JPH0354508B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color image forming method in which an image is formed by a plurality of arranged recording heads.

In general, a color inkjet printer is constructed as shown in FIG. Each nozzle head is provided with ink of each color, Y and black, respectively, and is supplied with ink of each color from an ink reservoir 4 through a flexible tube 3, and a large number of lead wires are arranged in each nozzle head. A drive signal is supplied to each of the flexible insulating belts 4-1 to 4-4, the relay plate 5, and the general energizing belt 6. An endless belt 8 connects the carriage 1 having such a configuration by placing it on two rails 7.
Main scanning is performed by driving the cartridge 1 by a pulse motor 9 to reciprocate in the X direction in the figure, and the pulse motor 14 connects the recording paper 11 spread out through a pair of rollers 12 and 13 to a pair of rollers 13. The ink is fed in the Y direction in the figure to perform sub-scanning, and a color image is recorded on the recording paper 11 with each color ink ejected from each nozzle head 2-1 to 2-4. In addition, stoppers 10-1 and 10-2 are provided at both ends of the reciprocating path of the carriage 1.
is placed to determine the main scanning range. Also,
A sensor 15 is provided on the carriage 1 to scan and detect the recorded image by each nozzle head 2-1 to 2-4 in the main scanning direction, and a sensor 16 is provided at a distance in the feeding direction of the recording paper 11 by a pair of rollers 13. are arranged and configured to scan and detect the recorded image in the sub-scanning direction.

In a color inkjet printer having such a configuration, the nozzle heads 2-1 to 2-4 of each color arranged in the order of cyan C, magenta M, yellow Y, and black K on the carriage 1 are scanned rightward in the figure to print on the recording paper 11. Comparing A and B and C and D in Figure 2, it is clear that when each color ink is sprayed in layers at the same point above, and when it is sprayed in layers while traveling to the left in the figure, it is clear from comparing A and B and C and D in Figure 2, respectively. Thus, the order of the overlapping color ink dots on the recording paper 11 is reversed. Therefore, in order to record a color image with intermediate tones using ink dots, inks of the complementary colors cyan C, magenta M, and yellow Y for the three primary colors red R, green G, and blue B are used, and the dots of these complementary color inks are overlapped. Intermediate tones are expressed by subtractive color mixing. Moreover, the spectral characteristics of each complementary color ink are
Density change at the boundary of each complementary color band from 0 to 100
% does not change clearly and changes slowly, making it impossible to obtain a pure complementary color. Therefore, when dots of such complementary color ink are deposited on the recording paper 11, the ink of the dots deposited directly on the recording paper 11 is well absorbed and does not spread, whereas the ink on the dots deposited directly on the recording paper 11 is The ink of the deposited dots is not well absorbed and spreads out, and if the order of deposition is different, the size relationship of the dots of each complementary color ink to be subtracted and mixed will be reversed, resulting in the spread of the spectral characteristics of each complementary color ink as described above. In addition to the difference in the color mixing state based on the difference in the order of ink dot adhesion, the state of absorption and reflection of the incident light of each ink dot, which differs depending on the vertical positional relationship of the ink dots, is also reversed. become noticeable. Therefore, in conventional color inkjet printers,
There is a drawback that the intermediate tone obtained by the main scanning of the ink nozzle head is different between the forward and backward passes of the main scanning, and the quality of the recorded color image is significantly degraded.

In view of the above-mentioned points, it is an object of the present invention to provide a color image forming method that can improve the image quality of color images obtained during forward and backward main scanning. .

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

First, a mode of masking for correcting a shift in intermediate tone during subtractive color mixing due to a shift in the spectral characteristics of ink, which is a complementary color material, will be described with reference to FIGS. 3A and 3B.

Therefore, the three complementary color signals C, M, Y, which are obtained by performing complementary color conversion on the three primary color image signals of R, G, and B, and the three corrected complementary color signals, which are obtained by correcting the deviation in the spectral characteristics of the complementary color ink.
The relationship between C ₀ , M ₀ , and Y ₀ is as follows, assuming that the masking coefficients between each complementary color are C _n , C _y , m _y , m _c , y _n , and y _{c ,} respectively.

