JPH0872315A - Image recording apparatus and method - Google Patents

Abstract

PURPOSE: To realize a wide range of gradation expression while suppressing the deterioration of resolving power. CONSTITUTION: A control circuit 1 outputs either one of signals STB1, STB2 determining the light emitting time of an LED head 6 to the LED head 6. The lasting time of the signal STB1 is shorter than that of the signal STB2 and the signal STB1 is outputted when the center of the image point of the odd number-th line is printed and the signal STB2 is outputted when the center of the image point of the even number-th line is printed. Therefore, two kinds of image points different in area ratio can be printed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording apparatus for expressing area gradation by forming different gradation patterns.

[0002]

2. Description of the Related Art Generally, for example, a dither method is known as a multi-gradation recording method. The gradation expression is "1",
Since it is "0", it is a so-called binary area gradation.

[0003]

In the conventional image recording apparatus, one pixel is expressed by a matrix consisting of n × n image point centers, and therefore the number of gradations that can be expressed includes the background density of the recording medium. a n ² +1, but the resolution is degraded in 1 / n. Therefore, as the number of gradations increases, the resolution of one pixel deteriorates, that is, the print image becomes blurry.

By the way, the image quality is evaluated in relation to the human visual field, but there is a visual acuity limit due to the relation between gradation and resolution. Generally, in order to obtain an image that is natural to the eyes, it is said that if the resolution of one pixel dot is 12 dots / mm, the number of gradations is 17 or more, and if the resolution is 8 dots / mm, the number of gradations is 65 or more. There is. When this is realized by a binary area gradation type image recording apparatus, a resolution of 48 dots / mm or more in a 4 × 4 matrix, and 8 × 8
A matrix requires a printhead with a resolution of 64 dots / mm. However, when recording with a thermal head or LED head, the resolution is 400 to 600 dp.
i, that is, 16 to 24 dots / mm is the limit, and in the case of realizing thermal transfer or electrophotography with a resolution of 48 dots / mm or more, the heating element becomes extremely small, and the parts and wiring to which the heating element is attached also generate heat. It has to be small to the device and is therefore difficult to manufacture and, if possible, very expensive.

Therefore, in order to solve this, the resolution is set to 1
Sublimation type thermal transfer printers and electrophotographic copying machines with 256 dots at 2 dots / mm have been realized. However, the increase in the number of gradations makes the circuit and control very complicated, thus reducing the device cost. There was a problem that it became expensive.

[0006]

In order to solve the above problems, the present invention relates to an image data storage means for storing gradation data for the main scanning direction, a matrix address designating circuit for designating the center of an image point, A pattern storage unit that stores a gradation pattern table of a plurality of matrices composed of image point centers in the main scanning direction m × the sub scanning direction n, a signal output unit that sends a plurality of strobe signals that change the energy applied to the printing element, and an image. Based on the gradation data of the data storage means and the specification of the matrix addressing circuit, the gradation pattern of the pattern storage means is selected and a plurality of strobe signals are selected, and the distance between the centers of adjacent image points in the main scanning direction is selected. Is also provided with control means for printing by shortening the distance between the centers of adjacent image points in the sub-scanning direction.

[0007]

When the matrix address designating circuit designates the center of the image point, the control circuit selects the gradation pattern of the pattern storing means according to the gradation data of the image data storing means and also selects one of the plurality of strobe signals. Then, the recording medium is fed and printed such that the distance between the adjacent image point centers in the sub-scanning direction is shorter than the distance between the adjacent image point centers in the main scanning direction.

[0008]

Embodiments of the present invention will be described below. In this embodiment, an electrophotographic recording device equipped with an LED head will be described as an example. The LED head is composed of an LED array, a substrate on which a drive IC for driving the LED array is mounted, a SELFOC lens array that collects light from the LED array, and the like, and causes the LED array to emit light in response to an input image data signal. The surface of the photoreceptor is exposed to light to form an electrostatic latent image on the surface of the photoreceptor. Toner of the developing device is attached to the electrostatic latent image portion by electrostatic force to form an image. In addition, the adhesion area of the adhesion toner depends on the energy applied to the printing element,
That is, it can be freely selected by controlling the light emission time of the LED array. The toner adhering to the surface of the photoconductor is transferred to the recording paper, and finally, the toner image on the recording paper is fixed by the fixing device to complete the printing. Hereinafter, a detailed description will be given with reference to the drawings. The elements common to the drawings are given the same reference numerals.

