JPH09331462A - Image verifying method and image forming device using the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide uniform color reproducibility over all area by performing the verification of output equipment while dividing an image forming area into plural areas, and correcting images outputted into respective areas through a three-dimensional look-up table(LUT). SOLUTION: The entire image forming area of an output medium is divided into N pieces of recording areas for printing a set of test patterns and after the test patterns are stored in the buffer areas of a memory 22 in the unit of sets, an image is formed through a CPU 21 onto the medium. Then, color information experiment data on the medium are verified for each area and the relation of color information is correlatively analyzed. The relation of color information to be recorded onto the medium corresponding to arbitrary image data found by this correlative analysis, is made into data and included into the application program of an image processing part 10 or inputted into an image output part 20 as a calculation expression or an LUT. Thus, print characteristics in the divided areas can be locally grasped, there is no difference in color reproducibility at both terminal parts of the image forming area, and non-uniformity can be avoided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image inspection method for a digital image formed from image data and an image forming apparatus having an output device tested by this image inspection method.

[0002]

2. Description of the Related Art As an image forming apparatus for forming an image on an output medium based on input image data composed of B, G, and R digital image data, various digital printing apparatuses such as CRT, film writer, and sublimation type thermal transfer printer are proposed. Has been done. In a digital system using such a digital image forming apparatus, an editor edits image information (hue, saturation, lightness, etc.) input to the system by combining a look-up table or a function including characteristics of individual system constituent devices. We widely acknowledge the need for a color management system that corrects and outputs the desired colors and gradations.

The performance of such a color management system lies in the creation of a look-up table or calculation formula in which the characteristics of the system constituent devices are sufficiently taken in. The look-up table or the calculation formula generally outputs a predetermined test pattern to a specific area such as a central portion of the image forming area, measures color information of this pattern with a scanner or a densitometer, and performs verification. It is created from the results of Karu test.

[0004]

If an image is recorded on the output medium with recording data obtained from a look apple table or a correction formula obtained by examining a test pattern formed only on a specific portion of the output medium as described above, This look-up table or function can form an image close to the desired image in the area where the test pattern is output.

However, the image formed in the area where the test pattern is not formed, particularly in the image area apart from the area where the test pattern is formed, causes a color difference from the desired image. This is due to problems such as variations in the performance of the recording element itself and installation accuracy of the recording body provided with the recording element. For example, if the image forming apparatus to be tested is a sublimation type printer, the thermal recording head places a glaze on a ceramic substrate, forms a heating resistor array with a spatter or prints, and prints such a heating resistor. T
It is covered with an a ₂ O ₅ layer to form a protective layer. Generally, the resistance value of each heating resistor varies. It is necessary to correct such variations. Since the thickness of the protective layer varies, the pressing force between the thermal head and the ink sheet is not uniform in the recording area. Therefore, the image formed in the image output for the same image data in the image forming area is not uniform according to the test for the specific portion of the image forming area. Even in a film writer using a CRT, the same problem occurs between the image areas of the CRT.

In view of the above technical problem, a first object of the present invention is to provide an image inspection method capable of obtaining a desired image in the entire image forming area of an output medium.

In view of the above technical problems, a second object of the present invention is to provide an image forming apparatus capable of forming a stable image in the entire image area of an output medium.

[0008]

The above object can be achieved by the following constitutions.

(1) The entire image forming area of the output medium is divided into a plurality of areas, and the color information of the recorded image and the arbitrary test pattern data when recording with arbitrary test pattern data for each divided area An image inspection method characterized by obtaining a look-up table or a relational expression indicating a correspondence relation. By providing the above configuration, it is possible to eliminate unevenness in color reproducibility at both ends of the image forming area of the output medium, for example.

(2) The image inspection method according to (1), wherein the arbitrary test pattern data is composed of a plurality of digital data sets. With the above configuration, correction can be performed over a wide range of lightness, saturation, and hue, so that the verification accuracy can be improved.

(3) The image test method according to (2), wherein the set of arbitrary test pattern data is common to each of the divided areas. With the above configuration,
It can be tested with stable accuracy.

(4) The image test method according to (2), wherein there are a plurality of sets of the test pattern data. By providing such a configuration, the verification accuracy can be further improved.

(5) The set of test pattern data is common to each area and there are a plurality of types (2)
Image test method. By providing the above configuration, the test can be performed with stable accuracy.

(6) The look-up table or calculation formula created by the method described in (1) to (5) is stored in a memory, and the input test pattern data is converted into recording data by the CPU by the look-up table or calculation formula. An image forming apparatus, which converts and forms an image on an output medium with the recording data. With the above configuration, stable image formation can be performed without causing uneven color reproducibility in the entire image forming area of the output medium of the same lot.

