JPH0712678B2 - Color image recording device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a color image recording apparatus, and more particularly to a color image recording apparatus which forms pixels by dots corresponding to a plurality of primary color inks and records a color image.

[Prior art]

A recording device such as an ink jet printer is known as a device for performing color image recording by this type of system.

In these recording devices, as is already known, yellow, magenta red, and cyan blue (hereinafter, in order respectively, which are complementary colors to the three primary colors of red, green, and blue light.
The colors other than these three primary colors are expressed by combining the inks of the three primary colors (denoted by the symbols Y, M, and C). However, in practice, it is difficult to express perfect black by mixing these three colors, so black (Bk) is added to this and multicolor recording is performed with four color inks.

For example, 8 of red (R), green (G), blue (B), yellow (Y), magenta (M), cyan (C), black (Bk), white (W)
When recording in color, red is expressed by mixing the inks of Y and M by overlapping and depositing dots of Y and M inks on the same pixel on the recording surface. It is expressed by mixing C and blue is expressed by mixing M and C. Of course, yellow, magenta, cyan, and black
It is expressed by a single color of Y, M, C, and Bk, and white is expressed by not attaching ink dots.

In addition, other colors are the same as Y, M, and
It is expressed by mixing any two or three colors of C, but in this case, it is expressed by changing the amount of ink mixed, that is, the size of the dots or the like.

However, in order to express the primary colors and colors other than black and white as described above, if a plurality of primary color inks are adhered and mixed on the same pixel on the recording surface so as to be mixed, the following problems occur.

That is, when a recording paper having a high recording density and poor absorption of ink such as coated paper is used, and particularly when the recording surface of the recording paper is arranged in the vertical direction, pixels or recording areas of color mixture due to the above mixing are If the ink is continuously applied, a plurality of inks that have been applied in an overlapping manner may not be completely absorbed by the recording paper and may flow downward due to its own weight. In this case, the image quality is significantly deteriorated.

In particular, when double recording is performed in order to emphasize a character or image of a part of the entire image by the above method, at least quadruple dot recording is performed on pixels or recording areas of mixed colors, and the amount of ink adhered on the same portion is Since the number is extremely large, the above phenomenon occurs frequently.

When a color image is recorded on an OHP film for a so-called overhead projector by this method, since the amount of ink adhered differs depending on the color for each pixel, the image is projected through this film. The image differs in the density of each pixel depending on the color, and is remarkably inferior in quality.

〔Purpose〕

The present invention has been made in view of the above circumstances, and in a color image recording system for recording a multi-color image by scanning the recording surface with the dots of the primary color ink of the above-described predetermined number of colors, the pixels of the recorded image are recorded. It is an object of the present invention to provide a color image recording apparatus capable of appropriately and uniformly depositing the amount of ink for each color and obtaining a high-quality recorded image.

〔Example〕

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIGS. 1 (a) to 1 (d) are for explaining the recording operation of one dot of an ink jet head of an ink jet printer to which the method of the present invention is applied.

As shown in these figures, the ink jet head is a pressure generator for ejecting ink droplets onto a glass thin tube 2 having a truncated cone-shaped orifice 3 having a discharge port 3a having a diameter of about 65 μm formed at its tip. It is configured by fitting a cylindrical piezo element 1.

FIG. 1 (a) shows the initial state, and during recording, a driving voltage of several tens of volts is applied to the piezo element 1 via an electrode (not shown), and as a result, as shown in FIG. 1 (b), the piezo element 1
Is deformed so that the diameter thereof is contracted, and the glass thin tube 2 is pressed by this deformation. As a result, the ink 4 in the glass thin tube 2 becomes an ink droplet D by the pressure and the discharge port 3a.
Is discharged from. The ink droplet D adheres to a recording surface (not shown) to perform one-dot recording.

Immediately after the above ejection, the drive voltage is cut off, the head is in the state shown in FIG. 1 (c), and the ink 4 near the ejection port 3a is emptied by the previous ejection. d)
As shown in FIG. 3, the surface tension of the ink 4 immediately replenishes the above-mentioned portion with ink, and the same initial state as in FIG.

The above is the recording operation for one dot, and a plurality of the above ink jet heads for performing this operation are provided for each primary color in the recording portion of the ink jet printer described later, and these heads are transferred in the main scanning direction. By repeating the recording operation for one dot and feeding the recording paper in the sub-scanning direction, scanning is performed with a dot matrix pattern, and color image recording is performed.

Next, FIG. 2 shows a schematic structure of an ink jet printer provided with the above ink jet head.

The above ink jet head is provided in parallel with the recording section 4 of the four printers for yellow, magenta red, cyan blue and black as indicated by reference numeral 7 and Y, M, C and B in FIG. There is.

