JPS6089165A - Picture recorder - Google Patents

Abstract

PURPOSE:To increase the number of contrast gradations by setting the contrast ratio of dark dots and light dots near a value satisfying the prescribed relation of an equation in a picture recorder representing the contrast with the space factor of dots in a block. CONSTITUTION:In expressing the contrast by means of the space factor of dots to a block comprising n (3X3 in this example) cells, a light dot threshold value matrix A and a dark dot threshold value matrix B where the contrast of one picture element of an original picture is represented by a changing threshold number are set so that the order of arrangement of the threshold values is inverted. The relation of the dot space factor is set near Dl:Dd=1:n+1, that is, (n+1)-sets of space factors of light dots are provided to one space factor of dark dots, where Dd is a reflection optical contrast when the dark dots are recorded with uniform density, and Dl is a reflection optical contrast when the light dots are recorded with the same density as that of the dark dots. Thus, the number of gradations to be expressed is a maximum of (n+1)<2>.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an image recording apparatus capable of reproducing halftones, and more particularly to an image recording apparatus capable of reproducing halftones using dots of different densities.

<Description of the Prior Art 1> As a conventional halftone recording method using dots, various methods have been proposed as follows.

The dot size is varied according to the shading of the original image.

11) Density modulation method: The size of the dots is constant, but the density of the dots is changed.

++)-1 Density pattern method: Divide a certain block of the output screen into several cells, and vary the number of cells in which dots of the same size are printed according to the density of one pixel of the original image. do.

1i) -2 dither method: Compares the gray level value of one pixel of the original image with a changing threshold value to control whether dots of the same size are printed or not.

Marshal: Use dots with different densities.

1) Combining with density modulation method using dots with different densities.

+:+, +i), *+i) have been proposed in the past, but 1) is highly dependent on the environment because it changes the dot size, especially in the case of inkjet recording because the flying speed of the droplet changes. , problems remain with high-speed recording. The method 11) requires a considerable amount of area in order to improve the gradation, and improving the resolution becomes a problem. In the method of No. 111), if an attempt is made to obtain many gradations only by warping, the scale of the apparatus becomes large. The method 1v) is a desirable form in terms of resolution, single gradation, and cost, and related to this method! Kaimei No. 58-608.78 and Kaimei No. 58-39468 have been proposed. 4;'i In the case of Kaikai No. 8-60878, 8 gradations are obtained when two types of dots, 0 and 0, are used, and the dither matrix is set to 2×2. Furthermore, in the case of Japanese Patent Application Laid-Open No. 58-39468, 155 gradations were obtained under the same conditions. In order to obtain more tones than ever before, it is necessary to increase the size of the dither matrix or increase the number of types of light and shade dots. Ordinary silver salt photograph I'i
The above proposal (1V) is still insufficient.

<Purpose> The present invention further improves the method of +v), and uses dots of 2 types of shading, and when expressing density by dot occupancy in a block consisting of n cells, at most (n+1). )2
The object of the present invention is to provide an image recording device capable of obtaining a gradation number of 1lIII.

<Description of Embodiment> An embodiment of the present invention will be specifically described below with reference to the drawings. In this embodiment, inkjet recording will be explained as an example, but the present invention is not limited to this and can be applied to various recording methods.

FIG. 1 is a diagram of the basic device of the present invention. 11 is recording paper,
12.13I'i Ink tanks that store inks with different concentrations, 12 stores dark ink, 13 stores light ink, and 014 and 15 are multi-nozzle heads with three nozzles in this example, for example. Television Society Journal VO
This is an inkjet head based on the bubble jet printing technology described in L37No. 2 ('83). 14 is a head for dark ink, and 15 is a head for thin ink. 16 is a power supply line for driving the bubble jet head. Reference numeral 17 denotes a head feeder which is moved left and right by a pulse motor 18. 1
9 is a synchronized belt that transmits the rotational force of the motor to the feed base 17. 20 is a paper feeding pulse motor.

FIG. 2(A) is a gray scale one-value matrix for light dots, and FIG. 2(B) is a threshold value matrix for dark dots, and the numbers in the matrix indicate the threshold values. As shown in the figure, the order of arrangement of threshold values is reversed for π9 dots and light dots. Second
Figure (C) shows the recorded dot pattern with respect to the signal level of the input pixel. The numbers above the matrix indicate the signal level or the number of gradations of the human-powered pixels.

