devices 3 for respective colors are arranged around the photosensitive drum 4 in the order of black K, yellow Y, cyan C, and magenta M from the upstream in the rotation direction. However, under the control of the printer control unit 109, the developing device 3 corresponding to the formed color comes into contact with the photosensitive drum 4 at the timing of developing the latent image formed on the photosensitive drum 4.

On the other hand, the transfer drum 5 around which the recording paper 6 supplied from the recording paper cassette or the like is wound is rotated once for each forming color, and the toner image on the photosensitive drum 4 is transferred to the recording paper 6. After a total of four rotations, the four color toner images are transferred in an overlapping state.

After the transfer, the recording paper 6 is separated from the transfer drum 5, the toner image is fixed by the fixing roller pair 7, and the printing of the full-color image is completed.

Further, in the printer engine section 100, the surface potential sensor 12 is provided upstream of the latent image forming position of the photosensitive drum 4.
An environment sensor 33 for measuring the amount of water contained in the air inside the device, and an optical reader 40 including an LED light source 10 (having a main wavelength of about 960 nm) and a photodiode 11 are provided.
As will be described later in detail, the surface potential sensor 12 is used by the printer control unit 109 to detect the charged state of the photosensitive drum 4 based on its output, and to control the grid potential of the primary charger 8 and the developing bias of the developing unit 3. Optical reader 40
Is for the printer controller 109 to detect the amount of reflected light of the toner patch pattern formed on the photosensitive drum 4. Further, a cleaner 9 is arranged upstream of the primary charger 8 to clean the toner remaining on the photosensitive drum 4 without being transferred.

In the printer control unit 109, the CPU 28 controls the RO
According to a program stored in advance in M30 or the like, the printer engine unit 100 and the entire printer unit B including the following respective components are controlled, and communication with the CPU 214 of the reader unit A is performed to perform operations such as copying in cooperation. The RAM 32 is used as a work area by the CPU 28, and the ROM 30 stores control parameters as well as control programs. Further, a part of the ROM 32 has a test pattern storage area 30a in which test patterns described later are stored in advance.

The look-up table (LUT) 25, which will be described in detail later, is used to match the density of the original image with the density of the output image, and is composed of, for example, RAM. It is set.
The pattern generator 29 generates a test print 2 described later, and the density conversion circuit 42 converts a brightness signal input from the optical reading device 40 into a density signal.

FIG. 5 is a diagram for explaining image processing for obtaining a gradation image according to this embodiment.

The luminance information of the original image output from the CCD 105 is converted by the image processing unit 108 into frame sequential density information. This density information is image data corrected according to the gamma characteristic of the printer at the time of initial setting. LUT25 is
The density characteristics of the image data input from the image processing unit 108 are converted so that the density of the original image and the density of the output image match. The image data output from the LUT25 is input to the PWM26.

FIG. 6 is a quadrant chart showing how gradations are reproduced. The first quadrant shows the reading characteristics of the reader unit A for converting the document density into a density signal, and the second quadrant shows the density signal as a laser output signal. In the third quadrant, the conversion characteristics of the LUT25 for converting to
And the fourth quadrant shows the relationship between the document density and the output density, that is, the total gradation reproduction characteristic of the apparatus. It should be noted that the number of gradations is 256, because 8-bit digital processing is performed.

In this embodiment, in order to make the gradation reproduction characteristic shown in the fourth quadrant linear, the non-linear recording characteristic of the printer section B shown in the third quadrant is converted by the conversion characteristic of the LUT25 in the second quadrant. to correct. The conversion characteristic of the LUT 25 is set by the calculation result described later.

FIG. 7 is a flowchart showing an example of the procedure of the image adjustment processing of this embodiment, which is executed by the CPU 214 of the reader unit A and the CPU 28 of the printer unit B in cooperation. Step S1
Adjusts the tone characteristics of the printer, adjusts the color reproduction characteristics of the printer in step S2, and ends the image adjustment processing. Hereinafter, each processing will be described in order.

[Gradation control of system including reader and printer (first feedback system)] Next, a control system for stabilizing the gradation reproduction characteristics of the system including both the reader unit A and the printer unit B will be described. To do.