First Embodiment FIG. 1 is a block diagram showing a control system of an electrophotographic recording apparatus according to the first embodiment of the present invention, and FIG. 2 is a matrix floor of the electrophotographic recording apparatus according to the first embodiment. It is an explanatory view of a tonal pattern forming method. FIG. 3 is a diagram showing a gradation pattern used in the electrophotographic recording apparatus of the first embodiment.

First, a method of forming a gradation pattern will be described with reference to FIG. As shown in FIG. 2A, one pixel has two image points in the main scanning direction (column direction) indicated by the arrow A direction and seven images in the sub scanning direction (row direction) indicated by the arrow B direction. It is composed of a dot-centered matrix, that is, it is composed of 2 × 7 image points and has the same length and width (D × D). Centers of image points (1, 1), (1, 2), (2,
1), (2, 2) ... (7, 1), (7, 2) are LE
This is the emission center point of the D head. 2 (c), (e),
As shown in (g), L is in the second, fourth, and sixth rows, that is, the even rows.
When the ED array emits light, the shaded area in the figure is (D / 2) ×
An image point A having a width of (D / 2) is printed. With this one image point A, an area ratio of 4/16 can be obtained for a matrix of one pixel. When the LED array emits light in the first, third, fifth, and seventh rows, that is, the odd-numbered rows, as shown by the hatched portions in FIGS. Image point B, which is ¼ the size of point A, is printed. With this one image point B, an area ratio of 1/16 can be obtained for the matrix of one pixel. The gradation pattern shown in FIG. 3 is formed by the combination of the image points A and B.
In this manner, the recording paper is fed and printed in the D / 8 direction in the sub-scanning direction (row direction) while selectively emitting light at the center of each image point. In FIG. 3, in the gradation 0, the centers of all the image points are not printed, and the area ratio of this one pixel is 0/16. For gradation 1, only the image point B at the image center (5, 1) is printed, and this one pixel has an area ratio of 1/16. Gradation 2 is the center of the image point (3,
Two image points B of 1) and (5, 1) are printed, and the area ratio of one pixel is 2/16. Gradation 3 is the center of the image point (3,
Three image points B of 1), (5, 1) and (7, 1) are printed, and the area ratio of one pixel is 3/16. For gradation 4, one image point A at the image center (4, 1) is printed, and one pixel has an area ratio of 4/16. As described above, gradation 5
Area ratio is 5/16, and the area ratio of gradation 6 is 6/16
Thus, the area ratio of gradation 7 is 7/16. The area ratio of gradation 8 is 8/16, and the area ratio of gradation 9 is 9/1.
6 and the area ratio of gradation 10 is 10/16. Further, the area ratio of gradation 13 becomes 13/16, the area ratio of gradation 14 becomes 14/16, and the area ratio of gradation 15 becomes 15 /.
16, and the area ratio of gradation 16 is 16/16. In this way, a gradation pattern having a continuous area ratio can be obtained. The light emission control and print control of the image points A and B will be described later.

Next, the control system of the first embodiment is shown in FIG.
This will be described with reference to FIG. FIG. 4 is a diagram showing the gradation pattern data of the first embodiment. In the figure, the center of an unprinted image point is indicated by "0", and the center of an image point printed is indicated by "1".