(7) The image forming apparatus according to (6), wherein the image forming apparatus is a sublimation type thermal transfer printer.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a conceptual diagram of an image forming apparatus for carrying out the image inspection method according to the present embodiment.

The image forming apparatus comprises an image processing section 10 and an image output section 20 connected by an interface 30 as shown in FIG.

The image processing unit 10 includes a CPU 11 and a memory 12.
The memory 12 is written with an operating system, an image test test pattern data, and an application program for generating a look apple table or a calculation formula obtained by the image test.

The image output unit 20 is an image recording device such as a sublimation type thermal transfer printer, a fusion type thermal transfer printer, an ink jet printer, a film writer, etc., and a CPU
21 and a memory 22. The memory 22 writes a control program for receiving the image data from the image processing unit 10 and recording the image on the output medium.

In the image inspection method according to the present embodiment, the entire image forming area of the output medium is divided into a plurality of areas, and the color information of the recording image and the arbitrary information when recording with the arbitrary test pattern data for each divided area. For obtaining a look-up table or a relational expression showing the corresponding relation with the test pattern data of 1., which will be described with reference to FIGS.

FIG. 2 shows the concept of division of the test area in this embodiment, and FIG. 3 shows the concept of the test digital data used in this embodiment.

FIG. 2 shows an output medium 2 used in the image output section 20.
3 shows that the entire image forming area of the output medium 23 is divided into N areas. Such an N-divided area corresponds to a recording area for printing a set of test pattern data, and does not necessarily have to have the same size. The data format of the test pattern data is the image output unit 2
Anything that can be analyzed with 0 will do. The image output unit 20 stores the test pattern data for each set in the buffer area of the memory 22 and then controls the output medium 2 under the control of the CPU 21.
3 is drawn as an image.

The test pattern recorded on the output medium 23 is measured by a densitometer or a chromaticity measuring instrument. It is preferable to select such a measuring device in consideration of the characteristics of the image output unit 20 and the output medium 23, as long as it can obtain the measurement data necessary for creating the lookup table or the relational expression.
By this measurement processing, experimental data of color information (color, saturation, brightness, gradation) on the output medium 23 corresponding to the specific test pattern data is obtained for each area.

Next, in order to apply the relationship between the test pattern data and the color information of the image formed on the output medium 23 corresponding to the test pattern data to the correction of arbitrary image data, analysis is performed using a known correlation analysis method such as multiple regression analysis. To do. The test pattern data set is preferably data adapted to the correlation analysis method.

The relational expression between the color information recorded on the output medium 23 with respect to arbitrary image data obtained by the correlation analysis may be used as a calculation formula for correction, or may be used for all image data. On the other hand, a relational expression may be calculated in advance to form a lookup table.

The recording color correction method using the look-up table is advantageous in terms of processing speed, but since the capacity becomes too large when handling a full-color image, it is desirable to combine the relational expression and the look-up table.

The lookup table or the relational expression is shown in FIG.
The data is incorporated into the application program of the image processing unit 10 shown in FIG.
It is incorporated into the image forming apparatus by using a means such as a ROM. However, the present invention is not limited to this, and a look-up table or a calculation-type image forming apparatus may be incorporated by using other possible known means.

The image forming apparatus tested by the image checking method according to the present embodiment divides the entire image forming area of the output medium 23, and locally grasps the printing characteristics of the image forming apparatus within the divided area. Therefore, it is possible to eliminate the non-uniformity of the color management effect such that there is a difference in color reproducibility at both ends of the image forming area.

Next, an image output operation in the image forming apparatus incorporating the look-up table or the relational expressions described above will be described.

When an image is formed on the output medium 23 by using the image forming apparatus tested by the above-described test method, the CPU of the image processing unit 10 or the image output unit 20 stores the input image data in the recording medium 23. After determining which portion of the entire image forming area is to be output and performing correction using a look-up table or a relational expression of the corresponding area, the image output unit 20 forms an image on the output medium 23. Just go. The finally formed image may be a transmission image or a reflection image.

[0031]

FIG. 4 is a block diagram showing a digital color image processing system to which the present invention is applied.

The digital color image processing system comprises a scanner 110, a personal computer 120 and a sublimation type thermal transfer printer 130.

