JPH07306482A - Image forming device - Google Patents

Abstract

(57) [Summary] [Structure] The image data of three pixels a to c in the main scanning direction are fetched from the line memory 41 into the shift register 42. In the processing by the LUT 43, the pixel b is set as the target pixel, and the recording density of the target pixel b is determined by adding the density value obtained from the density values of the adjacent pixels a and c to the density value of the target pixel b. It Further, the recording area of the pixel of interest is set to a length corresponding to the above-described recording density centered on the center position of the pixel of interest b by the processing of the LUT 43, the data latches 44 and 45, and the comparators 46 and 47. . The recording area of the target pixel b is designated, and the modulation signal including the recording density is given to the image forming unit to obtain an image. [Effect] Compared with the case where image data of a plurality of pixels is simply averaged to obtain a modulation signal for image formation, an image with good image quality can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a digital copying machine which forms an image based on image data.

[0002]

2. Description of the Related Art In an image forming apparatus such as a digital copying machine, the number of gradations and the resolution are main factors that influence the image quality. Of these, the number of gradations affects the reproducibility of halftones. Conventionally known methods for reproducing halftones include a dither pattern, a power modulation method, and a pulse width modulation method.

In the method using the dither pattern, the resolution decreases as the number of gradations increases, while the number of gradations decreases as the resolution increases, which makes it difficult to achieve high image quality. Further, in the method using the power modulation and the method using the pulse width modulation, when the density data is processed on a pixel-by-pixel basis, the operating frequency of the circuit becomes high, so that it is difficult to improve the gradation and the capacity used as a memory for this processing is large. There is a problem that a large one is required.

On the other hand, Japanese Unexamined Patent Publication No. 1-204741 discloses a method in which the pulse width modulation is performed by a triangular wave having a period which is a multiple of a video clock having a period of one pixel. According to this method, the above problems can be solved, and although the resolution is slightly rough, gradation expression by the area is facilitated, and an image with smooth halftone and stable image quality can be obtained. There is.

[0005]

However, in the technique disclosed in the above publication, since the image data of a plurality of pixels are simply averaged and processed, the center of each recording area by this averaging is It is not aligned in the sub-scanning direction, and is displaced to the right or left side, which is the higher density side, with respect to the sub-scanning direction. As a result, the obtained image has a problem that it is difficult to see.

[0006]

In order to solve the above problems, the image forming apparatus according to the invention of claim 1 visualizes the image data by the image forming section based on the modulation signal generated from the image data. In an image forming apparatus in which an image forming operation is performed, storage means for storing image data including density values of respective pixels of an image to be formed and main scanning direction or sub-direction corresponding to each image data stored in the storage means. For each pixel lined up in one of the scanning directions, a target pixel that is a pixel to be recorded is set for each of a plurality of predetermined pixels, and the density values of adjacent pixels that are adjacent to the target pixel in the front and rear in the one direction are set. Is added to the density value of the pixel of interest to obtain the recording density of the pixel of interest, and a recording area having a length corresponding to the above-described recording density centered on the center position of the pixel of interest is arranged in the one direction. Generates a modulated signal for designating the rear direction, the modulated signal characterized by comprising a modulation signal output means for supplying to the image forming unit.

The image forming apparatus according to the second aspect of the invention is
2. The image forming apparatus according to claim 1, wherein the modulation signal output means sets the center of the recording area for the target pixel to the center pixel of the target pixel and the adjacent pixel on the higher density value side of the adjacent pixels on both sides. It is characterized by being moved in the direction.

The image forming apparatus according to the third aspect of the invention is
In the image forming apparatus according to the invention of claim 1, the recording density calculation means distributes the density values of the adjacent pixels between each two target pixels according to the density values of the two target pixels, The feature is that the recorded density of each target pixel is obtained by adding the distributed density value to the density values of the two target pixels.

[0009]

According to the structure of the first aspect, the target pixel which is the pixel to be recorded is set for every predetermined plural pixels, for example, for every two pixels. The recording density of the pixel of interest is determined by adding the density value of the adjacent pixel that is adjacent to the pixel of interest in the main scanning direction or the sub-scanning direction to the density value of the pixel of interest. . The recording area of the target pixel is set to have a length centered on the center position of the target pixel and corresponding to the recording density. Then, the recording area of the pixel of interest is designated, and the modulation signal including the recording density is given to the image forming section, and the image forming operation is performed.

As described above, in the image forming apparatus of the present invention,
Instead of simply averaging the image data of a plurality of pixels to obtain a modulation signal for image formation, the recording density of the pixel of interest is added by adding the density value of the pixel adjacent to the pixel of interest to the density value of the pixel of interest. Since it is determined, the centers of the recording areas are aligned in the sub scanning direction or the main scanning direction.
As a result, an image that is easy to see can be formed.

According to the configuration of claim 2, in addition to the processing according to the configuration of claim 1, the center of the recording area for the pixel of interest is moved toward the adjacent pixel on the side of higher density of the adjacent pixels to the pixel of interest. It is moving. Therefore, in the image forming apparatus of the present invention, the recording positions of the respective target pixels can be brought close to each other, that is, the dots can be gathered together. As a result, it is possible to avoid the occurrence of streaks in the line portion of the recorded image, which occurs when the recording position of the pixel of interest is distant, and it is possible to improve the reproducibility of the image especially at the edge portion of the character. . That is, in the image forming apparatus of the present invention, the image quality can be improved in forming a character image.

According to the third aspect of the present invention, the recording density of the target pixel is the density value of the pixel between each two target pixels.
It is determined by distributing according to the density value of each target pixel and adding this to the density value of each target pixel. Therefore, the image of the pixel of interest can be recorded in close proximity. As a result, the lines can be recorded clearly, so that the edge portion of the character becomes clear. That is, in the image forming apparatus of the present invention, the image quality can be improved in forming a character image.

[0013]

【Example】

[Embodiment 1] An embodiment of the present invention will be described below with reference to FIGS. As shown in FIG. 2, a digital copying machine (hereinafter, simply referred to as a copying machine) 1 as an image forming apparatus according to the present embodiment has an original placing table 2 made of hard transparent glass on the upper surface thereof. A scanner 3 is provided below the mounting table 2. Below the scanner 3, an image forming section 25 centering on the photosensitive drum 14 is provided.
The scanner 3 includes a lamp unit 4, mirrors 5 to 7, a lens unit 8 and a CCD (Charge Coupled Device) sensor 9. In the scanner 3, the original placed on the original placing table 2 is irradiated with light from the lamp unit 4, and the reflected light from the original is guided to the light receiving surface of the CCD sensor 9 by the mirrors 5 to 7 and the lens unit 8. , Electrical signals, that is, image data.

The image data is processed by the image processing unit 31 shown in FIG. 4, and then supplied to the laser driver unit 10 of the image forming unit 25. The laser driver unit 10 emits a laser beam based on the image data supplied from the image processing section 31, and this laser beam is reflected by the polygon mirror 11 by the photosensitive drum 1 as shown in FIG.
4 and the photosensitive drum 14 is exposed.

Around the photosensitive drum 14, a charging charger 15, a developing layer 16, a transfer charger 17, a peeling charger 18, a cleaning device 19 and a charge eliminating lamp 2 are provided.
0 is provided. The photoconductor drum 14 is uniformly charged by the charging charger 15 prior to the above exposure, and an electrostatic latent image is formed by the above exposure. This electrostatic latent image is developed by the toner supplied from the developing layer 16, and the toner image formed by this is transferred by the transfer charger 17 to the paper supplied from the paper feeding unit 21. A suction force acts between the paper after the transfer and the photoconductor drum 14. Therefore, the peeling charger 18 applies an AC corona to the paper to adjust the potential of the paper to the photosensitive drum 1.
By lowering the potential to the same level as the surface of No. 4, the suction force is erased, and the paper is peeled from the surface of the photoconductor drum 14 due to its rigidity. On the other hand, after the transfer, the photosensitive drum 1
The toner remaining on the surface of No. 4 is the cleaning device 1
It is scraped off by 9 and collected. The residual potential of the photoconductor drum 14 is removed by reducing the electric resistance of the photoconductor layer by irradiation with light from the charge eliminating lamp 20.

