JPH05345442A - Method and device for image forming - Google Patents

Abstract

PURPOSE:To improve the picture quality of a curved section and a diagonal section by forming the distribution shape of light energy on a photosensitive element for forming one pixel in a manner of including 1/4 zone of diagonal direction of adjoining pixel by combination of ON/OFF times of lighting. CONSTITUTION:The emission of laser beam R forming one pixel by horizontal synchronizing signals CLKH1 and CLKH2 output from a pulse width modulation circuit 8 of a printer controller 2 is divided into a plurality of ON/OFF times of lighting by a semiconductor laser 14 forming a printer engine section, and the distribution shape of light energy on a sensitive element for forming one pixel is so formed as to include the 1/4 zone almost in the diagonal direction of adjoining pixel. For instance, the pulse width for forming one pixel is divided into ten, and the semiconductor laser 14 is ON/OFF at respective time points, and the pixel is formed on the photosensitive element surface by the distribution of light energy formed by the laser light R. The pixel, for instance, is so formed as to include both ends of the sub-scanning direction in the 1/4 zone of the diagonal direction of the sub-scanning direction of the adjoining pixel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method and an image forming apparatus for forming an image composed of a plurality of pixels as a latent image on the surface of a photoconductor based on an image signal such as characters and figures.

[0002]

2. Description of the Related Art Conventionally, a laser printer using a semiconductor laser as a light source generally irradiates a rotating photosensitive member with laser light deflected and scanned by a rotating polygon mirror or the like to form an electrostatic latent image corresponding to an image. It is formed on the surface of the photoconductor and then developed.
An image is recorded on a transfer sheet through processes such as transfer and fixing. The scanning direction by the rotary polygon mirror as described above is called the main scanning direction, the rotation direction of the photoconductor is called the sub-scanning direction of the transfer sheet, and the rotation speed of the photoconductor is the rotation speed of the rotary polygon mirror. It is relatively slow and can be ignored.

By the way, in forming an electrostatic latent image on the surface of a photoconductor as described above, a laser printer turns on a semiconductor laser for a certain period of time (this turn-on time is called a pulse width) to form one pixel. The transfer sheet 1 is provided with light energy for performing the above operation, by forming one line of such pixels in the main scanning direction and then forming the above line in the sub scanning direction. A dot matrix for one sheet is formed on the surface of the photoconductor. In addition, the shape of one pixel formed on the surface of the photoconductor as described above is determined according to the recording density of the laser light with which the photoconductor is irradiated. The elliptical shape is often used as the spot shape due to the far-field pattern characteristics of the semiconductor laser.

Therefore, when the irradiation spot of the laser beam on the photosensitive member is elliptical (the diameter in the main scanning direction is Wx and the diameter in the sub-scanning direction is Wy), the light energy received by the photosensitive member has a certain value. (This constant value is, for example, a [μJ
/ Cm ² ] or more, the region where the light energy a [μJ / cm ² ] becomes the above-mentioned constant value) or more becomes a shaded portion shown in FIG.
Since the light energy density of the laser light has a Gaussian distribution, if the light irradiation conditions such as laser output, pulse width, scanning speed in the main scanning direction, and elliptical beam diameter are used as input parameters, the light received by the photoconductor will be The energy distribution can be obtained numerically, and the region of the light energy thus obtained at a [μJ / cm ² ] or more has a substantially elliptical shape.

Usually, one pixel of 300 dpi (dot per inch) is a substantially oval shape having a diameter of about 80 to 100 μm. For this reason, the slanted portion such as characters and figures forms stair-like jaggies, which is not preferable in terms of image quality. If the recording density is increased to, for example, about 600 dpi, the jaggies in the inclined portion become inconspicuous. However, if the recording density is doubled, a quadruple memory is required, resulting in a significant cost increase. Therefore, in order to achieve high image quality of the inclined portion and the like without adding memory, for example, Japanese Patent Laid-Open No. 53-202019
Japanese Patent Application Laid-Open No. 58-150978.
Many techniques, such as the one disclosed in Japanese Patent Publication, have been created to improve the jaggies of the inclined portion by reducing the diameter of the pixel or moving the pixel.

FIG. 17 is an example of printing a diagonal line in which the diameter of the pixel is reduced, and FIG. 18 is an example of printing a diagonal line in which the pixel is moved. In order to reduce the diameter of the pixel as described above, the diameter conversion is performed in five steps by changing the pulse width (lighting time) of the writing laser.
Pixels are moved within a movement range of ± 1/3 of the diameter by changing the laser writing timing (lighting start time).

