JPH099085A - Image forming device and image processing method - Google Patents

Abstract

PURPOSE: To properly calibrate an image processing condition without regard to the timewise fluctuation of the device by executing print output plural times based on the same print data in an image forming device. CONSTITUTION: The luminance signal of an original image in a reading part is obtained from CCD 21. This luminance signal is converted to the signal of a digital value by an A/D conversion circuit 22 and an error caused by the sensitivity variation of an individual CCD element is corrected by a shading circuit 23. Corrected luminance signals R0 , G0 and B0 are processed to be signals m0 , c0 , y0 and k0 by a log conversion circuit 24. The luminance signal obtained by reading is inputted to the log conversion circuit 24 from a memory 30 in the image processing condition. Furthermore, the signals m0 , c0 , y0 and k0 are masking-processed to obtain signals m1 , c1 , y1 and k1 . These signals become print data of a printer part and expresses 256 gray levels.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to calibration of image processing conditions.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine having an image reading unit and a printing unit for forming an image based on the read data, an image of a read original is basically printed out. It is known to calibrate image processing conditions as one method for faithful reproduction. For example, N sets of input signals An whose density values are known are given as print data, and the printing section forms a specific pattern on the printing material based on this. Then, the pattern on the printed material is
The reading unit reads the luminance data, and the data is subjected to image processing such as masking processing to obtain a signal value Cn as print data. The image processing conditions such as the masking coefficient are calibrated by using, for example, the least square method so that the signal values An and Cn thus obtained are substantially equal to each other. With the above configuration, the read image can be faithfully reproduced, and a desired image quality can be obtained in print output.

[0003]

However, in the conventional image forming apparatus as described above, the reading condition and the printing condition of the reading unit and the printing unit respectively calibrate the image processing conditions as described above. Sometimes it is slightly different. Especially in the print section, such a variation is relatively likely to occur. Therefore, even if the above-described image processing conditions are calibrated, the calibration result depends on the state of the printing unit at that time, and therefore the state when actually forming an image is different from that at the time of calibration. If they are different, appropriate image processing cannot be performed.

Further, the fluctuations in the image forming apparatus as described above sometimes appear as uneven distribution of spatial errors. That is, the reading state and the printing state of the reading unit and the printing unit are not uniform, and the states may be different depending on the parts such as the reading unit. In this case, the calibrated image processing conditions are different from those of the image forming. It may be inappropriate for some parts.

The present invention has been made in order to solve the above problems that may occur when calibrating image processing conditions in a conventional apparatus, and its purpose is to calibrate image processing conditions. It is an object of the present invention to provide an image forming apparatus capable of appropriately performing the above regardless of the temporal or spatial variation of the apparatus.

[0006]

Therefore, according to the present invention, in an image forming apparatus for printing on a print material based on image-processed data, an image processing means for performing image processing, and a print Based on the print result and the print data output by the print means by the print control means, and the print control means for performing the print output to the print means a plurality of times based on the same print data. And condition setting means for calculating and setting the image processing conditions of the image processing means.

Further, in an image forming apparatus for printing on a printing material based on image-processed data, image processing means for performing image processing, printing means for performing printing, and predetermined print data are used. Error detection means for comparing the print result output by the printing means with the predetermined print data to determine whether there is an error of a predetermined value or more, and the error detection means has an error of a predetermined value or more. If it is determined that the print data is output from the predetermined print data in the vicinity of the print data having the error, the print control means causes the print means to perform print output, and the print control means performs the print operation. The print result output by the means is output by the print means based on the predetermined print data. The printed result and based on the predetermined print data, calculates the image processing conditions of said image processing means, characterized in that comprises a, a condition setting unit configured to set.

Further, in an image forming apparatus for printing on a printing material based on the image-processed data, image processing means for performing image processing, printing means for performing printing, and predetermined print data are used. Error detection means for comparing the print result output by the printing means with the predetermined print data to determine whether there is an error of a predetermined value or more, and the error detection means has an error of a predetermined value or more. If it is determined that the processing is ended, and if it is not determined that there is an error of a predetermined value or more, the control means for calculating and setting the image processing condition of the image processing means based on the comparison is provided. It is characterized by

Further, the image processing condition is a masking coefficient in a masking process.

Further, based on the test pattern data, the image output means outputs the test pattern, the image reading means reads the test pattern, the test pattern read data is input, and the test pattern and the test pattern read. An image processing method for generating a processing parameter based on data, wherein a test pattern output based on the test pattern data is performed a plurality of times, and based on the test pattern read data obtained as a result of outputting the test pattern a plurality of times. It is characterized in that the processing parameters are generated.