The sheet on which the toner image is transferred is fixed in the fixing device 2 provided in the sheet conveying direction from the photosensitive drum 14.
At 2, the paper is heat-fixed. Then, the sheet is guided to the switching gate 23 and discharged to the outside of the machine or sent to the duplex unit 24 for re-copying.

As shown in FIG. 3, the semiconductor laser 10a of the laser driver unit 10 and the collimator lens have a specific configuration for irradiating the surface of the photosensitive drum 14 with laser light during the exposure operation of the photosensitive drum 14. 1
2. The polygon mirrors 11 and f which are rotary polygon mirrors
-It will be equipped with theta lens 13. In this configuration, the semiconductor laser 10a included in the laser driver unit 10 emits laser light based on the output signal of the image processing unit 31. This laser light is made into a parallel beam by the collimator lens 12, is deflected by the polygon mirror 11 at an equal angular velocity, and is then corrected by the f.theta. Lens 13 so as to be deflected at an equal velocity, and is irradiated onto the surface of the photosensitive drum 14. To be done. Further, in this configuration, the main scanning with the laser light beam is performed by the rotation of the polygon mirror 11 in the A direction, and the sub-scanning in the direction orthogonal to the main scanning direction is the B direction photosensitive drum. 14 rotations.

As shown in FIG. 4, the image processing section 31 includes an A / D converter 32, an image memory 33, a modulation signal generating section 34 and a density processing section 35. The A / D converter 32 converts analog data of a document image obtained from the CCD sensor 9 into digital data. The image memory 33 stores the image data output from the A / D converter 32. The density processing unit 35 converts density data in the image data into 0 to 10 level data.

The modulation signal generating section 34 calculates the density at the time of forming an image, that is, the recording density from the image data, and the modulation signal according to the recording density is supplied to the laser driver unit 10.
Is output to. The modulated signal is obtained by pulse width modulation. This pulse width modulation is shown by an example in which one pixel shown in FIG. 5 is divided into ten. First, a signal S1 indicating the rising position of the writing pulse S3 and a signal S2 indicating the falling position of the writing pulse S3 are obtained from the recording density of the pixel of interest. A writing pulse S3 having a pulse width corresponding to the recording density is generated from these signals S1 and S2.
The write pulse S3 in this example, that is, the pulse width modulation signal is
The rising position is 3, the falling position is 17, and the recording density is 14.

As shown in FIG. 1, the modulation signal generator 34 includes a line memory 41 as a storage means, a shift register 42, a look-up table (hereinafter referred to as LUT) 43, data latches 44 and 45, and a comparator. 46.4
7, AND gate 48 and CPU (Central Processin
g Unit) 49.

Image data in the main scanning direction is sequentially fetched from the image memory 33 into the line memory 41 as the image forming operation progresses. This image data is 0-10
The level indicates the concentration, which is 4-bit data.

The shift register 42 has three pixels a in the main scanning direction from the line memory 41 in response to the first pixel clock.
Image data of up to c are captured. These 3 pixels a-
In c, the pixel b at the center is the pixel of interest. In addition, the shift of the image data from the line memory 41 to the shift register 42 is performed for each of the processing for the three pixels a to c by 2
It is done pixel by pixel.

The LUT 43 has address input terminals A0-A.
11, and data output terminals D0 to D3 and data output terminals D4 to D8. The LUT 43 is a ROM (Read
Only ROM), and the formula of 10 ± {[b] + ([a] + [c]) / 2} / 2 (1) is written in this ROM. In this equation, for example, [a] is the density level of the pixel indicated by the image data a. From the LUT 43, the shift register 4
By inputting the image data of 2 to 3 pixels a to c, the calculated value by the above formula (1) is obtained. This calculation is performed by the CPU 49. That is, from the LUT 43, the calculated value of 10-{[b] + ([a] + [c]) / 2} / 2 (2) is used as the value of the rising position to the data output terminal D.
0 to D3, and the calculated value of 10 + {[b] + ([a] + [c]) / 2} / 2 (3) is used as the value of the falling position to the data output terminal D.
It is output from 4 to D8. The recording density set for the target pixel is [b] + ([a] + [c]) / 2 (4) included in the expressions (2) and (3). Also, the value obtained by each of the above calculation formulas is
The number after the decimal point is rounded off.

The data latch 44 holds the value of the rising position, while the data latch 45 holds the value of the falling position. The data latch 44 has a capacity of 4 bits, and the data latch 45 has a capacity of 5 bits.

The comparators 46 and 47 respectively have input terminals A and B for comparison. The output of the data latch 44 is input to the input terminal B of the comparator 46, and the output of the data latch 45 is input to the input terminal A of the comparator 47.
Further, the input terminal A of the comparator 46 and the input terminal B of the comparator 47 are connected to the second terminal having a period 10 times as long as the first pixel clock.
Pixel clock is input. The comparator 46 compares the output of the data latch 44 (input of the input terminal B) with the value of 0 to 20 (input of the input terminal A) indicated by the second pixel clock, while the comparator 47 outputs the data latch. Four
5 (the input of the input terminal A) is compared with the values 0 to 20 (the input of the input terminal B) indicated by the second pixel clock, and the input value A of the input terminal A and the input of the input terminal B are respectively compared. When the relationship with the value B is A <B, 0 is output, and otherwise 1 is output.

The AND gate 48 is the comparator 46.4.
The logical product of the outputs of 7 is calculated, and the result is given to the laser driver unit 10 as a pulse width modulation signal.

In this embodiment, the shift register 42, the LUT 43 and the CPU 49 constitute a recording density calculating means, and the LUT 43 and the CPU 4 are provided.
9, the data latches 44 and 45, the comparators 46 and 47, and the AND gate 48 constitute a modulation signal output means.

The image forming operation of the copying machine 1 having the above-mentioned structure will be described below. The image of the original document placed on the original document table 2 is read by the scanner 3, and the image data of the original document is obtained from the CCD sensor 9. This image data is input to the image processing unit 31 shown in FIG. 4, converted into digital data by the A / D converter 32, and then stored in the image memory 33.

Next, the image data stored in the image memory 33 is sequentially taken into the line memory 41 shown in FIG.
Further, the image data is sent from the line memory 41 to the shift register 42 by three pixels in response to the first pixel clock. The image data is data arranged in the main scanning direction and indicates the density at 0 to 10 levels.

Next, as a result of the processing in the LUT 43, the calculated value by the above equation (2) is supplied to the data latch 44 as the rising position, and the calculated value by the above equation (3) is supplied to the data latch 45 as the falling position. It

For example, in the line memory 41, as shown in FIG.
As shown in (a), the image data has addresses j0 to jn.
If the image data is stored in, the image data of the addresses j0 to j2, that is, the image data of the pixels j0 to j2 is first sent to the shift register 42. The pixel of interest in this case is j1, and the rising position output from the LUT 43 is
From the equation (2), 10- {10+ (0 + 8) / 2} / 2 = 3. Further, the falling position is 10+ {10+ (0 + 8) / 2} / 2 = 17 from the equation (3).

Next, the data latch 44 holds the value of the rising position (= 3), and the data latch 45 holds the value of the falling position (= 17). Therefore, the output of the comparator 46 rises at 3 at the value of 0 to 20, that is, S1 shown in FIG. 5, and the output of the comparator 47 falls at 17 at the value of 0 to 20, that is, the figure. S2 shown in FIG. As a result, AND gate 4
From S8, S3 shown in the figure is obtained. The recording density in this case is 14 according to the equation (4) or (17-3). The recording area in this case is as shown in FIG.
As shown in (b), since the range of the recording density is distributed from the center position of the pixel of interest to the left and right adjacent pixels,
The pixels are projected from the pixel of interest j1 to the right and left adjacent pixels by 2/10.

Further, in the processing in the modulation signal generating section 34, the target pixel is every other pixel. That is, the image data of the pixel captured in the shift register 42 next to the image data of the pixels j0 to j2 has a shift amount of 2
The image data of pixels j2 to j4 is obtained for the pixels.

