JP3241986B2 - Construction method of test sheet for color balance adjustment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image processing system including a color image scanner such as a digital color copying machine and a full color printer, and a test comprising a plurality of color patches output from a printer in order to perform color balance adjustment. The present invention relates to a method of forming a sheet.

[0002]

2. Description of the Related Art As a prior art, for example,
As described in JP-A-153139, a density wedge formed on a recording material is scanned and read with a known image signal, and a look-up table for automatically adjusting a relationship between the image reading value and the image recording signal is automatically generated. In setting, there is a method of determining a reading position by detecting a black frame formed at each density step of the wedge. In this method, it is necessary to detect a black frame for each density step, and the processing becomes complicated. In addition, as described in Japanese Patent Application Laid-Open No. 2-76760, a grayscale image is output from a color printer using a built-in grayscale signal, and the grayscale image is read by a scanner. There is a method of detecting a shift and correcting the characteristics of an output tone conversion circuit for correcting a color image signal. When inputting a gray scale image, it is set at a predetermined position on the scanner. Although this shows a relatively simple pattern and no accuracy problems have surfaced, it is necessary to guarantee the test sheet set position accuracy in practice, and software It is practical to correct it logically.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a color image processing system including a color image scanner and a full-color printer and a digital color copying machine. Color balance adjustment that facilitates processing when performing automatic color balance setting according to unique characteristics, and also facilitates operator work and ensures setting accuracy and system reliability. The purpose of the present invention is to realize a method of constructing a test sheet.

[0004]

SUMMARY OF THE INVENTION According to the present invention, there is provided a test sheet which simplifies arithmetic processing for calculating a color balance condition and for setting a balance, and which can be easily operated by an operator. Specifically, according to the first aspect of the present invention, a test sheet of a color patch in which a color balance condition is easily calculated from a measurement result is configured. According to the second aspect of the invention, a color balance condition is set for each of a plurality of density patterns that may be used for a test sheet.
According to the third aspect of the present invention, a position detection mark is attached to the test sheet to enable correction or warning for a set position deviation. According to the fourth aspect of the present invention, a description of the handling is described on the test sheet so that the operator can easily perform the operation. According to the fifth aspect of the present invention, the test sheet is clearly indicated on the test sheet so that the operator can easily recognize the setting position or the setting direction of the test sheet . According to the sixth aspect of the present invention, the test can be performed without being limited to the setting direction of the test sheet.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings.

<Test Sheet> FIGS. 1 to 3 show that when setting and adjusting the color balance,
4 shows a configuration example of a test sheet output from a printer.

The test sheet 100 shown in FIG. 1 has patches 111, 112, 113, and 114 of C, M, Y, and K toners of a single color of n + 1 levels, and three colors of C, M, and Y (3K). This is an example composed of 120 patches.
Appropriate density indication values are assigned to density levels 0 to n, and patches in the horizontal direction are unified by the same density indication value.

[0008] The test sheet 200 of FIG.
This is an example in which patches 210 and 220 of a set are output.
Since the output characteristics of the printer differ depending on the dither pattern used when outputting the color patch, it is necessary to switch the setting conditions for each dither pattern to be used in order to strictly set the color balance. The test sheet 200
"Type 1" and "Type 2" in the table correspond to the type of dither pattern. The test sheet 100 is provided with a description 23 so that the operator can easily operate it.
0 and the operator to set the test sheet
An arrow mark 243 is printed so that the cut direction can be easily recognized . Further, two “+” marks 241,
Reference numeral 242 is designed so that alignment (soft skew correction) when reading with a scanner described later can be performed.