The control circuit 1 comprises a microprocessor, a working memory, a timer, etc., and controls the entire circuit shown in the figure. A line memory 2, a matrix addressing circuit 4, and a gradation pattern table 3 are connected to the control circuit 1. The line memory 2 stores multi-tone image data for one line (pixels for the main scanning direction) input from an image memory (not shown). The information on the gradation of each pixel of this data is stored in advance in the image memory from a higher-level device (not shown). The line memory 2 incorporates a counter (not shown), counts the signal each time the signal from the control circuit 1 is input, and outputs the data to the gradation pattern table 3 one pixel at a time. The matrix addressing circuit 4 is composed of a counter or the like, counts a column of pixels, and outputs the counting result to the gradation pattern table 3 as a signal. The gradation pattern table 3 is for determining the gradation pattern shown in FIG. The gradation pattern table 3 is specifically composed of a ROM and is shown in FIG.
The pattern data of is stored. When the gradation pattern table 3 inputs the signal from the line memory 2, one of the 17 gradations shown in FIG. 4 is selected, and every time the signal from the matrix addressing circuit 4 is input, the selected floor is selected. The key pattern data is sequentially output to the LED head 6.

The LED head 6 has a shift register 6d, a latch circuit 6c, and a light emitting element array 6a including a driver. The shift register 6d is adapted to store pattern data for one row, and the gradation pattern table 3
The pattern data sent from is input sequentially. When the latch signal L output from the control circuit 1 is input, the latch circuit 6c transfers the pattern data for one row held in the shift register 6d to the latch circuit 6c at that timing. Latch circuit 6c and light emitting element array 6
It is connected to a through an AND gate circuit group 6b. The light emitting elements are arranged in a line along the main scanning direction.

Further, the control circuit 1 alternately outputs a strobe signal (STB) 1 and a strobe signal (STB) 2 which determine the light emission time of the LED head 6 to the OR gate 5. That is, when printing the center of the dot on the even line,
The signal STB2 is output, the signal STB1 is not output,
Further, when printing the center of the image points on the odd-numbered lines, the signal ST
B1 is output and the signal STB2 is not output. Then, the output signal STB1 and signal STB
2 is ORed by an OR gate 5 and is output to the AND gate circuit group 6b. The duration of the signal STB1 is shorter than the duration of the signal STB2 (signal STB1 <signal STB2). Therefore, when the signal STB1 is selected, the image point B in FIG. 2 is selectively printed, When STB2 is selected, the image point A is selectively printed. In this way, by setting two types of energy to be applied to the LED head 6, two types of image area can be selected.

Next, the operation of printing the gradation pattern of the first embodiment will be described with reference to FIG. FIG. 5 is a timing chart of the first embodiment.

When multi-gradation image data for one line is sequentially input to the respective addresses D ₀ -D _m of the line memory 2 by the image memory, the control circuit 1 sends a signal to the line memory 2. Output. As a result, one pixel of data is sent from the address D ₀ of the line memory 2 to the gradation pattern table 3. When the gradation of this pixel is gradation 14, for example, 14 pattern data of gradation 14 of FIG. 4 are selected in the gradation pattern table 3. The matrix addressing circuit 4 counts the first column and outputs a signal to the gradation pattern table 3. As described above, the pattern data “0” at the center of the image point (1, 1) is selected from the 14 pattern data selected in the gradation pattern table 3. Then, the selected pattern data is sent to the shift register 6d. Further, the matrix addressing circuit 4 counts the second column and outputs a signal to the gradation pattern table 3, and the gradation pattern table 3
The pattern data "1" of the center (1, 2) of the image point is selected by and is sent to the shift register 6d. As described above, one row of one pixel is stored in the shift register 6d.

Next, the control circuit 1 outputs a signal to the line memory 2 again, whereby the address D of the line memory 2 is output.
The data No. ₂ is sent to the gradation pattern table 3. In the gradation pattern table 3, 1 of the same gradation as this data is
Each time four pieces of pattern data are selected and a signal is output from the matrix addressing circuit 4, the selected pattern data is sequentially sent to the shift register 6d, whereby one row of one pixel is stored in the shift register 6d. To be done. Similarly, the data stored in the remaining addresses are sequentially output to the gradation pattern table 3, and the pattern data for one row of one pixel is stored in the shift register 6d.

When all the pattern data for one row in the line memory 2 is stored in the shift register 6d, the control circuit 1 sends the latch signal L to the latch circuit 6c and is stored in the shift register 6d. The pattern data for one row is transferred to the latch circuit 6c, and the AND gate circuit group 6b
Send to Then, the control circuit 1 outputs the signal STB1,
It is sent to the AND gate circuit group 6b. AND gate circuit group 6
In b, the logical product of the pattern data sent from the latch circuit 6c and the signal STB1 is calculated, and the value is the LED
It is output toward the light emitting element array 6a. At this time, the LED light emitting element whose pattern data corresponds to “1” is the signal ST.
It emits light while B1 is on. When the pattern data is "0", no light is emitted even if the signal STB1 is on.
With the above, printing of the first line is completed.