[0007]

However, in the case of improving the jaggy of the inclined portion by reducing the diameter of the pixel or moving the pixel as in the above-mentioned conventional method, the diameter conversion in five steps, the complicated combination of the moving range, etc. It becomes difficult to control the irradiation of the beam, and furthermore, since the pixels forming the inclined portion are substantially oval, there is a problem that the jaggy of the inclined portion is not completely removed when outputting enlarged characters and the like. Have Therefore, in the present invention, by appropriately controlling the pulse width of the writing laser to change the pixel shape and removing the jaggies such as the slanted portions, the above-mentioned problem can be solved. An object is to provide a forming device.

[0008]

In order to solve the above-mentioned problems, the image forming method according to claim 1 of the present invention exposes the surface of the photoconductor by the exposing means and exposes the exposing means by the exposure controlling means. In the image forming method of controlling the exposure operation of 1) based on the image signal of characters or figures to form an image composed of a plurality of pixels as a latent image on the surface of the photoconductor, the following means are taken.

That is, the exposure control means divides the irradiation of light forming one pixel into a plurality of lighting times and a plurality of extinguishing times, and one pixel is determined by combining these lighting times and extinguishing times. The distribution shape of the light energy on the photoconductor required for forming is formed so as to include a substantially diagonal 1/4 region of one pixel adjacent to the one pixel.

Further, in order to solve the above-mentioned problems, the image forming method according to the second aspect of the present invention is such that the surface of the rotating body which rotates in the sub-scanning direction is orthogonal to the sub-scanning direction by the exposing means. Exposure is performed by scanning in the scanning direction, and the exposure control means controls the exposure operation of the exposure means on the basis of image signals such as characters and figures to form an image composed of a plurality of pixels as a latent image on the surface of the photoconductor. The following measures are taken in the image forming method.

That is, the exposure control means divides the irradiation of light forming one pixel into a plurality of lighting times and a plurality of extinguishing times, and one pixel is determined by combining the lighting time and the extinguishing time. The distribution shape of the light energy on the photoconductor required for forming is such that it also includes a substantially diagonal ¼ area of one pixel adjacent in the main scanning direction or the sub scanning direction of the above one pixel. , A pixel that also includes a substantially diagonal direction 1/4 region of an adjacent pixel in the main scanning direction formed by the light energy, and an approximately diagonal direction 1 of an adjacent pixel in the sub scanning direction.
The pixels also including the / 4 region are arranged so that the ¼ regions in the substantially diagonal direction are in contact with each other, so that the pixels in the ¼ region in the substantially diagonal direction are provided in the portions adjacent to both the pixels. Pixels in a substantially diagonal ½ area are formed.

Further, in order to solve the above-mentioned problems, the image forming apparatus according to the third aspect of the present invention exposes the surface of the photoconductor to an exposure means and the exposure operation of the exposure means to form an image such as characters and figures. An image forming apparatus that includes an exposure control unit that controls on the basis of a signal and forms an image composed of a plurality of pixels as a latent image on the surface of a photosensitive member takes the following measures.

That is, the exposure control means divides the irradiation of light forming one pixel into a plurality of lighting times and a plurality of extinguishing times, and forms one pixel by combining these lighting times and extinguishing times. The distribution shape of the light energy on the photoconductor required for this is formed in such a shape that it also includes a substantially diagonal 1/4 region of one pixel adjacent to the one pixel.

In order to solve the above-mentioned problems, the image forming apparatus according to the fourth aspect of the present invention scans the surface of the photoconductor rotating in the sub-scanning direction in the main scanning direction orthogonal to the sub-scanning direction. And an exposure control means for controlling the exposure operation of this exposure means on the basis of an image signal such as a character or a figure, and an image consisting of a plurality of pixels is formed as a latent image on the surface of the photoconductor. The following measures are taken in the image forming apparatus.

That is, the exposure control means divides the irradiation of light forming one pixel into a plurality of lighting times and a plurality of extinguishing times, and one pixel is formed by combining these lighting times and extinguishing times. The distribution shape of the light energy on the photoconductor required for this is such that it also includes a substantially diagonal 1/4 region of one pixel adjacent to the one pixel in the main scanning direction or the sub scanning direction. At the same time, approximately 1/4 in the diagonal direction of one adjacent pixel in the main scanning direction formed by the above light energy.
A pixel including a region and a pixel also including a substantially diagonal direction 1/4 region of one adjacent pixel in the sub-scanning direction are provided in a region adjacent to both pixels from the pixels in the substantially diagonal direction 1/4 region. The light energy distribution portion is controlled so that the respective substantially diagonal ¼ regions are in contact with each other so that pixels in the substantially diagonal ½ region can be formed.

[0016]

According to the constitutions of claims 1 and 3 above,
By dividing the irradiation of light from the exposure means into a plurality of lighting times and a plurality of extinction times by the exposure control means, the distribution shape of the light energy forming one pixel on the photoconductor is set to the above-mentioned 1
Since the pixel is formed in a shape that also includes a substantially diagonal direction 1/4 region of one pixel adjacent to the pixel, the shape of the pixel formed on the surface of the photoconductor is approximately 1/4 of the diagonal direction of the adjacent one pixel. The shape can include a region. Since the pixels formed in this way are provided with the inclined portion, the image quality of the inclined portion or the curved portion can be improved by arranging these pixels at appropriate positions.