A test sheet 300 shown in FIG. 3 is an example in which the operator can set the test sheet on a scanner without worrying about the orientation of the sheet. 310 and 34
Reference numerals 0, 320 and 330 denote patches having the same pattern. As described above, the same pattern is used for the test sheet 3
Since they are arranged point-symmetrically about the intersection of the 00 diagonal lines, the same processing routine can be applied regardless of the direction of the set. In the case of the test sheet 300, since two sets of data can be collected, an effect of improving the reliability including a diagnostic function described later can be expected. Reference numeral 350 denotes an explanatory note, and reference numerals 351 to 354 denote position marks.

<Image of Scanner Reading> FIG. 4 shows a conceptual diagram when a test sheet is read by a scanner and developed on a memory. FIG. 4A shows the positional relationship on the memory, and FIG. 4B shows an example of the correspondence between the reference position (mark) on the test sheet and the relative position of the color patch.

As shown in FIG. 4A, by detecting the position marks 411 and 412 on the memory, the address (X ₀ , Y ₀ ) and the inclination (θ) of the reference position (P ₁ ) on the memory are detected. ) can be known, it is possible to calculate the address in the memory of each patch based on it can be read correctly patch data. In this embodiment, two position marks 411 and 412 are used. However, it is needless to say that one mark may be used when a mark that can detect the tilt angle by itself such as a “+” mark is used.

Also, as shown in FIG. 4B, the read area for each patch is generally limited to a stable narrow area (a × b) at the center with little flare. In this case, when it is detected that the two position marks are in a specific area on the memory, the patch data may be read in association with a fixed memory address.

<Color Image Processing System> FIG. 5 shows a functional block diagram of an embodiment of a color image processing system to which the present invention is applied. This system is an example of a digital color copying machine, and includes an image scanner 500, a scanner γ (density) setting unit 501, a color system conversion unit 502, a gray γ setting unit 503, a tone γ setting unit 504, a changeover switch 505, a dither processing unit. 506, a laser printer 520, an arithmetic processing unit 530, and a color patch generator 540. Also,
FIG. 5 shows a system capable of interfacing an image signal in the R, G, B system or the C, M, Y, (K) system with the outside. 5, 501 to 506 are also collectively called an image processing unit (IPU) 510. The gray γ setting unit 503 and the tone γ setting
The arrangement relation of the fixed units 504 may be reversed.

In a normal copy mode, the changeover switch 5
05 is set in the state shown in the figure. The original set on the image scanner 500 is read as an image signal separated into three primary colors of R, G, and B. First, the scanner γ setting unit 501 ensures the gray balance and the output characteristics are appropriate. Thus, the γ correction (density correction) is performed. In the next color system conversion unit 502, R, G, and B are converted into complementary color densities (C _p , M _p , and Y _p ), and the arithmetic processing unit 530 is provided with the printer 520 in advance.
It is adjusted to the dynamic range set according to the state of. In the next gray γ setting unit 503, γ correction that guarantees the gray balance is performed by the parameters set by the arithmetic processing unit 530 in advance according to the state of the printer 520, and the toner color (toner density instruction value) is changed. Is performed. The next tone γ setting unit 504 is a γ for adjusting tone of gradation.
The main purpose is to make corrections, but in some cases,
The gamma correction for changing the color tone is also performed here. Thereafter, in the dither processing unit 506, as the final stage of the image data processing, dither processing according to a designated dither table is performed, and the processing result (this corresponds to the modulation level of the laser beam) is input to the laser printer 520. Is done. However, depending on the specification, the data may be output without performing the dither processing.

On the other hand, in the color balance setting / adjustment mode, the changeover switch 505 is connected to the lower side (color patch generator side). The process of setting the color balance
The color patch generator 540 designates a single color toner of C, M, Y, and K and a mixture of three colors (3K), and specifies a toner density indication value (for example, 8, 16, 32, 48, 64, 96,
This is started by repeatedly outputting color patch output data of 128, 198, and 255 (9 gradations). According to the data, the dither processing unit 506 performs dither processing.
Output as 0. The color patches on the test sheet 100 are read from the image scanner 500. The reading data of the color patch is stored in the scanner γ setting unit 5.
R prepared under the same conditions as in the copy mode at 01,
The signals are taken into the arithmetic processing unit 530 as G and B signals. The arithmetic processing unit 530 fetches the C, M, and Y toner density indication values when the color patch data is output from the color patch generator 540, and outputs the R, G, B corresponding patches from the scanner γ setting unit 501. The characteristic values of the toner and the output characteristics of the printer 520 are obtained from the relationship with the values, and the respective parameters (density correction) of the color system conversion unit 502, the gray γ setting unit 503, and the tone γ setting unit 504 are set.