Since the target pixel b in this case is the pixel j3, the rising position is 10- {3+ (8 + 2) / 2} / 2 = 6 from the equation (2), and the falling position is (3 From the expression), 10+ {3+ (8 + 2) / 2} / 2 = 14. Further, the recording density is expressed by the formula (4) or (14-
From 6), it becomes 8. The recording area in this case is shown in FIG.
As shown in (b), it is recorded in the range of 4/10 to the left and right from the center of the target pixel j3. Less than,
In this way, for every other pixel of interest,
The recording density, that is, the recording area is set.

The pulse width modulation signal generated as described above is supplied to the laser driver unit 10, and laser light is emitted from the laser driver unit 10 at a timing according to the pulse width modulation signal. afterwards,
The above-mentioned image forming operation is performed. The image formed by the recording operation based on the pulse modulation signal is as shown in FIG.
As shown in, dots are connected in the sub-scanning direction. Therefore, in the processing by the LUT 43, it is possible to obtain an easily viewable image in which lines are aligned in the sub-scanning direction.

As described above, in the modulated signal generator 34, the pixels of interest arranged in the main scanning direction are set in units of two pixels, that is, every other pixel, and only the pixels of interest are recorded. . This is for the following reason.

That is, the laser light has a Gaussian distribution, and the light amount distribution on the surface of the photosensitive drum 14 when recording only one dot with the laser light is as shown in FIG. 8 (a). In this case, what is actually developed is the range from the broken line to the upper part, and the skirt portion of the distribution is not developed.

On the other hand, when two dots are recorded at the adjacent positions by the laser light, the respective light quantity distributions have a two-hump shape due to the sum of the light quantity at the overlapping portions as shown in FIG. Become. Therefore, the hem portion which has not been developed when only one dot is printed is developed due to the influence of the adjacent dots.

Here, when the pulse width modulation is performed on a pixel-by-pixel basis, that is, on a pixel-by-pixel basis based on the pixels arranged in the main scanning direction, uneven driving in the sub-scanning direction, for example, the photosensitive drum 1
When rotation irregularity 4 occurs, the laser light has a Gaussian distribution as described above, so that the beams largely overlap in the sub-scanning direction, as shown in FIG. At this time, a large number of overlapping portions in the sub-scanning direction are generated in the portion where the pitch is reduced due to the drive unevenness, and the overlapping portion is reduced in the portion where the pitch is increased. The difference in the number of overlapping portions appears as a difference in density, which causes image distortion due to drive unevenness.

If the beam diameter of the laser light is reduced,
Although the above-mentioned overlapping portion is reduced as a whole, black solid recording may not be possible in some cases. Therefore, it is difficult to solve the above problem by adjusting the beam diameter.

On the other hand, like the modulation signal generator 34,
When pulse width modulation is performed for each pixel, that is, for every two pixels,
When the drive unevenness occurs, the overlapping of the beams due to the Gaussian distribution in the sub-scanning direction similarly occurs, as shown in FIG. However, since the overlapping portion in the main scanning direction shown by the shaded portion does not occur, the density change due to the overlapping in the sub scanning direction becomes small. Therefore, image distortion due to the drive unevenness is reduced. As a result, by performing pulse width modulation in units of 2 pixels,
It is possible to obtain a good image with less image disturbance due to uneven driving in the sub-scanning direction.

The modulation signal generator 34, that is, the LUT
In the processing by 43, the recording density of each pixel of interest is set to the density value of that pixel of interest instead of averaging the densities of the pixel of interest and its adjacent pixels to set the recording density of that pixel of interest. It is set by adding the density values of the left and right pixels in the main scanning direction. Therefore, it is possible to obtain an easy-to-see image in which the lines are aligned in the sub-scanning direction.

[Embodiment 2] Another embodiment of the present invention will be described below with reference to FIGS. Incidentally, for convenience of explanation, the same reference numerals are given to the means having the same functions as those shown in the above-mentioned embodiment, and the explanation thereof will be omitted.

The copying machine 1 of this embodiment is provided with a modulation signal generating section 53 instead of the modulation signal generating section 34. The modulation signal generator 53 includes a LUT 51 shown in FIG. 9 instead of the LUT 43 shown in FIG. The other structure is the same as that of the first embodiment.

In the processing by the LUT 51, the values indicating the rising position and the falling position of the pulse width modulation signal are calculated as follows from the recording density obtained from the image data of 3 pixels in the equation (4). . That is,
In the LUT 43 of the first embodiment, the rising position is set by 10 − {[b] + ([a] + [c]) / 2} / 2 (2) so that the pulse becomes thicker from the center. It was On the other hand, in the LUT 51 of the present embodiment, the rising position is determined by determining the shift amount of the rising position from the density values of the left and right adjacent pixels a and c with respect to the target pixel b, and using the value of the rising position obtained by the above equation (2). On the other hand, the shift amount is adjusted and set. For example,
The shift amount is 5 ([c]-[a]) / {[b] + ([a] + [c]) / 2} (5). The value obtained by this calculation shall be rounded off to the nearest whole number.

In the LUT 43 of the first embodiment, the fall position is such that the pulse becomes thicker from the center, and 10 + {[b] + ([a] + [c]) / 2} / 2 ( 3) was set by. On the other hand, in the LUT 51 of the present embodiment, the fall position is determined from the density value of the left and right adjacent pixels a and c with respect to the pixel of interest b, and the shift amount is determined from the density value of the rise position obtained by the equation (3). Calculated by adjusting the shift amount. This shift amount similarly becomes the value of the above equation (5).

Here, when the value of the rising position is smaller than 0, the value of the rising position is set to 0, and the value added to set it to 0 is added to the value of the falling position. To be Similarly, when the value of the fall position is larger than 20, the value of the fall position is 2
The value set to 0 and subtracted to make it 20 is also subtracted from the value of the rising position. LUT51
In this way, the rising position and the falling position are set in this way.

Thereafter, a pulse width modulation signal is generated from the rising position and the falling position obtained as described above in the same manner as in the case of the first embodiment, and image formation is performed based on this signal. Be seen.

In the present embodiment, the shift register 42, the LUT 51 and the CPU 49 constitute a recording density calculating means, and the LUT 51 and the CPU 4 are provided.
9, the data latches 44 and 45, the comparators 46 and 47, and the AND gate 48 constitute a modulation signal output means.

Next, the processing by the LUT 51 will be described with reference to FIG.
Will be described more specifically. This figure shows the relationship between the image data of the document stored in the line memory 41 ((a) in the figure) and the recording state of the image data ((b) in the figure).

For the pixel of interest x shown in FIG. 9A, the temporary rising position obtained from the equation (2) is 10- {3+ (0 + 10) / 2} / 2 = 6, and the equation (3) is obtained. The tentative fall position obtained from the above is 10+ {3+ (0 + 10) / 2} / 2 = 14. Incidentally, these provisional rising and falling positions are the ones shown in FIG. 7C in which the recording position is not shifted. On the other hand, the shift amount is 5 (10-0) / {3+ (0 + 10) / 2} = 6.3 from the equation (5).
It becomes 6. Here, comparing the densities of the right and left adjacent pixels of the target pixel x, the right adjacent pixel has a higher density, so the recording position of the target pixel x is shifted rightward from the center by the shift amount. . Therefore, the rising position of the pulse width modulated signal corrected by the above shift amount is 12
(= 6 + 6), the fall position is 20 (= 14 + 6), and the recording density is 8.

Similarly, when the pulse width modulation signal for the target pixel y is calculated, the temporary rising position according to the equation (2) is 5, the temporary falling position according to the equation (3) is 15, and
The shift amount according to the equation (5) is 10. Further, the density of the left and right adjacent pixels with respect to the target pixel y is higher in the pixel adjacent on the left side, and the shift direction is the left direction, so the rising position of the pulse width modulation signal for the target pixel y is 0, and the falling position is 10. And the recording density becomes 10.

In the processing by the LUT 51 as described above, the recording positions of the target pixel x and y can be brought close to each other, that is, the dots can be gathered, as shown in FIG. Therefore, as shown in FIG.
It is possible to avoid the occurrence of streaks in the line portion of the recorded image, which occurs when the recording positions of y are distant from each other. Thereby, it is possible to improve the reproducibility of the image particularly at the edge portion of the character. The reason for this will be described in more detail below.