The scanner 110 emits a light source for illuminating an original placed on the platen glass and a reflected light from the original to B,
By having a spectroscopic system for separating G and R components, a photoelectric conversion element for photoelectrically converting the decomposed light from the decomposition optical system, and an MTF correction circuit for performing MTF correction on the output signal from the photoelectric conversion element , B, G, and R image data obtained by photoelectrically converting the color-separated light from the original image are output.

The personal computer 120 is
An application program for performing various image processing and editing processing on G and R image data is stored in a memory, and various image processing and editing processing is executed on B, G, and R image data input from the scanner 110. Then, the image data is sent to the sublimation type thermal transfer printer 130.

The sublimation type thermal transfer printer 130 uses the personal computer 120 to print an image at the print start position and R,
The image data of G, B is received, the image data of R, G, B is stored in the page memory, and the image data of R, B, G is input to the look-up table and the recording of Y, M, C is performed. The data is converted and output to the driver of the thermal recording head, and by driving the thermal recording head with the recording data, the dye is sublimated by overheating from the back surface of the ink sheet and is dyed to the image receiving layer to form the image receiving sheet. A 24-bit color image is recorded at a desired position.

The ink sheet has a sublimable ink layer made of a binder and a paint on a PET base. The image receiving sheet is a support provided with an image receiving layer.

The sublimation type thermal transfer printer is tested by the following method.

FIG. 5 is a schematic diagram showing how to divide an image forming area formed in the memory space of a personal computer.

The image forming area shown in FIG. 5 shows a memory space having a storage capacity calculated from the recording density of the sublimation type thermal transfer printer 130 and the size of the image receiving sheet, and it corresponds to three colors of B, G and R. Is a storage area having a combined storage capacity. The personal computer 120 divides the storage area shown in FIG. 5 into six areas.

FIG. 6 shows a set of test pattern data for verification used in this embodiment.

The test pattern data set for verification shown in FIG. 6 is data to be stored in the divided areas described with reference to FIG. 5, and a patch including B, G, and R image data as a set. It is a collection of 27 sets of data. Such a set of test pattern data corresponds to one of the six divided areas. Therefore, there are as many sets of test pattern data as the number of divided areas. Moreover, in the present embodiment, the density value of the patch data forming the set of test pattern data is set to B, in order to improve the test accuracy.
It has a set of at least three types of test pattern data obtained by recombining G and R.

The personal computer 120 divides the entire image forming area of the image receiving sheet into six as shown in FIG. The personal computer 120 is the same as the personal computer 120 shown in FIG.
A set of test pattern data composed of seven patch data is stored in each divided area on the memory. The personal computer 120 sends the image print start position and the test pattern data to the sublimation thermal transfer printer 130.

As a result, the sublimation thermal transfer printer 130 prints a patch image on the image receiving sheet with the test pattern data.

Next, the B.P. from the 27 patches recorded on the recording paper is recorded. The reflection densities of G and R components are measured by Xrite
Measure with Status A. The relationship between the density data of the B, G, and R components obtained by such measurement processing and the corresponding test pattern data is independently calculated in the six regions shown in FIG. 27 by the square method
Individual parameters were obtained.

Assumed functional formula [B] = (KY1 × [Y] ² + KY2 × [Y] + KY
3) × (KM1 × [M] ² + KM2 × [M] + KM3)
× (KC1 × [C] ² + KC2 × [C] + KC3) [G] = (LY1 × [Y] ² + LY2 × [Y] + LY
3) × (LM1 × [M] ² + LM2 × [M] + LM3)
× (LC1 × [C] ² + LC2 × [C] + LC3) [R] = (TY1 × [Y] ² + TY2 × [Y] + TY
3) x (TM1 x [M] ² + TM2 x [M] + TM3)
× (TC1 × [C] ² + TC2 × [C] + TC3) where [B] is the B gradation value to be input to the printer, and [G] is the G gradation value to be input to the printer,
[R] is an R gradation value to be input to the printer.

[Y] is a yellow density value output by the printer, [M] is a magenta density value output by the printer, and [C] is a cyan density value output by the printer.

KY1, KY2, KY3, KM1, KM
2, KM3, KC1, KC2, KC3, LY1, LY
2, LY3, LM1, LM2, LM3, LC1, LC
2, LC3, TY1, TY2, TY3, TM1, TM
2, TM3, TC1, TC2 and TC3 are 27 parameters obtained by the above-mentioned least square method.

The values of [B], [G], and [R] are 0, 8, 16 and, respectively, in the functional expressions obtained as described above.
24, 32, 40, 48, 56, 64, 72, 80, 8
8, 96, 104, 112, 120, 128, 136,
144, 152, 160, 168, 176, 184, 1
92, 200, 208, 216, 224, 232, 24
By giving 33 data of 0, 248, 255, 33 [Y] data, 33 [M] data and 33 [C]
Ask for data. As a result, a look-up table including 33 × 33 × 33 three-dimensional input image data and three-dimensional recording color data including 33 × 33 × 33 elements was created.

