JP2000089541A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color image forming device constituted so that a resist pattern is accurately detected at a high speed. SOLUTION: This color image forming device is provided with image stations 1a, 1b, 1c and 1d having photoreceptor drums 2a, 2b, 2c and 2d and developing means 4a, 4b, 4c and 4d, plural exposure means 6a, 6b, 6c and 6d forming a latent image on the drums 2a, 2b, 2c and 2d, a transfer means 7 forming a synthetic image on an intermediate transfer belt 12 from the toner images of respective colors formed at the stations 1a, 1b, 1c and 1d, a resist pattern forming means 13 forming the resist pattern at the stations 1a, 1b, 1c and 1d, a pattern detection means 14 detecting the resist pattern transferred on the transfer means 7 and a positional deviation correction means 15 correcting positional deviation based on a result detected by the detection means 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic color image forming apparatus having a plurality of photoreceptors,
The present invention relates to a technique for detecting a position shift of each color toner image formed on a photoreceptor, accurately aligning these on a recording medium, and transferring the image.

[0002]

2. Description of the Related Art Conventionally, in a color image forming apparatus employing an electrophotographic technique, a photoreceptor as an image carrier is charged by a charging means, and light is applied to the charged photoreceptor in accordance with image information. A latent image is formed, the latent image is developed by a developing unit, and the developed toner image is transferred to a sheet material or the like to form an image.

On the other hand, a plurality of image stations in which such a series of image forming processes are developed in accordance with colorization of an image are provided, and each color image of a cyan image, a magenta image, a yellow image, and preferably a black image is formed. A tandem-type color image forming apparatus that forms a full-color image by forming the image on each image carrier and superimposing and transferring each color image on a sheet material at a transfer position of each image carrier has also been proposed. Such a tandem-type color image forming apparatus has an image forming unit for each color, and is therefore advantageous for speeding up.

[0004] However, such a color image forming apparatus has a problem in how to properly perform registration (registration) of each image formed in a different image forming unit. This is because a shift in the image forming position of the four colors transferred to the sheet material or the like finally appears as a position shift or a change in color tone.

By the way, as shown in FIG. 12, the type of positional deviation of the transferred image is a positional deviation in the moving direction of the transfer material (the direction of arrow A in the figure) (hereinafter referred to as "sub-scanning positional deviation"). (FIG. 12A), displacement in the scanning direction (direction orthogonal to the direction of arrow A in the figure) (hereinafter referred to as “main scanning displacement”) (FIG. 12B), and position in the oblique direction. Deviation (hereinafter referred to as “skew error”) (FIG. 12)
(C)), a deviation of the magnification error (FIG. 12 (d)), and a deviation of the bending error (FIG. 12 (e)).

The main cause of the displacement is shown in FIG.
The sub-scanning position shift in FIG. 12A is caused by a shift in mounting of each image station and the scanning optical system, and a shift in mounting of a lens and a mirror (not shown) in the scanning optical system. The same applies to the case of a main scanning position shift.

The main causes of the inclination shift in the oblique direction in FIG. 12C are due to the angle shift of the rotating shaft of the photosensitive drum in the image station and the mounting angle shift of the scanning optical system. The main cause of the deviation due to the magnification error in d) is the deviation of the scanning line length due to the error in the optical path length from each scanning optical system to the photosensitive drum of the image station, and the deviation due to the curvature error in FIG. The main cause of this is that the lens is misaligned in each scanning optical system.

In order to correct these five types of shifts, a reference pattern (hereinafter referred to as a “resist pattern”) is drawn in advance and detected by a plurality of sensors (position shift detection). It has been proposed to calculate a shift amount from a result and perform position adjustment (position shift correction) of each image according to the shift amount.

Hereinafter, a conventional resist pattern detection and misregistration correction operation will be described.

FIG. 13 is an explanatory view showing the structure of a conventional resist pattern detecting means (hereinafter, referred to as "pattern detecting means"). FIG. 14 shows a conventional arrangement of a resist pattern and a pattern detecting means on an intermediate transfer belt. FIG. 15 and FIG. 16 are explanatory diagrams showing the arrangement of a resist pattern on an intermediate transfer belt, a pattern detecting unit, and an output signal of the pattern detecting unit in the related art.