FIG. 8 is a flow chart for explaining the calibration of the printer unit B using the reader unit A.
When the operator presses the automatic gradation correction mode setting key provided on the operation unit 217, the CPU 214 of the reader unit A and the CPU 28 of the printer unit B cooperate to start this control.
When this control is started, information or keys as shown in FIGS. 9A to 11E are displayed on the display unit 218 which is, for example, a liquid crystal operation panel (touch panel display) of the operation unit 217.

First, in step S51, the CPU 214
The "Test Print 1" key for starting the test print is displayed on the display 218 (Fig. 9A), and the operator presses this key to display an image of the test print 1 from the printer section B as shown in Fig. 12 by way of example. Printed out. FIG. 9C is a display example of the display 218 during printing of the test print 1.

At this time, the CPU 28 judges whether or not there is a recording medium for printing the test print 1 and then the CPU 2
Notify 14. CPU214 is an indicator when there is no recording medium
Display a warning at 218 (Figure 9B). It should be noted that when the test print 1 is formed, the value of the standard state corresponding to the environment is registered as the initial value, and thus this value is used as the contrast potential described later.

The apparatus of this embodiment is provided with a plurality of recording paper cassettes, and a plurality of recording medium sizes such as B4, A3, A4 and B5 can be selected. However, the recording medium used for printing the test print 1 should not be mistaken for placing the test print 1 on the platen glass 102 during the subsequent reading operation, that is, vertical placement and horizontal placement. Therefore, the so-called large size (B4, A3, 11 × 17, LGR, etc.) is set.

In the test pattern 1 shown in FIG. 12, a band-shaped pattern 61 having intermediate gradation densities of YMCK four colors is formed. The band pattern 61 is visually inspected to confirm that there is no streaky abnormal image, density unevenness, or color unevenness. If the belt pattern 61 is abnormal, the test print 1 is printed out again. If the belt pattern 61 is still abnormal, processing such as calling a service person is required. Also, the pattern 62 is the maximum density patch of each color of YMCK (density signal value 255 in the case of 8 bits).
Is.

The size of the pattern 61 in the main scanning direction is the patch pattern 62 and the gradation pattern 71 shown in FIG.
And is set to cover 72. It is also possible to read this band pattern 61 by the reader unit A and automatically determine whether or not to perform the subsequent control based on the density information in the main scanning direction.

Subsequently, in step S52, the operator
The platen glass 10 is arranged so that the main scanning direction and the sub-scanning direction when the test print 1 is formed and the main scanning direction and the sub-scanning direction when the test print 1 is read.
2 Place test print 1 on top (Fig. 14) and press the "Read" key shown in Fig. 10A. At this time, as shown in FIG. 10A, the CPU 214 displays guidance for the operator on the display device 218, and instructs the method of placing the test print 1 on the platen glass 102. That is, FIG. 14 is a view of the document table as viewed from above, and the wedge-shaped mark T on the upper left is a document positioning (abutting) mark on the document table, and the band pattern 61 is on the mark T side. In addition, the test print 1 needs to be placed on the platen glass 102 so that the front side and the back side are not mistaken.

The reading of the patch pattern 62 by the reader unit A is performed as follows. That is, when scanning is started from the position of the mark T and gradually scanned, the first rapid density change (density gap) is detected at the corner (point A) of the band pattern 61. The position of each patch pattern 62 is calculated relative to the coordinates of
Read the density value of 62. The display on the display 218 during this reading is as shown in FIG. 10B, and when the orientation or position of the test print 1 is incorrect and the patch pattern 62 cannot be read, the CPU 214 causes the display 218 to display the image. After displaying the message shown in 10C, the operator reloads the test print 1 and presses the "read" key, and the patch pattern 62 is read again.

At this time, the CPU 214 causes the line delay unit 20 to
The image signal is controlled to pass from 4 to the density conversion unit 220, and the conversion formula (or equivalent conversion table) shown in the formula (3) is set in the density conversion unit 220, and the read RGB value is converted into the optical density. Convert to. In addition, the density conversion unit 220 uses the correction coefficient to convert the conversion result in order to obtain the same value (absolute density) as a commercially available densitometer
Adjusted in km, kc, ky, kk. M = -km × log (G / 255) C = -kc × log (R / 255) Y = -ky × log (B / 255)… (3) K = -kk × log (G / 255) The base of logarithm is 10.