<Example of Hardware Configuration> FIG. 6 shows an example of a hardware configuration of the color image processing system shown in FIG. 5 from the viewpoint of hardware. 6, a scanner interface unit 601, an image buffer 602,
Color system conversion table 603, CPU 604, operation unit interface unit 605, printer interface unit 60
6, a dither table 607, a gamma correction table 608, a parameter memory 609, a system controller 610, and the like are connected on a system bus 620. Then, vinegar
The scanner interface 500, the keyboard / display 630, and the scanner interface unit 601; the operation unit interface unit 605;
The printer 520 is connected. The image buffer 602, the tables 603, 607, 608, and the parameter memory 609 may be prepared on the same storage device. The following briefly describes the functions of the main parts.

Image buffer 602: A buffer for a full page is not necessarily required, but if it is present, processing becomes easy. Here, test sheet 1 by scanner 500
The read color patch data such as 00 is temporarily stored.

Color system conversion table 603: A conversion formula based on parameters set to satisfy the color balance conditions is tabulated to speed up processing in the normal copy mode. A plurality of tables can be stored for each dither pattern to be mounted.

[Gamma] correction table 608: A correction curve for adjusting tone (gamma characteristic) and color tone of a density is tabulated to speed up processing in the normal copy mode.

Dither table 607: A plurality of tables are stored and selectively used. A table is formed in the form of a density pattern so as to support high-speed dither processing, and a plurality of tables are accommodated in correspondence with a plurality of output modes and selectively used.

Parameter memory 609: Stores parameters used for creating the color system conversion table 603 and the γ correction table 608. It also stores the default values set initially, their history, or parameter sets for special applications that are not normally used.

CPU 604: This unit includes various processing programs and a work memory necessary for arithmetic processing. In the CPU 604, arithmetic processing for setting color balance and arithmetic processing for creating the table are executed.

<Color Balance Setting / Adjustment Flow> FIG. 7 is a diagram showing an example of a processing flow for color balance setting / adjustment.

When setting / adjusting the color balance, a test sheet including single color patches of C, M, Y, and K toners and three-color superimposed patches of C, M, and Y as shown in FIG. Is output (step 701). This test sheet is set on the image scanner (Step 7)
02).

The test sheet set on the scanner is read to determine whether the set state is appropriate (step 7).
03). That is, the determination of the front and back of the test sheet, the determination of the set position shift, and the like are performed. As a result, when a setting abnormality is determined, a warning to that effect is issued and a resetting operation is prompted (no in step 704).

On the other hand, if the set state of the test sheet is within the proper range (yes in step 704), logical position correction is performed based on the detected value of the positional deviation including the skew, as shown in FIG. The address on the memory corresponding to each color patch is associated (step 705). Then, based on the memory address associated with each patch, data (patch data) in the designated area is read and statistically processed (step 706). Basically, the average value is used as the measured value of the patch. The output state of the printer is diagnosed by referring to the deviation value and the absolute value. afterwards,
Assuming that the read value of the color patch is normal (yes in step 707), the color balance is set and adjusted based on the data (step 708). Since the color balance setting / adjustment process itself is not the gist of the present invention, the description is omitted.