According to the second and third aspects of the invention, the pixel including the above-mentioned 1/4 region in the substantially diagonal direction of the adjoining one pixel is arranged in the substantially diagonal direction of the adjoining one pixel in the main scanning direction. 1/4
A pixel including a region and a pixel including a substantially diagonal 1/4 region of an adjacent one pixel in the sub-scanning direction are arranged, and these two pixels are arranged so that the substantially diagonal 1/4 regions are in contact with each other. Then, the pixels in the substantially diagonal direction ½ region are formed by these two pixels in the substantially diagonal direction ¼ region at the adjacent portions of both pixels. Therefore, by representing the slanted portion or the curved portion of the image by the pixels in the approximately diagonally 1/2 area formed in this way, it is possible to further improve the image quality of the slanted portion or the curved portion.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention is shown in FIGS.
The explanation is based on the following. In this embodiment, the image forming apparatus is set to 300 dpi (dot per inch).
), Which is an example of a laser printer having a low recording density.

The laser printer 1 according to this embodiment is shown in FIG.
As shown in FIG. 3, a printer controller 2 as an exposure control unit that generates page information composed of dot data D based on code data C transmitted from an external host computer 4 and the like, and the printer controller 2 transmits the information. A printer engine unit 3 as an exposure unit that forms an image on a photoconductor (not shown) based on the dot data D.
It has and.

As shown in FIG. 2, the printer controller 2 includes a decoder 5, a latch circuit 6, a pattern matching circuit 7, a pulse width modulation circuit 8 and an AND gate 9.1.
It is composed of 0 · 11, an OR gate 12, and a transistor 13. The decoder 5 converts the bit numbers of the image signals of characters and figures sent from the host computer 4 for the optical printer and outputs them to the latch circuit 6.
The latch circuit 6 latches the image signal input from the decoder 5 by inserting a delay line into the transfer clock shown in FIG. 3A, and latches the latched image signal for each AN.
Output to D gates 9, 10 and 11.

On the other hand, the pattern matching circuit 7 performs pattern matching processing, which will be described later, on the image signals of characters and figures sent from the host computer 4 or the like to identify and detect the curved portions of the characters and figures. And the information in the shaded area is output to the pulse width modulation circuit 8. The pulse width modulation circuit 8 modulates the pulse width of the frequency clock shown in FIG. 3B with the information input from the pattern matching circuit 7, The clock horizontal synchronizing signals CLKH1, CLKH2, and CLKH3, which will be described later, shown in (c), (d), and (e), respectively, are output to the AND gates 9, 10, and 11.

The AND gates 9, 10 and 11 respectively multiply the image signals of characters and figures latched by the latch circuit 6 and the respective clock horizontal synchronizing signals CLKH1, CLKH2 and CLKH3 from the pulse width modulation circuit 8. Then, the pulse-width-modulated character and figure image signals are output to the transistor 13 through the OR gate 12,
Outputs the above signal to the semiconductor laser 14 forming the printer engine unit 3.

The pulse-width-modulated image signals of characters and figures are converted into laser light R by the semiconductor laser 14, are deflected and scanned by a rotating polygon mirror (not shown), and are then irradiated on the rotating photosensitive member. To be done. At this time, light energy is applied to the surface of the photoconductor that is irradiated with the laser beam R, and an image composed of a plurality of pixels is formed as an electrostatic latent image. After that, images of characters and figures are printed on the recording paper through each process such as development, transfer and fixing.
The scanning direction by the rotary polygon mirror as described above is called the main scanning direction, the rotation direction of the photoconductor, that is, the conveyance direction of the recording paper is called the sub-scanning direction, and the rotation speed of the photoconductor is the rotation speed of the rotary polygon mirror. It is relatively slow and can be ignored.

By the way, the clock horizontal synchronizing signals CLKH1 and CLKH2 output from the pulse width modulation circuit 8 as described above.
3 (c) and (d) of FIG. 3, in order to form the shape of one pixel into a desired shape, the turning-on time t ₁ · t _{2 to} t _{10 of the} laser light R and the turning-off time s ₁ are previously set.・ A combination with s _{2 to} s ₉ is set. That is, CLKH1 and CLKH2 are
The pulse width T ₀ for forming one pixel is divided into ₁₀ , and the semiconductor laser 14 is turned on at each time t ₁ · t _{2 to} t ₁₀ , while at each time s ₁ · s _{2 to} s ₉ . The semiconductor laser 14 is turned off. These ON / OFF times are set such that the distribution of light energy formed by the laser light R (pixels formed on the surface of the photoconductor) has a shape as shown in FIGS. Is set.