Similar to the printing operation of the first line, the control circuit 1 outputs a signal to the line memory 2 again to print the second line. That is, the matrix addressing circuit 4 counts the columns, and the gradation pattern table 3 outputs the pattern data of the second row to the shift register 6d. Then, when all the pattern data of the second row is stored in the shift register 6d, the control circuit 1 sends the latch signal L to the latch circuit 6c and sends the pattern data of the second row to the AND gate circuit group 6
Send to b. The control circuit 1 outputs the signal STB2 and sends it to the AND gate circuit group 6b. In the AND gate circuit group 6b, the logical product of the pattern data and the signal STB2 is calculated, and the value is output to the LED light emitting element array 6a.
At this time, the recording paper (not shown) is fed 8 / D lines in the sub-scanning direction. With the above, printing of the second line is completed. Similarly, the pattern data output from the gradation pattern table 3 is stored in the shift register 6d row by row, and the control circuit 1 outputs the latch signal L and then outputs the signal STB1 and the signal S.
TB2 is alternately output, and the recording paper is printed up to the 7th line while feeding 8 / D lines at a time. By the above, each gradation pattern shown in FIG. 3 can be selected.

When the printing of all the pattern data of the 7th line is completed, the multi-gradation image data of the next line is stored in the line memory 2, and the printing of the next line is performed according to the above-described printing operation.

FIG. 6 is a diagram showing another gradation pattern of the first embodiment. Thus, depending on the combination of the image points A and B shown in FIG. 2, the gradation pattern shown in FIG. A gradation pattern having the same area ratio can be obtained. In the operation, in the same manner as described above, the recording paper is fed by D / 8 rows in the sub-scanning direction, and the light emitting element array 6a emits light to perform printing. In this way, the gradation pattern shown in FIG. 6 can be selected.

In the first embodiment, the dither pattern corresponds to the center of 2 × 2 image points. Therefore, in this case, although only 4 gradations can be realized by the dither pattern, 17 gradations including 0 gradation (base density) can be realized at the center of 2 × 2 image points in the first embodiment.

Here, if a resolution of 600 dpi (about 24 dots / mm) is used for the LED head in the first embodiment, the resolution of one pixel is 300 dpi, and the number of gradations is 17 including the background density. It becomes gradation, and desired resolution and gradation can be realized.

Second Embodiment In the second embodiment, the shift register of the LED head is divided into two, and the pattern data sent from the gradation pattern table is sent in parallel. FIG. 7 is a block diagram showing the control system of the electrophotographic recording apparatus of the second embodiment.

The control circuit 11 comprises a microprocessor, a working memory, a timer, etc., and controls the entire circuit shown in the figure. The line memory 12 stores two lines of multi-gradation image data input from an image memory (not shown) and each has a counter (not shown).
It is divided into A and 12B. Each counter has the same function as in the first embodiment. Line memory 12A
Stores multi-gradation image data for the first half of 1/2 line, and the line memory 12B stores multi-gradation image data for the second half of 1/2 line. Accordingly, the multi-gradation image data for 1/2 line in the first half and 1 in the second half
If you join the multi-tone image data of / 2 line,
Multi-tone image data for one line is constructed. The gradation pattern tables 3A and 3B are the same as the gradation pattern table 3 of FIG. Gradation pattern table 3A, 3B
Are respectively connected to the matrix addressing circuit 4.

The LED head 16 is an L including a driver.
ED light emitting element array 16a, AND gate circuit group 16b, latch circuit 16c, and shift registers 16dA, 16d
It consists of B. The LED head 16 stores 1/2 line of pattern data from the gradation pattern table 3A in the shift register 16dA and 1/2 line of pattern data from the gradation pattern table 3B in the shift register 16dB. It is supposed to do. The pattern data of both shift registers 16 are transferred to the latch circuit 16c at the timing of the latch signal L from the control circuit 11. Other structures are the same as in the first embodiment.