Subsequently, in step S53, the CPU 28 obtains the target contrast potential B for obtaining the target density based on the density information obtained from the patch pattern 62 for each color component.

FIG. 15 is a diagram showing the relationship between the relative drum surface potential and the image density. A method for obtaining the target contrast potential B from the obtained density information and correcting the maximum density will be described with reference to FIG.

The patch pattern obtained when the difference between the developing bias potential and the surface potential of the photosensitive drum 4 discharged by the laser beam corresponding to the maximum density level after the primary charge, that is, the contrast potential is A 62 concentration is D
Let it be a. Further, the target image density is set to, for example, 1.6, but for the following reason, the target value Dr of the maximum density is set to 1.7 and the contrast potential is determined by further considering a margin of 0.1, for example. This is because the image density with respect to the relative drum surface potential in the maximum density region almost changes linearly as shown by the solid line L in FIG.
In the two-component developing system, when the toner density in the developing device 3 fluctuates and decreases, as shown by the broken line N, it may show non-linearity in the maximum density area.
We are expecting a margin of 0.1.

Here, the image density D means an optical density and is defined by the following equation. D = -log (I / Io) (4) However, Io: Incident light I: Reflected light The base of logarithm is 10

Specifically, the contrast potential B with respect to the target value Dr is obtained by using the equation (5).
Is a correction coefficient, and it is preferable to optimize the value depending on the type of developing system. B = (A + Ka) × Dr / Da… (5)

As a representative example of the correction coefficient Ka, in the case of an actual electrophotographic system, the image density cannot be adjusted unless the setting of the contrast potential is changed according to the surrounding environment, and the image density in the air inside the apparatus is changed. The contrast potential setting is changed as shown in FIG. 16 according to the output of the environment sensor 33 that monitors the amount of water contained. A specific method of correcting the contrast potential according to the amount of water in the environment is to use the correction coefficient Vcont.rate obtained from Equation (6) as the backup area 3 of the RAM 32.
It is stored in 2a, for example, the environment (moisture content) is monitored every 30 minutes, and the correction coefficient Vcont.rate and the image forming operation according to the detection result are displayed as shown in equation (7). Contrast potential Atem calculated according to the amount of water in the environment
The corrected contrast potential B'is calculated from p and. Vcont.rate = B / A… (6) B '= Vcont.rate × Atemp… (7)

Subsequently, the CPU 28, in step S54,
It is determined whether the target contrast potential B of each color component is within the control range. If the target contrast potential B is out of the control range, it is determined that the developing device 3 or the like has an abnormality, and in step S55, the developing device 3 of the corresponding color is detected.
After setting an error flag corresponding to, and correcting the target contrast potential B to a value close to the control range, the process proceeds to step S56. The error flag instructs the serviceman to check the part corresponding to the error flag when the serviceman executes a predetermined service mode.

Subsequently, in step S56, the CPU 28 sets the grid potential and the developing bias potential of the primary charger 8 so that the target contrast potential B can be obtained. Here, a method for obtaining the grid potential and the developing bias potential from the target contrast potential B will be briefly described.

The surface potential VL of the photosensitive drum 4 when the grid potential of the primary charger 8 is set to -200 V and the laser beam corresponding to the lowest density level is scanned, and the laser beam corresponding to the highest density level is scanned. The surface potential VH of the photosensitive drum 4 at that time is measured by the surface potential sensor 12. Similarly, an example of the result of measuring the VL and VH when the grid potential is set to -400V and determining the relationship between the grid potential and the surface potential by interpolation and extrapolation from the -200V data and the -400V data is given below. It is FIG. The control for obtaining the potential data is called potential measurement control.

To prevent so-called toner fog in which toner adheres to a portion where toner does not originally adhere, a voltage difference Vbg
(For example, 100V), the development bias VDC is VL-Vb
Set to g. Therefore, the contrast potential Vcont is a difference voltage between the developing biases VDC and VH, and as described above, the larger the Vcont, the larger the maximum density can be. As described above, the grid potential and the developing bias potential required to obtain the target contrast potential B can be calculated based on the relationship shown in FIG.