Between the grids on the color coordinates are [B], [G],
An interpolation formula is created by each quadratic formula of [R], and the gradation value to be given to the sublimation type thermal transfer printer is calculated based on this interpolation formula.

Six three-dimensional lookup tables corresponding to the areas 1 to 6 are created by the above method, and the verification of the sublimation type thermal transfer printer to be used is completed.

Next, the image processing and output process will be described.

The scanner 110 sends to the personal computer 120 image data obtained by color-separating B, G, and R from the original document placed on the platen glass. The personal computer 120 subjects the input image data to edge enhancement processing that does not involve color correction, and converts the gradation of each pixel into a reflection density from a known relational expression. In this embodiment, since the scanner 110 is previously tested with a known image pattern, the relationship between the reflection density from the document and the input gradation of the scanner is known in advance.

The personal computer 120 determines which of the six areas shown in FIG. 5 is to be printed, based on the image size and the coordinates of the print start point.

When the output area is determined by the above-mentioned judgment, the personal computer 120 accesses the three-dimensional lookup table stored in advance at the address indicated by the number associated with the area, and the reflection density of the pixel is accessed. The values are converted into output gradation values of the sublimation type thermal transfer printer, and then transferred to the sublimation type thermal transfer printer 130 and printed on the output sheet.

When a digital image with a uniformly gray background was output by the digital color image system of this embodiment, an output print with good color reproduction of the original and the output image in the entire image area of the image receiving sheet was produced. I was able to get it.

Comparative Example FIG. 7 shows the output location of the test data in the comparative example.

The same sublimation type thermal transfer printer as in the above-mentioned embodiment was tested in the same manner as in the embodiment using the same test pattern data as in the embodiment placed in the area 1 as shown in FIG. Twenty-seven parameters were obtained by the method of least squares, and a three-dimensional look apple table of the area shown in FIG. 7 was created.

The image processing and output process was the same as that of the embodiment except that there was only one three-dimensional lookup table.

When a person image having the same background (gray) as in the embodiment is output, although the color reproduction of the image near the area 1 shown in FIG. The density was different, and the one side was a little lighter and magenta gray, and the reproducibility of the entire image was deteriorated.

[0060]

According to the present invention, the verification of the output device is performed in a small area obtained by dividing the image forming area of the output device, and the image output in this area is a three-dimensional look effective in the area. Since the correction is performed by the up table, the image forming apparatus having uniform color reproducibility over the entire image forming area can be verified.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of an image forming apparatus that implements an image inspection method according to the present embodiment.

FIG. 2 shows the concept of division of a test area in the present embodiment.

FIG. 3 is a conceptual diagram of verification digital data used in the present embodiment.

FIG. 4 is a block diagram showing a digital color image processing system to which the present invention is applied.

5 is a diagram showing a memory space having a storage capacity calculated from the recording density of the sublimation type thermal transfer printer 130 and the size of an image receiving sheet. FIG.

FIG. 6 shows a set of test pattern data for verification used in this example.

FIG. 7 shows an output location of test data in a comparative example.

[Explanation of symbols]

 10 Image Processing Section 11, 21 CPU 12, 22 Memory 20 Image Output Section 30 Interface 110 Scanner 120 Personal Computer 130 Sublimation Thermal Transfer Printer

Claims (7)

[Claims] 1. The entire image forming area of the output medium is divided into a plurality of areas, and the color information of the recorded image and the arbitrary test pattern data when recording with arbitrary test pattern data for each divided area An image inspection method, characterized in that a look-up table or a relational expression indicating a relation is obtained. 2. The image inspection method according to claim 1, wherein the arbitrary test pattern data is composed of a plurality of sets of digital data. 3. The image inspection method according to claim 2, wherein the set of arbitrary test pattern data is common to each of the divided areas. 4. The image test method according to claim 2, wherein there are a plurality of sets of the test pattern data. 5. The image inspection method according to claim 2, wherein a set of the test pattern data is common to each region and there are a plurality of types. 6. A lookup table or a calculation formula created by the method according to claim 1 is stored in a memory,
An image forming apparatus, wherein input image data is converted by U to print data by the look-up table or the calculation formula, and an image is formed on an output medium by the print data. 7. The image forming apparatus according to claim 6, wherein the image forming apparatus is a sublimation type thermal transfer printer.