JPH02182079A - Gradation display method in picture output device - Google Patents

Abstract

PURPOSE:To increase the lump of colored minute picture elements displaying gradation of a low density and to reproduce low density gradation stably by connecting colored minute picture elements of plural adjacent picture elements in the case of displaying the low density gradation with a prescribed level or below. CONSTITUTION:One picture element consists of minute picture elements S of 6X6=36. Then all the minute picture elements S are not colored in a 0-th gradation and only the minute picture elements S marked by caption 1 in figure are colored in 1st gradation. Then the minute picture elements marked by the caption 1 in figure and the minute picture elements 8 marked with captions 2-4 in figure in 2nd-4th gradation are colored sequentially. A picture read section 11 converts a reflected luminous quantity in each picture element of the original into an electric signal. The electric signal is sent to a picture processing section 12 as a density data. The picture processing section 12 converts the density data to dot area rate and into a binary serial data for each scanning line so that it is outputted as a raster picture by a laser scanner 13.

Description

Detailed Description of the Invention A0 Object of the Invention (1) Industrial Application Field The present invention relates to a gradation display method in an image output device, and in particular, to a method for dividing an image to be reproduced into pixels of a minute area, and further dividing the pixels into The present invention relates to a gradation display method in which the pixel is divided into micropixels having a microscopic area, and the gradation is displayed based on the ratio of colored micropixels forming a halftone dot within the pixel to the total micropixels.

(2) Conventional technology Conventionally, when creating an image with gradation in an image output device such as a printing press, printer, or digital copying machine,
A method of displaying gradations in a pseudo manner has been adopted.

In the pseudo gradation display method, the gradation is determined by dividing the image into minute unit pixels, and dividing the image into minute unit pixels (
For example, depending on the size of the area occupied by the dots or lines, the shading is displayed in a manner similar to continuous tone.

A method is often used in which regularly arranged large and small halftone dots are used as minute elements within the unit pixel.

A density pattern method (ie, area gradation method) is known as a method using the halftone dots. This density pattern method is applied to the display side (image output device side) corresponding to one pixel of the original image.
Divide one pixel into multiple micropixels, select a predetermined number of micropixels corresponding to the gradation of the pixel from among the micropixels, and color the selected micropixels in a predetermined color (for example, black). This is a method of displaying the In this method, a halftone dot is formed from a predetermined number of colored fine pixels corresponding to the gradation.

In the density pattern method, gradation display can be performed in stages corresponding to the number of fine pixels forming one pixel on the display side.

For example, Figures 12A and 12B are explanatory diagrams in the case where the number of micropixels S forming one pixel is 6X6=36, and each micropixel S performs binary display;
6) Can be reproduced with +1=37 gradations. In other words, the 0th gradation is when all of the micropixels S are white, and the 0th gradation is when only one of the 36 micropixels S (the micropixel labeled 1 in FIG. 12A) is colored. The first gradation is when only two of the 36 micropixels S (the micropixels labeled l and 2 in FIG. 12A) are colored, the second gradation..., 3
34 of the 6 fine pixels S (in Figure 12B, reference numeral 35
．． The 34th gradation is when all the micropixels (excluding the micropixels marked with 36) are colored, and the 35th of the 36 micropixels S (the first
(All micropixels except the micropixel marked 36 in Figure 2B)
The 35th gradation is when the pixel is colored, and the 36th gradation is when all 36 of the 36 micropixels S are colored, so that the pixel is displayed with a total of 37 gradations. be able to.

Generally, if the number of micropixels forming one pixel is m,
The number of gradations that can be expressed is m+1.

As described above, halftone dots are formed from colored micropixels among a plurality of micropixels forming one pixel, and the gradation is determined by the number of colored micropixels forming the halftone dot.

(3) Problems to be Solved by the Invention Normally, the size of the fine pixels forming a halftone dot is set close to the resolution limit of an image output device, so for example, the number of colored fine pixels forming a halftone dot is When the number of uncolored fine pixels is as small as 1 or 2 (see Figure 12A), or when the number of non-colored fine pixels is as small as 1 or 2 (see Figure 12B), halftone dots are accurately reproduced. It's not easy. That is,
High resolution is required to reproduce minute colored and non-colored areas as images, and reproduction of such areas is unstable with normal image output devices, so it is difficult to set the colored area of the image to a predetermined value. difficult to maintain and reproduce.

- When performing gradation display using halftone dots for boat fishing, ll
The relationship between the f-tone display input signal B and the output density D o u L is as shown in FIG. Figure 11 shows that when displaying a certain gradation, even if you try to color the micropixels to form halftone dots corresponding to that gradation, the density of the micropixels that should be colored is small on the low density side, so it is difficult to color the pixels. In some cases, fine pixels are not stably colored and are displayed as uncolored, or on the high density side, the cluster of fine pixels that should be uncolored is small, so even those fine pixels are displayed as colored. It shows that there is a lot to do.

As mentioned above, in the conventional gradation display method using halftone dots, when attempting to display a low density gradation, a gradation lower than the desired gradation is likely to be displayed; When attempting to display density gradations, a higher gradation than the desired gradation is likely to be displayed, making it impossible to stably reproduce images with low and high density gradations, resulting in poor reproduction. There were 8 problems where image quality deteriorated.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to stably reproduce low-density gradations or high-density gradations in a gradation display method using halftone dots, and improve image quality.