FIG. 18 is a diagram showing an example of the density conversion characteristic. As described above, in the maximum density control in this embodiment, the maximum density is set higher than the final target value, so the solid line J shows the printer characteristic diagram in the third quadrant. If such control is not performed, the printer characteristics may not reach 1.6, as indicated by the broken line H. In the case of the characteristic of the broken line H, it is impossible to reproduce the density between the density DH and 1.6 because the LUT25 does not have the ability to increase the maximum density no matter how the LUT25 is set. On the other hand, as shown by the solid line J, if the density is set to slightly exceed the maximum density, the density reproduction range can be surely guaranteed with the total gradation characteristics of the fourth quadrant.

Subsequently, in step S57, the CPU 214
Displays a message to start test print 2 on the display 218 and the "test print 2" key (Fig. 1
1A), when the operator presses this key, the image of the test print 2 as shown in FIG. 13 is printed out from the printer section B. FIG. 11B is a display example of the display device 218 during printing of the test print 2. In addition,
The test print 2 is generated by the pattern generator 29 and output without passing through the LUT 25.

The test print 2 has four columns 16 for each color component.
It consists of patches with gradations of rows (total 64 gradations). Here, the laser output level is set such that the low density region of the total 256 gradations is allocated to 64 gradations and the high density region is thinned and allocated. By doing so, it is possible to satisfactorily adjust the gradation characteristics especially in the highlight portion.

As shown in FIG. 13, the test print 2 has a pattern 71 with a resolution of 200 LPI (lines / inch) and 400 L.
A PI (lines / inch) pattern 72 is provided, and 73 represents each patch. In this embodiment, for example, the gradation image is 200 LPI
Since the line image such as characters is formed with the resolution of 400 LPI at the resolution of, the pattern of the same gradation level is output with these two types of resolution, but if the gradation characteristics greatly differ due to the difference in resolution, the resolution is It is more preferable to set the previous gradation level according to the above. Note that the formation of images with different resolutions can be realized in the PWM 26 by making the triangular wave to be compared with the image data to be processed into a cycle corresponding to the resolution.

Then, in step S58, the operator
The platen glass 10 is placed so that the main scanning direction and the sub-scanning direction when the test pattern 2 is formed and the main scanning direction and the sub-scanning direction when the test pattern 2 is read.
2 Put test print 2 on top (Fig. 19) and press the "Read" key shown in Fig. 11C. At this time, as shown in FIG. 11C, the CPU 214 displays guidance for the operator on the display 218, and instructs the method of placing the test print 2 on the platen glass 102. Figure 19 is a view of the platen from above.
It is necessary to place the test print 2 on the platen glass 102 so that the pattern of K is on the above-mentioned upper left wedge-shaped positioning mark T side and that the front and back are not mistaken.

The reading of the patterns 71 and 72 by the reader unit A is performed as follows. That is, when scanning is started from the position of the mark T and gradually scanned, the first abrupt density change (density gap) is detected at the corner (point B) of the pattern 72. The position of each patch 73 is relatively calculated from the coordinates, and the density value of each patch 73 is read.

FIG. 20 is a view showing an example of reading points for one patch 73. For example, reading points are provided inside the patch.
The 16 read values are averaged, and the 16 read values are averaged, and the average read value (RGB signal) is converted to a density value by the conversion formula (2) for optical density shown above. The number of reading points depends on the reader unit.
It is preferable to optimize according to A and the printer unit B.

FIG. 21 is a diagram showing an example of the relationship between the output density and the laser output level obtained in this way. The vertical axis on the right side of the figure shows the base density (0.08 in the figure) of the recording medium as the density level " 0 ”and set as the maximum density of this device
1.60 is normalized to the density level "255".

If the obtained density value is specifically high as shown by point C in FIG. 21 or is low as shown by point D, there are stains and scratches on the platen glass 102. Since the test print 2 may be defective, the CPU 28 limits the inclination of the characteristic and performs correction so that the continuity is preserved in the data string. For example, when the slope is 3 or more, this limit is fixed to 3, and when the slope shows a negative value, the density value is set to the same value as the density value immediately before that.

Subsequently, the CPU 28 creates and sets the table of the LUT 25 in step S59. As described above, the table can be obtained by simply replacing the coordinates of the density level of FIG. 21 with the input level (density signal axis of FIG. 6) and the laser output level of the output level (laser output signal axis of FIG. 6). Easy to create. For density levels that do not correspond to patches, table values are obtained by interpolation calculation. At this time, a limiting condition is set so that the output level becomes “0” with respect to the input level “0”. Note that the CPU 214
During the processing of S59, the display shown in FIG. 11D is displayed on the display 218, and when the automatic gradation correction is completed, the display shown in FIG. 11E is displayed.