Y ₀ M ₀ Y ₀ =1 m _y C _y y _n 1 C _n y _c C _n 1Y MC Therefore, Y ₀ =Y+y _n M+y _c CM ₀ =m _y Y+M+m _c C C ₀ =C _y Y+C _n M+C In actual masking processing, the gradations of each corrected complementary color signal corresponding to the 16 gradations to be represented by each complementary color signal are created in advance in a table and stored in random access memory, and each complementary color to be recorded is By accessing the gradations of the signals C, M, and Y, the corresponding modified complementary color signals C ₀ ,
The M ₀ and Y ⁰ gradations are read out and applied to each color ink nozzle head for recording. That is, as shown in FIG. 3A, each of the above-mentioned masking coefficients is appropriately set by operating the console 17, and these masking coefficients are supplied to the arithmetic processing unit (CPU) 18, and the processing is performed based on the above-mentioned relational expression. each complementary color signal C,
The gradation data of each corrected complementary color signal C ₀ , M ₀ , Y ₀ corresponding to each of the 16 gradations of M and Y is calculated, and the results of the calculation are stored in random access memory (RAM) 1.
Store it in 9. When storing that data,
As shown in Figure 3B, address (ADR) 20
Using the 16 gradation data of the three auxiliary signals C, M, and Y, write each gradation data of the three corrected complementary color signals C ₀ , M ₀ , and Y ₀ corresponding to each corresponding address in the memory 21 to create a so-called masking table. Create it.

The masking table creation in the arithmetic processing unit (CPU) 18 described above is performed according to the flowchart shown in FIG. In the illustrated flowchart, first, starting from the state of Y=M=C=0, Y ₀ , M ₀ , Y ₀ are calculated in step S1, and the calculation results are stored in memory in step S2. At this time, in steps S3 and S4, the corresponding gradation data of Y ₀ , M ₀ , and C ₀ are calculated while stepping each of C and Y by 16 gradations. Next, starting from the state of M=1, C=0, and Y=0, in steps S5 to S8, M and Y are stepped by 16 gradations, respectively, and the corresponding Y ₀ , M ₀ , and C are Calculate and store the gradation data of ₀ , then M=0, Y=1, C=1
Starting from the state, in steps S9 to S12, C
The corresponding gradation data of Y ₀ , M ₀ , and C ₀ are calculated and stored while incrementing 16 gradations of and M, respectively.

Next, FIG. 5 shows an example of the configuration of the recording signal control circuit in the color inkjet printer of the present invention. In the illustrated configuration, the three primary color image signals R, G, B from the color television camera 22 are converted to each analog-digital (A-D) converter 23-1.
~ 23-3, each of which is converted into an 8-bit digital primary color image signal, and then supplied to each of adders 24-1 to 24-3,
A digital primary color image signal R' for recording with 16 gradations represented by the upper 4 bits obtained by adding a random signal from a dither circuit 26 driven by a counter (CNT) 25 to the lower 4 bits of each digital primary color image signal. , G', and B' are temporarily stored in each of the buffer memories 27-1 to 27-3, and then supplied to the masking memory 28.

