JP2003345076A - Image processor and method for controlling it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of a sweeping phenomenon caused by development. <P>SOLUTION: The edge part of an image data on a downstream side in a subscanning direction is detected, and processing so as to shorten the turn-on time of a laser stepwise by modulating a pulse width is performed from the certain specified picture element of the picture element of the edge part on an upstream side in the subscanning direction to the picture element of the edge part on the downstream side. The turn-on time of the laser is shortened stepwise, so that the leveling effect of an increased toner quantity at the edge part of the image data on the downstream side in a main scanning direction due to the sweeping phenomenon is obtained. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus for forming a visible image on a predetermined recording medium according to input information and a control method therefor.

[0002]

2. Description of the Related Art An electrophotographic image forming apparatus of an electrophotographic system such as a laser beam printer or a copying machine uses a powdery developer (hereinafter referred to as toner).

As one of the developing methods, a jumping developing method is known in which the latent image on the image carrier is developed while the developer carrier of the image forming apparatus is held in non-contact with the image carrier. ing. A conventional image forming apparatus shown in FIG. 8 will be described as an example of the image forming apparatus adopting the jumping developing method.

In the figure, reference numeral 1 is a main body of an image forming apparatus which is a printer engine. Reference numeral 2 denotes a cylindrical photosensitive drum that is an image bearing member, and rotates in one direction around its axis. After the surface of the photosensitive drum 2 is uniformly charged by the charging device 3,
A latent image is formed by the exposure device 4. The developing device 5 includes a hopper, which is a toner storage device for storing and storing the toner 6, and a developing sleeve 8, which is a toner carrier.
Toner 6 is supplied to the latent image formed on the photosensitive drum 2 to develop the latent image. A developing blade 9, which is a toner regulating member, is installed near the developing sleeve 8. Then, by the engine control unit 7 having a power supply for driving the image forming apparatus and a high voltage circuit for supplying a bias for forming an image, a DC bias and an AC bias are applied between the photosensitive drum 2 and the developing sleeve 8. Is applied to the developing bias. The image on the photosensitive drum 2 visualized by the toner 6 is transferred to the transfer material 11 by the transfer device 10. The transfer material 11 is stored in a paper feed cassette 17, is fed by a paper feed roller 12, and is fed by a registration roller 13
Is synchronized with the image on the photosensitive drum 2 by the transfer device 1
Sent to 0. The visible image formed by the toner 6 transferred to the transfer material 11 by the transfer device 10 is conveyed to the fixing device 14 together with the transfer material 11 and is fixed to the transfer material 11 by heat or pressure to form a recorded image. On the other hand, the toner 6 remaining on the photosensitive drum 2 without being transferred after the transfer is cleaned by the cleaning device 1.
It is removed by the cleaning blade 16 in 5. The surface of the photosensitive drum 2 from which the toner 6 has been removed is charged again by the charging device 3.
Are charged by and the above steps are repeated.

[0005]

By the way, in the jumping developing system, there is a phenomenon called "hikiyose".

This is because a large amount of toner flies to the trailing edge of the latent image, the density of the trailing edge of the latent image increases, and the trailing edge of the latent image develops as if it spreads. It is a phenomenon.

This mechanism is based on the potential at which the toner coated on the developing sleeve corresponding to the charging portion is energetically stable at the boundary from the latent image portion to the charging portion on the photosensitive drum as shown in FIG. This is because of flying to the side or to the side of the latent image portion having a low potential due to the edge effect. The edge effect occurs when the electric field distribution between the developing sleeve and the surface potential of the photosensitive drum is as shown in FIG. Therefore, as shown in FIG. 10, the toner adhesion amount increases at the rear end portion of the latent image on the photosensitive drum, so that the density becomes high and the image tends to be crushed due to fixing.

For example, in black image data of m dots in the main scanning direction × n dots in the sub scanning direction as shown in FIG.
The image after fixing becomes an image in which the trailing edge of the image is widened as shown in FIG.

In addition, the scattering that occurs in the transfer and fixing process,
Moisture contained in the transfer material is generated as water vapor when passing through the fixing device, and when the height of the toner is high, a trailing phenomenon, which is a phenomenon in which the water vapor escapes and the toner is spilled out, becomes noticeable.

These phenomena are mainly noticeable in the non-contact developing system such as the jumping developing system.