The recording unit 4 includes a DC motor 6 for driving a carriage (not shown) equipped with the ink jet heads 7 and the heads 7, a pulse motor 5 for feeding a recording paper sheet (not shown), and a driver 8 for driving these. The recording operation is performed under the control of a CPU (Central Processing Unit) that controls the entire printer via a PIA 13 which is an input / output controller.

The CPU9 has a ROM 10 storing information such as control programs,
A RAM 11 that stores information such as recorded data and a timer 12 that counts the time required for various operations are connected.
Based on these configurations, U9 controls the recording unit 4 according to the above control program to perform the recording operation.

The recording unit 4 is an interface 14 connected to the PIA 13.
Receive recording data and commands from outside via.

Although the configuration itself of the ink jet printer described above is already known, by appropriately configuring the control program in the ROM 10, the color image recording is performed by the method described below.

FIG. 3 illustrates the color image recording system according to this embodiment.

In the figure, image data to be recorded is schematically shown on the left side, and images actually recorded by the embodiment method are schematically shown on the right side, and the dots corresponding to each pixel are shown by a circle. The above-mentioned colors are indicated by the English letters, and the dots indicate that they are mixed colors.

That is, in the case of the present embodiment, as shown on the left side of the drawing, there are two or more regions of the color (red (R) in this case) represented by the color mixture in the recording image data in the main scanning direction and the sub scanning direction. When the pixels are continuous, as shown on the right side of the figure, the dots of the two types of primary colors (Y and M in this case) forming the above-mentioned color mixture are connected to a plurality of adjacent pixels (in both directions). By alternately recording in 4 pixels in this case, the above-mentioned color mixture is expressed as the whole of these pixels.

According to the above recording method, when the structure of the image data to be recorded is as shown in FIG. 4 (A), actual recording is performed as shown in FIG. 4 (B). Both figures are shown here in the same format as in FIG.

That is, in FIG. 4A, red (R), which is continuous over two or more pixels in the main scanning direction and the sub-scanning direction,
As shown in FIG. 4 (B), the mixed color area indicated by diagonal lines of green (G) adjoins dots Y and M in the case of red, and dots Y and C in the case of green in the main scanning direction and the sub scanning direction. It is expressed by recording alternately on each pixel.

Further, in FIG. 4 (A), since the two R pixels from the right of the top row are continuous only in the main scanning direction, only these two pixels are indicated by R as they are in FIG. 4 (B).
The dots of Y and M are overlaid and recorded on the same pixel as in the conventional case.

Here, according to the above-mentioned conventional method, the dots of the primary color ink are double-printed for all the pixels (30 pixels in this case) in the R and G regions indicated by diagonal lines in FIG. 4A. As is clear from a comparison between the case of the method of the present embodiment and the case of the method of the present embodiment described above, according to the method of the present embodiment, the proportion of the mixed color pixels that are double-printed by the dots of different primary color inks is the same as that of the conventional method. Remarkably smaller than the case.

Therefore, even when the above-mentioned recording paper with poor ink absorption is used, unlike the conventional method, the ink adhesion amount for each pixel does not become excessive on the whole, so the image quality is deteriorated by the ink flow. Will never occur. In other words, the degree of freedom in selecting recording paper is increased.

In other words, in the case of the method of this embodiment, the amount of ink adhered to each pixel is substantially uniform, so that even when an image is recorded on the above-mentioned OHP film, the image is projected through this film. The image has a small difference in density due to the difference in color of each pixel and high quality is obtained.

By the way, the recording method of the present embodiment as described above is specifically realized by the CPU 9 converting the contents of the image data stored in the RAM 11 in the configuration of FIG. 2 and recording according to the converted data. To be done. The details of one example will be described below.

Like the CRT's bit map memory, the RAM 11 is a bit map memory that stores image data by associating the presence or absence of each color dot to be recorded on each pixel of the recording paper with "1" or "0" of each bit. Are provided for four colors of Y, M, C, and Bk. These bit map memories are configured as buffer memories having, for example, m rows and n columns, that is, n.times.m bits corresponding to the rows and columns of the dot matrix of image data. This n × m is set as desired according to the specifications of the printer.

FIG. 5 (A) shows a state in which the above-described image data of FIG. 4 (A) is stored in such a bit map memory. In the figure, reference numerals 14, 15, and 16 respectively indicate Y.
Bitmap memory for M, C, and C. Note that here
The bit map memory for Bk is omitted.

Y of the bit map memories 14 to 16 shown in FIG.
The data contents of M and C are converted by the processing of the CPU 9 as shown in FIG.