With the above, the contrast potential control and the creation of the gamma conversion table by the control system using the reader unit A are completed.

[Gradation Supplementary Control] Next, supplementary control regarding gradation will be performed after the above-described automatic gradation correction (hereinafter sometimes referred to as "first control system"). explain. As described above, the maximum density is corrected by controlling the contrast potential according to the environmental change, but in the present embodiment, the gradation is also corrected.

FIG. 22 is a diagram showing an example of the table values of the LUT 25 stored in the ROM 30 in advance. The table values correspond to the case where the environment changes while the first control system is disabled.

The CPU 28 stores the water content data when the control by the first control system is performed in the backup area 32a, and obtains the LUT.A corresponding to the water content from the ROM 30.
After that, each time the environment changes (or the measurement of water content),
The LUT.B corresponding to the water content is obtained from the ROM 30, and the LUT.1 obtained by the first control system is used by using LUT.B and LUT.A.
Correct according to equation (8). LUT.present = LUT.1 + (LUT.B-LUT.A)… (8)

By this control, the device can obtain a linear characteristic with respect to the density signal, and as a result, it is possible to suppress the variation of the density gradation characteristic among the devices and set the standard state. Become.

Further, when this control is released to the general user and the user judges that the gradation characteristic of the device is deteriorated,
By executing this control, the reader can
/ It is possible to easily correct the gradation characteristics of the system including both printers, and it is also possible to appropriately correct environmental changes.

[Correspondence to service maintenance] A serviceman can set to enable or disable the first control system, and disable the first control system during service maintenance. This makes it possible to properly determine the state of the device. If the first control system is disabled, the standard contrast potential and gamma conversion table for that model is
It is called from M30 etc. In this way, the characteristic deviation from the standard state becomes clear during service maintenance, and optimum maintenance can be performed efficiently.

[Control of Color Reproduction Characteristics (Second Feedback System)] Next, a control system for adjusting the color reproduction characteristics of a system including both the reader unit A and the printer unit B will be described.

FIG. 23 is a flow chart for explaining the adjustment of the color reproduction characteristic of the printer unit B using the reader unit A. After the adjustment of the gradation characteristic described above is completed, the CPU 21 of the reader unit A is
4 and the CPU 28 of the printer section B cooperate to start this control.

In step S11, the CPU 28 causes the pattern generator 29 to output a predetermined MCYK signal, and sets the table obtained from the above-mentioned gradation characteristic adjustment result in the LUT2.
It is sent to the printer engine unit 100 via 5 and a predetermined test chart 300 is formed on the recording medium. FIG. 24 is a diagram showing an example of the test chart 300, in which color patches 301 to 356 corresponding to various combinations of MCYK signals are formed.

Subsequently, in step S12, the CPU 214 displays a message for placing the test chart 300 at a predetermined position on the platen glass 102 on the display 218, and the operator follows the instruction to place the test chart 300 on the platen glass. Glass 102
After placing it on top, for example, pressing the "Read" key,
The reading optical system unit is driven to read the image of the test chart 300. This reading operation is almost the same as the procedure for adjusting the gradation characteristics described above, and thus detailed description thereof will be omitted. However, data of a plurality of points is read for each color patch and averaged. At the same time, the averaged MCYK data is stored in the RAM 215 or the like in correspondence with the read coordinate position, that is, the combination of the MCYK signals of the color patches.

Subsequently, in step S13, the CPU 214 uses, for example, the well-known least squares method, from the MCYK data forming each color patch and the MCYK data reading each color patch stored in the RAM 215, the expression The matrix coefficients b11 to b44 shown in (2) are calculated, and in step S14, the obtained matrix coefficients are stored in the RAM 215 or the like and set in the masking / UCR unit 208.