In order to deal with this phenomenon, adjustments have been made so far in terms of hardware. Specifically, the magnitude of the magnetic force of the magnet in the developing sleeve, the developing bias, the peripheral speed difference of the developing sleeve with respect to the photosensitive drum, and the like are appropriately adjusted to suppress the boil-off phenomenon to the extent that it is inconspicuous.

However, the adjustment in terms of hardware is limited because it may cause other adverse effects.

Therefore, an object of the present invention is to provide an image capable of easily obtaining an image with uniform density without easily changing the hardware, such as scuffing, splattering, and tailing which tend to occur at the trailing edge of the image. It is to provide a processing device.

[0014]

In order to achieve the above object, a first aspect of the present invention relates to an image carrier for carrying an image, an image carrier for charging the carrier, and a charged image carrier. Laser exposure by scanning method to form an electrostatic latent image,
An image processing apparatus that carries a developer on a developer carrier and conveys the developer to a developing unit facing the image carrier to develop an electrostatic latent image on the image carrier to form a visible image. In, the edge portion of the image data on the downstream side in the sub-scanning direction is detected, and the pulse width modulation is performed from a certain pixel upstream of the pixel of the edge portion in the sub-scanning direction to the pixel of the edge portion on the downstream side. It is characterized by performing a process of gradually shortening the laser lighting time.

In the above construction, by shortening the laser lighting time stepwise, there is an effect of smoothing out the increase in the amount of toner at the edge portion on the downstream side in the main scanning direction of the image data due to the repelling phenomenon. As a result, It is possible to prevent the density at the trailing end of the output image from becoming dark, and it is possible to suppress image deterioration such as tailing and scattering.

According to a second aspect of the present invention, in claim 1, the laser is applied by pulse width modulation from a certain pixel upstream of the image data in the sub-scanning direction to a pixel at an edge portion downstream of the sub-scanning direction. It is characterized in that the pixels for performing the processing for shortening the lighting time of are gradually two edge portions of the image data in the main scanning direction.

In the above structure, the amount of toner spreading to the skirt at the edge portion of the image data in the sub-scanning direction due to the blotting phenomenon can be canceled by pulse width modulation, and an image faithful to the image data can be output. it can.

A third invention according to the present application is characterized in that, in claim 1, the image is a binary image such as a character / line drawing image.

The present invention is particularly effective for binary images.

In a fourth aspect of the present invention, in claim 1, the developing means for visualizing the image processing apparatus is a non-contact developing means.

According to the above-mentioned structure, the non-contact developing means which is apt to cause the repelling phenomenon can output an image faithful to the image data.

The fifth to sixth aspects of the present invention are directed to an image bearing member carrying an image, a charging of the bearing member, and a laser exposure of the charged image bearing member by a scanning method to form an electrostatic latent image. The image is formed, the developer is carried on the developer carrier, and the developer is conveyed to the developing section facing the image carrier, and the electrostatic latent image on the image carrier is developed to form a visible image. In the control method of the image processing apparatus, the edge portion on the downstream side in the sub-scanning direction of the image data is detected, and the pixel at the edge portion on the downstream side from the certain pixel on the upstream side in the sub-scanning direction of the pixel of the edge portion On the other hand, it is characterized in that the laser lighting time is reduced stepwise by pulse width modulation.

Further, a pixel for performing a process of stepwise shortening the laser lighting time by pulse width modulation from a certain pixel upstream of the sub-scanning direction of the image data toward the pixel of the edge portion downstream of the sub-scanning direction. Are two edge portions of the image data in the main scanning direction.

The image is a binary image such as a character or line drawing image.

The developing means for visualizing the image processing apparatus is a non-contact developing means.

In the control method having the above-described structure, the problem of the blushing phenomenon can be easily prevented, and an image having a uniform density that is faithful to the image data can be output.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) FIG. 2 shows a block diagram of a printing apparatus according to an embodiment of the present invention.

In FIG. 2, 100 is a CPU for controlling the entire apparatus, 200 is a ROM for storing the operation processing procedure of the CPU 100, font data, etc., and 300 is a C.
It is a RAM that functions as a work area of the PU 100 and a reception buffer. Reference numeral 400 is a bitmap memory for expanding bitmap data to be printed out, and 500 is an interface for receiving print data from a host computer which is a higher-level device or sending status information to the higher-level device. Reference numeral 600 is an operation panel having a display section for giving various instructions to the apparatus and displaying various messages, and 700 is image data expanded in the bitmap memory 400, and a visible image is recorded on a recording medium (recording paper). An image processing circuit for outputting to the printer engine unit 800 for recording on.