B1 Structure of the Invention (1) Means for Solving the Problems In order to solve the above problems, the gradation display method in the image output device of the first invention of the present application divides an image into pixels of minute area, and The pixel is further divided into micropixels having a microscopic area, the colored micropixels within the pixel form a halftone dot, and the gradation is displayed according to the ratio of the colored micropixels to the total micropixels, and the colored micropixels are further divided into subpixels having a microscopic area. In a gradation display method for an image output device in which pixels are determined corresponding to each gradation, when displaying low density gradations below a predetermined level, colored fine pixels of adjacent pixels are connected to each other. It is characterized by:

Further, the gradation display method in the image output device according to the second invention of the present application divides the image into pixels with a minute area, further divides the pixels into fine pixels with a minute area, and displays a colored image within the pixel. A gradation display method in an image output device, wherein the micropixels form a halftone dot, and the gradation is displayed according to the ratio of the colored micropixels to all the micropixels, and the colored micropixels are determined corresponding to each gradation. The present invention is characterized in that when displaying a high density gradation of a predetermined level or higher, uncolored fine pixels of a plurality of adjacent pixels are connected to each other.

(2) Effect In the gradation display method in the image output device of the first invention having the above-described configuration, when displaying a low density gradation below a predetermined level, colored fine pixels of a plurality of adjacent pixels are mutually separated. Since they are connected, the cluster of colored fine pixels becomes large when displaying low density gradations.

Therefore, the reproducibility of low-density gradation images is stabilized.

Further, in the gradation display method in the image output device of the second invention having the above-described configuration, when displaying a high density gradation of a predetermined level or higher, uncolored fine pixels of a plurality of adjacent pixels are connected to each other. As a result, the cluster of non-colored fine pixels becomes large when displaying a high density gradation. Therefore, the reproducibility of images with high density gradations is stabilized.

(3) Embodiments Hereinafter, embodiments of the gradation display method in the image output device according to the present invention will be described with reference to the drawings.

First, a first embodiment of the present invention will be described with reference to FIGS. 1 to 6.

Figures 1A to IC are explanatory diagrams of reproduced images of the first embodiment,
The reproduced image according to the first embodiment will be briefly explained with reference to these figures.

As you can see from these figures, the lii element is 6×6-36
It is composed of minute pixels S. At the 0th gradation, all the micropixels S are uncolored, and at the 1st gradation, only the micropixels S labeled with the symbol l in FIG. 1A are colored. Then, in the second to fourth gradations, the fine pixels labeled 1 and the fine pixels S labeled 2 to 4 in FIG. 1A are sequentially colored.

In the fifth gradation, only the five fine pixels S labeled 5 in FIG. 1B are colored. In the 6th to 31st gradations, all the fine pixels numbered 6 to 31 in FIG. 1B are sequentially colored.

Then, in the 32nd gradation, 32 fine pixels indicated by diagonal lines in FIG. 1C are colored. In the 33rd to 36th gradations, in addition to the colored micropixels in FIG. 32 that are shaded in FIG.

Next, a description will be given of the configuration of an image output device that performs the display shown in the first A-IC diagram.

FIG. 2 is an overall explanatory diagram of a digital copying machine F to which the present invention is applied. The digital copying machine F is composed of a machine main body F1 and a cover F2 hinged to the top surface of the machine main body F1.

The machine main body F is provided with a platen (original holder) l made of transparent glass on its upper surface. An exposure optical system 2 is disposed below the platen 1. This exposure optical system 2 includes a movable lamp unit 3
The lamp unit 3 is constructed by integrating a lamp 4 for illuminating the document and a first mirror 5. Further, the exposure optical system 2 includes a movable mirror unit 6 that moves at half the moving speed of the lamp unit 3. This moving mirror unit 6 is composed of a second mirror 7 and a third mirror 8. Further, the exposure optical system 2 includes a lens 9, a fourth mirror 10
etc. Then, when the lamp unit 3 moves in the front-back direction parallel to the original, and the movable mirror unit 6 moves by a distance of 1/2 at a speed of 1/2 of the moving speed of the lamp unit 3, the original Since the distance between the lens 9 and the lens 9 is kept constant, the reflected light from the original illuminated by the lamp 4 passes through the exposure optical system 2 and is converged on the image reading section 11. has been done. The image reading section 11 converts the amount of reflected light at each pixel of the document into an electrical signal. This electric signal is converted into density data and sent to the image processing unit 12.The image processing unit 12 converts the density data into an area ratio of halftone dots, and scans each scan so that it can be output as a rask image by a laser scanner 13, which will be described later. Convert to binary serial data for each line. An image is written on a photoreceptor 15 on a drum by turning on or off a laser beam 14 emitted from a laser scanner 13 in accordance with this serial data.

A charging charger 16, a developing unit 17, a transfer charger 18, a cleaner unit 19, etc. are arranged around the photoreceptor 15 along the rotational direction of the photoreceptor 15. Further, the machine main body part F includes a transfer paper storage tray 20, and transfer paper in the transfer paper storage tray 20 is transferred to the photoreceptor 15 and the transfer charger 18.
A paper feeding mechanism 21 is disposed between the
A conveyance mechanism 22 is also provided that passes between the photoreceptor 15 and the transfer charger 18 and conveys the transfer-completed paper on which the transfer has been completed, peeling it off from the photoreceptor 15. Further, the machine main body F is provided with a fixing unit 23 for fixing the transfer-completed paper conveyed by the conveyance mechanism 22, and a paper discharge tray 24 for receiving and receiving the transfer-completed paper discharged from the fixing unit 23. It is set up.

