JPH089174A - Color conversion circuit and color printer - Google Patents

Abstract

PURPOSE:To obtain the color conversion circuit and the color printer employing inexpensive semiconductor memories on market in which print data are obtained properly. CONSTITUTION:Correction data to correct a component mixed from a color other than a color to be printed out are read from a 1st data conversion table 17 by using image data and a color selection signal from latch circuits 161, 162 as addresses and fed to a 2nd data conversion table 18. The 2nd data conversion table 18 reads print data and feeds the data to a latch circuit 19 by using the image data from a latch circuit 163, the correction data from the 1st data conversion table 17 and the MSB of the image data and the color selection signal from the latch circuits 161, 162 as addresses. Then the image data are printed on recording paper.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color conversion circuit and a color printer, for example, when a color image is printed on a recording paper by using a so-called thermal head, a color image is formed by superposing a plurality of color print images. To obtain a color printer and the like.

[0002]

2. Description of the Related Art A color printer employs a method of forming a color mark image on a recording sheet using a thermal head or a method of forming a color mark image by spraying mist-like ink on the recording sheet. .

In these color printers, the principle of obtaining a color printed image by superposing printed images of three or four colors is usually used, and so-called transfer ribbons or inks of three or four colors are used. These colors are yellow, magenta, cyan, and black, and a desired color printed image is obtained by superimposing these colors on a recording paper at a desired density.

By the way, the spectral characteristics of yellow, magenta, and cyan are not independent of each other, as shown in FIG.
The colors are distributed so that they overlap. Therefore, for example, assuming that the density (level) of yellow and magenta is the maximum, if yellow is printed at the maximum density, the yellow component mixed in magenta is superimposed on this, and yellow is emphasized by that amount. Become. In order to prevent this, the yellow component mixed in advance with magenta and cyan may be taken into consideration to print yellow.
Similarly, when printing magenta and cyan, the components included in other colors may be taken into consideration.

[0005]

Various methods have been proposed to achieve the above object, and one of them has been proposed.
There is a method of using a data conversion table. In particular,
For example, the image data of each of the three primary colors consists of 8 bits, and the image data consisting of 24 (= 8 × 3) bits in total is used as an address, and the printing data is stored in advance in a data conversion table (memory) of 8 bits. There is a method of reading print data. By the way, in this method, in order to obtain the print data of one color, 2 ²⁴ bytes, that is, 16M
A memory having a capacity of bytes (128 Mbits) is required. Furthermore, in order to obtain print data of three colors, a memory having a capacity three times as large as this is required. If such a large-capacity memory is configured by, for example, a semiconductor memory that is generally commercially available, the number of semiconductor memories increases and
The circuit becomes complicated, and it becomes large-scale and expensive.
Therefore, in such a case, it is conceivable to develop a dedicated semiconductor memory to reduce the number, but it takes time to develop and the price becomes expensive.

Further, for example, as disclosed in Japanese Patent Application Laid-Open No. 59-52968 filed by the applicant of the present application, the second data conversion table allows the components mixed from colors other than the color to be printed. A method is known in which a correction signal (data) for correction is obtained, and image data of the color to be printed and this correction signal are used as addresses to obtain the print data from the first data conversion table. By the way, with this method, when a commercially available semiconductor memory is used, only 256 (= 2 ⁸ ) kinds of correction signals can be obtained although there are 16 (= 8 × 2) -bit addresses to obtain the correction signals. Cannot be performed, and fine correction cannot be performed.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a color conversion circuit and a color printer which can obtain appropriate print data by using a commercially available inexpensive semiconductor memory. To aim.

[0008]

In order to solve the above-mentioned problems, a first color conversion circuit according to the present invention forms a print on a recording paper for each print data of each color based on print data of a plurality of colors. A color conversion circuit for converting image data in a color printer for forming a color print image by superposing the obtained print images to print data, and correcting the first image data and the second image data as addresses. A first data conversion table for outputting data and a second data conversion table for converting the third image data into print data are provided.

Then, the third image data, the correction data from the first data conversion table and the most significant bit of the first image data are input as addresses to the second data conversion table, and the print data is output. It is characterized by doing.

The second color conversion circuit according to the present invention is
In the first color conversion circuit, the most significant bit of the second image data is also input as an address to the second data conversion table.

A third color conversion circuit according to the present invention is
A color conversion circuit for converting image data into print data in a color printer that prints on a recording paper for each print data of each color based on print data of plural colors and forms a color print image by superposing the obtained print images. A first data conversion table for outputting correction data using the first image data and the second image data as addresses, and a second data conversion table for converting the third image data into print data. Equipped with.

Then, the third image data, the correction data from the first data conversion table, and 2 bits or more of the first image data and the second image data are input as addresses to the second data conversion table. Then, the print data is output.

A color printer according to the present invention is characterized by including any one of the first to third color conversion circuits.