The image forming apparatus in this embodiment is shown in FIG.
The description is omitted because it is the same as that described in the related art.

Although the effect of the present invention can be obtained for any image data, in the present embodiment, for the sake of convenience, attention is paid to image data of m dots in the main scanning direction × n dots in the sub scanning direction in which the outermost shell is all black. explain.

FIG. 1 is a block diagram of the image forming apparatus described above.
In the image data of m dots in the main scanning direction × n dots in the sub scanning direction in which the outermost shell is all black, the image processing circuit 700 that regulates the toner developing area at both ends of the image trailing end.
It is a block diagram of.

When image data of m dots in the main scanning direction × n dots in the sub scanning direction in which the outermost shell is all black is printed, with respect to multi-valued image data of m dots in the main scanning direction × n dots in the sub scanning direction. The edge detecting section detects the edge section.

Here, the edge detecting means may be constituted by a primary or secondary differentiating circuit. For example, an appropriate window including a target pixel is prepared, and the maximum density and the minimum density are detected in the window. When there is a difference of a predetermined value or more, it is determined that the pixel of interest exists in the edge portion.

The edge portion is detected, and further, it is the both end portions of the rear end of m dots in the main scanning direction × n dots in the sub scanning direction.
Attention is paid to 1 dot and m dots in the main scanning direction of the n-th dot in the sub scanning direction (f = arbitrary integer).

Sub-scanning direction n-fth dot main scanning direction 1
Regarding the dots and the m dots, according to the size of the m dots, to the extent that the m dot width of the n-th dot in the sub-scanning direction of the print image does not change, for example, as shown in FIG. Change the lighting time in the scanning direction.

As described above, with respect to the first dot and the m-th dot in the main scanning direction at the trailing edge of the image data, the laser lighting time is shortened as the n dots in the sub-scanning direction are approached. Then, the amount of toner at the trailing edge of the image data becomes large due to the blushing phenomenon when visualized, and the toner spreads to the hem due to the crushing and scattering at the subsequent transfer and fixing steps. The areas in which the lighting time is shortened are offset, and a more faithful image can be output based on the image data.

According to the study of the inventor of the present invention, the effect of the present embodiment can be obtained better when m and n ≧ 3 dots.

In this embodiment, an image forming apparatus having a resolution of 1200 dpi is used.

In that case, f is determined by the table 1 as shown in Table 1, and the pulse width modulation (laser emission time) is determined by the table as shown in Table 2 by the f value.

[0040]

[Table 1]

[0041]

[Table 2]

For example, when m = 50 dots in the main scanning direction × n = 40 dots in the sub scanning direction, f = 3, and the image data is corrected as the lighting time of the laser in the main scanning direction as shown in Table 3.

[0043]

[Table 3]

According to the image processing of Table 3, t was 5 μm in the conventional case as shown in FIG.
The image can be stored within μm, and an image that is faithful to the image data that is visually unnatural can be output.

Here, since the value of f and the pulse width modulation of the laser for correction are largely dependent on the characteristics of the image forming apparatus, it is necessary to determine it according to the characteristics of the image forming apparatus. Therefore, the present embodiment is only an example, and the value of f and the pulse width modulation of the laser for correction are not uniquely determined.

As described above, in the image data of m dots in the main scanning direction × n dots in the sub scanning direction, 1 dot in the main scanning direction, m dots, and n-f dots in the sub scanning direction are pulse-width-modulated by the laser pulse width modulation. By changing the lighting time appropriately and printing the image data, it is possible to regulate the amount of toner for the first dot and the mth dot in the main scanning direction, and it is possible to prevent the occurrence of the cleansing phenomenon, which was a problem. .

(Embodiment 2) In the present embodiment, the image trailing edge portion which spreads like a hem described in the first embodiment is suppressed, and further the image trailing edge portion of the image trailing edge portion is suppressed by the image trailing edge phenomenon. The purpose is to prevent the density from becoming high due to the large amount of toner attached.

The feature of the present invention is that FIG.
In order to suppress the toner swelling at the trailing edge of the image, the laser is turned on toward the downstream side in the sub-scanning direction for the pixel at the trailing edge of the image data by pulse width modulation as shown in FIG. Turn on the light while shortening the time, as shown in Fig. 4.
The toner height is made uniform as in (b).