Therefore, in the clock horizontal synchronizing signal CLKH1 divided as shown in FIG. 3 (c), the light energy distribution of the laser beam R forming one pixel is 1 as shown in FIG. 4 (a). Both ends of the pixel in the sub-scanning direction are adjacent to each other in the sub-scanning direction.

Further, in the clock horizontal synchronizing signal CLKH2 divided as shown in FIG. 3D, the light energy distribution of the laser light R forming one pixel is 1 as shown in FIG. 4B. Both ends of the pixel in the main scanning direction are adjacent to each other in the main scanning direction.

The clock horizontal synchronizing signal CLKH3 shown in (e) of FIG. 3 is not divided in pulse width T _{0 and} is designed to continuously turn on the semiconductor laser.
With this clock horizontal synchronization signal CLKH3, the light energy distribution of the laser light R forming one pixel is formed into a substantially elliptical shape as shown in FIG. However, in the figure,
In order to facilitate the explanation, they are shown in a substantially square shape. The light energy distribution formed by the irradiation control of the laser light R as described above is formed under a constant scanning speed, a constant laser output, and a constant laser diameter.

Here, a description will be given based on a pixel array for smoothly expressing a shaded portion or a curved portion using each pixel formed by the above light energy distribution.

For example, as shown in FIG. 5A, the pixel formed by the clock horizontal synchronizing signal CLKH2 is arranged at the lower right position of the pixel formed by the clock horizontal synchronizing signal CLKH1. By arranging each of the approximately diagonally 1/4 region parts adjacent to each other, a 1
It is possible to form a pixel having a size of ½ of the pixel facing direction.

Further, as shown in FIG. 5B, a pixel formed by the clock horizontal synchronizing signal CLKH2 is arranged at a position on the lower left side of the pixel formed by the clock horizontal synchronizing signal CLKH1. By adjoining the substantially diagonal ¼ area portions, a pixel having a size of ½ of one pixel in the facing direction can be formed on the upper left side of the portion adjacent to both pixels.

Although not shown, similar to the above,
By arranging the pixel formed by the clock horizontal synchronization signal CLKH1 and the pixel formed by the clock horizontal synchronization signal CLKH2 at predetermined positions, the right side lower part and the left side lower part of the part adjacent to both pixels are respectively provided. 1 pixel facing direction 1 /
Pixels having a size of 2 can be formed.

Next, an example of pattern matching for identifying and detecting a curved portion or a shaded portion of a character or a figure by the pattern matching circuit 7 will be described below.

As shown in FIG. 6, the laser printer 1 stores a cross-shaped pattern matching pattern (hereinafter, referred to as a memory pattern) which is composed of five pixels. This memory pattern has 32 types in total (see FIG. 6) depending on whether 5 pixels form dots (printing pixels, black circles in FIG. 6) or do not form dots (non-printing pixels, white circles in FIG. 6). A).

With respect to the five pixels forming the cross shape, A, B and C are sequentially scanned in the main scanning direction (the right direction in FIG. 6) for scanning the laser beam R, and the sub scanning direction (the lower direction in FIG. 6). ) Are sequentially assigned addresses 1, 2, and 3, and when the pixel at the address A2 forms a dot, A
2. When dots are not formed, it is expressed as (A2), and when these memory patterns are expressed by a character expression, for example, when all five pixels form dots (A in FIG. 6), A
2B1B2B3C2, and when all five pixels do not form dots (a in FIG. 6), (A2) and (B1)
(B2) (B3) (C2).

Next, an image signal of a character or a graphic to be printed (hereinafter, referred to as an input from the external host computer 4 or the like.
(Referred to as a figure pattern), the same cross shape as the memory pattern is applied to the figure pattern, as shown in FIG. When the dot arrangement of the five pixels in the figure pattern of the portion to which the cross shape is applied is examined, the dot arrangement of the five pixels always matches any one of the above 32 kinds of memory patterns.

At this time, in the method of applying the same cross shape as the above-mentioned memory pattern to the graphic pattern, first, from the starting point (the upper left corner in FIG. 7) of scanning the laser light R of the graphic pattern,
Applying while moving one pixel at a time in the main scanning direction A, then moving one pixel in the sub-scanning direction B, and similarly,
The pixels are applied while moving one pixel at a time in the main scanning direction A, and finally, the pixels are applied one pixel at a time toward the scanning end point (lower right corner in FIG. 7) of the laser light R.

Then, with respect to the figure pattern of the portion to which the cross shape is applied in this way, a memory pattern which matches the figure pattern of the portion to which the cross shape is applied,
The memory pattern that matches the figure pattern of the portion to which the cross shape has been applied immediately after moving one pixel in the main scanning direction A is compared.