[0014]

According to the present invention, correction data is obtained from the first data conversion table using the first image data and the second image data as addresses, and the second data is obtained by using the correction data and the third image data as addresses. When the print data is obtained from the conversion table, a bit having a great influence of the image data of the mixed color, for example, the most significant bit is used as an address.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a color conversion circuit and a color printer according to the present invention will be described below with reference to the drawings. A color printer to which the present invention is applied is, for example, as shown in FIG. 1, sample hold circuits (hereinafter referred to as S & H circuits) 11R, 11G and 11B for sampling and holding image signals of three primary colors, and the S & H circuit 11R.
To amplifiers 12R, 12G, and 12B for amplifying the image signals sample-held by 11B and the amplifiers 12R to 1B.
A / D converters 13R, 13G, and 13B for converting the image signal from 2B into image data, and the A / D converters 13R to
Memory 14 for storing image data from 13B for each color
With.

The S & H circuits 11R to 11B simultaneously sample and hold the image signals of the three primary colors consisting of, for example, the R signal, the G signal, and the B signal, respectively, and the amplifiers 12R to 12R to 11B.
It supplies to A / D converters 13R-13B via 12B, respectively.

Each of the A / D converters 13R to 13B converts each image signal into image data of, for example, 8 bits and supplies the image data to the memory 14. The memory 14 is composed of, for example, three so-called frame memories having a storage capacity for one printed image, and stores image data for each color.

Further, this color printer is similar to that shown in FIG.
As shown in FIG. 3, a bus switcher 15 for switching the output destination of the image data of the three primary colors from the memory 14 and latch circuits 16 ₁ , 16 ₂ , 16 ₃ for holding the image data supplied via the bus switch 15. And the latch circuit 1
_First data conversion table 17 for outputting correction data using image data from 6 ₁ and 16 ₂ as addresses, image data from the latch circuit 16 ₃ , correction data and latch from the first data conversion table 17 Circuit 1
A second data conversion table 18 for converting the image data from the latch circuit 16 ₃ into print data by using the most significant bit of each image data from 6 ₁ and 16 ₂ as an address.

The image data stored in the memory 14 is switched by the bus switcher 15 and supplied to the latch circuits 16 _{1 to} 16 ₃ . Specifically, the bus switcher 15 outputs a B signal as shown in FIG. 2A, for example, based on a 2-bit color selection signal supplied from a controller (not shown) that controls the entire color printer. When performing printing based on the image data of the R signal (hereinafter, simply referred to as image data R), the image data G, and the image data B are latch circuits 16 ₁ , 1 respectively.
Supply to 6 ₂ and 16 ₃ .

When printing based on the G signal, the bus switcher 15 latches image data R, image data G, and image data B with latch circuits 16 ₂ , 16 ₃ , and 16 ₁ as shown in FIG. 2B. 2C to perform printing based on the R signal, image data R, image data G, and image data B are supplied to the latch circuits 16 ₃ , 16 ₁ , and 16 ₂ , respectively, as shown in FIG. 2C. The latch circuits 16 _{1 to} 16 ₃ hold (latch) the image data supplied via the bus switcher 15 in this manner.
To do.

The image data held in the latch circuits 16 ₁ and 16 ₂ is supplied to the first data conversion table 17 as an address, and the image data held in the latch circuit 16 ₃ is converted into the second data conversion as an address. It is supplied to the table 18.

In the first data conversion table 17, for example, 8-bit correction data for correcting a component mixed from a color other than the color to be printed is stored in advance for each printing color. . Then, the first data conversion table 17 uses the image data from the latch circuits 16 ₁ and 16 ₂ and the color selection signal described above as an address.
The correction data is read out and the second data conversion table 18 is read.
Supply to. That is, since the first data conversion table 17 uses two 8-bit image data and a 2-bit color selection signal as an address,
For example, commercially available 2M (= 2 ^{(16 + 2)} × 8 = 2097152)
The bit can be configured by a commercially available semiconductor memory.
It should be noted that two commercially available 1 Mbit semiconductor memories,
It may be configured with four 512 Kbit semiconductor memories or the like.

On the other hand, in the second data conversion table 18, printing data consisting of, for example, 8 bits of the color to be printed is stored in advance for each printing color. Then, the second data conversion table 18 has the latch circuit 1
Image data from the 6 _3, the first data conversion table 17
From the latch circuits 16 ₁ and 16 ₂ and the most significant bit (hereinafter referred to as MSB: Most Signi) of the image data from the latch circuits 16 ₁ and 16 _2.
It is called ficant Bit. ) And the color selection signal as an address, the print data is read and supplied to the latch circuit 19. That is, the second data conversion table 18 is
8M image data, 8-bit correction data, 2-bit color selection signal, and 1-bit MSB are used as addresses.
(= 2 ^{(8 + 8 + 2 + 2 )} × 8 = 8388608) bits, that is, for example, two commercially available 4M bit semiconductor memories, 2M
It can be composed of 4 bit semiconductor memories, 8 1M bit semiconductor memories and the like.