How to mount the toner on the photosensitive drum is shown in FIG.
As shown in FIG. 5A, since the toner is dragged to the downstream side in the paper carrying direction in the transfer and fixing steps, the toner amount increases toward the downstream side in the paper carrying direction. By shortening the laser lighting time toward the downstream side in the sub-scanning direction and lighting the laser, the height of the toner on the photosensitive drum becomes uniform as shown in FIG. 4B.

The image forming apparatus of this embodiment has the same structure as that of the first embodiment.

FIG. 6 shows the image forming apparatus described above.
6 is a block diagram of an image processing circuit 700 that regulates the height of toner at the trailing edge of an image in image data of m dots in the main scanning direction × n dots in the sub scanning direction in which the outermost shell is all black. FIG.

In the present embodiment, when image data of m dots in the main scanning direction × n dots in the sub scanning direction in which the outermost shell is all black is printed, multi-valued m dots in the main scanning direction × n dots in the sub scanning direction. The edge detection unit detects the edge portion of the image data.

For two edge portions in the sub-scanning direction,
Similar to the first embodiment, from Tables 1 and 2, f is determined according to the values of m and n in the image data of m dots in the main scanning direction × n dots in the sub scanning direction, and is executed according to the f value. Pulse width modulation is performed as in the first embodiment.

Further, in the non-edge portion in the sub-scanning direction, P value is determined from Table 4 according to the size of n dots in the sub-scanning direction.

[0055]

[Table 4]

[0056]

[Table 5]

Based on this P value, attention is paid to the pixel of the nth image data from nP in the sub-scanning direction.

Then, in the non-edge portion in the sub-scanning direction, pulse width modulation is performed on each of the nth to nth pixels from the table of Table 5 to change the laser lighting time.

In the present embodiment, as shown in FIG. 5, the edge portions on one side in the main scanning direction of a pixel are only provided, although the laser non-lighting portion is evenly provided on both edge portions in the main scanning direction. The laser non-lighting portion may be provided in this case, and in this case, the laser non-lighting portion needs to be provided at the edge portion on the same side of all pixels, which is the non-edge portion in the sub-scanning direction.

When the image data is output based on the above-described embodiment, the phenomenon that the trailing end of the output image spreads to the skirt with respect to the image data can be suppressed, and the height and density of the toner of the output image become uniform. , It was confirmed that the scattering of letters was reduced.

As described above, in the present embodiment, with respect to the image data, the phenomenon that the trailing edge of the image data is widened at the rear end portion of the output image, that is, the phenomenon of spreading, and the rear end portion of the image data, It is possible to prevent the phenomenon that the density becomes high at the portions other than the edge portions.

(Third Embodiment) In the present embodiment, the present invention described in the first embodiment is controlled more precisely to prevent the scuffing phenomenon in which the trailing edge of the image spreads like a hem. I am trying.

In this embodiment, the interval between two image data in the sub-scanning direction is detected and the image processing is controlled according to the distance of the interval.

As described with reference to FIG. 9, the repelling phenomenon occurs when the toner on the developing sleeve corresponding to the charging potential position near the latent image potential flies to the latent image potential side which is energetically stable.

Therefore, if the latent image potential due to the next image data in the sub-scanning direction is immediately available, the degree of the blushing phenomenon also changes.

For example, as shown in FIG. 7, it is assumed that after the latent image A of n dots in the sub-scanning direction is formed, the latent image B of y dots is formed after h dots. When h is small, a part of the toner on the developing sleeve corresponding to the latent image of h dots flies to the latent image A side and the latent image B side, and the amount of toner flying to the latent image A side is small. The cleansing phenomenon is inconspicuous.

Therefore, by controlling the dot formation depending on the size of the h dot between the latent image A and the latent image B, the latent image A
Prevent the hem from being too wide or too narrow.

The image forming apparatus of this embodiment has the same structure as that of the first embodiment.

In this embodiment, when the image data A of m dots in the main scanning direction × n dots in the sub scanning direction in which the outermost shell is all black is printed, multivalued m dots in the main scanning direction ×
The edge detecting section detects the edge of the image data A of n dots in the sub-scanning direction.