For example, as shown in FIG. 11 (a), when a document with diagonal lines 52 is read, the image data shown in FIG. 11 (b) can be obtained. The numbers shown in FIG.
The density is 0 to 10 levels indicated by the image data of each pixel. Also, the downward arrows indicate the arrangement of the target pixel.

Next, when the LUT 43 that does not shift the recording position is applied to the target pixel, the dot arrangement becomes as shown in FIG.
A streak-like blank portion is generated between the target pixels, and this appears as a streak in the diagonal line 52. On the other hand, when the LUT 43 for shifting the recording position is performed on the target pixel, the dots of the target pixel are gathered as shown in FIG. There is no occurrence of the above-mentioned streak-like blank portion. As a result, the diagonal line 52 can be reproduced well.
The numbers shown in (c) and (d) of the figure are the recording densities of the target pixels.

As described above, in the above processing by the LUT 51, the line can be recorded clearly, so that the edge portion of the character becomes clear. Therefore, the copying machine 1 of the present embodiment is
It is particularly suitable for recording character images.

In the processing by the LUT 51, the target pixel is set for each fixed number of pixels, and the recording position of the target pixel is shifted toward the pixel having the higher density of the left and right adjacent pixels to thereby obtain the target pixel. The recording positions of the two are close to each other. On the other hand, instead of performing the shift operation, for example, in a pixel arrangement in the main scanning direction, a pixel having a high density level, for example, a pixel having a density level of 10 is set as a target pixel, and the target pixel is recorded. If the density is set according to the density values of adjacent pixels, dots will not be connected in the sub-scanning direction, and the balance of the entire image will be disturbed. Further, in this method, it is necessary to read the density of each pixel and determine the level of the density, which complicates the configuration. Therefore, such a system cannot be adopted.

[Embodiment 3] Still another embodiment of the present invention will be described below with reference to FIGS. Incidentally, for convenience of explanation, the same reference numerals are given to the means having the same functions as those shown in the above-mentioned embodiment, and the explanation thereof will be omitted.

The copying machine 1 of this embodiment is provided with a modulation signal generating section 63 instead of the modulation signal generating section 34. The modulation signal generator 63 includes a shift register 61 and an LUT 62 shown in FIG. 12, instead of the shift register 42 and the LUT 43 shown in FIG. The other structure is the same as that of the first embodiment.

The shift register 61 stores 5 pixels a in the main scanning direction from the line memory 41 in response to the first pixel clock.
The image data for ~ e is captured. These 5 pixels a-
In the image data for e, the central pixel b is the data of the target pixel. Further, the shift of the image data from the line memory 41 to the shift register 61 is performed by 2 pixels for each of the above 5 pixels.

In the processing by the LUT 62, the value of the rising position of the pulse width modulated signal is calculated by the following expression (6), and the value of the falling position is calculated by the expression (7). The recording density is obtained by the equation (8).
The values obtained by these equations are rounded off to the right of the decimal point.

10-{[b] + [d] × [b] / ([a] + [b]) + [e] × [b] / ([b] + [c])} / 2 (6) 10 + {[b] + [d] × [b] / ([a] + [b]) + [e] × [b] / ([b] + [c])} / 2 ( 7) [b] + [d] × [b] / ([a] + [b]) + [e] × [b] / ([b] + [c]) (8) After that, the above rise As described above, the pulse width modulation signal is obtained from the falling position and the falling position.

As can be seen from the above equations (6) and (7), in the processing by this LUT 62, the target pixel is weighted by its density value, and the density values of the left and right adjacent pixels to the target pixel are weighted according to this weighting. The recording density of the target pixel is determined by allocating the density value of the target pixel.

That is, the LUT 43 shown in the first embodiment,
In the processing by the LUT 51 shown in the second embodiment, as shown in FIG. 13A, the density value of the target pixel b is added with 1/2 of each density value of the adjacent pixel d · e to obtain the target pixel b. The recording density of is obtained. In other words, with this method,
The recording density of the target pixel b is [b] + ([d] + [e]) /
2 is obtained, and the pixel d is
Further, the pixel e evenly distributes the densities of 1/2 to the target pixels b and c.

On the other hand, in the processing by the LUT 62 of this embodiment, the density values of the pixels d and e are not evenly distributed to the target pixels a, b, and c adjacent to them, but in FIG. ), The pixels are distributed according to the density values of the target pixels a, b, and c. Therefore, in this method,
The shift register 61 stores image data of 5 pixels.

In the present embodiment, the shift register 61, the LUT 62 and the CPU 49 constitute recording density calculation means, and the LUT 62 and the CPU 4 are provided.
9, the data latches 44 and 45, the comparators 46 and 47, and the AND gate 48 constitute a modulation signal output means.

Next, the processing by the LUT 62 will be described with reference to FIG.
Will be described more specifically. This figure shows the relationship between the image data of the document stored in the line memory 41 ((a) in the figure) and the recording state of the image data ((b) in the figure).

With respect to the pixel of interest x shown in FIG. 7A, the rising position of the pulse width modulated signal is calculated by the equation (6) as follows: 10- {1 + 0 × 1 / (0 + 1) + 10 × 1 / (1+
9)} / 2 = 9, and the fall position is calculated from the equation (7) as follows: 10+ {1 + 0 × 1 / (0 + 1) + 10 × 1 / (1+
9)} / 2 = 11, and the recording density becomes 2. For the pixel of interest y, the pulse width modulation signal has a rising position of 0, a falling position of 20, and a recording density of 20. Comparing these target pixels x and y, since the target pixel y has a higher density, the distribution amount of the density value in the pixels between the target pixel x and y with respect to the target pixel x and y is larger in the target pixel y. Has become. The recording density of the pixel of interest z is 0. That is, all the density values of the pixels between the target pixels y and z are distributed to the target pixel y.

On the other hand, the density value of pixels other than the target pixel is not sorted according to the density value of the target pixel, that is, the first embodiment.
In the processing by the LUT 43 shown in FIG. 7, as shown in FIG. 7C, the pulse width modulation signal for the target pixel x has a rising position of 7 from the equation (2) and a falling position of the pulse width from the equation (3). 13 and the recording density is 6 according to the equation (4). For the target pixel y, the pulse width modulation signal has a rising position of 3 and a falling position of 18
And the recording density becomes 15. For the pixel of interest z, the pulse width modulation signal has a rising position of 10, a falling position of 11, and a recording density of 1. In this case, the recording positions of the target pixels are dispersed.

As is clear from the above description, according to the above processing by the LUT 62 of this embodiment, it is possible to record the image of the pixel of interest in close proximity. As a result, the lines can be recorded clearly, so that the edge portion of the character becomes clear. Therefore, the copying machine 1 of the present embodiment is particularly suitable for recording a character image, like the copying machine 1 of the second embodiment.

[Embodiment 4] Still another embodiment of the present invention will be described below with reference to FIGS. Incidentally, for convenience of explanation, the same reference numerals are given to the means having the same functions as those shown in the above-mentioned embodiment, and the explanation thereof will be omitted.

As shown in FIG. 15, a copying machine 71 as an image forming apparatus of this embodiment uses an LED instead of a laser beam.
(Light Emitting Diode) The light emitted from the array 72 exposes the photosensitive drum 14.
As shown in FIG. 16, the LED array 72 includes LEs.
The D driver unit 73 is connected, and the LED driver unit 73 drives the LED array 72 based on the modulation signal output from the modulation signal generation unit 75.

As shown in FIG. 17, the modulation signal generator 75 comprises line memories 81 to 83 as storage means, a shift register 84, a LUT 85, a shift register 86 and a CPU 87.

Image data in the main scanning direction is sequentially fetched from the image memory 33 into the line memories 81 to 83 in accordance with the progress of the image forming operation. This image data is 0
The density is shown at 10 levels and is 4-bit data. The shift register 84 receives the image data of one pixel from each of the line memories 81 to 83 in accordance with the pixel clock, for a total of three pixels (a to c). Therefore, the three pixels (a to
The image data for c) is image data arranged in the sub-scanning direction, and the pixel b corresponding to the image data sent from the line memory 82 is always the pixel of interest.