Further, based on the test pattern data, the image output means outputs the test pattern, the image reading means reads the test pattern, the test pattern read data is input, and the test pattern and the test pattern read. An image processing method for generating a processing parameter based on data, wherein an error between the test pattern data and the test pattern read data is compared with a predetermined value, and when the result of the comparison is a predetermined value or more, The image forming means outputs an image based on image data.

Further, based on the test pattern data, the image output means outputs the test pattern, the image reading means reads the test pattern, the test pattern read data is input, and the test pattern and the test pattern read. An image processing method for generating a processing parameter based on data, wherein an error between the test pattern data and the test pattern read data is compared with a predetermined value, and the processing parameter is generated when the comparison result is a predetermined value or more. If the result is not more than the predetermined value, the processing parameter is generated.

Further, based on the test pattern data, the image output means outputs the test pattern, the image reading means reads the test pattern, the test pattern read data is input, and the test pattern and the test pattern read. An image processing method for generating a processing parameter based on data, wherein the image output means outputs the same test pattern at different positions, and the processing parameter is generated based on the test pattern output at the different position. Characterize.

[0014]

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

(Embodiment 1) FIG. 1 is a schematic sectional view showing the internal structure of a copying apparatus according to an embodiment of the present invention.

In the copying machine shown in the figure, the data of the original read by the reading unit 100 provided on the upper side is
It is converted into a print signal through certain image processing. The printing unit 102 prints based on this print signal. That is, the laser driver 106 uses the laser 103
Is driven to emit a laser beam, and the laser beam is reflected by the polygon mirror 1 and the mirror 2 and is irradiated onto the photosensitive drum 4. The photosensitive drum 4 on which a latent image has been formed by scanning with the laser light in this way rotates in the direction of the arrow shown in the drawing, and development is performed for each color by the rotary developing device 3. The state shown in FIG. 1 shows development with yellow toner.

On the other hand, each time the print material is wound around the transfer drum 5 and makes one rotation, the print material is rotated and rotated in the order of M (magenta), C (cyan), Y (yellow) and Bk (black) as described above. The toner image is transferred by the photosensitive drum 4 developed by the developing device 3. The transfer paper on which the toners of all colors have been transferred is separated from the transfer drum 5, fixed by the fixing roller pair 7, and then ejected to the outside of the machine.

FIG. 2 is a block diagram showing the arrangement of the image processing circuit in the copying apparatus.

In the reading unit 100, the original image is obtained by the CCD 21 as a luminance signal. This brightness signal is converted into a brightness signal of a digital value by the A / D conversion circuit 22, and the shading circuit 23 corrects the error in the brightness signal due to the sensitivity variation of each CCD element. It is generally known that an optical system using a CCD maintains good measurement reproducibility by performing shading correction as described above.

Modified luminance signal (R0, G0, B0)
In the log conversion circuit 24, the following processing is performed.

[0021]

M0 = −255 * log ₁₀ (G0 / 255) /1.59 c0 = −255 * log ₁₀ (R0 / 255) /1.59 y0 = −255 * log ₁₀ (B0 / 255) / 1 .59 k0 = min (m0, c0, y0) (1) The log conversion circuit 24 stores the luminance signal obtained by the reading by the reading unit 100 in the memory 30 in the calibration of the image processing condition as described later. Input from.

Further, the signals m0, c0, y0, k0 obtained by the log conversion as described above are subjected to the following masking processing.

[0023]

[Equation 2]

The signals m1 and c thus obtained
1, y1 and k1 are print data of the printer unit.
Since the luminance signal and print data are processed by 8-bit digital signals, 256 gradations can be represented.

The pulse width conversion circuit 26 uses the above signals m1 and c.
1, 1, y 1, k 1 are converted into signals corresponding to the dot width and sent to the laser driver 106.

Then, as described with reference to FIG.
A latent image having gradation characteristics corresponding to a dot area change is formed on the photosensitive drum 4 by laser scanning, and development, transfer,
A printed image is obtained through the fixing process.

Predetermined print data is output from the test pattern generator 29 to the pulse width modulation circuit 26 in a calibration process of image processing conditions described later.

The toners used in this embodiment are yellow, magenta, cyan and black toners as described above, and are formed by dispersing the color materials of the respective colors with the styrene copolymer resin as the binder. ing.

In each of the above circuits, the CPU 28 is a ROM
RAM 32 based on the program stored in 31
Is used as a work memory for control.