[0013] As shown in FIG.
0 is an image sensor (hereinafter referred to as “CCD”) 4
1. A light source 42 such as a lamp and a selfoc lens array 43 for forming reflected light on the CCD 41.
Then, such pattern detecting means 40a, 40b
Are the CCDs 41a,
The pixels in 41 b are arranged on a line that intersects at right angles to the conveyance direction A of the intermediate transfer belt 12. And
As shown in FIG.
Two pieces are arranged in the vicinity of two end portions in the width direction of No. 2 in total, one each.

In the above-described configuration, the operation of detecting and correcting the registration pattern is performed, as shown in FIG. 14, by a predetermined registration pattern such as a straight line or a figure (for example, perpendicular to the conveyance direction A of the intermediate transfer belt 12). On the intersecting lines, the toner images 44, 45, 4 for each color at predetermined intervals.
6, 47), and the pattern detecting means 40a, 40b
The position shift (resist shift) of each color is measured by.

By the way, as shown in FIG. 15A, the deviation of the sub-scanning position shown in FIG.
2 resist patterns 44, 45, 46, 47 for each color
Is a time difference between the time when the light passes through the CCD 41a in the pattern detecting means and a predetermined design value (ΔT1 = T−T1,
T is determined by calculating a positional shift (ΔY1 = ΔT1 · v) for each color from the predetermined design value) and the transport speed v of the intermediate transfer belt 12.

As shown in FIG. 16A, the main scanning position shift shown in FIG. 12B is caused by the fact that the scanning start position of each color resist pattern 44, 45, 46, 47 on the intermediate transfer belt 12 is a pattern detecting means. The position shift of each color is calculated from the pixel position difference ([Delta] X1) passing through the CCD 41a.

The skew error shown in FIG.
As shown in FIG. 5B, resist patterns 44, 4 of the same color formed on both sides of the intermediate transfer belt 12 in the width direction.
5, 46 and 47 are the CCs in the respective pattern detection means.
D41a and the time difference (ΔT
The skew error of each color (ΔY2 = ΔT2 · v) is calculated from 2) and the transport speed v of the intermediate transfer belt 12.

The magnification error shown in FIG.
As shown in (a) and (b), the scan start and scan end positions of the same color resist patterns 44, 45, 46, and 47 on the intermediate transfer belt 12 are pixels passing through the CCD 41a and the CCD 41b in the respective pattern detection means. From the position difference (ΔX2, ΔX1), the magnification error of each color (ΔX3 = ΔX3)
X2−ΔX1).

Then, the above 4 calculated as above
A position shift correction operation is performed based on the types of position shift amounts.

Here, with respect to the sub-scanning position shift shown in FIG. 12A and the main scanning position shift shown in FIG. 12B, the shift amount is corrected by adjusting the scanning timing of each color (not shown). .

For the skew error shown in FIG. 12C and the magnification error shown in FIG. 12D, the optical system in the exposure means (not shown) is connected to an actuator (not shown).
(Not shown).

The curvature error shown in FIG. 12 (e) cannot be measured accurately, and is dealt with by increasing the assembling accuracy of the lens and the like of the exposure means (not shown). No correction was made.

With the above-described configuration and operation, the displacement amounts of the four colors are detected and corrected according to the displacement amounts.

[0022]

However, in the above-mentioned conventional techniques, since an expensive CCD is used for detecting a resist pattern, it has been difficult to obtain a low-cost color image forming apparatus.

A CCD for detecting a resist pattern
Requires a predetermined accumulation time to ensure the detection accuracy. In order to read the resist pattern on the intermediate transfer belt moving at high speed in a high-speed color image forming apparatus, it is necessary to shorten the accumulation time. Increasing the illuminance of the light source to increase the amount of light
There is a problem that a CD is required and the cost is increased. As for the accumulation time in a high-speed color image forming apparatus, a predetermined accumulation time can be secured by making the moving speed of the intermediate transfer belt slower than that in the normal printing. However, there is a problem in that it is impossible to accurately detect a displacement in a normal printing state.