After the edge portion of the nth dot in the sub-scanning direction is detected, at least 1 in the main scanning direction of the image data A is detected.
The edge portion of the image data B of the main scanning direction x dots × sub scanning direction y dots, which is the next image data including the dot or the m dot, is detected. Therefore, in the sub-scanning direction, from n dots of the image data A to 1 of the image data B
The number of dots h up to a dot can be counted.

In the present embodiment, for the sake of simple explanation,
Image data A and image data B having the same main scanning position are set (m = x).

According to the number of dots h between the image data A and the image data B, the image data A is obtained in the same manner as in the first embodiment.
Main scanning direction 1 of the sub-scanning direction n-f dot which is both ends of the rear end of m dots in the main scanning direction × n dots in the sub-scanning direction
Focus on dots and m dots (f = any integer).

In the present embodiment, when the image forming apparatus used in the first embodiment is examined, the image data A
When the number of dots h between the image data B and the image data B was 100 dots or less, the degree of the repelling phenomenon was small. That is, the h value is 1
Within 00 dots, there is no need to control the dot formation as in the first embodiment.

Therefore, when the number of dots h between the image data A and the image data B exceeds 100 dots, the control as in the first embodiment is performed.

By performing the control as described above, regardless of the number of dots h between the image data A and the image data B, the same image as the data can be always developed, and an image more faithful to the image data can be obtained. I was able to output.

As described above, by controlling according to the size of the image data A and the size of the space between the image data A and the image data B, the cleansing phenomenon can be prevented more accurately, and the data is appropriate for the data. It is possible to output various images.

[0077]

As described above, according to the first invention of the present application, an image carrier for carrying an image, a charged carrier for the image, and a laser for the charged image carrier by a scanning method. An electrostatic latent image is formed by exposure, a developer is carried on a developer carrier, and the developer is conveyed to a developing section facing the image carrier, and the electrostatic latent image on the image carrier is In an image processing apparatus that develops to form a visible image, an edge portion of the image data on the downstream side in the sub-scanning direction is detected, and is located downstream of a certain pixel upstream of the pixel of the edge portion in the sub-scanning direction. It is characterized in that a process for shortening the lighting time of the laser stepwise is performed by pulse width modulation toward the pixels in the edge portion.

The above arrangement has the effect of smoothing out the increase in the amount of toner at the edge portion on the downstream side in the main scanning direction of the image data due to the wiping phenomenon, and as a result, the density at the trailing edge portion of the output image is high. It is possible to prevent the deterioration of the image, and it is possible to suppress image deterioration such as tailing and scattering.

According to the second invention of the present application, in claim 1, pulse width modulation is performed from a certain pixel upstream of the image data in the sub-scanning direction toward a pixel at an edge portion downstream in the sub-scanning direction. Thus, the pixels for performing the processing for shortening the lighting time of the laser in stages are two edge portions of the image data in the main scanning direction.

With the above-described structure, it is possible to cancel the spread of the toner at the edge portion of the image data in the sub-scanning direction to the hem due to the repelling phenomenon by the pulse width modulation, and it is possible to output an image faithful to the image data. did it.

According to a third invention of the present application, in claim 1, the image is a binary image such as a character / line drawing image.

The present invention is particularly effective for binary images.

According to a fourth invention of the present application, in claim 1, the developing means for visualizing the image processing apparatus is a non-contact developing means.

With the above arrangement, the effect of the present invention can be obtained, and an image faithful to the image data can be output, especially in the non-contact developing means in which the repelling phenomenon is likely to occur.

According to the fifth to sixth inventions of the present application,
An image bearing member carrying an image, the carrier is charged, and the charged image bearing member is exposed to a laser by a scanning method to form an electrostatic latent image, and a developer is carried on the developer bearing member. In the control method of the image processing apparatus, which conveys the developer to a developing unit facing the image carrier and develops the electrostatic latent image on the image carrier to form a visible image, the sub-scanning of the image data is performed. The edge part on the downstream side in the direction is detected, and the laser lighting time is gradually increased by pulse width modulation from a certain pixel on the upstream side in the sub-scanning direction of the pixel on the edge part to the pixel on the edge part on the downstream side. It is characterized in that processing for shortening is performed.

Further, a pixel for performing a process of stepwise shortening the laser lighting time by pulse width modulation from a certain pixel upstream of the sub-scanning direction of the image data toward the pixel of the edge portion downstream of the sub-scanning direction. Are two edge portions of the image data in the main scanning direction.

The image is a binary image such as a character / line drawing image.