That is, as shown in FIG. 7, a memory pattern matching the figure pattern (a, b, c, d in FIG. 7) of the portion to which the cross shape is applied, and the main scanning direction as shown in FIG. A dot pattern of 5 pixels is obtained by comparing with a memory pattern that matches the figure pattern (a ', b', c ', d'in FIG. 8) of the portion to which the cross shape is applied immediately after moving 1 pixel to A. By identifying the change in the, the boundary between the curved portion or the shaded portion of the character or graphic to be printed and the blank portion without the character or graphic to be printed is detected.

By the way, considering the relationship between a curved portion or a shaded portion of a character or figure to be printed and a blank portion around which there is no printed character or figure, the curved portion or the shaded portion contacts,
It is classified into the following four categories. (1) There is a character or figure on the lower side with the boundary rising to the right (for example, a in FIG. 7). (2) There is a character or figure on the upper side with the boundary rising to the right (for example, b in FIG. 7). (3) There is a character or figure on the lower side with the boundary falling to the right (for example, c in FIG. 7). (4) There is a character or figure on the upper side with the boundary falling to the right (for example, d in FIG. 7).

For these four cases, a memory pattern matching the figure pattern (a, b, c, d in FIG. 7) of the portion to which the cross shape is applied, as shown in FIG. 7, and the memory pattern as shown in FIG. , The figure pattern of the portion to which the cross shape is applied immediately after moving one pixel in the main scanning direction A (a ′ in FIG. 8,
b ', c', d ') is compared with the memory pattern that matches the pixel pattern, the change of the dot arrangement of the five pixels is the above-mentioned character expression, and (1) is (A2) (B1) (B2) (B3 ) C2 changes to (A2) (B1) B2B3C2. That is, the dot arrangement of the five pixels changes from (D) to (N) in FIG. (2) is from A2B1B2 (B3) (C2) to A2 (B
1) Change to (B2) (B3) (C2). That is, the dot arrangement of the five pixels changes from (nu) to (f) in FIG. (3) is A2 (B1) B2B3 (C2) to A2 (B
1) Change to (B2) (B3) (C2). That is, the dot arrangement of the five pixels changes from (F) to (F) in FIG. (4) changes from (A2) (B1) (B2) (B3) C2 to (A2) B1B2 (B3) C2. That is, the dot arrangement of the five pixels changes from (D) to (G) in FIG.

Therefore, in order to detect a curved portion or a shaded portion of a character or figure to be printed, it is sufficient to identify the change in the dot arrangement of the five pixels of the above-mentioned four types, as shown in FIG. Pixels corresponding to the curved portions or the shaded portions of the characters and figures are identified and detected by pattern matching, as indicated by the white circles in FIG.

As described above, when the curved portion or the shaded portion of the character or figure to be printed is detected, the pixel array for smoothly expressing the shaded portion or the curved portion is applied to the detected pixel.

Specifically, in the case of the change in the dot arrangement of the five pixels shown in (1) of FIG. 9, the pixels in the figure pattern (a in FIG. 7) of the portion to which the cross shape is applied are changed. C2
For forming pixels, that is, for each of B3 and C2 of the pixels in the figure pattern (a ′ in FIG. 8) of the portion to which the cross shape is applied immediately after moving by one pixel in the main scanning direction A, Irradiation of the laser light R is controlled by the above-described clock horizontal synchronization signals CLKH1 and CLKH2, and the pixel B in a ′ of FIG.
The lower right side of 2 and the substantially ½ area in the facing direction are formed as pixels.

Further, in the case of the change of the dot arrangement of the five pixels shown in (2) of FIG. 9, the pixel B2 in the figure pattern (b of FIG. 7) of the portion to which the cross shape is applied is formed. For the pixels for doing so, that is, for each of A2 and B1, the irradiation of the laser beam R is controlled by the above-described clock horizontal synchronization signals CLKH2 and CLKH1, and the left upper upper half of the pixel B2 in the substantially opposite direction is defined as a pixel Form ((b) of FIG. 5)
reference).

In the case of the change in the dot arrangement of the five pixels shown in (3) of FIG. 9, in order to form B2 of the pixel in the figure pattern (c in FIG. 7) of the portion to which the cross shape is applied. Of the pixel B, that is, A2 and B3, respectively, by controlling the irradiation of the laser beam R by the above-mentioned clock horizontal synchronization signals CLKH2 and CLKH1 to form a left lower lower substantially opposed direction half area of the pixel B2 as a pixel. ..

In the case of the change in the dot arrangement of the five pixels shown in (4) of FIG. 9, in order to form C2 of the pixel in the figure pattern (d in FIG. 7) of the portion to which the cross shape is applied. , That is, the clock horizontal for each of the pixels B1 and C2 in the figure pattern (d ′ in FIG. 8) of the portion to which the cross shape has been applied immediately after moving one pixel in the main scanning direction A. Irradiation of the laser light R is controlled by the synchronization signals CLKH1 and CLKH2, and the upper right half region of the pixel B2 in b ′ of FIG. 8 is formed as a pixel (FIG. 5).
(A)).