Further, in a color image forming apparatus using the intermediate transfer system, a resist pattern must be formed on the intermediate transfer belt. The color of the intermediate transfer belt is generally black because it must contain carbon by its nature. Here, when a resist pattern based on a black toner image on the intermediate transfer belt that is black is detected, a difference between the intermediate transfer belt and the resist pattern is hardly obtained, so that there is a problem that detection accuracy is very poor. .

SUMMARY OF THE INVENTION It is an object of the present invention to provide a low-cost color image forming apparatus capable of detecting a resist pattern at high speed and with high accuracy and accurately correcting misregistration.

[0026]

In order to solve this problem, a color image forming apparatus according to the present invention develops a photosensitive member on which a latent image is formed and a latent image formed on the photosensitive member as a toner image. A plurality of image stations provided with developing means corresponding to the developing colors, a plurality of exposing means for irradiating light to each photoconductor to form a latent image, and a plurality of image stations for each color formed by the plurality of image stations. A toner image is sequentially superimposed on a transfer material and transferred to form a composite image on the transfer material, and a resist pattern is generated on a plurality of exposure devices, and a predetermined pattern is provided to an image station provided corresponding to the exposure device. A resist pattern generating means for forming a resist pattern, a semiconductor laser for irradiating the resist pattern with laser light and a photosensor for detecting reflected light from the transfer means, And pattern detecting means for detecting an image by the resist pattern transferred to the transfer means, in which a structure having a positional deviation correcting means for correcting the positional deviation on the basis of the result detected by the pattern detection means.

Thus, it is possible to obtain a low-cost color image forming apparatus capable of detecting a resist pattern with high speed and high accuracy and accurately correcting positional deviation.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to a first aspect of the present invention, there is provided a photosensitive member on which a latent image is formed and a developing means for developing the latent image formed on the photosensitive member as a toner image into a developing color. A plurality of image stations provided correspondingly, a plurality of exposure means for irradiating each photoconductor with light to form a latent image, and a toner image of each color formed by the plurality of image stations are sequentially transferred to a transfer material. A transfer means for transferring by superposition and forming a composite image on a transfer material; and a resist for generating a resist pattern in a plurality of exposure means and forming a predetermined resist pattern in an image station provided corresponding to the exposure means. It is composed of a pattern generating means, a semiconductor laser for irradiating the resist pattern with laser light, and a photosensor for detecting reflected light from the transferring means, and is developed and transferred on the transferring means. This is a color image forming apparatus having a pattern detecting means for detecting a distant pattern and a displacement correcting means for correcting a displacement based on a result detected by the pattern detecting means. , It is possible to accurately correct the displacement and to obtain an image with high print quality.

According to a second aspect of the present invention, in the first aspect of the present invention, the pattern detecting means includes a lens for optically focusing laser light output from the semiconductor laser and a light incident on the photosensor. A color image forming apparatus including at least one of a lens that optically stops down,
The registration pattern can be accurately detected by detecting the resist pattern at higher speed and with higher precision, and an image having high printing quality can be obtained.

According to a third aspect of the present invention, in the first or second aspect, the pattern detecting means comprises:
A color image forming apparatus equipped with a comparison unit that outputs a comparison result between the output of the photo sensor and a predetermined comparison value. It can detect a resist pattern at high speed and with high accuracy to accurately correct positional deviation. And an effect that an image with high print quality can be obtained.

According to a fourth aspect of the present invention, in the third aspect of the invention, the pattern detecting means includes a comparison value varying means for varying a value of the comparison value with respect to the output of the photosensor. It is a forming device that can correct the mounting variation of the pattern detection means, the optical axis deviation of the semiconductor laser, the optical axis deviation of the photo sensor, detect the resist pattern with high speed, high accuracy and high reliability, This has the effect of enabling accurate misregistration correction and obtaining an image with high print quality.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the pattern detecting means amplifies the output of the photosensor and sends it to the comparing means. The color image forming apparatus has a function of detecting a resist pattern at high speed and with high accuracy, accurately correcting positional deviation, and having an effect of obtaining an image with high print quality.