The developing means for visualizing the image processing apparatus is a non-contact developing means.

With the control method having the above-described structure, it is possible to easily prevent the problem of the blushing phenomenon and output an image having a uniform density, which is faithful to the image data.

[Brief description of drawings]

FIG. 1 is a block diagram of an image processing circuit according to a first embodiment.

FIG. 2 is an overall configuration diagram of a printing apparatus according to an embodiment.

FIG. 3 shows a latent image state when pulse width modulation according to the first embodiment is performed.

FIG. 4 is a diagram showing an effect on the toner adhesion amount according to the present invention.

FIG. 5 shows a latent image state when pulse width modulation according to the second embodiment is performed.

FIG. 6 is a block diagram of an image processing circuit according to a second embodiment.

FIG. 7 is image data A and image data B according to the third embodiment.
FIG.

FIG. 8 is a side sectional view of the image forming apparatus.

FIG. 9 is a view showing a mechanism of occurrence of the battering phenomenon.

FIG. 10 is a diagram showing the amount of toner adhered due to the repelling phenomenon.

FIG. 11 is a diagram showing a cleansing phenomenon.

[Explanation of symbols]

1 Image forming device 2 photosensitive drum 3 charging device 4 Exposure equipment 5 Development device 6 toner 7 Power control unit 8 developing sleeve 9 Development blade 10 Transfer device 11 Transfer material 14 Fixing device 16 Cleaning member 17 cassettes 100 CPU 200 ROM 300 RAM 400 bitmap memory 500 interface 600 operation panel 700 image processing circuit 800 printer engine

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 1/23 103 (72) Inventor Takayuki Namiki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. Inner F term (reference) 2C362 AA57 AA64 CB24 CB28 CB80 2H027 DA50 DE04 DE07 EA02 EC11 EC19 FD08 ZA07 2H076 AB05 AB76 DA11 DA19 2H077 DA01 DA57 DB13 EA16 5C074 AA02 BB17 DD01 DD07 DD11 EE02 GG02FF02

Claims (8)

[Claims] 1. An image carrier carrying an image, the carrier is charged, and the charged image carrier is laser-exposed by a scanning method to form an electrostatic latent image, and a developer is carried on the developer. In an image processing apparatus that carries a developer on a body and conveys the developer to a developing unit facing the image carrier, develops the electrostatic latent image on the image carrier to form a visible image, The edge part on the downstream side in the sub-scanning direction is detected, and the lighting time of the laser is stepped by pulse width modulation from a certain pixel on the upstream side in the sub-scanning direction of the pixel on the edge part toward the pixel on the edge part on the downstream side. An image processing apparatus that performs a process of shortening the image. 2. The image processing apparatus according to claim 1, wherein the laser lighting time is changed by pulse width modulation from a certain pixel upstream of the image data in the sub-scanning direction toward a pixel at an edge portion downstream in the sub-scanning direction. An image processing apparatus, wherein pixels to be subjected to the process of shortening in stages are two edge portions of the image data in the main scanning direction. 3. The image processing apparatus according to claim 1, wherein the image is a binary image such as a character / line drawing image. 4. The image processing apparatus according to claim 1, wherein the developing means for visualizing the image processing apparatus is a non-contact developing means. 5. An image carrying member carrying an image, the carrying member is charged, and the charged image carrying member is exposed to laser by a scanning method to form an electrostatic latent image, and a developer is carried on the developer. In a method of controlling an image processing apparatus, which carries a developer on a body and conveys the developer to a developing unit facing the image carrier to develop an electrostatic latent image on the image carrier to form a visible image, The edge part of the image data on the downstream side in the sub-scanning direction is detected, and the laser is turned on by pulse width modulation from a certain pixel upstream of the edge part pixel in the sub-scanning direction toward the downstream edge pixel. A control method characterized by performing processing for shortening the time stepwise. 6. The control method according to claim 5, wherein the laser lighting time is stepped by pulse width modulation from a predetermined pixel upstream of the image data in the sub-scanning direction to a pixel at an edge portion downstream in the sub-scanning direction. The control method is characterized in that the pixels to be subjected to the process of shortening the image are two edge portions in the main scanning direction of the image data. 7. The control method according to claim 5, wherein the image is a binary image such as a character / line drawing image. 8. The control method according to claim 5, wherein the developing means for visualizing the image processing apparatus is a non-contact developing means.