As described above, in this embodiment, the printer unit B is executed by executing the series of image adjustment processing shown in FIG.
In addition to stabilizing the tone reproduction characteristics of, the color reproduction characteristics of mixed colors are also stabilized. As a result, the gradation and color reproducibility of the printer unit B alone are assured, and for example, even for an image signal input from an external device via an external interface (not shown), the expected result is obtained. The image quality is obtained, and the user does not feel the individual difference of the printer unit B. Furthermore, since the color reproduction characteristics are adjusted for the colors output from the apparatus itself, good color reproducibility can be obtained even in the case of a copy of a document, so-called "grandchild copy".

[0084]

Second Embodiment An image recording apparatus according to the second embodiment of the present invention will be described below. It should be noted that in the second embodiment, substantially the same configurations as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

For example, as the cumulative number of copies increases, the amount of charge applied to the toner fluctuates, the surface conditions of the photosensitive drum 4 and the transfer drum 5 change, and the tone characteristics can be maintained. It is well known that this is not possible, and the device is not always in the range where the above-mentioned image adjustment is possible.

Here, for example, a toner density sensor (not shown) becomes dirty and cannot supply an optimum amount of toner, and a problem occurs in toner density control, and a predetermined maximum density cannot be obtained. Suppose you have gone. When the gradation control described above is performed in this state, as shown in FIG.
Almost linear gradation characteristics can be obtained up to the middle of the density level, but above a certain density level, the density does not increase and reaches a ceiling. As a result, area E shown in FIG.
Then the gradation becomes flat.

In controlling the color reproduction characteristic, it is not preferable to use the density data included in the area E because it tends to cause an error when calculating the matrix coefficient by the least square method.

Therefore, when the gradation control is performed, the region where the gamma characteristic becomes flat on the high density side, that is, the region E in FIG. 25 is recognized and included in the region E in the control of the color reproduction characteristic. Do not perform the calculation related to the color patch that uses the density data. By taking such measures, even if the printer section B is not in an ideal state, it is possible to effectively control the color reproduction characteristics. Good image quality can be obtained.

Further, in controlling the color reproduction characteristic, FIG.
As an example, the color patch using the density data included in the area E may not be output. In this way, the area E where the concentration cannot be controlled
Since the color patch including the density data of is not output,
Operators and service personnel can use this test chart 300
By providing information useful for maintenance of the device, it is possible to know the deterioration of the developing ability by observing and to easily obtain information such as which color component of the developing device has a problem. You can

In the above description, the case where the developing ability is lowered due to the problem of toner density control has been described. Needless to say that the control of this embodiment is effective even when the same occurs due to other factors. Nor.

Further, in the above-mentioned embodiment, the masking coefficient is explained by taking the 4 × 4 matrix coefficient as an example.
Higher-order color correction including secondary or higher terms may be performed.

Further, as the first feedback system, the system including both the reader and the printer has been described in the above embodiment, but the feedback system of the type for reading the reference image formed on the photosensitive drum inside the printer. May be

In each of the above-described embodiments, an example in which a color image is formed by an electrophotographic method has been described, but a method of forming a full color image by digital processing, such as ink jet, sublimation dye type, dot impact, etc. It goes without saying that the above-mentioned image adjustment processing is also effective for all image forming apparatuses using the method.

The present invention may be applied to a system composed of a plurality of devices such as an image scanner, a host computer and a printer, or to an apparatus composed of a single device such as a copying machine.

It goes without saying that the present invention can also be applied to the case where it is achieved by supplying a program to a system or an apparatus.

[0096]

As described above, according to the present invention,
It is possible to provide an image recording apparatus and a method thereof that can obtain good image quality by adjusting the image forming parameters in consideration of the fluctuation of the image forming conditions.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of an image recording apparatus according to a first embodiment of the present invention,

FIG. 2 is a block diagram showing a configuration example of an image processing unit shown in FIG.

FIG. 3 is a timing chart example of each control signal in the image processing unit shown in FIG.

FIG. 4 is a block diagram showing a configuration example of a printer control unit shown in FIG.

FIG. 5 is a diagram for explaining image processing for obtaining a gradation image,

FIG. 6 is a quadrant chart showing how tones are reproduced.

FIG. 7 is a flowchart showing an example of the procedure of image adjustment processing of the present embodiment,

FIG. 8 is a flowchart for explaining calibration of the printer unit using the reader unit according to the present embodiment,

9A is a diagram showing an example of information and keys displayed on the display shown in FIG. 2.

9B is a diagram showing an example of information and keys displayed on the display shown in FIG. 2.