Next, the pattern data transmitted from each of the gradation pattern tables 3A and 3B is transferred to the shift register 16
The operation up to storage in dA and 16 dB will be described. The operation after storing in the shift registers 16dA and 16dB is the same as that in the first embodiment, and therefore the description is omitted.

When the control circuit 11 sends a signal to the line memory 12A in a state where the image data is stored in the image memory, the image data for the first half of the 1/2 line is supplied to a plurality of addresses in the line memory 12A pixel by pixel. Stored in order. After that, when the control circuit 11 sends a signal to the line memory 12B, the image data for the latter half ½ line is sequentially stored pixel by pixel at a plurality of addresses in the line memory 12B. When the image data of 1/2 line is stored in both line memories 12, the control circuit 11 outputs the signal to each of the line memories 12A and 12B again. As a result, the data for one pixel from the line memories 12A and 12B is converted into the corresponding gradation pattern tables 3A and 3B, respectively.
Sent to B. Further, the matrix addressing circuit 4 counts the columns and outputs them as signals to the gradation pattern tables 3A and 3B. As described above, one pattern data of one row of one pixel is output from each of the gradation pattern tables 3A and 3B and stored in the shift registers 16dA and 16dB of the LED head 16. Similarly, the remaining image data stored in the line memories 12A and 12B are sequentially output pixel by pixel to the gradation pattern tables 3A and 3B, and the pattern data for one row of one pixel is stored in the shift registers 16dA and 16dB. To do.

1/2 of each line memory 12A, 12B
All the pattern data for the rows are shift registers 16dA,
When stored in 16 dB, the control circuit 1 sends the latch signal L to the latch circuit 6c, and the shift register 16d
The 1/2 row pattern data stored in A and 16 dB is transferred to the latch circuit 6c, and the AND gate circuit group 16
send to b. Then, the control circuit 1 outputs the signal STB1 and sends it to the AND gate circuit group 16b. In the AND gate circuit group 16b, the logical product of the pattern data sent from the latch circuit 6c and the signal STB1 is calculated, and the value is output to the LED light emitting element array 16a. This time,
The LED light emitting element whose pattern data corresponds to "1" emits light while the signal STB1 is on. When the pattern data is "0", no light is emitted even if the signal STB1 is on. With the above, printing of the first line is completed. Similarly, the recording paper is fed 8 / D lines at a time and the 7th line is printed. As described above, the gradation pattern shown in FIG. 3 can be selected.

In the second embodiment, the shift register 16 is set to 2
By providing the individual pieces and reducing the number of pattern data stored in each shift register 16dA, 16dB as compared with the first embodiment, the transmission time of the pattern data to the shift register 16 can be shortened to half of the first embodiment. . As described above, the speed can be increased without increasing the amount of hardware. Further, if the shift register 16 is not limited to being divided into two, but is divided into more than two, higher speed can be achieved. In this case, it is necessary to divide the line memory and the gradation pattern table according to the number of divisions of the shift register 16.

If the first and second embodiments are applied to the center of 2 × 4 image points, (32 + 1) gradation can be realized and 3 ×
When applied to the center of three image points, (36 + 1) gradation can be realized. Furthermore, when applied to the center of 4 × 4 image points, (64+
1) Gradation can be realized. It should be noted that the center of 3 × 3 image points and 4 ×
In the case of the center of four image points, for example, in the column direction, for example, the output pulse of the matrix addressing circuit 4 is counted by the control circuit 11 and the column number is determined based on the counting result. Good.

Third Embodiment In the third embodiment, the control circuit outputs three kinds of strobe signals (STB), prints three kinds of image points having different area ratios, and expresses gradation. It will be described below with reference to the drawings. FIG. 8 is a block diagram showing the control system of the electrophotographic recording apparatus of the third embodiment. FIG. 9 is a diagram showing the gradation pattern of the third embodiment, which is the same as the first and second embodiments.
Pixels are arranged in a matrix in which the main scanning direction is the center of two image points and the sub-scanning direction is the center of seven image points, and has the same length and width. The value in parentheses in FIG. 9 indicates the area ratio of one pixel.

