JPS63270165A - Color video printer - Google Patents

Abstract

PURPOSE:To obtain a printed image with high color-reproducibility, by a method wherein a color masking treatment is applied to density data converted from pixel data of a television image to eliminate a turbidity of color contained in a coloring material etc. CONSTITUTION:Each image data for one line respectively outputted from line memories 40, 42, 44 is subjected to a reverse gamma correction in a reverse gamma correction circuit 48 and operated by a digital logarithmic computing element, whereby density data Db, Dg, and Dr are generated. the density data Db, Dg, and Dr are supplied to a color masking circuit 50 and operated, whereby density data DY, DM, and DC are outputted to be supplied to a density-time conversion circuit 52. Gradation data CY, CM, and CC for one line respectively corresponding to the density data DY, DM, and DC are supplied to a thermal head 54 in a predetermined order from the density-time conversion circuit 52. Here, one line of heating resistors generte heat for a time directed by the corresponding gradation data CY, CM, and CC, whereby pixels corresponding to respective pixels of a television image are printed on one printing line.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a color video printer that prints color television images, and in particular to a color video printer that removes color turbidity contained in coloring materials, etc., and prints images with high color reproducibility. It was designed to obtain

(Prior Art) Color video printers permanently record color television images as hard copies, and are increasingly being used in various fields as simple printing devices that can replace photography and printing.

The recording method of color video printers is thermal.

There are various types such as inkjet type and light spot scanning type, but all of them are yellow (Y) or magenta (M).

Color reproduction is performed using a subtractive color method by mixing three cyan (C) color materials.

In the transfer type thermal type, when printing one sheet, Y,
It is easy to obtain multi-recorded color images by using M and C color ink ribbons, and recently, full-color ink ribbons that give each pixel (recorded dot) itself a density gradation are available.
With the advent of video printers, video receivers, image processing devices,
It is expected to be used as an external output device (hard copy v2) connected to a personal computer or the like.

In such density gradation control, a constant voltage is applied to each heat generating resistor element of the thermal head and the energization time is controlled to give a gradation to the heat generated energy. gradation is given to the amount of transfer and thus to the density of the pixel.

(Problems to be Solved by the Invention) By the way, the color reproducibility of images printed by conventional color video printers has not been very good. The cause is mainly the color of general coloring material (Y.

The reason is that M and C) are not pure and contain some turbidity, so when their primary colors overlap on the printing paper,
The resulting mixed color will be shifted from the color of the original image.

The present invention has been made in view of such problems, and it is an object of the present invention to provide a color video printer that removes color turbidity contained in coloring materials and obtains printed images with high color reproducibility. .

(Means for Solving the Problems) In order to achieve the above object, the present invention converts pixel data forming a color television image into density data, and then converts the density data to indicate the density gradation of each pixel. A color video printer that creates a print image corresponding to a television image by converting it into print data and performing printing drive according to the print data is configured to include means for performing color masking processing on the density data.

(Function) The pixel data that forms color television images is generally blue (
B), green (G), and red (R) pixel data PB
, PG, and PR. Then, the corresponding density data D b, D g, Dr
The following relationship holds true.

DY=Db DM=, [)g...
...■DC=Dr In conventional video printers, the amount of each coloring material attached to the surface of the printing paper was controlled based on the density data DY, DM, and DC obtained from the above formulas ■ and ■. Since the actual color of the coloring material contains a turbidity component, if printing is performed using the Y, M, and C data obtained by formula (2), the printed image will have low color reproducibility.

Therefore, in the present invention, the concentration data Db+D obtained in 2〇
For example, the following primary color masking process is applied to g, [) r.

That is, DY = a IIDb + a 12D
g + a 13DrDM = a 21Db
+ a 22Dg + a 23Dr ・=・・・・−
■DC=a31Db +a32Dg +a33Dr Each correction coefficient (matrix coefficient) a is selected at a value that theoretically or statistically cancels out the turbidity components of each color depending on the characteristics of the ink sheet, printing paper, etc. used. It will be done.

Therefore, the data DY obtained by calculating 2〇 or ■
When printing is performed based on , DM, and DC, a printed image with high color reproducibility in which the turbidity of the coloring material is reduced is created.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows the main structure of a thermal transfer color video printer according to this embodiment.

The input terminal 10 includes a standard method for assembling a television image;
For example, NTSC color television video signal SNTS
C is input. This TV video signal 5NTSC is RG
B decoder 12: SR (red), SG (green), SB (blue)
is decoded into each primary color video signal. Those primary color video signals S R, S G, S R are sent to the A/D converter 18.2.
0.22, a digital video signal, that is, pixel data PR, at a predetermined sampling rate (for example, a frequency four times the color subcarrier frequency) and a predetermined number of quantization bits (for example, 6 bits).

The data are converted into PC and PB and stored in frame memories 24, 26, and 28 frame by frame, respectively. At this time, each pixel data of 6 and 7) is written in the order corresponding to the rask scan of the television image.