Next, the configuration of the image processing section 12 in the first embodiment of the present invention will be explained in detail.

In the image processing unit I2 shown in FIG. 3, one pixel is composed of a total of 36 micropixels S forming a 6×6 matrix, and at the 0th gradation, all the micropixels S are uncolored. , in the first gradation, one micropixel S is colored, and the other 35 micropixels S are left uncolored, ..., in the 36th gradation, all the micropixels S are colored, resulting in a total of 37 gradations. The display is configured to display the key.

The image processing section 12 includes a threshold type halftone dot generator, and receives image data B from the image reading section 11 . This image data B is a signal obtained by analog-to-digital conversion of an analog output signal obtained by a sensor such as COD in the image reading section 11, and is stored in the line buffer 121 of the image processing section 12. . This image data B is "00oOoo" for displaying the 0th to 36th gradation (i.e. 37th floor 1M in total) (7)
It is 6-bit data of ~r100100J.

The line buffer 121 is composed of a register, a memory, etc., and stores 1542 pieces of image data B. This line buffer 121 is connected to the controller 12
2 controls its reading and writing. The controller 122 is composed of a counter, etc., and includes an X clock signal synchronized with the timing at which the laser beam 14 (see FIG.
an X reset signal generated every time the laser beam scans one line on the photoreceptor 15; It operates using an X reset signal that is generated every time a line (including pixels) is scanned, a page clear signal that is generated at the beginning of printing one page, and a line clear signal that is generated at the beginning of each line scan. The timing of generation of each of these signals is shown in Figures 3B and 3C. Then, in response to these signals, a 3-bit X address signal rXYX+XoJ (see Figure 3B) and a 3-bit Y address signal rYt
(see figure C) is output from the controller 122. Said X address rXtX,x.

J and Y addresses r ``y', Y+ Yo J are ``o'', respectively, as shown in FIGS. 3B and 3C.
.

The value is between ``0'' and ``101'', and the value specifies which @pixel in the 6×6 matrix.

The image processing unit 12 generates a total of three darkness value tables T, r
It is equipped with T tr and T yu. As shown in FIGS. 4A and 4B, the dark value table T is based on the address ('0IOJ, r101') of the 36 fine pixels specified by the X and Y addresses, that is, the
Threshold data r000001 for the fine pixel S specified by the address "olo" and the Y address "lOl"
' is memorized. Also, the fine pixels S, , S, and S
4, threshold data "000010", rooollJ and rooolQo are stored. In all remaining fine pixels srs, darkness value data greater than ``roooloo'' and +, for example, ``rOQllll'' is stored. Then, these dark value data are sent to the controller 12.
The signal is successively outputted by two address signals X and Y, and is input to the first selector SL+.

Further, as shown in FIGS. 5A and 5B, the dark value table T8 includes three
Among the six micropixels, the address (roloJ, robo
”), threshold data r00 is applied to the fine pixel S specified by
0001J is stored. Also, the fine pixels S, ,S,
and threshold data “0OOOIO” in S4, roooo
ll'' and roooloo'' are stored. Then, threshold data rol111 is used for all the remaining fine pixels SIS.
1" is stored. These dark value data are successively output by the address signals X and Y of the controller 122, and are input to the first selector SL1.

Further, the dark value table T, as shown in FIGS. 6A and 6B, has three
Among the six micropixels, the address ('0IOJ, r011
”), (roll.

roll”), (’100J,’011J).

(rollJ, '100J), ('100' rlo
Threshold data rooo101J is stored in five fine pixels S specified by oJ). In addition, the fine pixel S
, -S3. Threshold data “000110J~r0111
11" is stored.

In all the remaining fine pixels Sig, dark value data greater than "rollllll", for example "rlooooo", is stored. Then, these dark value data are read out by the address signals X and Y of the controller 122,
Second selector SL.

It is now entered into

Further, the X reset signal is input to the clock terminal of the first D flip-flop FF, the line clear signal is input to the clear terminal CL of the first D flip-flop FF, and the Y reset signal is input to the second D flip-flop FF. The page clear signal is input to the clock terminal of the D flip-flop FF, and the page clear signal is input to the clear terminal CL of the second D flip-flop FFz. Each of the D flip-flops F F
The Q terminals and D terminals of + and FF are connected, and the output of each Q terminal is input to the circuit EXOR1. And each D flip-flop F F t
The outputs of the Q terminals of and FF are shown in FIGS. 3B and 3C.

The selector S L + is the EXO of the EXom circuit.
When the output signal of Rl is "l", the dark value table T
Select the dark value data from 1, and when it is "0", select the dark value data from the dark value table T, and select the second selector S.
It is configured to output to L. The image data B passes through the arithmetic unit 123 and becomes B', which is input to the comparator 124 and is also input to the discrimination port! 125 and 126. The discrimination circuit 125 is "1" when 4<B<32.
The discrimination circuit 126 outputs "1" when B≧32.
Output.

The selector SL is configured such that the output of the discrimination circuit 125 is
It is configured to output the threshold value data A from the dark value table T to the comparator 124 when it is "1", and to output the threshold value data A from the selector SL to the comparator 124 when it is "0". ing.

The comparator 124 compares the dark value data 8 input from the selector SL with the image data B' manually input from the calculation section 123, and when the image data B' is greater than the dark value (that is, A≦ B') outputs "l" and A>B
' Outputs "0". The output signal of the comparator 124 is configured to be output to the laser scanner 13 (see FIG. 2) through the EX01 circuit EXOR2. The laser scanner 13 receives an input signal of “1”.
'', the laser beam 14 is turned off, and when the value is 0, the laser beam 14 is turned on.