According to a sixth aspect of the present invention, in the color image forming apparatus according to the fifth aspect, the pattern detecting means is provided with an amplification rate changing means for changing the amplification rate of the amplification means. In addition, it is possible to detect a resist pattern at high speed and with high accuracy, and to accurately perform misregistration correction, thereby obtaining an image having high print quality.

According to a seventh aspect of the present invention, in the first aspect of the present invention, the pattern detecting means includes a laser power control means for controlling an output value of the semiconductor laser. It is a color image forming apparatus that can correct the variation in the mounting of the pattern detection means, the optical axis deviation of the semiconductor laser, and the optical axis deviation of the photo sensor. It is possible to accurately detect and correct the misalignment and obtain an image with high print quality.

According to an eighth aspect of the present invention, in the invention according to any one of the first to seventh aspects, the pattern detecting means uses the optical axis of the semiconductor laser and a normal to the surface of the transfer means. This color image forming device has the same angle as the angle between the optical axis of the photosensor and the normal to the surface of the transfer means, and detects the resist pattern at high speed and with high accuracy to accurately correct misregistration. This makes it possible to obtain an image with high print quality.

According to a ninth aspect of the present invention, there is provided a color image forming apparatus according to the eighth aspect, wherein the angle between the optical axis of the semiconductor laser and the normal to the surface of the transfer means is 30 ° or less. Yes, it is possible to detect the resist pattern at high speed and with high accuracy and accurately correct the positional deviation,
This has the effect that an image with high printing quality can be obtained.

According to a tenth aspect of the present invention, in the invention according to any one of the first to ninth aspects, the beam diameter of the laser beam output from the semiconductor laser is 200 μm or less on the transfer means. The color image forming apparatus has a function of detecting a resist pattern at high speed and with high accuracy to accurately correct positional deviation, and has an effect of obtaining an image with high print quality.

According to an eleventh aspect of the present invention, in the first aspect of the present invention, the photosensor is divided and installed at two locations in the width direction of the transfer means. The color image forming apparatus has a function of detecting a resist pattern at high speed and with high accuracy to accurately correct positional deviation, and has an effect of obtaining an image with high print quality.

According to a twelfth aspect of the present invention, there is provided a color image forming apparatus according to any one of the first to eleventh aspects, wherein the density sensor detects a toner density by a pattern detecting means. Since there is no need to provide a separate device, there is an effect that the cost can be reduced.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. In these drawings, the same members are denoted by the same reference numerals, and duplicate description is omitted.

(Embodiment 1) FIG. 1 is a schematic diagram showing a configuration of a color image forming apparatus according to Embodiment 1 of the present invention.
FIG. 2 is an explanatory diagram showing an arrangement of a resist pattern and a pattern detecting unit on an intermediate transfer belt in a transfer unit of the color image forming apparatus according to the first embodiment of the present invention, and FIG. 3 is a first embodiment of the present invention. FIG. 4 is an explanatory view showing a configuration of a pattern detecting means of the color image forming apparatus in FIG. 4, and FIG. FIG. 5 is a graph showing the relationship between the angle between the optical axis of the semiconductor laser and the optical axis of the photodiode of the color image forming apparatus according to the first embodiment of the present invention and the normal to the surface of the intermediate transfer belt, and the detection error. FIG. 6 is a graph showing the relationship between the spot diameter of the laser beam on the intermediate transfer belt of the color image forming apparatus according to Embodiment 1 of the present invention and the detection error, and FIG. 7 is the present invention. FIG. 8 is a waveform diagram showing an output signal of one of the pattern detecting units in the color image forming apparatus according to the first embodiment. FIG. 8 shows an output signal of the one of the pattern detecting units in the color image forming apparatus according to the first embodiment of the present invention. FIG. 9 is a waveform diagram showing an output signal of the other pattern detecting means in the color image forming apparatus according to Embodiment 1 of the present invention, and FIG. 10 is a color image forming apparatus according to Embodiment 1 of the present invention. FIG. 8 is a waveform diagram showing an output signal of the other pattern detection means.