FIG. 11 shows the same figure pattern in which the shaded portions or curved portions of the characters or figures to be printed are printed with the pixels each having a size approximately 1/2 in the diagonal direction. In addition, for the sake of schematic representation, there is a portion in which a line is formed by arranging one pixel in a line, and an inaccurate portion cannot be fitted to a pixel having a size of approximately 1/2 in the diagonal direction. Although it is formed, it does not affect the actual printing. Further, the pattern matching as described above is merely an example, and by incorporating memory patterns of various shapes in the laser printer 1, more various pattern matching can be performed.

As described above, the laser printer 1 of this embodiment
Forms a pixel including a substantially diagonal ¼ area of one pixel adjacent in the main scanning direction or the sub-scanning direction, and is adjacent to both pixels in the substantially diagonal ¼ area of these two pixels. Pixels each having a size of ½ of one pixel in a diagonal direction are formed in a portion to be printed, and when an oblique line portion or a curved line portion of a character or figure to be printed is detected, it corresponds to the shape. It is possible to form a pixel that is ½ the size of one pixel in the diagonal direction.

Therefore, the laser printer 1 according to the present embodiment.
When a line printing comparison is made with a conventional laser printer having a recording density of about 300 dpi, a clear difference appears.

Lines printed by a conventional laser printer have a substantially elliptical shape in one pixel as shown in FIGS. 12 (a) to 12 (e).
12A except the horizontal line shown in FIG. 12A and the vertical line shown in FIG. 12E, a diagonal line close to the horizontal line shown in FIG.
An oblique line with an inclination angle of 45 ° shown in (c), and FIG.
The slant line close to the vertical line shown in FIG. 3A, and in any of the slant lines, stair-like jaggies are generated between pixels in the vertical direction, and the smoothness of the line is impaired.

On the other hand, the diagonal lines printed by the laser printer 1 are, as shown in FIG. 11, described above, in any diagonal lines, at both ends in the width direction of the line, a diagonal direction of one pixel is formed. Pixels that fill the 1/2 area are formed continuously. Therefore, in the conventional laser printer, the jaggies have a step shape of a substantially right angle, whereas in the laser printer 1, the shaded portion and the curved portion can be printed smoothly, and the blank space that should be originally formed by black pixels is formed. Since the area of the portion is reduced, it can be seen that the image quality of the inclined portion is significantly improved as compared with the conventional laser printer at the normal visual distance. The horizontal and vertical lines printed by the laser printer 1 are the same as those printed by the conventional laser printer.

Further, in FIG. 11, one pixel has a substantially diagonal direction 1
Although the example in which the pixels that fill the / 2 area are formed continuously has been shown, as shown in FIG.
It can be seen that the image quality of the shaded portion and the curved portion of the character is greatly improved. It should be noted that FIG. 14 is an example of printing, which is shown for reference, in which pixels that fill a half area in a substantially diagonal direction of one pixel are not applied.

The above embodiment is not intended to limit the present invention, and various modifications can be made within the scope of the present invention.
For example, in the above-described embodiment, since the shape of one pixel is made to include the substantially diagonal ¼ area of the adjacent one pixel,
Each clock horizontal synchronizing signal CLKH1 and CLKH2 obtained by dividing the pulse width T ₀ for forming one pixel into 10 is used.
In particular, the number of divisions of such pulse width T ₀ is not limited. In addition, the clock horizontal synchronization signal CLKH1CL
Specific numerical values of the time _{t 1 ~t1 10 · S 1 ~S} 9 in KH2, the light irradiation conditions, and may have various numerical by the recording density or the like. Then, in the case of forming a light energy distribution having a desired shape under each light irradiation condition, if the values of the respective times t _{1 to} t ₁₀ · S _{1 to} S ₉ are appropriately taken, the values shown in FIG.
It is possible to create a pixel also including a substantially diagonal ¼ region of adjacent pixels having a shape as shown in (a) and (b).

Further, the present invention can be applied not only to an optical printer using a photoconductor but also to heat mode recording using a laser such as a laser thermal transfer printer and an LED printer lamp using an LED as a light source. is there.

[0055]

As described above, in the image forming method according to the first aspect of the present invention, irradiation of light for forming one pixel is performed in a plurality of lighting periods and a plurality of extinguishing periods by the exposure control means. By dividing and dividing the lighting time and the extinction time, the distribution shape of the light energy on the photoconductor required to form one pixel is determined by dividing the pixel into a substantially diagonal direction 1 / This is a method of forming a shape that also includes four regions.

Therefore, the shape of a pixel formed as a latent image on the surface of the photoconductor can be made to include a substantially diagonal 1/4 region of an adjacent pixel having an inclined portion. By arranging the pixels at appropriate positions, it is possible to improve the image quality by improving jaggies in the shaded portions and curved portions.