That is, the formation of the test pattern by the laser driver 106 and the reading of the test pattern by the CCD 21 are controlled.

FIG. 3 is a flow chart showing the calibration processing of the image processing conditions according to this embodiment.

When a predetermined key on the operation panel (not shown) in the copying machine shown in FIG. 1 is operated, this process is started, and in step S1 the pattern generator 29 (see FIG. 2) causes the pattern generator 29 shown in FIG. Like 256 colors of M,
The print signals A0n of C, Y and K are output. That is, the signal A0n is a quaternary vector indicating any of the four gradations of 0, 68, 128, 255 for each color, and 256 colors can be expressed by n = 0 to 255 depending on the combination. 256 based on this print signal
A color pattern image is formed on the printing material.

Next, in step S2, a predetermined key for instructing the operator to place the print medium on the document table of the reading unit to read the pattern image printed out and to start the reading process. The display prompts the user to perform an operation, and waits for the predetermined key operation in step S3.

When the printout sample is placed on the platen of the reading section and a predetermined key operation is performed, the above-described reading process is performed in step S4, and the luminance signal Bnk (k = 0, ...) Corresponding to each color is performed. , N-1). And
In step S5, this signal Bnk is transferred to the memory 30 shown in FIG.
To be stored.

Next, at step S6, the luminance signal Bnk is obtained.
It is determined whether the processing up to storing is performed N times, and if it is determined that the processing is not performed N times, the process returns to step S1 to print out the same pattern again, and similarly, the luminance signal Bnk (n = 1, ~, n) are obtained.

When it is determined in step S6 that the above processing has been completed N times, the brightness signal Bnk (k = 0, 1, ..., N-1) stored in the memory 30 in step S7 is processed N times for each color. The average luminance signal Bn is obtained, input to the log conversion circuit 24 (see FIG. 2) for log conversion, and then masked to convert it into a print signal. In the masking process at this time, the matrix shown in the equation (2) is set by the unit matrix. That is, here, the log-transformed data is output as it is. Then, the squared error between the converted print signal Cn and the signal A0n output from the pattern generator 29 is obtained, and the masking coefficients a ₁₁ , a ₁₂ , and ..., compute the a ₄₄ by the least square method, we set this as a new factor.

As described above, when the image processing condition (masking coefficient in this example) is calibrated, the printing based on the same print signal is performed a plurality of times and the reading is performed, so that the printing unit and the reading unit are particularly time-consuming. It is possible to improve the accuracy of the tint adjustment by reducing the calibration error due to the uniform variation by making it uniform.

(Embodiment 2) In the first embodiment, the same print data is printed out a plurality of times, and the tint correction condition (masking coefficient) is calibrated using the data obtained by averaging the data. In the example, print output is performed based on a signal in the vicinity of a color signal having an error of a predetermined magnitude or more, the print output is read, and the tint correction condition is calibrated by adding it to the first data.

FIG. 5 is a flow chart showing the calibration process of this embodiment. In the following, only a part different from the process shown in FIG. 3 of the first embodiment will be described.

First, the brightness signals Bnk corresponding to the respective colors are obtained and stored in the memory 30 by the processes of steps S201 to S205.

Next, in step S206, the luminance signal Bnk is log-converted by the circuit shown in FIG. 2 and then masked to be converted into print data. At this time, the matrix shown in the formula (2) related to the masking process is a unit matrix in which a ₁₁ = a ₂₂ = a ₃₃ = 1 and the others are 0. Therefore, the signal after the log conversion is directly output from the masking circuit 25. Then, the error between the converted print signal Cn and the first print signal An output from the pattern generator is taken, and the masking coefficient is calculated and set by the least square method so that the squared error is minimized.

Next, in step S207, it is determined whether or not the print output of the pattern has reached 5 times. If it is within 5 times, in step S208 the memory brightness Bn stored in the memory is log-converted. Further, masking processing is performed using the masking coefficient set above to obtain the print signal Cn, and the norm representing the distance between the corresponding signals An and Cn in a predetermined color space is obtained. Next, in step S209,
It is determined whether or not this norm is a predetermined value x or more.

When it is determined in the above determination that there is a signal whose norm is x or more, in step S210, print output is performed based only on a certain signal near that signal as shown in FIG. For example, if a signal An having an error of x or more is represented by (x, y, z, w), x
16 sets of signals obtained by a combination of ± 5, y ± 5, z ± 5, w ± 5 (here, 0 or less is 0, 255 or more is 25
5) and print out.