On the other hand, the masking coefficient set to the desired value by the console 29 is sent to the arithmetic processing unit (CPU).
30, and two types of masking table values are supplied to the masking table circuits 31 and 32 so as to properly correct and align the deviations in mixed tones that occur in the forward and backward passes of the main scan as described above with reference to FIG. The masking table values are respectively stored and driven by the changeover switch 33 depending on whether the main scanning is forward or backward, and the masking table values are read out and transferred to the masking memory 28 described above. Therefore, the masking memory 28 stores a masking table suitable for use during the forward or backward main scan immediately before the start of the forward or backward main scan. The corrected complementary color signals C, M, Y forming the masking table are read out as the above-mentioned recording digital primary color signals R', G', B' as address signals, and are applied to each pattern generator 34-.
1 to 34-3, and supply density pattern signals for each complementary color corresponding to the signal level of each corrected complementary color signal,
Each density pattern formed by a 4 x 4 dot matrix is read out sequentially in column units and temporarily stored in recording buffer memories (PBM) 35-1 to 35-3 at a timing suitable for the running of each complementary color ink nozzle. The color tones are read out by the respective head drivers 36-1 to 36-3, and supplied to the complementary color nozzle heads 37-1 to 37-3 to drive them, respectively, so that uniform color tones are obtained in the forward and backward passes of the main scan. Record color images sequentially.

Therefore, in the recording signal control circuit having such a configuration, for example, while visually observing the intermediate tone of the recorded color image, the console 29 is operated to readjust the state of mixed tone correction in the forward and backward passes of the main scan. Therefore, any desired masking can be performed immediately.

As is clear from the above description, according to this embodiment, the difference in intermediate tone of the recorded color image due to the difference in the order of subtractive color mixing by the multi-recording head in the forward and backward passes of main scanning in a color printer can be corrected. By appropriately differentiating the masking coefficient values used in masking processing, which is essential for color printers, in the forward and backward passes of main scanning, corrections can be made reliably and easily using extremely simple signal processing.
A special effect can be obtained in that a color image with a much better intermediate tone can be recorded compared to the conventional method.

Moreover, according to the present embodiment, the color tone of the recorded image can be arbitrarily adjusted in response to the recording state.

Although the case of a color inkjet printer has been described above as an embodiment of the present invention, the present invention is not limited to this.
It is also applicable to other recording methods such as a thermal transfer method and a wire yard method.

The method of the present invention is a color image forming method in which a color image is formed by reciprocating recording heads of a plurality of colors arranged in order to record a plurality of color materials, respectively, with respect to a medium. Since different color processing is performed when printing with the heads of the plurality of colors during the forward movement and backward movement, it is possible to ensure that the image quality of the color images obtained during the forward movement and the backward movement are both good. can.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a schematic configuration of a color inkjet printer, FIGS. 2 A to D are diagrams showing examples of how ink dots are deposited during recording, and FIGS. 3 A and B are similar diagrams. FIG. 4 is a block diagram showing the configuration of a masking circuit for correcting deviations in mixed tones based on the manner of ink dot deposition, FIG. 4 is a flowchart showing the manner of operation of the masking circuit, and FIG. 1 is a block diagram showing an example of the configuration of a recording signal control circuit in a jet printer. FIG. 1... Carriage, 2-1 to 2-4... Nozzle head, 3... Flexible tube, 4... Ink reservoir, 4-1 to 4-4... Flexible insulating belt,
5...Relay plate, 6...Electric belt, 7...Rail, 8...Endless belt, 9, 14...Pulse motor, 10-1, 10-2...Stopper, 11...
Recording paper, 12, 13...Roller pair, 15, 16
... Sensor, 17 ... Console, 18 ... Processing unit (CPU), 19, 21 ... Random access memory (RAM), 20 ... Address circuit,
22...Color television camera, 23-1~
23-3...Analog-digital (A-D) converter, 24-1 to 24-3...Adder, 25...
Counter, 26...Dither circuit, 27-1 to 27
-3...Buffer memory, 28...Masking memory, 29...Console, 30...Arithmetic processing unit, 31, 32...Masking table, 33...
...Selector switch, 34-1 to 34-3...Pattern generator, 35-1 to 35-3...Buffer memory, 36-1 to 36-3...Head driver, 37-1 to 37-3...Nozzle head .

Claims (1)

[Claims] 1. A color image forming method in which a color image is formed by reciprocating recording heads of a plurality of colors arranged in order to record a plurality of color materials, respectively, relative to a medium, wherein the forward movement, the backward movement A color image forming method characterized in that different color processing is performed when each of the plurality of color heads prints.