When the processing of the image data for three lines fetched in the line memories 81 to 83 is completed, the image data for the last one line is left and the image data for the other two lines is stored in the next line. Replaced with image data.
For example, when the image data of the first to third lines is first fetched from the image memory 33 into the individual line memories 81 to 83 and the processing for these first to third lines is completed, the images for these three lines are imaged. The data will be erased. Next, the image data of the third to fifth lines are loaded into the individual line memories 81 to 83. In this case, the target pixel is a pixel on every other line such as the second line and the fourth line.

In the processing by the LUT 85, the image data of 3 pixels (a to c) input from the shift register 84 is converted into the image data of 20 bits and is given to the shift register 86 as a modulation signal. That is, in the processing by the LUT 85, as shown in FIG.
It is assumed that the LEDs are divided, and a signal that generates 1 when each LED 72a of the LED array 72 is turned on in each region and 0 when not turned on is generated based on the densities of the three pixels (a to c). In this case, in the processing by the LUT 85, the LED 72a is turned on only in the area of [b] + ([a] + [c]) / 2 (4), and this area is 10b.
It is distributed before and after the it-th eye in the sub-scanning direction. This processing is performed 5000 times with respect to the data of three lines taken in the line memories 81 to 83. Therefore, the shift register 86 takes in 5000 pieces of 20-bit data.

On the other hand, in the LED array 72, 5000 LEDs 72a ... Are arranged in parallel so as to face the peripheral surface of the photosensitive drum 14. The juxtaposed region of the LEDs 72a corresponds to the width of the image forming region of the photosensitive drum 14. The LED driver unit 73 includes the above L
ED 72a and LED drivers 73a ... Corresponding to each are provided.

In the present embodiment, the shift register 84, the LUT 85 and the CPU 87 constitute a recording density calculating means, and the LUT 85 and the CPU 87.
The modulation signal output means is constituted by the shift register 86 and the shift register 86.

Next, the processing by the LUT 85 will be described with reference to FIG.
Will be described more specifically. The figure shows line memories 81-
Image data of the original document stored in 83 ((a) in the figure),
The relationship between the recording state of the image data ((b) in the figure) is shown. It should be noted that the numbers shown in FIG. 9A are density values of 0 to 10 levels in each pixel.

In FIG. 11A, the first pixel of interest is j1 of the line memory 82. The recording density of the target pixel j1 is 8+ (6 + 10) / 2 = 16 from the equation (4). A signal indicating the recording density and the recording position is 0011111111111111111100, and this signal is obtained from the LUT 85 and supplied to the shift register 86. The next pixel of interest is j2 of the line memory 82, and its recording density is similarly 1+ (4 + 6) / 2 = 6. The signal indicating the recording density and the recording position is 00000001111110000000. In the same manner, the signal obtained from the LUT 85 is supplied to the shift register 86.

After that, the above-mentioned signal from the shift register 86 is used as a modulation signal for each L of the LED driver unit 73.
The LED driver 73a is output to the ED driver 73a.
The LED 72a of the LED array 72 is turned on by being driven to. As a result, the target pixels j1 and j2 are recorded as shown in FIG. In this case, the pixel of interest is printed with the print density being evenly distributed in the direction of the adjacent pixels in the sub-scanning direction, with the center position of the pixel of interest in the sub-scanning direction as the center. Further, the recording is performed only on the target pixel as in the above-described embodiments, and the dots are connected in the main scanning direction. Therefore, it is possible to obtain an easy-to-see image in which the lines are aligned in the main scanning direction.

[Embodiment 5] Still another embodiment of the present invention will be described below with reference to FIGS. 20 and 21. Incidentally, for convenience of explanation, the same reference numerals are given to the means having the same functions as those shown in the above-mentioned embodiment, and the explanation thereof will be omitted.

The copying machine 71 of this embodiment is provided with a modulation signal generating section 92 instead of the modulation signal generating section 75. The modulation signal generating section 92 includes a LUT 91 shown in FIG. 20 in place of the LUT 85 shown in FIG. Other configurations are
This is the same as the fourth embodiment.

In the processing by the LUT 85 shown in the fourth embodiment, the pixel of interest of the recording density obtained by the equation (4) based on the data of three pixels is centered at the 10th bit, that is, in the sub-scanning direction of the pixel of interest. Printing is performed with the printing density values evenly distributed in the direction of adjacent pixels in the sub-scanning direction, centered on the center position of. On the other hand, in the processing by the LUT 91 of the present embodiment, for example, 5 ([c] − [a]) / {[b] + ([a] + [c]) / 2} (5) The recording position of the pixel of interest, that is, L
The lighting position of the ED 72a is designed to shift in the direction of higher density of the vertically adjacent pixels in the sub-scanning direction. The value obtained by this calculation shall be rounded off to the nearest whole number.

Here, when the value of the lighting start position of the LED 72a becomes smaller than 0, the value of the lighting start position is set to 0, and the value added to set it to 0 is the LED
It is also added to the value of the lighting end position of 72a. Similarly, L
When the value of the lighting end position of the ED 72a becomes larger than 20, the value of the lighting end position is set to 20, and this is set to 2
The value subtracted to make it 0 is also subtracted from the value of the lighting start position. In the processing by the LUT 91, the lighting start position and the lighting end position of the LED 72a, that is, the recording position for the target pixel is set in this manner.

In the present embodiment, the shift register 84, the LUT 91 and the CPU 87 constitute a recording density calculating means, and the LUT 91 and the CPU 87 are provided.
The modulation signal output means is constituted by the shift register 86 and the shift register 86.

Next, the processing by the LUT 91 will be described with reference to FIG.
Will be described more specifically. The figure shows line memories 81-
Image data of the original document stored in 83 ((a) in the figure),
The relationship between the recording state of the image data ((b) in the figure) is shown.

For the pixel of interest x shown in FIG. 7A, the recording density obtained from the equation (4) is 8+ (0 + 10) / 2 = 13, and the recording density and the signal representing the temporary recording position are It becomes 000111111111111110000. In addition, the shift amount of the recording position of the target pixel x is 5 (10-0) / {8+ (0 + 10) / 2} = 3.8 → 4 from the expression (5), and the recording start for the target pixel x is started. Position, ie LE
The lighting start position of D72a is 8. In this case, comparing the densities of the adjacent pixels in the sub-scanning direction with respect to the pixel of interest x, the lower pixel has a higher density, so the recording start position is shifted downward. That is, the signal indicating the recording density and the recording position for the pixel of interest x is 00000001111111111111111.

Next, following this, the line memory 81
The image data for 3 lines in the main scanning direction stored in .about.83 are similarly processed. When this process is completed, the data in the line memories 81 to 83 is rewritten, the image data previously stored in the line memory 83 is written in the line memory 81, and the line memories 82 and 83 respectively store the next data. The image data of the line is written. The pixel of interest in this case is y.

For this target pixel y, the recording density is 13 according to the equation (4), and the signal indicating the recording density and the temporary recording position is 000111111111111110000. The shift amount of the recording position of this target pixel y is (5)
The calculation of the formula gives -4, and the recording start position becomes 0. Therefore, the signal indicating the recording density and the recording position for the target pixel y is 11111111111110000000.

In the processing by the LUT 91 as described above, the recording positions of the target pixel x and y can be made close to each other in the sub-scanning direction, that is, the dots can be gathered, as shown in FIG. Therefore, as in the case of the processing by the LUT 85 shown in FIG.
It is possible to avoid the occurrence of streaks in the line portion of the recorded image, which occurs when the recording positions of y are separated. As a result, especially the edge portion of the character can be recorded clearly and the reproducibility of the character becomes good. Therefore, the configuration of this embodiment is particularly suitable for recording character images.

[Embodiment 6] Still another embodiment of the present invention will be described below with reference to FIGS. 22 and 23. Incidentally, for convenience of explanation, the same reference numerals are given to the means having the same functions as those shown in the above-mentioned embodiment, and the explanation thereof will be omitted.