Further, in the image forming method according to the second aspect of the invention, as described above, the exposure control means divides the irradiation of light forming one pixel into a plurality of lighting periods and a plurality of extinguishing periods.
By combining these lighting time and extinguishing time, the distribution shape of the light energy on the photoconductor required to form one pixel can be determined by comparing the one pixel with the adjacent one in the main scanning direction or the sub scanning direction. A pixel is formed so as to include a 1/4 region in the diagonal direction, and one pixel adjacent to one pixel in the main scanning direction formed by the above light energy also includes a pixel also including a 1/4 region in the diagonal direction and an adjacent pixel in the sub scanning direction. By arranging a pixel that also includes a substantially diagonal 1/4 region of one pixel so that the respective substantially diagonal 1/4 regions are in contact with each other, the regions substantially adjacent to both pixels are substantially Diagonal direction 1 consisting of quarter area in the angular direction
This is a method of forming pixels in the / 2 area.

Therefore, it is possible to form a pixel having a size of ½ of one pixel in the diagonal direction. Therefore, the tilt of the image is formed by the pixels in the ½ region of the diagonal direction thus formed. By representing the curved portion and the curved portion, it is possible to further improve the image quality of the inclined portion and the curved portion.

Further, in the image forming apparatus according to the third aspect of the invention, as described above, the exposure control means divides the irradiation of the light forming one pixel into a plurality of lighting times and a plurality of extinguishing times. By combining the lighting time and the extinguishing time, the distribution shape of the light energy on the photoconductor required to form one pixel is determined by the diagonal direction 1 of one pixel adjacent to the one pixel.
The configuration is such that it also includes a / 4 region.

Therefore, in addition to the effect similar to that of the above-mentioned claim 1, the image quality improvement by the above-mentioned jaggie improvement does not require an increase in recording density. It is possible to avoid the cost increase of itself.

As described above, in the image forming apparatus according to the present invention, the exposure control means divides the irradiation of the light forming one pixel into a plurality of lighting times and a plurality of extinguishing times. By combining the lighting time and the extinction time, the distribution shape of the light energy on the photoconductor required for forming one pixel can be determined by comparing the one pixel with a pair of adjacent pixels in the main scanning direction or the sub scanning direction. The pixel is formed so as to include a quarter area in the angular direction, and a pixel including a substantially quarter area in the diagonal direction of one pixel adjacent in the main scanning direction formed by the above light energy and a pixel in the sub scanning direction. Approximately 1/4 diagonal direction of adjacent 1 pixel
Pixels that also include regions are provided in a region adjacent to both pixels in a substantially diagonal direction 1/4 that is composed of pixels in these approximately diagonal directions 1/4 regions.
Each diagonal direction 1 so that pixels in two regions can be formed.
This is a configuration for controlling the above-mentioned light energy distribution region so that the / 4 regions are in contact with each other.

Therefore, the same effects as those of the above-described claim 3 are achieved, and it is possible to provide an apparatus capable of further improving the image quality of the inclined portion and the curved portion.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an outline of a laser printer according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing each component that constitutes a printer controller of the laser printer.

3 (a), (b), (c), (d), and (e) are explanatory diagrams showing transfer clocks, frequency clocks, and pulse waveforms of clock horizontal synchronization signals CLKH1, CLKH2, and CLKH3, respectively. is there.

4 (a), (b), and (c) are explanatory diagrams showing respective shapes of light energy distributions formed by clock horizontal synchronization signals CLKH1, CLKH2, and CLKH3, respectively.

5 (a) and 5 (b) are substantially diagonal directions 1 of adjacent pixels formed by the energy distributions shown in FIGS. 4 (a) and 4 (b).
It is explanatory drawing which shows an example of the arrangement | sequence of the pixel containing / 4 area | region.

FIG. 6 is an explanatory diagram showing 32 types of memory patterns each of which is composed of 5 pixels and is used for pattern matching.

FIG. 7 is an explanatory diagram showing a state in which the same cross shape as a memory pattern is applied to a figure pattern in order to perform the pattern matching.

FIG. 8 is an explanatory diagram showing a state in which the same cross shape as a memory pattern is applied to a figure pattern in order to perform the pattern matching.

FIG. 9 is an explanatory diagram showing a method of identifying and detecting a curved portion or a shaded portion of a character or a figure by performing the pattern matching.

FIG. 10 is an explanatory diagram showing a state in which a curved portion and a shaded portion of a character and a figure are identified and detected from the figure pattern.

FIG. 11 is an explanatory diagram showing a state in which the above-mentioned graphic pattern is printed using the pixel array of the present invention. FIG. 11 is a diagram of a character in which pixels each having a size of ½ of one pixel in a diagonal direction are continuously arranged. It is an enlarged plan view.