First, a process of obtaining a color image will be described with reference to FIG.
This will be described with reference to FIG. In FIG. 1, four image stations 1a, 1b, 1c, 1d are arranged in a color image forming apparatus, and each image station 1a, 1b, 1c, 1d.
Denote photosensitive drums (photosensitive members) 2a, 2 as image carriers
b, 2c, 2d, respectively, around which charging means 3a, 3b, 3c, 3d for uniformly charging the surfaces of the photosensitive drums 2a, 2b, 2c, 2d, and an electrostatic latent image are visible. Developing means 4a, 4b, 4c, 4d for forming an image, cleaning means 5a, 5b, 5c, 5d for removing residual toner, and light corresponding to image information to each of the photosensitive drums 2a, 2b, 2
exposure means 6a, 6b,
6c, 6d, transfer means 8a, 8b for transferring a toner image to an intermediate transfer belt (transfer material) 12 constituting the transfer means 7;
8c and 8d are arranged respectively.

Here, the image stations 1a, 1b, 1
In c and 1d, a yellow image, a magenta image, a cyan image, and a black image are formed, respectively.
From b, 6c and 6d, a yellow image, a magenta image,
Exposure lights 9a, 9b, 9c and 9d, which are scanning lights corresponding to the cyan image and the black image, are output.

Each image station 1a, 1b, 1c, 1
d, the photosensitive drums 2a, 2b, 2c,
An endless belt-shaped intermediate transfer belt 12 supported by rollers 10 and 11 is disposed below 2d, and rotates in the direction of arrow A.

Further, a pattern detecting means 14 for detecting a resist pattern from the resist pattern generating means 13 is arranged to face the intermediate transfer belt 12, and further, each color is detected based on a detection result from the pattern detecting means 14. Is provided. The pattern detecting means 14 is provided for the intermediate transfer belt 1.
2 are arranged on both sides in the width direction.

The sheet material 17 stored in the sheet cassette 16 is fed by a sheet feeding roller 18 and is discharged to a sheet discharge tray (not shown) via a sheet material transfer roller 19 and a fixing means 20. You.

In the color image forming apparatus having the above configuration, first, in the image station 1d, the charging means 3d
A latent image of black component color, which is image information, is formed on the photosensitive drum 2d by a known electrophotographic process means using the exposure means 6d and the like. Thereafter, the image is visualized as a black toner image by a developing material having a black toner by a developing unit 4d, and the intermediate transfer belt 1 is formed by a transfer unit 8d.
2, a black toner image is transferred.

On the other hand, while the black toner image is being transferred to the intermediate transfer belt 12, a latent image of a cyan component color is formed in the image station 1c, and the cyan toner image of the cyan toner is visualized by the developing means 4c. Then, this is transferred by the transfer means 8 c and is superimposed on the black toner image previously transferred on the intermediate transfer belt 12.

Thereafter, image formation is performed in the same manner for the magenta toner image and the yellow toner image. When the superposition of the four color toner images on the intermediate transfer belt 12 is completed, the paper feed cassette The four color toner images are transferred and conveyed at once by a sheet material transfer roller 19 onto a sheet material 17 such as a sheet fed from a fixing device 2.
At 0, heat fixing is performed, and a full-color image is obtained on the sheet material 17.

Each of the photosensitive drums 2a, 2b, 2c, 2d after the transfer is completed is connected to a cleaning unit 5a,
At 5b, 5c, and 5d, the residual toner is removed, and the printing operation is completed in preparation for the subsequent image formation.

As described above, a color image can be obtained. Each of the image stations 1a, 1b, 1c,
The image stations 1a, 1b, 1c, 1d and the exposure means 6a, 6b, 6c, 6d, which are scanning optical systems, are changed due to the replacement of 1d, a change in the installation state of the color image forming apparatus, a change in the temperature or humidity in the apparatus. An attachment shift occurs, and an image position shift of each color occurs. Therefore, when the power is turned on or when each of the image stations 1a, 1b, 1c, 1d is replaced,
Furthermore, the detection of the position shift and the correction operation thereof are performed for each change in the temperature and humidity in the apparatus.