With respect to this partially printed pattern, first in step S202 and thereafter, a reading process is performed,
The data is added to the 256 luminance signals stored in the memory, and these luminance signals, that is, 256 + 1
The 6 luminance signals are converted into a print signal, and the masking coefficient is calculated and set by the least square method so that the square error between this and the first output value is minimized.

By repeating the above process up to 5 times (it is completed once if there is no large difference), the difference is reduced in the portion where the color change is large, and a high quality image is obtained as a whole. To be

In the above, as the data to be partially output, the pre-existing signal in the vicinity of the signal with a large error is output, but a signal of a finer portion is obtained by interpolation calculation, It is also possible to print out based on.

If the difference is not large, the calibration process may be terminated at that point.

According to this embodiment, since the pattern is formed based on where an error occurs at the set masking coefficient, the optimum masking coefficient can be efficiently obtained.

(Embodiment 3) In this embodiment, the above-mentioned embodiment 2 is used.
After the masking coefficient is corrected once, the correction result is judged, and if the error is large, the calibration of the correction condition is ended.

FIG. 7 is a flow chart showing the calibration processing of the image processing conditions of this embodiment. Only the points different from the above embodiment will be described below.

When the masking coefficient is calculated in step S306, log conversion and masking processing using the calculated masking coefficient are performed on the luminance signal stored in the memory in step S307 to obtain the print signal Cn. , The norm which is an index of the error between this and the signal An generated by the pattern generator is obtained. Next, in step S308, if the norm is greater than or equal to x, the calibration process is interrupted. In this case, the previous one is used without setting a new masking. Further, if there is no item with x or more, a masking coefficient is set in step S309. By performing the control further by the above processing, it is possible to eliminate erroneous control in which a certain color is further displaced.

According to the present embodiment, when the norm is more than X, the calibration process is stopped and the preset masking coefficient is used, so that the error increases by one color, for example. In this case, it is possible to prevent the other colors from being significantly displaced by the masking coefficient set in the case of That is, it is possible to prevent the other color from being significantly shifted by one color.

Since there is a possibility that color misregistration occurs by accident, the calibration process may be stopped and S301 may be restarted instead of using the preset masking coefficient.

(Fourth Embodiment) In the first embodiment, the same data is printed out a plurality of times, and the data is read. However, in the present embodiment, the same data as the read result is read. The masking coefficient is calibrated based on the print output based on the spatially rotated 180 degrees, the reading of the print output, and the combined result.

FIG. 8 is a flow chart showing the procedure of the calibration process according to this embodiment.

When the calibration process is activated by a predetermined key operation, the 256-color pattern shown in FIG. 9 is output, and this pattern is placed on the document table, as in the process of the first embodiment shown in FIG. A display prompting the user to give a reading instruction is displayed, and when the instruction is given, this pattern is read and the read data is stored in the memory as a luminance signal (step S
401-S406).

Next, in step S406, the pattern shown in FIG. 9 is rotated by 180 degrees from that shown in FIG.
The pattern shown in FIG.
Similarly, in 07 to S410, reading is performed and the read data is stored in the memory.

Next, in step S411, the average of the two types of read data obtained as described above is obtained, and the average value is subjected to log conversion and masking processing to obtain a print signal, which is generated by the pattern generator. Based on the error from the signal, the masking coefficient is calculated and set by the least squares method.

As described above, by rotating the data to be printed out by 180 degrees spatially and calibrating using the average, it is possible to appropriately avoid the influence of the spatial error bias occurring in the print section. Various calibration processes can be performed.

In this embodiment, the average value is obtained by using the one rotated by 180 degrees, but not limited to this, the one rotated by 90 degrees is repeatedly output twice, three times, and four times. The calibration may be performed based on the above.

In the above embodiment, the color copying machine is used for explanation, but it may be applied to a system composed of a scanner, a host and a color printer. Further, the output device may be an image display device such as a monitor.

[0062]

As is apparent from the above description, according to the present invention, the image processing conditions are set based on a plurality of print outputs, so that even if the printing conditions at each printing change. By performing the print output a plurality of times, the influence of the variation on the image processing condition setting is relatively reduced.

Further, even if the printing conditions are spatially biased, similarly, the influence is similarly reduced by spatially biasing the printing.

As a result, it is possible to always calibrate appropriate image processing conditions.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a copying apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of image processing of the copying apparatus.

FIG. 3 is a flowchart showing a calibration process of image processing conditions according to the first embodiment of the present invention.

FIG. 4 is a schematic diagram showing a print pattern output in the above processing.

FIG. 5 is a flowchart showing a calibration process of image processing conditions according to the second embodiment of the present invention.