12 (a), (b), (c), (d), and (e) are plan views showing pixel arrays in a conventional laser printer, and FIG. 12 (a) is a horizontal line and FIG. ) Indicates an oblique line close to a horizontal line, FIG. 7C shows an oblique line having an inclination angle of 45 °, FIG. 8D shows an oblique line close to a vertical line, and FIG.

13 is an enlarged plan view of characters printed by the laser printer of FIG.

FIG. 14 is an enlarged plan view of characters printed by a conventional laser printer.

FIG. 15 is an explanatory diagram showing an example of the shape of a pixel that also includes a substantially diagonal ¼ region of adjacent pixels.

FIG. 16 is an explanatory diagram showing a light energy distribution for forming one pixel in the conventional image forming apparatus.

FIG. 17 is an explanatory diagram showing a print example of diagonal lines in which jaggies are improved by reducing the pixel diameter.

FIG. 18 is an explanatory diagram illustrating a print example of diagonal lines in which jaggies are improved by moving pixels.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser printer (image forming apparatus) 2 Printer controller (exposure control means) 14 Semiconductor laser (exposure means) 21 Photoconductor drum (photoconductor) 27 Exposure device (exposure means)

Claims (4)

[Claims] 1. An exposure means exposes the surface of a photoconductor, and an exposure control means controls the exposure operation of the exposure means on the basis of an image signal such as a character or a figure to form a plurality of pixels on the photoconductor surface. In the image forming method for forming an image as a latent image, the exposure control means divides the irradiation of light forming one pixel into a plurality of lighting times and a plurality of extinguishing times, and these lighting times and extinguishing times are divided. By combining the above, the distribution shape of the light energy on the photoconductor required to form one pixel is made to include a substantially diagonal 1/4 region of one pixel adjacent to the one pixel. An image forming method characterized by the above. 2. The surface of a rotating body which rotates in the sub-scanning direction is exposed by scanning with the exposing means in the main scanning direction orthogonal to the sub-scanning direction, and the exposure control means performs the exposure operation of the exposing means by characters. In the image forming method in which an image composed of a plurality of pixels is formed as a latent image on the surface of the photoconductor by controlling based on an image signal such as an image or a figure, the exposure control means irradiates a plurality of lights forming one pixel. Lighting time and a plurality of extinguishing times, and by combining these lighting times and extinguishing times, the distribution shape of the light energy on the photoconductor required to form one pixel is calculated as follows. The shape is such that it also includes a substantially diagonal direction 1/4 region of one pixel adjacent in the main scanning direction or the sub-scanning direction, and a substantially diagonal direction 1 of the adjacent one pixel in the main scanning direction formed by the above light energy. Pixels including / 4 area and runner By arranging a pixel that also includes a substantially diagonal direction 1/4 region of one pixel adjacent in the direction so that the respective substantially diagonal direction 1/4 regions are in contact with each other, a portion adjacent to both pixels is provided. An image forming method characterized in that pixels in a substantially diagonal ½ area formed of pixels in the substantially diagonal ¼ area are formed. 3. An exposure means for exposing the surface of the photoconductor, and an exposure control means for controlling the exposure operation of the exposure means based on an image signal such as a character or a figure, and the surface of the photoconductor comprises a plurality of pixels. In an image forming apparatus for forming an image as a latent image, the exposure control means divides the irradiation of light forming one pixel into a plurality of lighting times and a plurality of extinguishing times. By the combination, the distribution shape of the light energy on the photoconductor required for forming one pixel is formed into a shape including a substantially diagonal 1/4 region of one pixel adjacent to the one pixel. An image forming apparatus characterized by the above. 4. An exposure unit for scanning and exposing the surface of a photosensitive member rotating in the sub-scanning direction in a main scanning direction orthogonal to the sub-scanning direction, and an exposure operation of the exposing unit for image signals such as characters and figures. In the image forming apparatus which forms an image composed of a plurality of pixels as a latent image on the surface of the photoconductor, the exposure control means controls the irradiation of light for forming one pixel. It is divided into a lighting time and a plurality of extinguishing times, and the distribution shape of the light energy on the photoconductor required for forming one pixel is determined by combining the lighting time and the extinguishing time. The shape is made so as to also include a substantially diagonal direction 1/4 region of one pixel adjacent in the scanning direction or the sub-scanning direction, and a substantially diagonal direction of the adjacent one pixel in the main scanning direction formed by the light energy. Image that also includes 1/4 area A pixel and a pixel that also includes a substantially diagonal 1/4 region of one adjacent pixel in the sub-scanning direction are provided in a region adjacent to both pixels in a substantially diagonal direction including the pixels in the substantially diagonal 1/4 region. An image forming apparatus, characterized in that the above-mentioned light energy distribution region is controlled so that the substantially diagonal ¼ regions are in contact with each other so that pixels in the ½ region in the direction can be formed.