Further, when the output signal of the discrimination circuit 126 is "1",
The calculation unit 123 calculates the maximum value of the image data '100100.
The value of input image data B is subtracted from J (36th gradation) and B' is outputted, and the circuit EXOR2
is configured to invert the output signal of comparator 124. On the other hand, when the output signal of the discrimination circuit 126 is "0", the arithmetic unit 123 converts the input image data B to B' as it is.
Output as .

Next, the operation of the first embodiment of the present invention having the above-mentioned configuration will be explained mainly with reference to FIGS. 3A to 6.

When scanning the first pixel row (6 rows of fine pixels),
D flip-flops FF and FF are cleared by the line clear signal and page clear signal shown in FIGS. 3B and 3C, respectively. At this time, the outputs from the respective terminals Q of the D flip-flops FF and FF are both "0" as shown in FIGS. 3B and 3C, and the X and Y When the reset signal becomes "0" and immediately thereafter becomes "1", the outputs of the Q terminals of the D flip-flops FF and FF both become rlJ. At this time, EX.

Since the output from the circuit EXOR1 is "0", as mentioned above, the selector SL outputs the dark value data of the threshold table T2 to the selector SL.The 0th order X reset signal is the clock of the D flip-flop FF. Each time a signal is input to the terminal, "l" and "0" are alternately output from the terminal Q of the D flip-flop FF, as shown in FIG. 3B.
Accordingly, EX, , rl, and rQ from circuit EXOR1
, are output alternately. That is, the selector SL alternately outputs the dark value data of the threshold table T1 and the dark value table T2 to the selector SL2. As described above, in this embodiment, when scanning the first pixel row (6 rows of fine pixels), the selector SL1 first scans the darkness value table T.
The dark value data of T1.2 is output to the selector SL, and each time the X reset signal is output, the dark value data of T1.
The dark value data of Tt is alternately output to the selector SL.

Further, the D flip-flop FF is initialized at the start of scanning each line by a line clear signal.

In this way, when the scanning of the first pixel row (6 rows of fine pixels, or 6 lines) is completed, and the scanning of the second row of pixels (6 rows of fine pixels) is started. ni, Y
When the reset signal is input to the clock terminal of the D flip-flop FF, "0" is output from the Q terminal of the D flip-flop FF and input to the EXoa circuit EXOR1.

At this time, the D flip-flop FF is initialized by the line clear signal as described above, and rl is output to the Q terminal by the X reset signal immediately thereafter. Therefore, at this time, the output of the D flip-flop FFx is "
0" and the output of FF is "1", so the output from the EXom circuit EXOR1 is rlJ, and as mentioned above,
The selector SL1 outputs the dark value data of the dark value table T1 to the selector SL.Every time the 0th order X reset signal is input to the clock terminal of the D flip-flop FF, a "0 " and "l" are output alternately, so the &NEXom circuit EX
OR1 also outputs "0" and "1" alternately. At this time, the selector SL1 alternately outputs the threshold table T1 and the dark value data of the threshold table T1 to the selector SL.

That is, in this embodiment, when scanning the second pixel row (six rows of fine pixels), the selector SL1 first outputs the threshold data of the darkness value table T to the selector SL, and then Every time the X reset signal is output, the threshold data of the dark value tables T, , T, are alternately output to the selector S L t.

Next, when scanning the third pixel row, the output of the terminal Q of the D flip-flop FF becomes rQJ as in the first pixel row, so the selector SL scans the first pixel row. Dark value table T, and T! in the same order as the rows of T! is selected and the threshold value data is output to the selector SLI.

Similarly, for the fourth pixel row and above, selector S! , 1 outputs the threshold data of the dark value table T first to the selector S when the number of pixel rows is odd, and outputs the threshold data of the dark value table T first to the selector S when the number of pixel rows is even.
Output to.

The D flip-flop FF is configured to return to the initial clear state by a page clear signal input to the clear terminal after scanning one page is completed and before processing of the next page begins.

The image data B is "000000" to "000100"
J (0th to 4th gradation), the discrimination circuit 12
5 outputs "0". At this time, as described above, the selector SL2 outputs the threshold data from the selector SL (that is, the dark value table T or the dark value data of T2) to the comparator 124.

At this time, the output of the discrimination circuit 126 is r□.

Next is the arithmetic section! 23 is not activated, the image data B is input as is to the comparator 124 as B', and the output signal of the comparator 124 is output as is to the laser scanner 13.

For example, the image data B is roooo.

When θ, as described above, the selector SL transfers the dark value data (that is, the threshold data of the threshold table T or Tt) from the selector SL to the comparator 124.
Output to. However, as shown in Figures 4B and 5B, each dark value table T + , T ! does not store threshold data A such that (M-value data A)≦(image data B), and the threshold data A of all 36 fine pixels of each table T, ,T, is ( Threshold direct data A) > (l
i image data B), at this time, the output signal of the comparator 124 is equal to all fine pixels s, -S4 and SIS (fourth A
, 5A) is "0" while being scanned. Therefore, the laser beam 14 is applied to all the fine pixels 5l-S and the SIS.
is irradiated, the shape of the output halftone dot becomes halftone dot P0 shown in FIG. 4C or FIG. 5C.

Next, when image data B is rooooool, +, the fourth
As shown in Figure B or Figure 5B, the threshold data A that satisfies the dark value data A≦image data B is X.

Y address value ('0IOJ, r101') or (r
micropixel S specified by oroJ, rooo, +)
t, and all other fine pixels S, ~S4
And threshold data A stored in the SIS is A>B. Therefore, the output signal of the comparator 124 is
fij only when l is scanned; otherwise r□. Therefore, all the fine pixels S2 to S except for the fine pixel S1
4 and S15, the shape of the output halftone dot becomes the halftone dot P shown in FIG. 4C or FIG. 5C. Then, image data B is continuously
oool'', the halftone dots P1 of FIG. 4C or FIG. 5C appear alternately from the beginning to the end of each pixel row (row consisting of six fine pixel rows). If the row of each pixel is an odd number, the first halftone dot P1 in that row is the halftone dot P1 in FIG. 5C, and if it is an even number, it is the halftone dot P1 in FIG. 4C.

Next, when image data B is "roooolo", the fourth B
As shown in the figure or FIG. 5B, the threshold data Δ such that dark value data A≦image data B is X.

Y address value (rolOJ, rlolJ), (rol
lJ, rlolJ) or (rolo, 1ro00'')
, (rollJ, '0OOJ), and the threshold direct data A stored in all other fine pixels S, , S, , S, , is A> It is B. Therefore, the output signal of the comparator 124 is
rl only when the fine pixels Sl and S8 are scanned, and
Otherwise, it is "0". Therefore, the fine pixels S+, S
Since all the fine pixels S i+ S 41 S + s except t are irradiated with the laser beam 14, the shape of the output halftone dot becomes the halftone dot P2 shown in FIG. 4C or FIG. 5C.

Then, in the same way, image data B is "000011"
, rooolooJ, the shape of the output halftone dot is
This results in a halftone dot P or P4 shown in FIG. 4C or FIG. 5C.

Further, the image data B is r000101r to r011
111'' (that is, the 5th to 31st gradations), the selector SL selects the interval (direct table T) as described above.
, is output to the comparator 124.

For example, when the image data B is "roolol" (fifth gradation), the dark value data A that becomes the threshold datum 5 image data B is specified by the values of the predetermined X and Y addresses, as shown in FIG. 6B. The threshold value data A is stored in five fine pixels S, and the threshold value data A is stored in all other fine pixels 34 to 532. Therefore, comparator 124
The output signal is rl only when five fine pixels SS are scanned, and is "0" otherwise. Therefore, the laser beam 1 is applied to all the micropixels Sb-53g except for the five micropixels S5.
4 is irradiated, the shape of the output halftone dot becomes halftone dot P shown in FIG. 6C.

Then, in the same way, image data B is roo.

110'' to r011 L L l'', the shapes of the output halftone dots are halftone dots P and P31 shown in FIG. 6C.

Further, the image data B is rloo000J to r100
100'', that is, at the 32nd to 36th gradations, the discrimination circuit 125 outputs ``o''. At this time, as described above, the selector S L z is the selector SL,
The dark value data (that is, the dark value table 1' or the dark value data of T2) is output to the comparator 124.

At this time, the discrimination circuit 126 outputs "1" and operates the calculation section 123.

At this time, the calculation unit +23 calculates the maximum value r of the image data.
100100" (36th gradation), the value of image data B input from
'') is input to the comparator 124 as B'.

At this time, the dark value data A stored in one pixel S+-3n of each dark value table T, T2 as shown in FIGS. 4B and 5B.
is (dark value data A)≦(data B'), and the threshold value data A of the other fine pixel S15 is (dark value data A)>(
data B'). At this time, the output signal of the comparator 124 is "1" while the fine pixels S1 to S4 (see Figures 4A and 5A) are scanned, and the output signal of the remaining fine pixels S+s
(See Figures 4A and 5A) is "0" while being scanned. The output signal of this comparator 124 is the Exo11 circuit EXO
Since it is inverted by R2, the signal input to the laser scanner 13 is "0" while the fine pixels S to S4 are being scanned, and is "1" while all the remaining fine pixels SI5 are being scanned. be.

Therefore, the fine pixels S1 to S4 are irradiated with the laser beam 14, and all the remaining fine pixels S+s are not irradiated with the laser beam 14, so that the shape of the output halftone dot is the halftone dot shown in FIG. 4C or 5C. Point P. becomes.

Then, in the same way, image data B is "100001"
~rlo0100'', the shape of the output halftone dot is
The halftone dots Pff3 to P3& shown in FIG. 4C or FIG. 5C are obtained.

As can be seen from the above description, in this first embodiment, gradation display as shown in FIGS. 1A to 1C is performed.

Next, a second embodiment of the image processing section will be described.

The image processing section 12' shown in FIG. 7 is composed of a font type halftone dot generator. In the description of this second embodiment, the same reference numerals are given to the same components as in the first embodiment, and redundant detailed explanation will be omitted.

As in the first embodiment, the image processing section 12' shown in FIG.
It is composed of 6 micropixels (see Figure 8A), and in the 0th gradation, all the micropixels are uncolored, and in the 1st gradation, 1 micropixel is colored and the other 35 micropixels are colored. The display is configured such that the pixels are not colored, and all the fine pixels are colored at the 36th gradation, thereby displaying a total of 37 gradations. The 0th to 4th gradations and the 32nd to 36th gradations are the first to 36th gradations.
It is configured to perform gradation display using halftone dots having exactly the same shape as in the embodiment. Further, the timing charts of each actuation signal (page clear signal, X reset signal, etc.) are the same as those shown in FIGS. 3B and 3C.

Further, the image processing section 12' includes a total of two font tables T4 and T.

Then, in the font table T4, the halftone dot P0 shown in FIG. 4C is added to the 36 fine pixels Sll to 5ai (see FIG. 8B) specified by the X and Y addresses according to the 0th to 4th gradations. - Data for generating halftone dots identical to P4 (see FIG. 9) are stored. As will be explained in detail later, by reversing the data in FIG.
The halftone dot p3t- shown in FIG. 4C at ~36 gradations
The same halftone dots as P3h are generated.

In addition, the font table T has the 36 fine pixels $1 to 5bh (see FIG. 8B) specified by the X and Y addresses, and the mesh shown in FIG. Point P. -Data for generating Plfl (see FIG. 10A) is stored. As will be explained in detail later, by inverting the data in FIG. 10A,
Halftone dots P19 to P shown in FIG. 10C at ~36 gradations
3& is generated. , and halftone dots P0 to P4 and P3□ to P3& generated by this font table Ts are set to have exactly the same shape as the halftone dots shown in FIG. 5C described above.

The image data B passes through the calculation section 123 and is input to the font tables T, , T, as well as to the discrimination circuits 125 and 128. Font table T a ,
Ts is the input data B' (fine pixel S I
It is configured such that data from I to sbh is read out. As a result, from the font table T-, Ts, the halftone dot P specified by the data B', (,=0.12.・
. . , 36) are read out.

The data from the font tables T, , T5 are input to the first selector SL, which selector SL,
When the output of the XO11 circuit EXORI is "1", the data from the font table T4 is output to the second selector SL, and when it is "0", the output from the font table T is output to the selector S L z. .

The discrimination circuit 1.25 outputs "1" when 4<B<32, and the discrimination circuit 12B outputs "1" when B>18.

The selector SL is configured so that the output of the discrimination circuit 125 is "
1'', the data A from the font table T is output to the laser scanner 13 through the circuit EXOR2, and when rQJ, the data A from the selector SL is output to the laser scanner 13 through the circuit EXOR2. is configured to print. The laser scanner 13 emits a laser beam 14 when the human power signal is "1".
It is configured to turn off and turn on when OJ is on.

Further, when the output signal of the discrimination circuit 128 is "1",
The calculation unit 123 outputs a value obtained by subtracting the value of the input image data B from the maximum value of the image data B, and otherwise outputs the value as is.

Then, when the font memory 123 is accessed using the X, Y address and data B' as the address, the data read out by the EXo++ circuit EXOR2 is "0" and "0" when the discrimination circuit 128 outputs "1". 1"
is inverted, otherwise it is output as is. This data is input to the laser scanner 13, and the laser scanner 13 is configured to turn off the laser beam 14 when the input signal is "1" and turn it on when the input signal is "0".

Next, the operation of the second embodiment of the present invention having the above-mentioned configuration will be explained mainly with reference to FIGS.

The selector SL of this second embodiment first outputs the data of the font table T5 to the selector SL when the number of rows of pixels is odd, and when the number of rows of pixels is even, it first outputs the data of the font table T to the selector SLt. Output. After that, the selector SL repeatedly selects the data of the font tables T 4 and T s and outputs it to the selector SL.

The D flip-flop FF is configured to return to the initial clear state by a page clear signal input to a clear terminal after scanning one page and before starting processing of the next page.

The image data B is r000000J~[000100
At the time of J, the discrimination circuit 12B outputs "0", so the image data B is input as is to the font tables T, , T, as B'. The fine pixel S specified by this data B' and the X, Y address signals,
The data stored in ~S66 is read out and input to the first selector SL1. Selector SL is Eχo8
The data of the font table T a + or T is output to the second selector SL in accordance with the output of the circuit. At this time, the discrimination circuit 125 outputs "OJ".

At this time, as described above, the selector SL-O transfers the data from the selector SL+ (that is, the data of the font table T4 or T) to the EX, 1 circuit E.
Output to XOR2. At this time, the output of the discrimination circuit 128 is "0", and the data output from the selector SL is output to the laser scanner 13 as is.

For example, the image data B is roooo.

O'', as shown in FIG. 9 or 10A, the total fine pixels Sll to T of the font tables T4 and T are
A value of "0" is stored in shh.

Therefore, the data read from the font table T4 or Ts remains "0" while all the fine pixels S++-5ii (see FIG. 8A) are scanned.

Therefore, the laser beam 1 is applied to all the fine pixels Sll to Sl,th.
4 is irradiated, the shape of the output halftone dot is the 4th C.
Halftone dot P shown in Figure or Figure 10B. becomes.

Next, when the image data B is "000001", the value "l" is stored as shown in FIG. 9 or FIG. 10A because the values of the X and Y addresses are (roto), respectively.
, rlol") or ("010J,'000"). Therefore, font table T4 or T,
The data that is successively output from font table T4 is scanned when fine pixel S&3 of font table T4 or fine pixel S13 of TS is scanned.
1", otherwise "0". Therefore, the fine pixel S 63 of the font table T4 or the fine pixel S of T,
Since the laser beam 14 is irradiated to all micropixels except 1,
The shape of the output halftone dot is the halftone dot P shown in FIG. 4C or FIG. 10B.

Then, in the same way, the value of image data B is "00001
0J to r000100'', the shapes of the output halftone dots are P2 to P4 shown in FIG. 4C or FIG. 10B.

Further, the image data B is “roooolol”~rolo
o10. ．． + (i.e., the 5th to 18th gradations), the discrimination circuit 128 outputs "0", so the image data B is stored as B' in the font tables T, , T.
, and the EXoi circuit EXOR2 outputs the output signal of the selector SL to the laser scanner 13 as it is. Also, at this time, since the output of the discrimination circuit 125 becomes "l", the selector SL2 transfers the data successively output from the font table T to the EXom circuit EXO.
Output to R2.

For example, when the image data B is rQOOlolJ (fifth gradation), as shown in FIG.
z4. S43. S44. Sst (8th A, 8B
(see figure) has a value of "1" stored therein, and all other fine pixels have a value of "0" stored therein.

Therefore, the data successively output from T is the fine pixel S 33r S 34r "' 4 of the font table T.
j, S44rS51 is "1" when scanned, otherwise it is [0]. Therefore, the font table T
.

Fine pixel S33+ S34+ S43* S4
4+ SS3 is excluded (since all the fine pixels are irradiated with the laser beam 14, the shape of the output halftone dot is halftone dot P shown in FIG. 10B).

Then, in the same way, the value of image data B is "00011
0'' to ro10010'', the shape of the output halftone dot becomes P& to P Il+ shown in FIG. 10B.

In addition, the image data B is
1114 (i.e., 19th to 31st gradations),
Since the discrimination circuit 12B outputs "l", the arithmetic unit 123 operates. That is, the calculation unit 123 sets the value obtained by subtracting the value of the input image data B from the maximum value "100Iot" (36th gradation) of the image data B as B' and sets the value in the font table T4. Input Ts and Eχo
11 circuit EXOR2 inverts the output signal of selector S L z and outputs it to laser scanner 13 . Also, at this time, the output of the discrimination circuit 125 becomes "1", so
Selector SL is the font table T.

The data successively output from EXO11 is outputted to EXOR2.

For example, when the image data B is "rolooll" (19th gradation), the calculation unit 123 calculates the maximum value r1 of the image data B.
00100" (36th gradation) to rollool"
(19th gradation), i.e. '0100OIJ
(17th gradation) is input into the font table T as data B'.

Therefore, from the font table T, dot Pl? However, this data is inverted by the EXO circuit EXOR2, so the data that generates the
Thus, halftone dot P19 (see FIG. 10c), which is the inversion of halftone dot PI7, is reproduced.

Then, in the same way, the value of image data B is "01010
0, (20th floor! II) to ro11111'' (31st gradation), the shape of the output halftone dot is P2° to Pal shown in FIG. 10C.

Also, the image data B is rlooooo”~r100
100'' (that is, the 32nd to 36th gradations), the discrimination circuit 128 outputs ``1'', so the arithmetic unit 123 operates. That is, the calculation unit 123 inputs the value obtained by subtracting the value of the input image data B from the maximum value "100100" (36th gradation) as B' into the font tables T, , T, and EX,
, the circuit EXOR2 inverts the output signal of the selector S L 2 and outputs it to the laser scanner 13. Further, at this time, since the output of the discrimination circuit 125 becomes "0", the selector SLz outputs the data input from the selector SL to the EXoi circuit EXOR2.

For example, when the image data B is "100000" (32nd gradation), the calculation unit 123 calculates the maximum value '1' of the image data B.
00100J (36th gradation) to rioooooJ
(32nd gradation), that is, rooolo
o'' (fourth gradation) is input into the font tables T a and T s as data B'.

Accordingly, data for generating halftone dots P in FIGS. 4C and 10B are read from font tables 1-4 and T, respectively. And font table T
, and T, are alternately selected pixel by pixel by the selector SL.
, is output to.

Since the output signal of the discrimination circuit 125 is "0" in this case, the selector SL outputs the output data of the selector SL to the EXo* circuit EXOR2.

The data for generating the halftone dot P4 of each of the font tables T4 and T is E X o *Circuit EXO
Since the halftone dot P3Z is inverted at R2, the halftone dot P3Z (see FIG. 1OC), which is an inverted halftone dot P4, is eventually reproduced by the laser scanner 13.

Then, in the same way, the value of image data B is set to "10000".
1" (33rd gradation) to "rlo0100" (36th gradation), the output halftone dot shape is P shown in FIG. 10C. ~ psb.

Therefore, by setting the data stored in the font tables T4 and T as shown in FIGS. 9 and 10A, the 4C
Halftone dots P0 to P4 shown in the figure. P, ~P3 and 10B
, halftone dot P shown in the IOC diagram. ~Pff& is output, 37
The stages are displayed.

In the halftone dots of this second embodiment, when the ratio of the colored micropixels to all pixels is 0.5 or more, the colored micropixels and the uncolored micropixels of the halftone dots when the ratio is 0.5 or less are reversed. Therefore, the halftone dots PI9 to P36 are formed by halftone dots PIT to P0, respectively.
It can be formed from the data of Therefore, the font table T4 contains dots P0 to P4, and the font table T contains halftone dots P.

Since it is only necessary to store the data of ~p+t and P11, the capacity of the font memory, which requires a large capacity, can be approximately halved.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above, and various design changes can be made without departing from the scope of the invention described in the claims. Is possible.

For example, in the first or second embodiment, the calculation unit 1
23 and EXOR circuit EX0R2 may be omitted, and the darkness values or data corresponding to all halftone dots may be stored in the darkness value table or font table.