FIG. 2 lists methods of combining two dark and light inks to form a pixel Jf# of 3×3 pixels per month.

In the figure, the loco indicates a light ink dot, the shadow 2 indicates a dark ink dot, and the shading indicates a dot recorded by overlapping a dark ink dot and a thin ink dot.

At this time, let Dd be the reflective optical density when the dark dots are recorded at a uniform density, and Dt be the reflective optical density when the light dots are recorded uniformly at the same density as the dark dots, then Dd: I)
z=n+1: Set near 1. Therefore, n is the number of cells of the dark value matrix.

As can be seen at a glance from Fig. 2 (C), when two types of ink, light and dark, are used and one pixel is formed with z x m = n dots, the number of gradations H that can be expressed is H = (J x m + 1) 2 - (n + 1). )2.

For example, in the case of e=m=3, the conventional density pattern method is used to express the gradation, ==/Xm+1-=IO. h2= =55 In this example, 1 becomes 1-1 = (J-x m +1)2 = 100, and it can be seen that this example has a much higher ability to express an old-fashioned tone than the conventional method.

Next, a specific example of the control circuit will be explained along with the timing charts of FIGS. 3 and 4.

In FIG. 3, 301 is a TV right camera 302 that reads image data of a subject (manuscript, etc.) is a frame memory;
3. 304 is an address selection circuit for the memory 302;
5 is a latch circuit, and 3061 is a distribution circuit for distributing input data into upper data and lower data, which is composed of, for example, a CPU. 307°308 are read-only memory (
5(a) is stored in 307, and 308 is stored in 308 as shown in FIG. 5(ILOM).
The output pattern of a dark dot as shown in b) is stored.

8I! In FIGS. 5(a) and 5(b), l'' indicates the position where a dot is placed, and 0'' indicates a position where no dot is placed. 309, 310 is 'and gate, 311
.

312 is a head driver; 313 is an inkjet head that forms light dots; :ul;] is an inkjet head that forms dark dots; 315 is a system controller; 316 is an external setting device; 1. Specify the η value matrix size, start operation command, etc. The signal line AXI/CXI from the system controller 315 is
The signal line AYl/CYI, which presets and increments the direction counter 303, presets and increments the Y direction counter 304, and the signal line R/W switches whether the frame memory 302 is in a write state or a read state. The signal lines LC are latch signal lines, CAL is a calculation start timing signal, SZ is a dark value matrix size signal, AX2 is an address signal indicating the position of the threshold matrix in the X direction, and CLK is a print clock signal.

The operation will be explained below.

An electrical signal corresponding to the reflected light from the subject is outputted from the TV right camera 01 and entered into the frame memory 302. The frame memory stores an image for one screen at a video rate of 1/30 seconds while converting it from an analog signal to a digital signal. Any location within the frame memory 302 is accessed two-dimensionally by address counters 303 and 304. The memory contents of the addressed location are read out by the R/W line, and the latch circuit 305 outputs the counter 3o3゜3.
The data at the position designated by 04 is temporarily held and sent to the distribution circuit 306. The distribution circuit 30G allocates the upper bits for which dark dots are to be placed and the lower bits for which light dots are to be placed. 1-1. Is there a threshold matrix for weight? XI!
In the case of (e2+]), the value is sent from the controller 315 to the controller 306 along the SET line. 305 to 306
Let D be the data sent to , calculate 306, and then find an integer Ai that satisfies the relationship A'-1<A≦A'. Then H= +nod (D, 12
-H) That is, let B be the remainder when divided by D2z2+1.

Let A and B be the outputs of 306. The output A of 306 is ■
'Output to LOMs 308 and 307, respectively. 1tOM3
07.308 is supplied with SZ wire for IJ rack size, and can be used in any size from 2x2 to lxl.
IJ Lux is selected. Similarly, the position in the row direction (X row direction) of the ext matrix is specified by AX2. Therefore, to implement Fig. 2, 5iZ
=010 (3rd counting from 0), AXI line is 00,0
1,10,00. ...Dan... is repeated. ROM307
, 308 is 3-bit parallel data in the example shown in FIG. 2, which is advanced by an AND gate 309, synchronized with the print clock CLK, and then sent to the head driver 311 . 31
2) multi-nozzle bubble jet spatula)” 31
3. Drive 314.

The movement in FIG. 3 will be explained using FIG. 4.