In FIG. 8, a control circuit 20 comprises a microprocessor, a working memory, a timer, etc., and controls the entire circuit shown in the figure. The control circuit 20 outputs to the OR gate 22 any one of the signals STB1, STB2 and STB3 that determine the light emission time of the LED head 6. The signals STB1 and STB2 are the same signals as in the first and second embodiments. The control circuit 20 outputs the signal STB1 and does not output the signals STB2 and STB3 while printing the first and seventh lines at the center of each image point. Further, when printing the second, fourth, and sixth lines at the center of each image point, the signal STB2 is output, and the signals STB1 and STB are output.
3 is not output. Further, when printing the third and fifth lines centering on each image point, the signal STB3 is output and the signal STB is output.
1 and the signal STB2 are not output. The relationship of the signal output time of each signal STB is as shown in the following equation.

Signal STB1 <Signal STB3 <Signal STB2 (1) When the signal STB3 is output, 3/4 image points of the size of the image point A shown in FIG. 2 are printed. There is. An area ratio of 3/16 can be obtained for a matrix of one pixel with one image point. The combination of this image point and the above-mentioned image points A and B forms the gradation pattern shown in FIG.

The gradation pattern table 21 determines the gradation pattern shown in FIG. This gradation pattern table 21 is specifically configured by a ROM, and information that the image points printed for each gradation pattern in FIG. 9 is "1" and the image points that are not printed are "0". Is stored. The other structure is similar to that of the first embodiment.

Next, the operation of printing the gradation pattern of the third embodiment will be described. The operation from the input of the pattern data to the line memory 2 to the storage of one row of the pattern data in the line memory 2 in the shift register 6d, the transfer to the latch circuit 6c, and the transmission to the AND gate circuit group 6b are as follows. The description is omitted because it is the same as the first embodiment.

When the pattern data for one row stored in the shift register 6d is sent to the AND gate circuit group 6b, the control circuit 20 outputs the signal STB according to the counted row.
Any one of 1 to signal STB3 is output and sent to the AND gate circuit group 6b. In the AND gate circuit group 6b, the pattern data and the signal S sent from the latch circuit 6c are sent.
The logical product with TB is taken and the value is the LED light emitting element row 6
It is output to a. At this time, the pattern data is "1"
The LED light-emitting element corresponding to (5) emits light while the signal STB is on. When the pattern data is "0", no light is emitted even if the signal STB is on. As a result, the gradation patterns shown in FIG. 9 are printed one after another. Needless to say, a gradation pattern other than that shown in FIG. 9 can be selected depending on the way of combining the image points formed by the signal STB.

In the third embodiment, a gradation pattern with more excellent continuity can be obtained at a large area ratio. In general, since the human visual organs have a logarithmic response characteristic to light and dark, it is necessary to make finer the areas where the density is high as in the third embodiment.

In the third embodiment, the dither pattern corresponds to the center of 2 × 2 image points, but 25 gradations including 0 gradation can be realized. Further, like the first and second embodiments, the third embodiment can be applied to the center of 2 × 4 image points, the center of 3 × 3 image points, and the center of 4 × 4 image points.

The line memory 2, the gradation pattern table 21, and the shift register 6d of the third embodiment are divided,
By transmitting the pattern data transmitted from each gradation pattern table in parallel, the transmission time of the pattern data to the shift register 6d can be shortened and the speed can be increased.

In the first to third embodiments, the signal STB output from the control circuit passes through the OR gate.
An OR gate may be incorporated in the control circuit.

Further, in the first to third embodiments, the matrix addressing circuit counts the column of one pixel, but the counter in the control circuit counts the column and the counting result is directly used in the gradation pattern table. You may make it output to.

Further, if the types of the size of the image points are increased, that is, the types of the signals STB having different output times are increased, the gradation expression can be further improved.

If the recording apparatus of the first to third embodiments is applied to a color recording apparatus, a full color image can be obtained.