The operation of detecting and correcting the positional deviation includes three steps of a resist pattern generating step, a resist pattern detecting step, and a positional deviation correction calculating step. Hereinafter, each of these steps will be sequentially described with reference to the drawings.

(Generation of Resist Pattern) FIG. 2 shows the arrangement of the resist pattern and the pattern detecting means on the intermediate transfer belt 12, and is a view of the intermediate transfer belt 12 viewed from the top of the apparatus. Pattern detection means 14a, 14b
Are arranged on both sides in the width direction of the intermediate transfer belt 12 so as to detect a state on the intermediate transfer belt 12 at a point L1 from an end of the intermediate transfer belt 12.

As shown in FIG. 2, the resist pattern generated from the resist pattern generating means 13 is composed of four pattern groups for each of the image stations 1a, 1b, 1c and 1d, and is opposed to each other. Two transfer belts are formed on both sides of the transfer belt 12 in the width direction. That is, in the illustrated case, the resist patterns in the image station 1d (black) are denoted by reference numerals 21a and 21a.
b, 21c, 21d, image station 1c (cyan)
Are the reference numerals 22a, 22b, 22
Reference numerals 23a, 23b, 23c, and 2 denote resist patterns at the image stations c and 22d and the image station 1b (magenta).
3d, reference numerals 24a, 24b, 24c and 24d indicate resist patterns in the image station 1a (yellow).

Here, the resist pattern in the image station 1d (black) is the first pattern 21
a, a second pattern 21b, a third pattern 21c, and a fourth pattern 21d. The first pattern 21a and the second pattern 21b, and the third pattern 21c and the fourth pattern 21d have a predetermined interval. X and predetermined angle θ
(Here 45 °). The intersection of the first pattern 21a and the second pattern 21b on the extension is the scanning start position, and the third pattern 21c and the fourth
The intersection on the extension of the pattern 21d is the scanning end position. Further, a plurality of image stations 1a, 1
resist patterns 21a to 21d, 22a to 22d, and 23a to 23d formed by b, 1c, and 1d, respectively.
d, 24a to 24d are formed at predetermined intervals Y.

The process of forming a resist pattern in the above configuration will be described. First, from the resist pattern generating means 13 shown in FIG.
For the image station 1d where a black image is formed, four pattern groups 21a, 21b, 21 shown in FIG.
The latent images c and 21d are formed on the photosensitive drum 2d. Then, the image is visualized by the developing unit 4d, and the black toner image is transferred to the intermediate transfer belt 12 in the transfer unit 7.

On the other hand, while the black toner image is being transferred to the intermediate transfer belt 12, the image station 1c operates at the timing shown in FIG. The latent images of the four pattern groups 22a, 22b, 22c, and 22d shown in FIG. 2 are formed on the photosensitive drum 2c from the generating unit 13 via the exposing unit 6c to the image station 1c where the cyan image is formed. You. And developing means 4c
And the intermediate transfer belt 12 in the transfer means 7
The cyan toner image is transferred.

Thereafter, image formation is performed in the same manner for the magenta toner image and the yellow toner image, and the resist pattern shown in FIG.

(Detection of Resist Pattern) FIG. 3 shows the structure of the pattern detecting means 14 (14a, 14b).

In FIG. 3, a semiconductor laser 25 for irradiating a laser beam having a wavelength of 780 nm and a laser driving circuit 26 for driving the semiconductor laser 25 are installed in the pattern detecting means 14. It is set so that an output of 3 mW is output from the semiconductor laser 25.