In other words, the second data conversion table 18 stores print data corresponding to four combinations of MSBs of image data from the latch circuits 16 ₁ and 16 ₂ and the correction data. 256 (= 2 ⁸ ) types can be expanded to 1024 (= 256 × 4) types,
As a result, it is possible to output more appropriate print data that has been finely corrected as compared with the related art, that is, in consideration of the influence of components mixed from other colors.

Further, this color printer is similar to that shown in FIG.
As shown in, a latch circuit 19 for holding the print data from the second data conversion table 18, a gradation conversion memory 20 for outputting a pulse signal having a width based on the print data from the latch circuit 19, A head unit 2 for printing an image on a recording sheet by a pulse signal from the gradation conversion memory 20.
1 and 1.

Then, the latch circuit 19 holds the print data supplied from the second data conversion table 18 and supplies it to the gradation conversion memory 20. Gradation conversion memory 2
In 0, for example, data for converting print data into pulse signals is stored in advance, and the gradation conversion memory 20 is
A pulse signal having a width based on the print data supplied from the latch circuit 19 is supplied to the head unit 20.

The head unit 20 includes, for example, a driver circuit, a transfer ribbon made of yellow, magenta, and cyan, a thermal head, and the like, and prints with the transfer ribbon based on a pulse signal supplied from the gradation conversion memory 20. That is, for example, when printing yellow, the head unit 20 prints based on the pulse signal in which the yellow component mixed with magenta and cyan is corrected as described above. Then, the above-described operation is repeated for each printing color, and the printing images of the respective colors are overlapped to form a color printing image on the recording paper.

In the above embodiment, the MSB of each image data from the latch circuits 16 ₁ and 16 ₂ is input as an address to the second data conversion table 18, but as shown in FIG. 3, for example, As the address of the second data conversion table 18, either one of the MSBs of the image data from the latch circuits 16 ₁ and 16 ₂ may be used. That is, for example, when printing cyan, the MSB of magenta image data, which is more affected by the mixed components, is used. As a result, the capacity of the second data conversion table 18 is half that of the above embodiment, that is, 4
It can be M bits.

Further, for example, when a more accurate correction is required, the bits necessary for obtaining the desired accuracy are alternately set from the MSB side of the image data from the latch circuits 16 ₁ and 16 ₂ to the second bit. Is input as an address to the data conversion table 18 of FIG. In this case, the second data conversion table 1
8 is configured by adding, for example, one 4M-bit semiconductor memory each time the address increases by 1 bit.

It is needless to say that the present invention is not limited to the above-mentioned embodiment, and the present invention can be applied to, for example, a color printer of the type that sprays mist-like ink as the head portion 21.

[0031]

As is apparent from the above description, according to the present invention, the first data conversion table is used with the first image data and the second image data as addresses, and the colors other than the color to be printed are changed. When the correction data for correcting the mixed component is obtained, and the correction data and the third image data are used as the addresses and the second data conversion table is used to obtain the print data, the influence of the mixed color image data By inputting even a large bit, for example, the most significant bit, as an address, a less expensive commercially available semiconductor memory was used to make a finer correction than before, that is, the effect of components mixed from other colors was considered. It is possible to obtain appropriate print data.

[Brief description of drawings]

FIG. 1 is a block diagram showing a specific configuration of a main part of a color printer to which the present invention is applied.

FIG. 2 is a diagram showing a switching state for explaining an operation of a bus switcher which constitutes the color printer.

FIG. 3 is a block diagram showing another specific configuration of the main part of the color printer to which the present invention is applied.

FIG. 4 is a diagram showing spectral characteristics of printing colors.

[Explanation of symbols]

 13R, 13G, 13B A / D converter 14 Memory 15 Bus switcher 17 First data conversion table 18 Second data conversion table 20 Gradation conversion memory 21 Head unit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location G06T 5/00 H04N 1/46 G06F 15/66 N 310 15/68 310 A H04N 1/46 Z

Claims (4)

[Claims] 1. Image data in a color printer for forming a color print image by printing print images on a recording paper for each print data of each color based on print data of a plurality of colors and converting the print data into print data. A color conversion circuit for converting, a first data conversion table for outputting correction data using the first image data and the second image data as addresses, and a second data conversion table for converting the third image data into print data. Of the third image data, the correction data from the first data conversion table, and the most significant bit of the first image data are input as addresses to the second data conversion table. , A color conversion circuit which outputs print data. 2. The second data conversion table contains a second data
2. The color conversion circuit according to claim 1, wherein the most significant bit of the image data is also input as an address. 3. Image data in a color printer that forms a color print image by printing print images on recording paper for each print data of each color based on print data of a plurality of colors and prints the print data as print data. A color conversion circuit for converting, a first data conversion table for outputting correction data using the first image data and the second image data as addresses, and a second data conversion table for converting the third image data into print data. Data conversion table, and the second data conversion table includes the third image data, the correction data from the first data conversion table, and 2 bits or more of the first image data and the second image data. Is a color conversion circuit, which inputs image data as an address and outputs print data. 4. The method according to any one of claims 1 to 3.
A color printer comprising the color conversion circuit according to the above paragraph.