The copying machine 71 of this embodiment is provided with a modulation signal generating section 108 instead of the modulation signal generating section 75. The modulation signal generator 108 is the line memory 8 shown in FIG.
Line memory 101 as storage means in place of 1 to 83
To 105, a shift register 106 is provided instead of the shift register 84, and a LUT 107 is provided instead of the LUT 85.
Is equipped with. The other structure is the same as that of the fourth embodiment.

Image data of 5 lines in total is fetched from the image memory 33 into the line memories 101 to 105, one line portion each. Line memories 101 to 1
When the processing of the image data for 5 lines captured in 05 is completed, the image data for 3 to 5 lines is left and the other 2
The image data for one line is replaced with the image for the next line. For example, when the image data of the first to fifth lines is first fetched from the image memory 33 into the individual line memories 101 to 105, and the processing of these first to fifth lines is completed, the images of these five lines are imaged. The data will be erased. Next, the image data of the third to seventh lines are loaded into the individual line memories 101 to 105. In this case, the target pixel is a pixel on every other line such as the third line and the fifth line.

In the shift register 106, image data of 5 pixels (a to e) in total is fetched from the line memories 101 to 105 one pixel at a time according to a pixel clock. The image data for 5 pixels are arranged in the sub-scanning direction. Each image data includes 4-bit density information of 0 to 10 levels. In the image data of 5 pixels (a to e), the central pixel b is the pixel of interest.

In the processing by the LUT 107, the image data of 5 pixels input from the shift register 106 is 20b.
It is converted into data of it and given to the shift register 86. That is, in the processing by the LUT 107, [b] + [d] × [b] / ([a] + [b]) + [e] × [b] / ([b] + [c]) (8) ), The recording density of the pixel of interest is set, and this pixel of interest is recorded in the recording area corresponding to the above recording density with the 10th bit as the center, that is, the center position of the pixel of interest in the sub-scanning direction as the center. The signal of is generated.

As can be seen from the above description, LUT10
In the process of 7, the target pixel is weighted by its density value, and the density value of the pixel adjacent to the target pixel in the sub-scanning direction is assigned to the target pixel according to this weighting, thereby determining the recording density of the target pixel. is doing.

In this embodiment, the shift register 106, the LUT 107 and the CPU 87 constitute a recording density calculation means, and the LUT 107, CP
The U87 and the shift register 86 constitute a modulation signal output means.

Next, the processing by the LUT 107 will be described with reference to FIG.
This will be specifically described with reference to No. 3. The figure shows a line memory 10
1 shows the relationship between the image data of the original document stored in Nos. 1 to 105 ((a) in the figure) and the recording state of the image data ((b) in the figure). The figure (a)
The number on the left end of the is the number of the line memories 101 to 105 storing the image data.

For the pixel of interest x shown in FIG. 10A, the recording density obtained from the equation (8) is 2 + 0 × 2 / (0 + 2) + 8 × 2 / (2 + 10) = 3.3.
→ 3, and the signals indicating the recording density and the recording position are 0000000011100000000. Next, following this, the line memory 103
The processing for one line is performed for the target pixel stored in. When this process ends, the line memory 10
The data of 1 to 105 are rewritten, and the line memory 10
The image data previously stored in the line memories 103 to 105 is written in the line memories 1 to 103.
Image data of the next line is written in 04 and 105, respectively. In this case, the target pixel is y, and the target pixel y has a recording density of 19 similarly obtained from the equation (8). Therefore, the signals indicating the recording density and the recording position are 11111111111111111110. Next, following this, the line memory 103
The processing for one line is performed for the target pixel stored in. When this process ends, the process for the target pixel z is performed through the same operation as described above. The recording density obtained from the equation (8) for this target pixel z is zero.

Here, comparing the original densities of the target pixel x · y, the target pixel y has a higher density than the target pixel x. Therefore, the density values of the pixels between the target pixel x and y are mostly distributed to the target pixel y side. Also, the target pixel y
The density values of the pixels between z are all distributed to the target pixel y side.

In the processing by the LUT 107 as described above, the recording positions of the target pixel x and y can be made close to each other in the sub-scanning direction, that is, the dots can be gathered, as shown in FIG. Therefore, as in the case of the processing by the LUT 85 shown in FIG.
It is possible to avoid the occurrence of streaks in the line portion of the recorded image when the recording positions of y are far apart.
As a result, especially the edge portion of the character can be recorded clearly and the reproducibility of the character becomes good. Therefore, the configuration of this embodiment is particularly suitable for recording character images.

[Embodiment 7] Still another embodiment of the present invention will be described below with reference to FIGS. 24 to 27. Incidentally, for convenience of explanation, the same reference numerals are given to the means having the same functions as those shown in the above-mentioned embodiment, and the explanation thereof will be omitted.

The copying machine of the present embodiment is the copying machine 1 shown in FIG. 2 in which the photosensitive drum 14 is exposed by laser light. The copying machine 1 of this embodiment includes a modulation signal generating section 113 shown in FIG. The modulation signal generation unit 113 has the LUT 43 of the first embodiment shown in FIG. 1 and the LUT 51 of the second embodiment shown in FIG.
It has an area determination unit 111 as an area determination unit and an LUT switching unit 112 as an area determination unit. The other configuration of the modulation signal generating section 113 is the same as that of the first or second embodiment.

In the above structure, the LUTs 43, C
PU49, data latches 44/45, comparators 46/47
A first modulation signal output means is constituted by the AND gate 48, the LUT 51, the CPU 49, and the data latch 44.
45, the comparators 46 and 47, and the AND gate 48 constitute second modulation signal output means.

The area determining section 111 is arranged to operate in the image memory 33.
It is determined based on the image data taken in from the image data whether the image data is in the character area, the photographic area, or the halftone dot area. The determination target in the area determination unit 111 is the same image data as the image data of the pixel of interest that is captured and processed in the shift register 42. The area determination section required for the modulated signal generation section 113 may be any area that can determine a character area and other areas.

The LUT switching unit 112 includes the area determining unit 11
According to the determination result of No. 1, which of the LUT 43 and the LUT 51 is used is selected. That is, when the area determination unit 111 determines that the image data to be processed is for a character area, the LUT switching unit 112 performs the LUT 51 for performing processing with good character reproducibility as described above.
On the other hand, when it is determined that the image data to be processed is other than the character area, the LUT 43 that is suitable for processing the image data of the area other than the character area is selected in comparison with the LUT 51. Further, the CPU 49 performs the calculation by the selected LUT 43 or LUT 51.

The area determination unit 111 described above is used, for example, in FIG.
3, the block memory 121, the maximum value detection circuit 122, the minimum value detection circuit 123, the main scanning direction difference value total calculation circuit 124, and the sub-scanning direction difference value total calculation circuit 12
5, subtractor 126, comparator 127 and determination circuit 128
Is equipped with.

The block memory 121 stores the image data of a plurality of lines fetched from the image memory 33. The maximum value detection circuit 122 finds the maximum signal level in the block of the image data stored in the block memory 121, and the minimum value detection circuit 123 finds the minimum signal level in the block. The subtractor 126 calculates the difference Pa between the maximum signal level and the minimum signal level. The main-scanning-direction difference value sum calculation circuit 124 sequentially adds the difference values between two consecutive pixels in the main scanning direction in the block to obtain the sum of the difference values. The sub-scanning direction difference value sum calculation circuit 125 sequentially adds the difference values between two consecutive pixels in the sub-scanning direction in the block to obtain the sum of the difference values. Comparator 12
7 is for obtaining the minimum value Pb by comparing the sum of the difference values in the main scanning direction and the sum of the difference values in the sub-scanning direction.
The judging circuit 128 judges from the Pa and Pb whether the block is a character area, a photographic area, or a halftone dot area. That is, the determination circuit 128 outputs the character area likeness, the photograph area likeness, and the halftone dot area likeness as numerical values by inputting the Pa and Pb.

The judgment circuit 128 has the structure shown in FIG. 26. In this structure, the input value of Pa is 6 bi.
t, more specifically, the upper 6 bits out of 8 bits are used, and I _{a0 to} I _a5 are used in the figure. The input value of Pb is 7bi
t, specifically, the upper 7 bits of 10 bits are used, and I _{b0 to} I _b6 are used in the figure. Output values are all 8 bits
Of these, 3 bits each are used for output values that represent the character area, O _{c0 to} O _c2 are used in the figure, and 2 bits each are used for output values that represent the photo area, and O _{p0 to} O _p1 are used in the figure. 3 bits are used for the output value representing the area, and O _{s0 to} O _s2 are used in the figure.