The processing procedure will be described below with reference to the flow chart of FIG. In addition, in this flow chart
What is indicated by m is the contents of the register provided in the CPU 9 for indicating the row and column addresses of each of the above-mentioned bit map memories, and those indicated by the symbols FR, FG, FB are respectively in the processing described below. It is a flip-flop that indicates whether or not the same color mixture data is continuous in each bit map memory data. In the same process, if there is the same color mixture data in the processing address, the next (right adjacent) address and the address one line below, Color (R, G, B) The corresponding flip flops FR, FG, FB are set by the CPU 9.

First, in the first step S1 in FIG. 6, the CPU 9 resets the contents n and m of the register and the flip-flops FR, FG and FB described above.

In the subsequent steps S2 to S4, each bit map memory 14,15,
Check the Y, M, and C data at the processing address indicated by the above 16 registers, that is, the first (0,0) address, and any two of the data are "1" and red (R) is green (G). It is determined whether or not the mixed color data of blue or blue (B).

That is, in step S2, it is determined whether the Y and M data are "1" and red (R), in step S3 it is determined whether Y and C are "1" and green, and in step S4 M And C
Is "1" and it is determined whether or not it is blue (B).

If the determination at each step is NO, step S
Proceed to 2, S3, S4 and proceed from S4 to step S8. On the other hand, if each step is YES, step S2 to S5, S3 to S6, S
From 4, proceed to S7.

Next, in steps S5, S6, S7, and S8, two or three color mixed flip flops that do not meet the above determination are reset.

Then, from Step S5 to Routine A, from S6 to Routine B, from Step S7 to Routine B, and when there is no color mixture data, from Step S8 to advance the processing address to the later-described routine of S20 and thereafter. Returning to step S2, the above processing is repeated for the next processing address.

Next, the routine A to be executed when red data is received will be described. The routines B and C will be described later, but are similar to this.

In step S9 of routine A, it is determined whether or not the flip-flop FR has been set, that is, whether or not the data of the already processed address immediately before the processing address (on the left side) is red (R).

If the determination is denied, the process proceeds to step S10. At step S10 and subsequent S11, it is determined whether the data at the address (n + 1, m), that is, the address next to (on the right of) the processing address is red (R), and one line at the address (n, m + 1), that is, the processing address. It is determined whether the data of the lower address is red (R).

If both of these judgments are YES, step S12 for judging whether or not the flip-flop FR has been set.
From S to S13, it is determined whether or not the M data at the address (n, m-1), that is, the address one line above the processing address is "1". If M is "1", the step S13 is executed. In S14, the M data of the processing address is set to "0", and if M is "0", the Y data of the processing device is set to "0" in Step S15.
Then, after the flip-flop FR is set at step S16, the process proceeds to step S20 and below, and the processing address is advanced by one.

On the other hand, if the determination is NO in any one of steps S10 and S11, the process proceeds to step S20 and the subsequent steps, and the processing of the next processing address is performed.

If the determination in step S9 is YES, that is, if the previous (left-hand adjacent) processed address is red, step S9 is executed.
S10 is skipped, and the process proceeds to step S11, and it is determined whether or not the data at the address one line below the processing address is red. And the judgment is
If YES, go to step S12 and proceed to step S17,
It is determined whether or not the address (n−1, m), that is, the data of the previous (left adjacent) M is “1”. If M is “1”, the data of M at the processing address is acquired in step S18. "0",
If the M data is "0", the Y data at the processing address is set to "0" in step S19. After that, the process proceeds to step S20 and below to process the next processing address.

On the other hand, if the determination in step S11 is NO, then the above step S11
Go to 20 or less.

As described above, in the routine A, when the right adjacent processing address and the lower processing address are red, the data of M at the upper processing address is “1”.
Depending on whether or not the data of one of Y and M of the processing address is set to "0", and when the processing addresses on the left side and the lower side are red, the data of M of the processed processing address on the left side is processed. Conversely, M is set to "0" or "1" depending on whether or not the data is "1". By doing so, when the red data is continuous in the left-right and up-down directions in the bit map memory and the Y and M data “1” are continuous, Y
And M data are alternately converted into "1" and "0".

Routines B and C perform the same processing on the Y and C data and the C and M data, respectively.

In the routine following step S20 for advancing the processing address, step S20 adds 1 to the content n of the register designating the processing address and returns to step S2, but before that, in step S21, n is the total number of columns of the bit map memory N. It is determined whether or not is exceeded, and if it is exceeded, n is set to "0" in step S22, 1 is added to m, and a line feed is performed, and m in which 1 is added in step S23 is stored in the bit map memory. It is determined whether or not the total number of rows M has been exceeded. If it does not exceed the limit, the process returns to step S2, and if it does, the process ends.