FIG. 6 is a schematic diagram showing a print pattern output in the second embodiment.

FIG. 7 is a flowchart showing a calibration process of image processing conditions according to the third embodiment of the present invention.

FIG. 8 is a flowchart showing a calibration process of image processing conditions according to the fourth embodiment of the present invention.

FIG. 9 is a schematic diagram showing a print pattern output in the fourth embodiment.

FIG. 10 is a schematic diagram showing a print pattern output in the fourth embodiment.

[Explanation of symbols]

 1 polygon mirror 2 mirror 3 developing device 4 photosensitive drum 5 transfer drum 7 fixing roller 21 CCD 22 A / D conversion circuit 23 shading circuit 24 log conversion circuit 25 masking circuit 26 pulse width modulation circuit 28 CPU 29 pattern generator 30 memory 103 laser 106 Laser driver

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H04N 1/46 H04N 1/46 Z

Claims (10)

[Claims] 1. In an image forming apparatus for printing on a printing material based on image-processed data, an image processing means for performing image processing, a printing means for performing printing, and the same print data based on the same print data. Based on the print result and the print data output by the print means by the print control means,
An image forming apparatus comprising: condition setting means for calculating and setting image processing conditions of the image processing means. 2. An image forming apparatus for printing on a printing material based on image-processed data, image processing means for performing image processing, printing means for performing printing, and based on predetermined print data. Error detection means for comparing the print result output by the printing means with the predetermined print data to determine whether or not there is an error of a predetermined value or more; and the error detection means has an error of a predetermined value or more. When it is determined that the print data is to be output to the print means based on the print data near the print data having the error among the predetermined print data, the print control means performs the print output. The print result output by the means is output by the print means based on the predetermined print data. Serial print results and based on the predetermined print data, calculates the image processing conditions of the image processing unit, an image forming apparatus, characterized in that it comprises a, a condition setting unit configured to set. 3. An image forming apparatus for printing on a printing material based on image processed data, image processing means for performing image processing, printing means for performing printing, and based on predetermined print data. Error detection means for comparing the print result output by the printing means with the predetermined print data to determine whether or not there is an error of a predetermined value or more; and the error detection means has an error of a predetermined value or more. If it is determined that the processing is terminated, and if it is not determined that there is an error of a predetermined value or more, the control means calculates and sets the image processing condition of the image processing means based on the comparison. An image forming apparatus characterized by the above. 4. An image forming apparatus for printing on a print material based on image-processed data, image processing means for performing image processing, printing means for performing printing, and space for the same print data. Print control means for respectively performing print output based on the plurality of data whose positions have been changed, and the image processing means based on the plurality of print results and the print data output by the print means by the print control means. An image forming apparatus comprising: a condition setting unit that calculates and sets the image processing condition of. 5. The image processing condition is a masking coefficient in masking processing.
5. The image forming apparatus according to any one of 4 to 4. 6. An image output means outputs a test pattern based on the test pattern data, the image reading means reads the test pattern, the test pattern read data is input, and the test pattern and the test pattern read. An image processing method for generating a processing parameter based on data, wherein a test pattern output based on the test pattern data is performed a plurality of times, and based on test pattern read data obtained as a result of outputting the test pattern a plurality of times. An image processing method, wherein the processing parameter is generated. 7. The image processing method according to claim 6, wherein the output of the test pattern based on the same test pattern data is performed a plurality of times. 8. An image output unit outputs a test pattern based on the test pattern data, the image reading unit reads the test pattern, and the test pattern read data is input to read the test pattern and the test pattern. An image processing method for generating a processing parameter based on data, wherein an error between the test pattern data and the test pattern read data is compared with a predetermined value, and when the result of the comparison is a predetermined value or more, An image processing method, wherein an image is output by the image forming means based on image data. 9. An image output unit outputs a test pattern based on the test pattern data, the image reading unit reads the test pattern, the test pattern read data is input, and the test pattern and the test pattern read. An image processing method for generating a processing parameter based on data, wherein an error between the test pattern data and the test pattern read data is compared with a predetermined value, and the processing parameter is generated when the comparison result is a predetermined value or more. The image processing method is characterized in that the processing parameter is generated when the result is not more than the predetermined value. 10. A test pattern is output by an image output unit based on the test pattern data, the output test pattern is read by an image reading unit, test pattern read data is input, and the test pattern and the test pattern are read. An image processing method for generating processing parameters based on data, wherein the image output means outputs the same test pattern to different positions, and the processing parameters are generated based on the test patterns output to the different positions. Characterized image processing method.