Freezing the data of one screen of the TV right camera 01 in the frame memory 302 has been done in the past, so we will skip the explanation and explain from the state where the data of one screen is stored in the frame memory 302.

AXl/CX1 and AYt/CYl lines are counter xl
.

AXt and AYI lines that preset the address to ¥1 and counters 303 and 304 are incremented.

There are CXI and CYt lines that are decremented.

Therefore, the starting position X, Y address Q AXI.

The counters 303 and 304 are set through the AYl line. Next, in order to read out the pixel data at the addressed position, it is output to the frame memory output line via the it/W line. The output data is latched in the latch 305 by the LC pulse. The latched data is sent via the SET line SE'v=tOC1=3
t = ] 0) Notemeter) γ start is started by CAL (g), completes the work within 11 hours, and the calculation result is stored in ROM 307°308.In this state, AX2
is 00 in Figure 4. Sz is 010.

Now, if the output data of latch 305 is 35, then 3
06 output is A=3. B=5. Therefore 1(,OM
308 selectively outputs pattern 3 in Figure 5(b), and 140M307 outputs pattern 5 in Figure 5(,'I).
is selected and output. Therefore, 35 dot data shown in FIG. 2(C) are printed.

As can be seen from the threshold arrays in Figure 2 (A) and (B), dark ink dots and thin ink dots are arranged next to each other so that they do not overlap as much as possible, and a large amount of ink is applied to a unit area to increase absorption. Unintentionally, ink bleeds, the recording paper curls, etc., which adversely affects image quality. In the present invention, the second
Figure (A).

Since the threshold array is reversed as shown in (B), the ink overlap is (α
It requires very little.

Each 3-bit data from 307 and 308 is
) 30.9.310 and heating time to the nozzle 1
Leave it there for just one minute.

When the frame memory data is stored in the latch 305, AX2 is OO-+01.01-+10°10-+
ROM307.308 (D changes to l) every time it changes to 00.
It is updated by CXl every time it changes from O to 00.

In the description of this embodiment, the distribution circuit 3 (1G is the CPU
However, if the number of cells in a block (for example, a threshold value matrix) is 9, a known binary coded decimal circuit that converts a binary number into a binary coded decimal number is used. Is possible. Even when using a CPU, it is sufficient to simply calculate the quotient and remainder by division.

In addition, although this example was used for all lines of bubble jet recording, it may also be used for other types of inkjet recording, such as thermal recording, etc.
It is applicable to all devices capable of forming dots with a density of 2 or more.

In addition, in this implementation V11, the #j degree turn method was explained as an example of the density modulation method, but -I! (
Of course, +1 core can also be applied to the dither method that makes the values correspond. In addition, the threshold 11u block is an example of VC type i.
A threshold 111 block of the form C opening ta s x'ilj can be used.

Also, in this example, a base color print is shown, but Y, I~
1. C. It is also possible to apply this method to recolor printing, in which all or part of the black dots are dots of two different shadings.

As explained above, the +tIli fψ recording device of the present invention is capable of recording 25 (changes in l/1) of light dots relative to dark dots.
Set to 1 + 1 near drop (n is the number of cells in the block), and for one occupied block in the dark dot block, (n + 1) occupied units of the disaster dot are set, so the two dark and light blocks are set. When dots are used, it is possible to obtain a maximum of (n+1)20 gradations.Therefore, it is possible to increase gradation compared to the conventional example, and to suppress deterioration in resolution. In the above explanation, two types of dots, light and dark, were used, but it is also possible to use three or more types of dots, 0 and 11), and in that case, it is possible to obtain a large number of gradations in I'i4. I can do it.

[Brief explanation of drawings]

Fig. 1 is a perspective view of a bubble jet printer that can be used by Hongen Meigyo, Fig. 2 (A) is a single cry value matrix for light dots, and Fig. 2 (B) is a sub-3 diagram for dark dots. The signal waveform diagrams of each part, iXs diagrams (a) and (b) are RO1' in Figure 3.
(A) CB) (C)

Claims (1)

[Scope of Claims] In an image recording apparatus that has a recording means for recording dots of different densities and expresses the density by the occupancy rate of the dots in a block consisting of n cells, the density D of a dark dot is
d. The relationship between the densities Dt of light dots is set in the vicinity of Dz: Dd= 1: a+ 1, and n-1-1 occupancy rates of light dots are set for one occupancy rate of a dark dot. An image recording device characterized by: