JPH09247438A - Multi-gradation printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multi-gradation printer extremely reduced in the deterioration of image quality by minimizing the deterioration in the effective resolution. SOLUTION: Print data are made up of k-bit picture element gradation data and i-bit picture element size data. A k-bit extract means 2 extracts the k-bit picture element gradation data from the print data and the extracted data are compares with a dither matrix 5 at a comparator 6. As the comparison result, a laser diode on/off signal is generated. On the other hand, an i-bit extract means 3 extracts the i-bit picture element size data from the print data and gives the data to a selector 9, which selects an output corresponding to the picture element size data from an output of a picture element size control circuit 8. The selector 9 outputs a picture element size control signal (b). When i-bits are 2 bits, a 1-dot is expressed by 4 kinds of sizes of dots. As other embodiment, one dot is expressed by plural small dots.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-gradation printing apparatus, and more particularly, it is possible to perform multi-gradation printing while minimizing the decrease in effective resolution and the deterioration of image quality. The present invention relates to a multi-tone printing device.

[0002]

2. Description of the Related Art In recent years, a laser beam printer (LBP) using an electrophotographic technique and a laser exposure technique has rapidly become popular. LBP is superior to other printing means in terms of printing speed and printing quality, but in principle,
Since the toner adhesion to the photoconductor is controlled by turning on / off the laser beam, only binary recording can be performed.

Various techniques have been disclosed for performing multi-gradation printing using this LBP. A schematic configuration of an example of a conventional LBP will be described with reference to the block diagram of FIG. The LBP 50 is composed of two modules: a controller 51 that receives print data from the host computer 53 and converts it into a printable data format, and a print engine 52 that receives the data from the controller 51 and actually prints on paper. ing. Here, the print engine 52 is a part that executes an electrophotographic process, and the image signal received by the print engine 52 is binary (= 1 bit) per pixel, which only controls the on / off of the laser beam. Signal.

Next, an example of the configuration of the controller 51 will be described with reference to the block diagram of FIG. The print data received by the host interface 54 is directly stored in the image memory 56 when the print data is in a bitmap format that can be received by the print engine 52. However, when the host interface 54 receives the code information, it is stored in the image memory 56 after being converted into a bitmap format by the image expanding unit 55.

If the bitmap data stored in the image memory 56 has a format of 1 bit per pixel, the next halftone processor 57 does not perform any processing on the bitmap data. The bitmap data is output to the print engine 52 via the engine interface 58. When the print engine 52 receives the bit map data, it controls on / off of the laser beam to print on the print paper.

On the other hand, when the bitmap data stored in the image memory 56 has a format having a certain number of bits of gradation information, the halftone processing unit 57 converts the data into a format that the print engine 52 can receive. Must. In general, when the print engine 52 that prints data having a density expression dynamic range of m bits has only n bits (= 2 ⁿ gradations) expression capability, the reproduction engine dynamic range of the print engine 52 is the same as the input data. If the number of data bits is reduced (m → n, where m> n), the upper and lower limits of the dynamic range do not change, and the gradation of the intermediate density expressed between them decreases. . For example, FIG. 21 shows an example in which m = 8, n = 2 (4 gradation printing) and n = 4 (16 gradation printing). That is, although the dynamic range of the print engine 52 is 0 to 255,
When the print engine 52 has only 2-bit expression capability, the gradation to be expressed is 4 gradations. Also, 4
If the bit has only the expression capability, the gradation to be expressed is 16 gradations. Pseudo reproduction of the reproduction gradation of the intermediate density using the area gradation technique is a process called halftone generation.

In the LBP that can only represent binary values, the density scale is replaced with the occupied area ratio of the color-developing body (toner) on the paper to artificially reproduce the intermediate density. To achieve that,
There are (1) density pattern method, (2) systematic dither method, and (3) error diffusion method. The density pattern method includes a method of changing the print dot diameter as shown in FIG. 22 (a) and a method of changing the number of dots per unit area as shown in FIG. 22 (b). When the dot diameter is fixed, the intermediate density is reproduced by the method shown in Fig. 2 (b), but the effective resolution of the print image is as shown below. The resolution will decrease.

Effective resolution = (resolution of print engine) / (dot matrix size used for gradation expression) As shown in FIG. 23, the systematic dither method passes through a filter of a certain pattern called a dither matrix. This is a method of binarizing multi-value gradation data. In the figure,
The case of using a 4 × 4 dither matrix is shown. The input image data is fetched from the input image buffer 61, while the threshold value is fetched from the dither matrix 62 sequentially by the switch means 63. The input image data fetched from the input image buffer 61 is compared with the density value of one cell of the dither matrix corresponding to each dot by the comparator 64, and only when the input image data density is high (dark), the printer engine A signal for turning on the laser beam of 65 is output. As a result, toner adheres to the corresponding portion on the photoconductor, and dots are printed on the paper 66. The higher the density of the input image data, the more dot-matrix is printed, thereby reproducing the intermediate density. As the dither matrix, there are a Bayer type, a halftone type, a fattening type and the like.

Next, according to the error diffusion method, the gradation error that occurs when determining 0 or 1 of each pixel, that is, the density value of the actual data and the determined density value (0 or 255)
This is a method of distributing the difference between and to unprocessed peripheral pixels. More specifically, referring to FIG. 24, the error Ei when the image data Gcom is binarized in the line buffer 71.
(= | Gcom-Gout |) is stored, the error Ei is taken out from the line buffer 71 before binarization of the input target pixel Gin, the load is calculated by the load calculator 73, and the adder 74 is used.
Then, binarization processing is performed after addition to the input target pixel Gin. By repeating this process, the pixel density truncated at a certain pixel is carried over to the peripheral pixels and reproduced, and when viewed in a certain size area, the intermediate density value of the input image data is reproduced almost faithfully. .

[0010]

However, among the density pattern methods, the method of changing the print dot diameter increases the number of gradations that can be expressed, which complicates the circuit configuration and stabilizes the linear density gradation. Will be difficult to obtain. Also, in the method of fixing the dot diameter and changing the number of dots per unit area, if the unit area size (number of dots) is increased in order to increase the number of gradations that can be expressed, the effective resolution will decrease. There was a problem. Similarly, in the systematic dither method, when the dither matrix is increased, the effective resolution is lowered, and a pattern (texture) peculiar to dither appears in the binarized print result, which causes a problem that the image quality is deteriorated. Further, the error diffusion method has a problem that the processing procedure is complicated, the circuit scale is large, and high-speed processing is difficult.

An object of the present invention is to eliminate the above-mentioned problems of the prior art and to provide a multi-gradation printing apparatus in which the deterioration of the effective resolution is minimized and the deterioration of the image quality is extremely reduced. Another object of the present invention is to provide a multi-gradation printing device capable of smoothly reproducing a gradation change in a light density region which is sensitive to a change in human perception characteristics.

[0012]

In order to achieve the above object, the present invention provides a multi-gradation printing apparatus having a printing means capable of marking 2 ⁱ (i is a positive integer) gradation,
A unit for inputting print data of j bits (j is a positive integer j> i) per pixel, and a pixel of k bits (k is a positive integer, j = k + i) from the input print data. A means for extracting gradation data is compared with the extracted k-bit pixel gradation data and corresponding data of matrix data representing a threshold value, and an ON / OFF signal of the drawing device is output according to the magnitude. Comparing means, means for extracting the i-bit pixel dimension data from the input print data, and 2 ⁱ kinds of pixel dimensions determined by the extracted i-bit pixel dimension data. Means for outputting one pixel size control signal and ON / ON output from the comparing means and the pixel size control signal output means
A means for controlling ON / OFF of the drawing device and its ON time by an OFF signal and a pixel size control signal is provided, and data of 2 ^j gradation is printed.
There is a feature.

According to the present invention, the i pixel is selected for specific pixel gradation data of the k-bit pixel gradation data.
A second feature is that bit pixel size data is validated and only the specific pixel gradation data is printed in a size represented by the i bit pixel size data. Further, the present invention provides a multi-gradation printing apparatus having a printing unit capable of printing at least two types of dots, a full size dot and a smaller size dot.
Matrix data having two kinds of threshold values, a threshold value of 2 and a second threshold value smaller than the threshold value, and means for outputting pixel size control signals of full size and smaller size. When the gradation of the multi-gradation print data is larger than a predetermined value, it is compared with the first threshold value of the matrix data, and when it is less than the predetermined value, the second threshold value of the matrix data is compared. A pixel size control signal output means for outputting a full size pixel size control signal when the first threshold value is selected, and the second threshold value. The third feature is that the pixel size control signal of the small size is output when is selected.

Further, according to the present invention, in a multi-gradation printing apparatus having a printing means capable of printing at least two types of dots of a full size dot and a dot of a size smaller than that, a first gradation is provided in one cell. Matrix data having two kinds of threshold values, a threshold value and a second threshold value smaller than the threshold value, and means for outputting a pixel size control signal of full size and smaller size, and a matrix of input data. Comparing means for comparing the gradation print data with the first and second threshold values is provided, and the pixel size control signal output means is full when the print data is equal to or more than the first threshold value. A pixel size control signal of a size is output, and when the print data is smaller than the first threshold value and equal to or larger than the second threshold value, a pixel size control signal of a size smaller than the full size is output. There is a fourth feature in that so as to force.

According to the first and second characteristics, the concentration change in the low concentration range can be increased in multiple stages. According to the third feature, the number of pixels at low density can be increased to a multiple of the number of pixels without changing the overall density, and the expressiveness of the entire density range can be increased. Like Further, according to the fourth feature, it is possible to reduce the density change in the low density range and increase the density change in the high density range.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing the configuration of one embodiment of the present invention. Print data is input from the input terminal 1. In the present embodiment, as shown in FIG. 2A, the print data is composed of, for example, 6 bits in total, and upper 4 bits are pixel gradation data and lower 2 bits are pixel size control data. Is used for. In the present invention, the pixel gradation data is not limited to the upper 4 bits and the pixel size control data, and the lower 2 bits. Therefore, in the following description, the pixel gradation data will be referred to as k bits, and the pixel size control data will be referred to as k bits. Will be called i bits.
The k-bit extraction means 2 in FIG. 1 extracts k-bit pixel gradation data from the print data. Further, the i-bit extraction means 3 extracts i-bit pixel size control data from the print data.

The dither matrix 5 is of the Bayer type, and the comparator 6 compares the pixel gradation data y extracted by the k-bit extraction means 2 with the threshold value x selected from the dither matrix 5. . If x> y, an L level signal for turning off the laser diode is turned on,
If x ≦ y, a signal for turning on the lighting is output.
As shown in FIG. 3, the laser diode drive circuit 7 includes a resistor 7a, a transistor 7b, a transistor 7b,
7c. 7d is a laser diode.

The pixel size control circuit 8 outputs pixel size control signals of four different sizes. The delay amounts of the delay element 1, the delay element 2 and the delay element 3 in the pixel size control circuit 8 are
Delay element 1 <delay element 2 <delay element 3. The selector 9 selects any one of the 11 terminal, 10 terminal, 01 terminal and 00 terminal by the i bit extracted by the i bit extracting means 3 and connects the selected terminal and the Y terminal which is an output terminal. To do. The pixel size control circuit 8 outputs a full dot pixel size control signal to the 11 terminal of the selector 9. Further, a pixel size control signal that sequentially becomes large to small is output to the ten terminal, 01 terminal, and 00 terminal. This means that the delay element 1 <the delay element 2 <
It is clear from the relationship of the delay element 3. The pixel size control signal b output from the selector 9 is input to the laser diode drive circuit 7.

To make the explanation easier to understand, if the print data input to the input terminal 1 is "001000" shown in FIG. 2B for all 4 × 4 pixels, the print data is The upper 4 bits of "0010" are k
It is extracted by the bit extraction means 2 and input to the comparator 6 as pixel gradation data y. On the other hand, the lower two bits “00” of the print data are extracted by the i-bit extraction means 3 and input to the A and B terminals of the selector 9. As a result, the selector 9
Connects the 00 terminal to the Y terminal.

Since the value of the pixel gradation data y is "2" in the decimal system, the comparator 6 outputs an H level ON signal when x≤2. On the other hand, the pixel size control signal b output from the selector 9 has the smallest dot size. As a result, the pixel gradation data y of "0010" (= 2) is reproduced as shown in FIG. 4 (b).

Next, assuming that the print data for all 4 × 4 pixels is “001001” as shown in FIG. 2 (c), the same operation as above is reproduced as shown in FIG. 4 (c). To be done. Similarly, the print data is as shown in FIG.
If it is "001010", it is reproduced as shown in FIG. 4 (d), and the print data is as shown in FIG. 2 (e).
If it is "001011", it will be reproduced as shown in FIG. As described above, according to this embodiment, 16 (2 ⁴ ) which can be originally expressed by a 4 × 4 matrix is used.
It is possible to express each gradation of 16 levels beyond the gradation by using a density that is further divided into four levels, and it is possible to express a multi-gradation density that minimizes a decrease in effective resolution. The pixel size control data (i bit) of the print data
It is obvious that other pixel gradation densities can also be expressed by four levels of density by using

Next, a second embodiment of the present invention will be described with reference to FIG. This embodiment is different from that of FIG. 1 in that the dither matrix 5 has a spiral shape (Fatten type).
The ing type) dither matrix 5a is used, and the i-bit data extracted by the i-bit extracting means is validated only when the comparator 6 outputs x = y.

To make the description easier to understand, if the print data input to the input terminal 1 is 4 × 4 pixels, for example, “001000” shown in FIG. 2B, the comparator 6 outputs “0010”. The pixel grayscale data y of “” and the individual values of the dither matrix 5a are compared. If x <y, an H-level ON signal is output, and if x = y, an H-level ON signal is output. When a signal of x = y is output from the comparator 6, it is converted into an L level by the inverter 10 and enters the OR gate 11. As a result, the i-bit extracted by the i-bit extracting means 3 becomes valid, and the selector 9 selects one from the four types of pixel size control signals output from the pixel size control circuit 8 based on the i-bit. On the other hand, when x and y are not equal, the output of the inverter 10 becomes H level, so the selector 9 always selects the 11th terminal, that is, the pixel size control signal of full dot size.

In the above example, since the gradation data y of 4 × 4 pixels has a decimal size of “2” and the pixel size control data is “00”, this is used as a dot pattern. When reproduced, it will look like Fig. 6 (b). Similarly, if the print data of 4 × 4 pixels input to the input terminal 1 is “001001” shown in FIG. 2C, the reproduced dot pattern will be as shown in FIG. 6C. Further, if the print data input to the input terminal 1 is "001010" and "001011" shown in FIGS. 2D and 2E, the reproduced dot patterns are shown in FIG.
It becomes like (d) and (e).

As described above, according to the present embodiment, by using the pixel size control data (i-bit) of the print data, each density can be displayed in four steps, and the effective resolution can be displayed. It is possible to express multi-tone density with a minimum reduction. Next, a third embodiment of the present invention will be described with reference to FIG. This embodiment is
By the density pattern method, multi-tone 1 pixel input is converted into a 4 × 4 matrix. In the figure, 21 is a comparator, 22 is a threshold register, 23 is an inverter, 24 is a full dot-intermediate dot size selecting means, 5b is the dither matrix of FIG. 8 or FIG. The same as or equivalent to FIG. 1 is shown. As shown in FIG. 8 or 10, the dither matrix 5b has two threshold values a in one cell,
b. The selection of the threshold values a and b depends on the output of the comparator 21 in FIG. That is, the threshold value a is selected when the output of the comparator 21 is H level, and the threshold value b is selected when the output of the comparator 21 is L level.

Next, the operation of FIG. 7 when the dither matrix 5b shown in FIG. 8 is used will be described. Now, if "4" is set in the threshold value setting register 22 and print data "000011" is input to the input terminal 1, the output of the comparator 21 becomes H level, and the switch 25 switches the dither matrix 5b. Select a. As a result, the pixel gradation data y “0000” of the print data is 1 of the dither matrix 5b sequentially input to the comparator 6.
The six x values are compared sequentially. Further, when the output of the comparator 21 becomes H level, the selector 24a of the full dot-intermediate dot size selection means 24 selects the terminal 1. That is, the selector 24a selects the intermediate dot size and supplies it to the laser diode drive circuit 7.

The comparator 6 uses the pixel gradation data y "000".
0 ”is sequentially compared with a data of the dither matrix 5b, and when x ≦ y, an ON signal is sent to the laser diode drive circuit 7. When this is reproduced in a dot pattern,
As shown in (b), the pattern has four intermediate dot sizes. The dot pattern shown in FIG. 3A is based on the conventional method. Also, FIGS. 6C, 6E, and 6G are dot patterns according to the conventional method.

Next, the print data "0" is input to the input terminal 1 of FIG.
"00111" is input, the a data is similarly selected in the dither matrix 5b, and the selector 24a operates in the terminal 1
Select As a result, the reproduced dot pattern is
As shown in FIG. 9 (d). That is, in the conventional method, a pattern represented by two full dot sizes as shown in FIG. 7C becomes a pattern with eight intermediate dot sizes as shown in FIG. Similarly, the input terminal 1 of FIG.
When the print data “001011” is input to, the dot pattern reproduced is as shown in FIG. 9F, and when the print data “001111” is input,
The reproduced dot pattern is as shown in FIG. 9 (h).

Next, the print data "0100" is input to the input terminal 1.
11 "is input, the output of the comparator 21 becomes L level, and the switch 25 selects the b data of the dither matrix 5b. Further, the selector 24a of the full dot-intermediate dot size selection means 24 selects the terminal 0. That is, the selector 24 a selects the full dot size and supplies it to the laser diode drive circuit 7. As a result, the reproduced dot pattern is represented by the conventional full dot size. When the pixel gradation data y of the print data is "0100" or more, it is obvious that the conventional full dot size is used.

In this embodiment, the dither matrix 5b
As a matrix of a swirling type (Fattening type) is used as the above, according to the conventional method, a pixel exists only in the center when the density is low, and as a result, an image with coarse grain size is obtained. However, in the present embodiment, the number of pixels having the intermediate density is increased four times and the pixel is output only when the density is low where the pixels are present in a part of the matrix, so that it is possible to prevent the granularity from becoming coarse. However, even if the number of pixels is quadrupled, each pixel has an intermediate density, and the overall density is the same as in the conventional method.

When the dither matrix 5b shown in FIG. 7 is used as the dither matrix 5b shown in FIG. 7, the dot pattern reproduced by the apparatus shown in FIG. 7 is obtained according to the value of the print data input to the input terminal 1. 11 (b), (d), (f)
And (h). In addition, (a) of the figure,
The dot patterns of (c), (e) and (g) are dot patterns obtained by the conventional method. When the pixel gradation data y of the print data is “0100” or more, it is obvious that the conventional full dot size is used. Also in this embodiment, the number of pixels at low density can be quadrupled without changing the overall density, and as in the case of FIG. 9, it is possible to prevent the granularity from decreasing.

Next, a fourth embodiment of the present invention will be described with reference to FIGS. 7 and 12. This embodiment is different from FIG. 7 in that the on / off signal generating means 30 of FIG. 7 is replaced with that of FIG. 12, and other configurations are the same as or equivalent to those of FIG. 7. ON / OFF signal generating means 30 of the present embodiment
Is composed of a matrix 30a and first and second comparators 30b and 30c as shown.
As the matrix 30a, for example, the one shown in FIG. 13 is used.

The comparator 30b compares the pixel gradation data y of the print data with the a value of the matrix 30a, and y ≧ a
If so, an ON signal is output to the laser diode drive circuit 7. Further, the comparator 30c compares the pixel gradation data y of the print data with the a value of the matrix 30a, and y ≧
If b, an L level signal is output, and if y <b, an H level signal is output. When the L level signal is output from the comparator 30c, the H level signal is input to the SEL terminal of the selector 24a to select the full dot size. On the contrary, when the H-level signal is output from the comparator 30c,
An L level signal is input to the SEL terminal of the selector 24a to select an intermediate dot size.

As a result, according to the present embodiment, as shown in FIG. 14, the incoming data y is expressed by an intermediate dot size when a <y <b, and a full dot when y ≧ b. It will be expressed in size. Therefore, the dot pattern reproduced by the present embodiment is as shown in FIG. 15, and in the low density region, that is, in the case of 0 ≦ y <6, one pixel is expressed by the pixel size of two stages, and in the medium density region, that is, 7 ≦. y <
In 11, the number of full dot pixels is increased by one pixel for each increment of the density value of 1.
In the case of ≤y <15, the number of full dot pixels is increased by 2 pixels with respect to the increase 1 of the density value.

Therefore, according to the present embodiment, FIG.
As shown in the characteristic p of 1., it is possible to reduce the density change in the low density range and increase the density change in the high density range. The characteristic p is a density change according to the conventional method. As a result, it becomes possible to reproduce a natural image suitable for human perception characteristics.

Next, a fifth embodiment of the present invention will be described with reference to FIGS. 17 and 18. FIG. 17 is a block diagram showing the configuration of the main part of this embodiment, and FIG. 18 is a waveform diagram of the main part. In this embodiment, the D / A converter 40 converts the pixel size data into the voltage level m of the analog signal.
On the other hand, the reference waveform oscillating circuit 41 uses the pixel clock (V-C
LK) to generate a triangular wave n. The voltage level m and the triangular wave n are compared by the comparator 42, and the comparator 4
2 outputs a signal p for turning on the laser diode only when the voltage level m ≦ triangle wave n. The offset voltage generation circuit 43 is a circuit that generates a DC voltage for adjusting the offset value of the comparator 42. According to this embodiment, as compared with the first embodiment, when the number of bits of pixel size data is large, it is possible to perform accurate pixel size control with a simpler circuit.

[0037]

As is apparent from the above description, according to the inventions of claims 1 and 2, the print data is composed of k-bit pixel gradation data and i-bit pixel size data. , The pixel gradation data can be expressed with 2 ⁱ different densities. Therefore, it is possible to reduce the change in the low-density pixel gradation data, and it is possible to smoothly reproduce the gradation change in the light density region that is sensitive to the change in human perception characteristics. Become.

According to the third aspect of the invention, since the i-bit pixel size data is converted into an analog signal and the analog signal is compared with the reference waveform signal, the number of bits of the pixel size control signal is changed. Even if the number of pixels increases, it becomes possible to perform accurate pixel size control with a simple circuit. Further, according to the invention of claim 4, the number of pixels at low density can be increased to a plurality of times without changing the overall density, and the expressive power in the entire density range can be increased. become able to.

Further, according to the invention of claim 5, it is possible to reduce the change in concentration in the low concentration region and increase the change in concentration in the high concentration region. As a result, it becomes possible to reproduce a natural image suitable for human perception characteristics. According to the invention of claim 6, a dither matrix or a density pattern matrix can be used as the matrix data, and a gradation change in a light density area can be smoothed as compared with a conventional reproduced image using these matrices. It will be possible to reproduce.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a configuration of a first exemplary embodiment of the present invention.

FIG. 2 is a diagram showing a structure of print data.

FIG. 3 is a circuit diagram showing a specific example of a laser diode drive circuit.

FIG. 4 is a diagram showing an example of a reproduction pattern according to the first embodiment.

FIG. 5 is a block diagram showing a configuration of a second exemplary embodiment of the present invention.

FIG. 6 is a diagram showing an example of a reproduction pattern according to the second embodiment.

FIG. 7 is a block diagram showing a configuration of a third exemplary embodiment of the present invention.

FIG. 8 is a diagram showing an example of a matrix used in the third embodiment.

FIG. 9 is a diagram showing an example of a reproduction pattern according to the third embodiment.

FIG. 10 is a diagram showing an example of another matrix used in the third embodiment.

FIG. 11 is a third view when another matrix is used.
It is a figure which shows an example of the reproduction pattern by embodiment of this.

FIG. 12 is a block diagram showing a configuration of a main part of a fourth embodiment of the present invention.

FIG. 13 is a diagram showing an example of a matrix used in the fourth embodiment.

FIG. 14 is a diagram showing dot sizes obtained according to this embodiment.

FIG. 15 is a diagram showing an example of a reproduction pattern according to the fourth embodiment.

FIG. 16 is a diagram showing a relationship between print data density values and print output densities according to the fourth embodiment.

FIG. 17 is a block diagram showing a configuration of a main part of a fifth embodiment of the present invention.

FIG. 18 is a waveform chart of signals of a main part of the embodiment.

FIG. 19 is a block diagram showing a schematic configuration of an example of a conventional LBP.

20 is a block diagram showing a specific example of the controller of FIG.

FIG. 21 is a diagram showing a relationship between 4 and 6 gradation printing and resolution.

FIG. 22 is an explanatory diagram of intermediate density reproduction by the density pattern method.

FIG. 23 shows multi-value gradation data obtained by the systematic dither method as 2
It is a block diagram which shows the method of value-izing.

FIG. 24 is a block diagram showing a method of binarizing multi-value gradation data by an error diffusion method.

[Description of Reference Signs] 1 ... Input terminal, 2 ... k-bit extracting means, 3 ... i-bit extracting means, 5 ... Dither matrix, 6 ... Comparator, 7 ... Laser diode drive circuit, 8 ... Pixel size control circuit, 9 ...
Selector, 24 ... Full dot-intermediate dot size selecting means, 30 ... ON / OFF signal generating means, 40 ... D / A converter, 41 ... Reference waveform oscillating circuit, 42 ... Comparator.

Claims (6)

[Claims] 1. A multi-gradation printing apparatus having a printing means capable of marking 2 ⁱ (i is a positive integer) gradation, and printing of j bits (j is a positive integer such that j> i) per pixel. Means for inputting data, means for extracting pixel gradation data of k bits (k is a positive integer, j = k + i) from the input print data, and the extracted pixel level of k bits Comparison means for comparing the key data with corresponding data of the matrix data representing the threshold value and outputting an ON / OFF signal of the drawing device according to the magnitude; and from the input print data, the i-bit Means for extracting pixel size data, means for outputting a pixel size control signal of one of the 2 ⁱ types of pixel sizes determined by the extracted i-bit pixel size data, the comparison means and the pixel size Control The ON / OFF signals and pixel size control signal outputted from the signal output means,
A multi-gradation printing apparatus, comprising: means for controlling on / off of the drawing apparatus and its on-time, and printing data of 2 ^j gradation. 2. The multi-gradation printing apparatus according to claim 1, wherein the i-bit pixel size data is made valid for specific pixel gradation data of the k-bit pixel gradation data, A multi-gradation printing apparatus, wherein printing is performed with a size represented by the i-bit pixel size data only for specific pixel gradation data. 3. A multi-gradation printing apparatus having a printing means capable of marking 2 ⁱ (i is a positive integer) gradation, printing of j bits (j is a positive integer such that j> i) per pixel. Means for inputting data, means for extracting pixel gradation data of k bits (k is a positive integer, j = k + i) from the input print data, and the extracted pixel level of k bits Comparison means for comparing the key data with corresponding data of the matrix data representing the threshold value and outputting an ON / OFF signal of the drawing device according to the magnitude; and from the input print data, the i-bit Means for extracting pixel size data, means for converting the extracted i-bit pixel size data into an analog signal, and comparing the analog signal of the pixel size data with a reference waveform signal to output a pixel size control signal You Means, and an ON / OFF signal and a pixel size control signal output from the comparison means and the pixel size control signal output means,
A multi-gradation printing apparatus, comprising: means for controlling on / off of the drawing apparatus and its on-time, and printing data of 2 ^j gradation. 4. A multi-gradation printing device having a printing means capable of printing at least two types of dots, a full size dot and a dot of a smaller size, and a first threshold value in one cell. , Matrix data having two kinds of second threshold values smaller than this, means for outputting pixel size control signals of full size and smaller size, and input multi-tone printing When the gradation of the data is larger than a predetermined value, it is compared with a first threshold value of the matrix data, and when it is less than the predetermined value, it is compared with a second threshold value of the matrix data. The pixel size control signal output means outputs a full size pixel size control signal when the first threshold value is selected, and the second threshold value is selected. Multi-tone printing apparatus is characterized in that so as to output the pixel size control signal of the small size when it is. 5. A multi-gradation printing device having a printing means capable of printing at least two types of dots, a full size dot and a dot of a smaller size, wherein a first threshold value is provided in one cell. , Matrix data having two kinds of second threshold values smaller than this, means for outputting pixel size control signals of full size and smaller size, and input multi-tone printing Comparing means for comparing the data with the first and second threshold values, and the pixel size control signal output means, when the print data is equal to or larger than the first threshold value, a full size pixel size. Outputting a control signal, and outputting a pixel size control signal of a size smaller than the full size when the print data is smaller than the first threshold and equal to or larger than the second threshold. Multi-tone printing apparatus, characterized in that the. 6. The multi-gradation printing device according to claim 1, wherein the matrix data is a dither matrix or a density pattern matrix.