The first to third embodiments can be applied to both line type and serial type recording devices. Further, the recording means can be applied to various forms. In the case of an electrophotographic image recording apparatus, as the image exposing means, the LED head 6 which can be miniaturized in this embodiment is desirable.
It goes without saying that laser means, liquid crystal shutter means, or the like may be used. Further, it goes without saying that if the LED head 6 is replaced with a thermal head, it can be applied to a fusion-type or sublimation-type thermal transfer image recording apparatus. Further, in the case of a serial inkjet image recording apparatus, if a plurality of print heads having different image sizes are arranged in the column direction for printing, the same gradation pattern as in the present embodiment can be printed.

For the sake of convenience, the area ratio of this embodiment was calculated using a quadrangle model, but the actual recording has a circular shape. In this case, each gradation pattern may be actually recorded and the density thereof may be measured and used.

It should be noted that the present embodiment is not limited to the gradation pattern described above, and various modifications can be made without departing from the spirit of the invention.

[0048]

As described in detail above, the present invention provides
A plurality of strobe signals that change the energy applied to the printing element are selectively transmitted from the signal output means, and the distance between the centers of adjacent image points in the sub-scanning direction is more than the distance between the centers of adjacent image points in the main scanning direction of one pixel. By shortening and printing, it is possible to obtain a wide range of area gradation while minimizing the deterioration of the resolution of one pixel. The method is also simple and can be realized with an inexpensive structure.

[Brief description of drawings]

FIG. 1 is a block diagram showing a control system of an electrophotographic recording apparatus according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a method of forming a gradation pattern of a matrix according to the first embodiment.

FIG. 3 is a diagram showing a gradation pattern of the first embodiment.

FIG. 4 is a diagram showing gradation pattern data according to the first embodiment.

FIG. 5 is a timing chart of the first embodiment.

FIG. 6 is a diagram showing another gradation pattern of the first embodiment.

FIG. 7 is a block diagram showing a control system of a second embodiment.

FIG. 8 is a block diagram showing a control system of a third embodiment.

FIG. 9 is a diagram showing a gradation pattern of a third embodiment.

[Explanation of symbols]

 1, 11, 20 Control circuit 2, 12 Line memory 3, 3A, 3B, 21 Grayscale pattern table 4 Matrix addressing circuit 6, 16 LED head

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuichiro Ogata 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd.

Claims (3)

[Claims] 1. An area gradation is expressed by forming different gradation patterns by a matrix consisting of image point centers in the main scanning direction m × the sub scanning direction n, and a recording medium is fed in the sub scanning direction to print. In the image recording apparatus, an image data storage unit that stores gradation data for the main scanning direction, a matrix addressing circuit that specifies the center of an image point, a pattern storage unit that stores the gradation pattern table of the matrix, The gradation pattern of the pattern storage means is selected by the signal output means for transmitting a plurality of strobe signals for changing the energy applied to the printing element, the gradation data of the image data storage means, and the designation of the matrix addressing circuit, and Select multiple strobe signals and select the center of adjacent image points in the sub-scanning direction from the distance between the centers of adjacent image points in the main scanning direction. Image recording apparatus is characterized by providing a control means for printing the distance shortened by. 2. A plurality of the image data storage means are provided, and the same number of pattern storage means as the image data storage means are provided, and the gradation data for the main scanning direction is divided and stored in each storage means. 2. The image recording apparatus according to claim 1, wherein each gradation pattern corresponding to each gradation data is selected from the pattern storage means. 3. An area gradation is expressed by forming different gradation patterns by a matrix consisting of image point centers in the main scanning direction m × the sub scanning direction n, and a recording medium is fed in the sub scanning direction to print. In the image recording method, the gradation pattern table of the plurality of matrices is stored in the pattern storage means, the gradation data for the main scanning direction is stored in the image data storage means, and the matrix addressing circuit sets the center of the image point. When designated, the control circuit selects a gradation pattern corresponding to the gradation data of the image data storage means from the pattern storage means, and at the same time, a strobe that changes the energy applied to the printing element depending on the position of the designated image point center in the sub-scanning direction. Send a signal,
An image recording method, wherein printing is performed by making a distance between adjacent image point centers in the sub-scanning direction shorter than a distance between adjacent image point centers in the main scanning direction.