The decision circuit 128 uses a two-dimensional lookup table whose input / output characteristics are predetermined by the neural network, or the neural network itself. The neural network in this case is a four-layer perceptron as shown in FIG. 27 (a), in the input layer, the normalized Pa is input to Ia, and the normalized Pb is input to Ib, In the output layer, a numerical value indicating the character area likeness is output to O _c , a numerical value indicating the photograph area likeness is output to O _p , and a numerical value indicating the halftone dot area likeness is output to O _s . Each input layer is connected to the inputs of all the neural elements of the intermediate layer, and the output of each intermediate layer is connected to the inputs of all the neural elements of the output layer.

Each neural element, as shown in FIG.
It is an element with multiple inputs and one output, and the input value to each neural element is x
Assuming that _{i is} the weight coefficient, w _{ij is} the output value, and y _j is the output value, each neural element performs the product-sum calculation of the following formula (9), and the product-sum calculation result X _j is the sigmoid function of formula (10) Used as an input to output y _j .

[0113]

[Equation 1]

In the neural network which has already been well learned, when the Pa and Pb obtained in the character area are input, O _c is 1, O _p is 0, and O _s is 0 in the output layer. The above values Pa and P obtained in the photographic area are output as close values.
When b is input, in the output layer, O _c is 0, O _p is 1, and O _s is a value close to 0. When Pa and Pb obtained in the halftone dot area are input, In the output layer,
Output values are 0 _c , 0 _p , and 0 _s , respectively. In the neural network for determining the input / output characteristics of the two-dimensional lookup table, each neural element in the input / output layer is 8b.
When it is used and used in the discrimination circuit, the number of bits of each neural element of the input / output layer corresponds to the number of bits of each input / output of the determination circuit.

In addition to the above-mentioned configuration, the area determination unit 111 may use a conventionally known technique such as a configuration using pattern matching or a configuration using conventional characteristic parameters. In addition, LUT43
The operation of the modulation signal generator 113 when 51 is used is as described above.

As described above, in the copying machine 1 of this embodiment,
LUT5 suitable for processing image data of character area
1 is used, on the other hand, the image data other than the character area is processed by the LUT 43, which is more suitable for processing this image data than the LUT 51. Therefore, it is suitable for processing a wide range of image data. It is possible to form an image with various image quality.

Further, as a modulation signal generating section having the same function as that of the above configuration, the modulation signal generating section 1 shown in FIG.
21, the modulation signal generator 131 shown in FIG. 29 and FIG.
The modulated signal generation unit 141 shown in can be configured.

The modulation signal generating section 121 shown in FIG. 28 is similar to the modulation signal generating section 113 shown in FIG. 24, but the copying machine 1 shown in FIG. Applied to. The modulation signal generator 121 compares the LUT 62 shown in FIG. 12 of the third embodiment with the LUT 62 suitable for processing the image data of the character area and the LUT 62 shown in FIG. It has an LUT 43 suitable for data processing, and also has the area determination unit 111 and the LUT switching unit 112. In addition, as the shift register, the line memory 41
Shift register 6 that captures image data for 5 pixels from
Have one. The other configuration of the modulation signal generation unit 121 is the same as that of the first or third embodiment.

In the modulation signal generating section 121, when the area determining section 111 determines that the image data to be processed is in the character area, the LUT switching section 112 sets L level.
While the UT 62 is selected, when it is determined that the image data to be processed is something other than the character area, the LUT switching unit 112 selects the LUT 43. LUT43
The operation of the modulation signal generation unit 121 when 62 is used is as described above. Further, in the processing by the LUT 62, the processing for the image data a to e held in the shift register 61 is performed, and in the processing by the LUT 43, the processing for the image data d, b, e is performed.

The modulation signal generator 131 shown in FIG.
This is applied to the copying machine 71 shown in FIG. 15 in which the photosensitive drum 14 is exposed by the ED array 72. The modulation signal generation unit 131 compares the LUT 91 shown in FIG. 20 of the fifth embodiment with the LUT 91 suitable for processing the image data of the character area and the LUT 91 shown in FIG. In addition to having an LUT 85 suitable for data processing, it also has the area determination unit 111 and the LUT switching unit 112. The other configuration of the modulation signal generator 131 is the same as that of the fourth or fifth embodiment.

In the above structure, LUT85, C
The PU 87 and the shift register 86 constitute a first modulation signal output means, and the LUT 91, the CPU 87 and the shift register 86 constitute a second modulation signal output means.

In the modulation signal generating section 131, when the area determining section 111 determines that the image data to be processed is in the character area, the LUT switching section 112 sets L level.
While the UT 91 is selected, when it is determined that the image data to be processed is something other than the character area, the LUT switching unit 112 selects the LUT 85. LUT85
The operation of the modulation signal generation unit 131 when 91 is used is as described above.

The modulation signal generation section 141 shown in FIG. 30 is similar to the modulation signal generation section 131 shown in FIG.
This is applied to the copying machine 71 shown in FIG. 15 in which the photosensitive drum 14 is exposed by the array 72. The modulation signal generator 141 compares the LUT 107 shown in FIG. 22 of the sixth embodiment with the LUT 107 suitable for processing the image data of the character area and the LUT 107 shown in FIG. In addition to having an LUT 85 suitable for data processing, it also has the area determination unit 111 and the LUT switching unit 112. Further, as the line memory and the shift register, in order to enable the processing by the LUT 107, the line memories 101 to 105 that take in the image data of 5 lines and the shift register 106 that holds the image data of 5 pixels are provided. . The other configuration of the modulation signal generator 141 is the same as that of the fourth or sixth embodiment.

In the modulation signal generation unit 141, when the area determination unit 111 determines that the image data to be processed is in the character area, the LUT switching unit 112 sets L.
While the UT 107 is selected, when it is determined that the image data to be processed is something other than the character area, the LUT switching unit 112 selects the LUT 85. LUT8
The operation of the modulation signal generator 141 when using 5 · 107 is as described above. Also, the LUT 107
In the processing by, the processing for the image data a to e held in the shift register 106 is performed, and the LU
In the process of T85, the process for the image data d, b, e is performed.

[0125]

As described above, the image forming apparatus according to the invention of claim 1 stores the image data including the density value of each pixel of the image to be formed, and the storage means stored in this storage means. For each pixel arranged in one of the main scanning direction or the sub-scanning direction corresponding to the image data, a pixel of interest, which is a pixel to be recorded, is set for each of a plurality of predetermined pixels, and the pixel in the one direction According to the recording density calculation means for adding the density values of the adjacent pixels before and after to the density value of the pixel of interest to obtain the recording density of the pixel of interest, and the recording density centered on the center position of the pixel of interest. A modulation signal output unit that generates a modulation signal that specifies the recording area of the length in the front-back direction of the one direction and supplies the modulation signal to the image forming unit is provided.

As a result, in the image forming apparatus of the present invention,
Since the recording density of the target pixel is determined by adding the density value of the pixel adjacent to the target pixel to the density value of the target pixel, the centers of the recording areas are aligned in the sub-scanning direction or the main scanning direction. As a result, it is possible to form an image that is easy to see, as compared with a case where the image data of a plurality of pixels are simply averaged to obtain a modulation signal for image formation.

According to the image forming apparatus of the invention of claim 2,
2. The image forming apparatus according to claim 1, wherein the modulation signal output means sets the center of the recording area for the target pixel to the center pixel of the target pixel and the adjacent pixel on the higher density value side of the adjacent pixels on both sides. It is configured to move in the direction.

As a result, in addition to the effect of the first aspect of the invention, the recording positions of the target pixels can be brought close to each other, that is, the dots can be gathered together. Therefore, it is possible to avoid the occurrence of streaks in the line portion of the recorded image, which occurs when the recording positions of the target pixel are distant from each other, and it is possible to improve the reproducibility of the image particularly at the edge portion of the character. That is, the image forming apparatus of the present invention has an effect that the image quality can be improved in forming a character image.

According to the image forming apparatus of the invention of claim 3,
In the image forming apparatus according to the invention of claim 1, the recording density calculation means distributes the density values of the adjacent pixels between each two target pixels according to the density values of the two target pixels, In this configuration, the distributed density value is added to the density values of the two target pixels to obtain the recording density of each target pixel.

As a result, in addition to the effect of the first aspect of the invention, the image of the pixel of interest can be recorded in close proximity. Therefore, since the line can be recorded clearly, the edge portion of the character becomes clear. That is, the image forming apparatus of the present invention has an effect that the image quality can be improved in forming a character image.

[Brief description of drawings]

FIG. 1 is a block diagram of a modulation signal generator included in a digital copying machine according to an embodiment of the present invention.

FIG. 2 is a schematic front view showing the structure of a digital copying machine including the modulation signal generating section.

FIG. 3 is a perspective view showing a configuration of exposing a photosensitive drum with laser light in the digital copying machine.

FIG. 4 is a block diagram showing a configuration of an image processing unit included in the digital copying machine.

5 is an explanatory diagram of a pulse width modulation signal generation operation by processing of the LUT shown in FIG.

6 is an explanatory diagram showing the density data and the target pixel stored in the line memory shown in FIG. 1, and the recording state of the target pixel by the processing of the LUT.

FIG. 7 is a front view showing an image formed by the digital copying machine.

FIG. 8A is a graph showing a light amount distribution of a laser beam on the surface of the photoconductor drum, and FIG. 8B is a light amount when two laser beams are irradiated to adjacent positions on the surface of the photoconductor drum. A graph showing the distribution, FIG. 7C is an explanatory view showing an overlapping state of laser beams when drive unevenness occurs in the sub-scanning direction when pulse width modulation is performed for each pixel, FIG. FIG. 3 is an explanatory diagram showing an overlapping state of laser beams when drive unevenness occurs in the sub-scanning direction when pulse width modulation is performed for every two pixels.

FIG. 9 is a block diagram of a modulation signal generation unit included in a digital copying machine according to another embodiment of the present invention.

10 is an explanatory diagram showing the density data and the target pixel stored in the line memory shown in FIG. 9, and the recording state of the target pixel by the processing of the LUT.

11A is an explanatory diagram showing an example of an original image with diagonal lines, FIG. 11B is an explanatory diagram showing the density data of FIG. 11A, and FIG. 11C is a recording position of a target pixel. 13A is an explanatory view showing the recording state of the original image shown in FIG. 7A when the image is not shifted, and FIG. 9D is the recording of the original image shown in FIG. 9A when the recording position of the pixel of interest is shifted. It is explanatory drawing which shows a state.

FIG. 12 is a block diagram of a modulation signal generator provided in a digital copying machine according to still another embodiment of the present invention.

FIG. 13A is an explanatory diagram of processing by an LUT that sets the recording density of the target pixel by evenly distributing the density values of adjacent pixels with respect to the target pixel; FIG. 13B shows the target pixel. FIG. 8 is an explanatory diagram of a process by the LUT that sets the recording density of the pixel by distributing density values of adjacent pixels to the target pixel according to the density value of the target pixel.

14 is a diagram showing the density data and the target pixel stored in the line memory shown in FIG. 12, the recording state of the target pixel by the LUT processing, and the target pixel when the density of the target pixel is not weighted. FIG. 7 is an explanatory diagram showing a recording state of FIG.

FIG. 15 is a schematic front view showing the structure of a digital copying machine according to still another embodiment of the present invention.

FIG. 16 is a block diagram showing a configuration of an image processing unit included in the digital copying machine.

FIG. 17 is a block diagram of a modulation signal generation unit included in the image processing unit.

18 is an explanatory diagram of a pulse width modulation signal generation operation by the processing of the LUT shown in FIG.

FIG. 19 is an explanatory diagram showing the density data stored in the line memory shown in FIG. 17 and the recording state of the target pixel by the processing of the LUT.

FIG. 20 is a block diagram showing a configuration of an image processing unit included in a copying machine according to still another embodiment of the present invention.

21 is an explanatory diagram showing the density data stored in the line memory shown in FIG. 20 and the recording state of the pixel of interest by the LUT processing.

FIG. 22 is a block diagram showing a configuration of an image processing unit included in a copying machine according to still another embodiment of the present invention.

23 is an explanatory diagram showing the density data stored in the line memory shown in FIG. 22 and the recording state of the target pixel by the processing of the LUT.

FIG. 24 is a block diagram showing a configuration of an image processing unit included in a copying machine according to still another embodiment of the present invention.

FIG. 25 is a block diagram showing a configuration of an area determination unit included in the image processing unit.

FIG. 26 is an explanatory diagram showing the determination circuit shown in FIG. 25.

FIG. 27 (a) is an explanatory diagram showing a neural network of the determination circuit, and FIG. 27 (b) is an explanatory diagram showing neural elements included in the determination circuit.

FIG. 28 is a block diagram showing a configuration of an image processing unit included in a copying machine according to still another embodiment of the present invention.

FIG. 29 is a block diagram showing a configuration of an image processing unit included in a copying machine according to still another embodiment of the present invention.

FIG. 30 is a block diagram showing a configuration of an image processing unit included in a copying machine according to still another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Copier (image forming apparatus) 34 Modulation signal generation section 41 Line memory (storage means) 42 Shift register (recording density calculation means) 43 Look-up table (recording density calculation means, modulation signal output means) 44 Data latch (modulation signal) Output means) 45 Data latch (modulation signal output means) 46 Comparator (modulation signal output means) 47 Comparator (modulation signal output means) 48 AND gate (modulation signal output means) 49 CPU (recording density calculation means, modulation signal output) 51) Look-up table (recording density calculation means, modulation signal output means) 53 Modulation signal generation section 61 Shift register (recording density calculation means) 62 Look-up table (recording density calculation means, modulation signal output means) 63 Modulation signal generation Part 71 Copier (image forming apparatus) 72 LED array 73 LED dry Bus unit 75 Modulation signal generator 81 to 83 Line memory (storage means) 84 Shift register (recording density calculation means) 85 Look-up table (recording density calculation means, modulation signal output means) 86 Shift register (modulation signal output means) 87 CPU (Recording density calculation means, modulation signal output means) 91 Look-up table (recording density calculation means, modulation signal output means) 92 Modulation signal generators 101 to 105 Line memory (storage means) 106 Shift register (recording density calculation means) 107 Look-up table (recording density calculation unit, modulation signal output unit) 108 modulation signal generation unit 111 area determination unit (area determination unit) 112 LUT switching unit (switching unit) 113 modulation signal generation unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Osamu Fujimoto 22-22 Nagaike-cho, Abeno-ku, Osaka, Osaka

Claims (3)

[Claims] 1. An image forming apparatus in which an image forming operation of visualizing image data by an image forming unit is performed based on a modulation signal generated from image data, and an image including a density value of each pixel of an image to be formed. With respect to the storage means for storing the data and the respective pixels arranged in one of the main scanning direction and the sub-scanning direction corresponding to the respective image data stored in the storage means, a pixel of interest to be recorded is set to a predetermined pixel. A recording density calculating unit that is set for each of a plurality of pixels, and adds the density values of adjacent pixels that are adjacent to the target pixel in the front and rear in the one direction to the density value of the target pixel to obtain the recording density of the target pixel; A modulation signal that specifies a recording area having a length corresponding to the recording density centered on the center position of the pixel of interest in the front-back direction of the one direction is generated, and this modulation signal is supplied to the image forming unit. An image forming apparatus characterized by comprising a modulation signal output means for. 2. The modulation signal output means moves the center of the recording area for the pixel of interest from the center position of the pixel of interest toward the adjacent pixel on the higher density value side of the adjacent pixels on both sides. The image forming apparatus according to claim 1, wherein the image forming apparatus is provided. 3. The recording density calculation means distributes the density values of the adjacent pixels between each two target pixels in accordance with the density values of the two target pixels, and the distributed density values 2. The recording density of each target pixel is obtained by adding the density values of two target pixels.
The image forming apparatus according to item 1.