In this case, halftone dots PI9 to P3 have halftone dots P0 to Pi11.
It is displayed by the same effect as. In addition, in the example,
Although each pixel is formed by a 6×6 matrix with a screen angle of 0° and each pixel is formed as an element, and 37 gradations are displayed, other matrix sizes, other screen angles, and other gradations are possible. It is also possible to display the key.

In that case, a configuration with a bit number corresponding to those numbers may be used. Furthermore, it is also possible to set the number of bits to 8 bits, use general-purpose components that are easily available, and use the required number of lower or upper bits. Furthermore, the micropixels forming the pixels may have other shapes instead of a square or rectangular matrix.

In the above embodiment, the case of monochrome display was shown, but it is also possible to apply to each color of color display, and although the case of application to a digital copying machine was shown, it is also possible to apply to a printer. It is. Furthermore, the present invention can be applied to other image output devices as long as they are capable of displaying gradations using halftone dots. Moreover, various shapes can be adopted as the shape of the halftone dots.

C9 Effects of the Invention According to the gradation display method in the image display device of the present invention having the above-described configuration, when displaying a low density gradation of a predetermined level or higher, colored fine pixels of a plurality of adjacent pixels are Since they are connected to each other, the cluster of colored fine pixels that display low density gradations becomes large. Therefore, it becomes possible to stably color small micropixels, and it becomes possible to stably reproduce low density gradations. In addition, when displaying high-density gradations of a predetermined level or higher, uncolored micropixels of adjacent pixels are connected to each other, so that when displaying high-density gradations, uncolored micropixels accumulate. becomes larger. Therefore, it becomes possible to stably leave small fine pixels uncolored, and it becomes possible to stably reproduce high-density gradations.

[Brief explanation of the drawing]

Figure 1A-IC is an explanatory diagram of the reproduced image of the first embodiment;
The figure shows the first embodiment (an embodiment applied to a digital copying machine)
FIG. 3A is an explanatory diagram of the configuration of the image processing section of the first embodiment, FIGS. 3B and 3C are timing charts of the respective actuation signals shown in FIG. 3A, and FIG. 4A is the same diagram. FIG. 4B is a diagram showing the relationship between the fine pixels constituting the pixel of the first embodiment and the dark value of the dark value table T1 for the fine pixel and the X, Y address. FIG. 4C is a diagram showing the relationship between the stored dark value data and the X and Y addresses. FIG. 4C is a diagram showing halftone dots generated in the dark value table T1 or the font table 1 of the second embodiment. FIG. FIG. 5B is a diagram showing the relationship between the fine pixels constituting the pixel of the first embodiment and the dark value of the dark value Chiful T8 for the fine pixel and the X and Y addresses, and FIG. 5B is the dark value table T of the first embodiment.
FIG. 5C is a diagram showing the halftone dots generated in the dark value table Tt, and FIG. 6A is a diagram illustrating the pixels of the first embodiment. The fine pixel and the threshold value of the dark value table T for that fine pixel and X,
FIG. 6B is a diagram showing the relationship between the dark value data stored in the dark value table T3 of the first embodiment and the X and Y addresses, and FIG. 6C is a diagram showing the relationship between the dark value table T3 of the first embodiment. ,
FIG. 7 is an explanatory diagram of the configuration of the image processing section of the second embodiment of the present invention, and FIG. 8A is a diagram showing the arrangement of fine pixels forming the pixels of the second embodiment. , FIG. 8B is a diagram showing the relationship between the fine pixels and the X, Y addresses, and FIG. 9 is a diagram showing the relationship between the data stored in the font table T4 of the second embodiment and the X, Y addresses. Figure 10A is a diagram showing the relationship between the data stored in the font table T5 and the X and Y addresses of the second embodiment, Figure 10B, IOc
The figure shows halftone dots generated in the font table T, FIGS. 11 and 12 are explanatory diagrams of the prior art, FIG. 11 is a characteristic diagram of output density with respect to input halftone dot area ratio B, and FIGS. FIG. 12B is a diagram showing halftone dot shapes of low gradation density and high gradation density, respectively. P0~P36...halftone dot, S1~S3b+ Sll~
S 66... fine pixel

Claims (2)

[Claims] (1) Divide the image into pixels with a minute area, and divide the pixels into fine pixels (S_1 to S_3_6; S_1_
1 to S_6_6), and the colored micropixels in the pixel form halftone dots (P_0 to P_3_6), and the gradation is displayed according to the ratio of the colored micropixels to the total micropixels, and the colored micropixels are divided into halftone dots (P_0 to P_3_6). In a gradation display method in an image output device in which pixels are determined corresponding to each gradation, when displaying a low density gradation below a predetermined level, colored fine pixels (S_1 to S_4) of a plurality of adjacent pixels are used. ;S_1
_3, S_1_4, S_1_5, S_2_3, S_5_
4, S_6_2, S_6_3, S_6_4) are connected to each other. (2) Divide the image into pixels with a minute area, and divide the pixels into fine pixels (S_1 to S_3_6; S_1_
1 to S_6_6), and the colored micropixels in the pixel form halftone dots (P_0 to P_3_6), and the gradation is displayed according to the ratio of the colored micropixels to the total micropixels, and the colored micropixels are divided into halftone dots (P_0 to P_3_6). In a gradation display method in an image output device in which pixels are determined corresponding to each gradation, when displaying a high density gradation of a predetermined level or higher, a plurality of adjacent uncolored fine pixels (S_3_3 to S_3_
6; S_1_3, S_1_4, S_1_5, S_2_3
, S_5_4, S_6_2, S_6_3, S_6_4)
A gradation display method characterized by connecting each other.