9C is a diagram showing an example of information and keys displayed on the display shown in FIG. 2,

10A is a diagram showing an example of information and keys displayed on the display shown in FIG. 2;

10B is a diagram showing an example of information and keys displayed on the display shown in FIG.

FIG. 10C is a diagram showing an example of information and keys displayed on the display shown in FIG. 2;

11A is a diagram showing an example of information and keys displayed on the display shown in FIG. 2;

11B is a diagram showing an example of information and keys displayed on the display shown in FIG. 2;

11C is a diagram showing an example of information and keys displayed on the display shown in FIG. 2;

11D is a diagram showing an example of information and keys displayed on the display shown in FIG. 2;

FIG. 11E is a diagram showing an example of information and keys displayed on the display shown in FIG.

FIG. 12 is a diagram showing an example of a test print 1,

FIG. 13 is a diagram showing an example of a test print 2,

FIG. 14 is a view showing a state in which the test print 1 is placed on the platen glass,

FIG. 15 is a view showing an example of the relationship between relative drum surface potential and image density,

FIG. 16 is a diagram illustrating a control for changing the setting of the contrast potential according to the amount of water contained in the air in the device,

FIG. 17 is a diagram showing an example of the relationship between the grid potential of the primary charger and the surface potential of the photosensitive drum,

FIG. 18 is a diagram showing an example of density conversion characteristics,

FIG. 19 is a view showing a state in which the test print 2 is placed on the platen glass,

FIG. 20 is a diagram showing an example of reading points per patch of the test print 2,

FIG. 21 is a diagram showing an example of the relationship between the output density and the laser output level obtained from the test print 2,

22 is a diagram showing an example of table values of LUTs stored in advance in the ROM shown in FIG. 4;

FIG. 23 is a flowchart for explaining adjustment of color reproduction characteristics of printer unit B using reader unit A;

FIG. 24 is a diagram showing an example of a test chart,

FIG. 25 is a diagram showing an example of an area in which gradation characteristics are flat and

FIG. 26 is a diagram showing an example of a test chart according to the second embodiment of the present invention.

[Explanation of symbols]

 A Reader unit 108 Image processing unit 214 CPU 217 Operation unit 218 Display unit 220 Density conversion unit B Printer unit 109 Printer control unit 25 LUT 28 CPU 29 Pattern generator 30a ROM test pattern storage area

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H04N 1/46 Z

Claims (6)

[Claims] 1. An image recording method for recording an image on a recording medium, comprising: adjusting a gradation characteristic by a first feedback system;
An image recording method characterized in that color reproduction characteristics are adjusted by a second feedback system. 2. An image recording apparatus for recording an image on a recording medium, comprising first feedback adjusting means for adjusting gradation characteristics, and adjusting color reproduction characteristics after adjustment by the first feedback adjusting means. An image recording apparatus comprising: a second feedback adjusting means. 3. A pattern forming device for forming a test pattern of at least one color on a recording medium, and a reading device for reading the test pattern formed on the recording medium by the pattern forming device, The second feedback adjusting means forms a test pattern by the pattern forming means, and sets the image processing parameter based on information obtained by reading the test pattern by the reading means. Image recording device. 4. The second feedback adjusting means comprises:
When there is an unadjustable area in which the gradation characteristic cannot be adjusted in the adjustment of the gradation characteristic by the first feedback adjusting means, the information of the test pattern whose gradation is included in the unadjustable area is set in the image processing parameter. 4. The image recording device according to claim 3, which is not used for setting. 5. The second feedback adjusting means comprises:
When there is an unadjustable area in which the gradation characteristic cannot be adjusted in the adjustment of the gradation characteristic by the first feedback adjusting means, the pattern forming means does not form a test pattern whose gradation is included in the unadjustable area. The image recording device according to claim 3, wherein 6. A first pattern forming step of forming a first test pattern on a recording medium, and a first reading step of reading the first test pattern formed on the recording medium in the first pattern forming step. A first adjusting step of adjusting gradation characteristics based on information of the first test pattern read in the first reading step, and a second pattern forming step of forming a second test pattern on a recording medium A second reading step of reading the second test pattern formed on the recording medium in the second pattern forming step, and color reproduction based on the information of the second test pattern read in the second reading step. And a second adjusting step for adjusting the characteristics.