By the above processing operation, the data of Y, M, C of each bit map memory in FIG. 5 (A) is changed as shown in FIG. 5 (B). Recording is performed according to the changed Y, M, and C data, so that the recording is performed according to the method of the present embodiment described above.

By the way, in the above-described embodiment method, when the mixed color area is continuous in two or more pixels along both the main scanning direction and the sub-scanning direction, the above-mentioned alternate recording is performed for the area. Even when the color mixture continues in two or more pixels along only one of the scanning directions, the above-mentioned alternate recording may be performed.

Further, as a modification of the embodiment method, when the image of the recorded image data is high density and small, one pixel of the image data is enlarged to four pixels adjacent to each other in the main scanning direction and the sub scanning direction, and recording is performed. Regarding the pixels of each color mixture in the print data, according to the method of the above-described embodiment, the dots of the two types of primary colors forming the above color mixture are alternately recorded in each of the four adjacent pixels. good.

According to this method, there is no pixel in which double dot recording is performed in all pixels of a recorded image, and a higher effect than the above can be obtained.

Since this method halves the resolution, it is preferably used when the pixel density is high. The human eye has about 10 lines per 1 mm for black, but there are only 4 to 5 lines for color and 2 to 3 lines for some colors. If it is applied to the case of about 10 pixels or more, the four pixels forming the above-mentioned color mixture are not identified at a normal viewing distance unless a method such as viewing with a magnifying glass is used, and a good image is obtained.

In the above method, the ratio of enlarging one pixel of the print data is not limited to 4 pixels, and it is needless to say that it may be enlarged to 9 pixels, for example, 3 pixels in the main scanning direction and 3 pixels in the sub scanning direction.

Further, the recording system of the above and the above-described embodiments is not limited to the ink jet printer, but may be a system of the type described first, that is, a system of scanning the recording surface with a dot of primary color ink of a predetermined number of colors to record a multicolor image. If it records, it can be applied to other recording devices such as a wire printer.

[Effect]

As is apparent from the above description, the present invention detects the pixel position where the data indicating the recording is continuously stored in any of the bit map memories corresponding to at least two primary color inks, and at least 2. The data indicating the recording, which is stored in the continuous pixel positions detected by the detecting means of the bitmap memory corresponding to the primary color inks, is converted into the data indicating the non-recording alternately, that is, the continuous mixed color area is detected. By alternately making non-recording (thinning out) these color mixing areas, it is possible to prevent deterioration of image quality due to ink flow even in continuous color mixing areas where ink overflow easily occurs. Since the recorded data is alternately set to non-recorded data in,
It is possible to provide an excellent color image recording apparatus capable of recording a high-quality color image in which color mixture is expressed by a plurality of pixels as a whole, that is, colors can be preserved even by thinning out recording data.

[Brief description of drawings]

1 (a) to 1 (d) are explanatory views sequentially showing the recording operation of an ink jet head of an ink jet printer to which the method of the present invention is applied, and FIG. 2 is a configuration of the ink jet printer adopting the method of the present invention. 3 and 4 (A), (B) are explanatory diagrams for explaining the recording method by the printer of FIG. 2, and FIG. 5 (A).
Is an explanatory view showing a storage state of image data in each bit map memory, FIG. 5 (B) is an explanatory view showing a state where the image data of FIG. 5 (A) is converted, and FIG. 6 is an image data conversion process. It is a flowchart chart which shows a procedure. 1 ... Piezo element, 2 ... Glass thin tube 3 ... Orifice, 5 ... Pulse motor, 6 ... DC motor, 7 ... Ink jet head, 8 ... Driver, 9 ... CPU, 10 ... ROM, 11 ... RAM 13 …… PIA 14,15,16 …… bitmap memory

Claims (2)

[Claims] 1. A color image recording apparatus for recording a color image by forming pixels by dots corresponding to a plurality of primary color inks, and a bit map memory for storing data indicating dot recording on each pixel of each primary color ink. Detection means for detecting a pixel position where the data indicating the recording is continuously stored in any of the bitmap memories corresponding to at least two primary color inks in the bitmap memory; and the at least two primary colors. Conversion means for alternately converting the data indicating the recording, which is stored in the continuous pixel positions detected by the detecting means of the bitmap memory corresponding to the ink, into the data indicating non-recording, and the conversion means. Recording that records dots corresponding to each primary color ink based on the bitmap memory that stores the recorded data A color image recording apparatus comprising: 2. The color image recording apparatus according to claim 1, wherein the recording means ejects ink to record dots corresponding to the respective primary color inks.