Note that the television video signal SNTSC is also supplied to the horizontal synchronization separation circuit 14, and the horizontal synchronization signal fB separated therein is
is supplied to the PLL circuit 16, and from the PLL circuit 16 A/
A sampling clock rank 4fH for D conversion is output.

The pixel data PR, PC, and PB for one frame stored in the frame memory 24, 28, and 28 are read out in the order corresponding to the rask scan of the TV image for still image monitoring, and are read out from the D/A. The signal is restored into analog primary color video signals S R, S G, and S H by converters 30 , 32 , and 34 , and then further restored into a television video signal S NTSC by an NTSC encoder 36 and sent to a monitor display 80 . If the display 80 is equipped with RGB terminals, the primary color video signals SR, SG, and SB are directly supplied without going through the NTSC encoder 36.

Now, to make a hard copy of a television image, pixel data is read out line by line from the first column of memory cells from frame memories 24, 2θ, and 28, and latched into line memories 40, 42, and 44, respectively. .

Each color pixel data for one line outputted from the line memories 40, 42, and 44 is sent to the inverse gamma correction circuit 48.
is input and undergoes inverse gamma correction here. In addition, in this circuit 48, the above equation
is calculated, and once the data ob + D g * o
r is generated.

These density data D b + D g + Dr are supplied to the color masking circuit 50, where the above-mentioned operation 2 or 3 is performed.

FIG. 2 shows a specific example of the configuration of the color masking circuit 50. This example uses look-up table 80.82.64 consisting of ROM, and density data D
b, Dg, and Dr are connected in parallel and input a total of 18 bits to the lookup table 60°62.64 as arguments (addresses), respectively. Each look up
Tables 80, 82 and 64 show the calculated values of formula (2) in ROM corresponding to all possible values of input data (18 bits).
is stored at a specified location. However, the concentration data D
b.

When Dg+Dr is input, the corresponding 8-bit density data DY, DM, and DC are read out and output.

Again, in FIG. 1, the corrected density data D Y, D M, and D C output from the color masking circuit 50 are supplied to the density one-time conversion circuit 52.

In the concentration one-time conversion circuit 52, each concentration data DY, DM
, gradation data CY, CM, CC, in which the DC density information indicates the thermal transfer time (the energization time of the heating resistor element) for each pixel.
are converted to respectively. That is, in the thermal transfer method of this embodiment, a constant voltage is applied to each heat generating resistor element (print element) of the thermal head (print head) 54 and the energization time is controlled to give a gradation to the heat generated energy. The transfer amount and thus the density of the image are given gradations, and each energization time corresponds to the density information of each density data.

Figure 3 shows the energization time and
The concentration characteristic curve is shown. Unit energization time Δt of heating resistor element
When energized for the energizing time tl corresponding to , the gradation level d
When a density of i is obtained and the current is applied for a current application time t2 corresponding to twice the unit current application time Δt, a gradation level d2 of 1 degree can be obtained. In this example, a maximum gradation level dG4 near the saturation density can be obtained by energizing for a energization time tG4 corresponding to 64 times the unit energization time Δt.

Therefore, each concentration data D is output from the concentration one-time conversion circuit 52.
One line of gradation data CY corresponding to Y, DM, DC
. Corresponding pixels (recorded dots) are printed on one printing line.

Note that the images of each color (Y, M, C") are not printed at the same time, but are printed one frame at a time sequentially as the ink sheet is switched. Therefore, the gradation data CY of each color,
CM and CC are sequentially supplied to the thermal head 54 one frame at a time.

The print image created as described above is color masked to remove (correct) the color turbidity of the ink sheet, etc.
Because of this, it has excellent color reproducibility.

In FIG. 1, a system controller 46 controls the overall operation of the printer. The machine control section 5θ controls the operation of the printer mechanism section, and the machine/sensor section 58 includes a head feeding mechanism 9, a paper feeding mechanism, and various sensors.

(Effects of the Invention) As described above, according to the present invention, color turbidity contained in color materials, etc. is removed by performing color masking processing on density data converted from pixel data of a television image. , print images with high color reproducibility can be obtained.

[Brief explanation of drawings]

1 is a block diagram showing the main configuration of a thermal transfer color video printer according to an embodiment of the present invention; FIG. 2 is a block diagram showing a specific example of the configuration of the color masking circuit 50 shown in FIG. 1; and FIG. 3 is a diagram showing an energization time/density characteristic curve used in the density gradation method. In the drawings, 12...RGB decoder, 24.28.28...frame memory, 40.42
．． 44... Line memory, 46... System controller, 48... Inverse gamma correction circuit, 50... Color masking circuit, 52... Density one-time conversion circuit, 54...・Thermal head, 60.82.84... Look up table.

Claims (1)

[Scope of Claims] Pixel data forming a television image is converted into density data, and then the density data is converted into gradation data indicating the density gradation of each pixel, and printing is driven according to the gradation data. A color video printer that creates a print image corresponding to the television image by performing the following: A color video printer comprising means for performing color masking processing on the density data.