On the other hand, when the read value of the color patch is not normal (No in step 707), that is, when the read data of the color patch is significantly reduced, or when the read data in one or more patches fluctuates. Is abnormal, the color balance setting / adjustment process is interrupted, and an abnormality diagnosis for the image forming process of the printer is performed in order to determine whether the image forming state is appropriate (step 7).
09). This can be dealt with by activating an imaging system abnormality diagnosis routine mounted on the system. If the abnormality diagnosis shows that the imaging system is normal (no in step 710), a test sheet is output again to restart the color balance setting / adjustment process.

In the processing flow of FIG. 7, part of the processing steps can be specified as follows due to the system (hardware) configuration and the like.

Prescan method: This method is convenient when the buffer memory is small. The set state diagnosis routine diagnoses the set state using only monochromatic data (for example, the G signal may be binarized and fetched), The pre-scan is performed up to the processing step of the translation, and the patch data is read by the main scan.

Registration omission method: The reading area from each color patch is limited, and when the reference position mark read by the scanner is at a predetermined position (range), a predetermined address (buffer memory) is set. The data at the fixed address is read.

[0031]

According to the first aspect of the invention, the processing routine for obtaining the color balance condition can be simplified. According to the second aspect of the present invention, even when a plurality of density patterns are used, a color balance suitable for each of the density patterns can be guaranteed. According to the third aspect of the present invention, the variation in the set position is removed, and the reliability of data is improved. Is improved. In addition, set failure can be prevented. According to the fourth aspect of the present invention, since the operation is explained, the operation is easy for the operator. According to the fifth aspect of the invention, the operator can easily set the test sheet.
According to the invention of claim 6, the test sheet can be set on the scanner without worrying about the direction of the test sheet.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration example of a test sheet.

FIG. 2 is a diagram illustrating another configuration example of a test sheet.

FIG. 3 is a diagram showing still another configuration example of the test sheet.

FIG. 4 is a conceptual diagram of a color patch read by a scanner.

FIG. 5 is a functional block diagram of an embodiment of a color image processing system to which the present invention is applied.

FIG. 6 is a diagram illustrating an example of a hardware configuration of the system in FIG. 5;

FIG. 7 is a diagram showing an example of a processing flow of color balance setting according to the test sheet configuration method of the present invention.

[Explanation of symbols]

100, 200, 300 Test sheets 111-114, 120 Patches 230, 350 Description 243 Arrow marks 241, 242, 351-350 Position marks 500 Image scanner 501 Scanner gamma setting unit 502 Color system conversion unit 503 Gray gamma setting unit 504 Tone γ setting unit 505 Changeover switch 506 Dither processing unit 510 Image processing unit 520 Laser printer 530 Operation processing unit 540 Color patch generator

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kiyoshi Suzuki 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N 1 / 46-1/64 G06T 1/00 510

Claims (6)

(57) [Claims] In a color image processing system including a color image scanner and a color printer, a method of configuring a test sheet including a plurality of color patches output from a printer for performing color balance adjustment,
A color balance adjustment test sheet including color patches output from the printer, including a single color and a mixed color of each toner used, and including a patch group generated with the same toner density instruction value. How to construct. 2. The color balance adjusting test sheet according to claim 1, wherein the test sheet includes a plurality of color patches corresponding to a plurality of density patterns. Construction method. 3. The method for constructing a test sheet for color balance adjustment according to claim 1, wherein the test sheet is provided with a mark for position detection, and the mark for position detection is provided.
A color balance adjustment test sheet, wherein a relative position between a color patch and a color patch is set. 4. A test sheet for color balance adjustment according to claim 1, wherein the test sheet is accompanied by a description of the handling of the test sheet. How to construct. 5. The method according to claim 1, wherein the test sheet is set on a scanner.
And a mark indicating the set position or set direction of the color balance adjustment test sheet. 6. The method of claim 1, in 3 or 4 color balance adjusting test sheet construction method described, the test sheet around the intersection of the diagonal lines of the test sheet
A method for configuring a color balance adjustment test sheet, wherein the same patterns are arranged symmetrically with respect to points.