The pattern detecting means 14 has a lens 27 for optically focusing the laser light on the optical path of the laser light emitted from the semiconductor laser 25 toward the intermediate transfer belt 12. A lens 28 for optically focusing the reflected light is disposed on the optical path of the reflected light. Further, behind the lens 28 in the reflected light traveling direction,
A photodiode (photosensor) 29 that converts light reflected from the intermediate transfer belt 12 into a photocurrent is provided. Then, the amplifying unit 30 that converts the photocurrent from the photodiode 29 into a voltage and amplifies the voltage compares the output value Vs of the amplifying unit 30 with a predetermined reference potential (comparison value) Vr,
A comparison unit 31 that outputs a high level when Vr is smaller than Vs is provided. The lenses 27 and 28
May not be provided, or only one of them may be provided.

As shown in FIG. 3, the angle between the optical axis of the semiconductor laser 25 and the optical axis of the photodiode 29 and the normal to the surface of the intermediate transfer belt 12 are both 20 °. Intermediate transfer belt 1
2 is arranged so that only the specularly reflected light component of the laser light applied to the laser beam 2 is incident.

FIG. 4 shows the relationship between the resist pattern, the laser beam, and the signal in the pattern detecting means 14.

In FIG. 4, reference numerals 32a, 32b, 32
Reference numerals c, 32d, 32e, and 32f denote laser beams (beam spots) on the intermediate transfer belt 12;
2a is a state immediately before the resist pattern 21a enters the irradiation range, and the laser beams 32b and 32e are
a is half the irradiation range, the laser beams 32c and 32
d indicates a state where the resist pattern 21a completely enters the irradiation range, and laser beam 32f indicates a state immediately after the resist pattern 21a completely exits the irradiation range. Although FIG. 4 shows that the laser beams 32a to 32f move with respect to the resist pattern 21a, the resist pattern 21a actually
It has moved in the direction of arrow A with respect to a to 32f. Also,
In the present embodiment, the intermediate transfer belt 12 is 200 mm /
The color image forming apparatus has a printing speed of 40 ppm.

First, when the laser beam emitted from the semiconductor laser 25 driven by the laser drive circuit 26 hits the background portion of the intermediate transfer belt 12 (the portion to which no toner is attached), the background of the intermediate transfer belt 12 is black. However, because of the glossiness, the laser light is specularly reflected by about 5%, and the specularly reflected light is incident on the photodiode 29. Then, the specularly reflected light incident on the photodiode 29 is converted into a photocurrent proportional to the amount of light, and is converted into a voltage proportional to the photocurrent by the amplifying unit 30 and then amplified.
A voltage of about 4 V is obtained as the output Vs (the laser beams 33a and 33f in FIG. 4).

Next, as shown in FIG. 2, the resist pattern 21a formed on the intermediate transfer belt 12 is conveyed to a position facing the pattern detecting means 14a, 14b, and when the resist pattern 21a starts to cover the laser beam, Most of the laser beam applied to the resist pattern 21a made of black toner is absorbed by the toner, and the rest is diffusely reflected (scattered) on the toner surface. Almost no incidence. Therefore, the photocurrent decreases, and the value of the output Vs of the amplifier 30 also decreases.

In the laser beams 33b and 33e of FIG. 4, when the resist pattern 21a covers half of the laser beams 33b and 33e, the amount of light incident on the photodiode 29 is smaller than that of the laser beams 33a and 33f. Since it is half, the output Vs of the amplifying means 30 becomes about 2.5V.
In the laser beams 33c and 33d of FIG. 4, since the resist pattern 21a covers the entire laser beams 33c and 33d, almost no light is incident on the photodiode 29, so that the output Vs of the amplifying unit 30 is about 1V. Accordingly, the change in the ratio of the resist pattern 21a in the laser beams 33a to 33f as described above causes
The output Vs of the amplification means 30 shown in FIG. 4 can be obtained.

Further, by comparing the output Vs of the amplifying means 30 with a predetermined reference potential (2.5 V in this case),
The output Vo of the comparing means 31 shown in FIG. 4 can be obtained, and the resist pattern 21a can be detected.

Also, with respect to the cyan, magenta, and yellow resist patterns, which are the color toners, part of the irradiated laser light is absorbed by the toner, and the rest is diffusely reflected (scattered) on the toner surface. It hardly occurs, and it is possible to detect the resist pattern as in the case of the black toner.

FIG. 5 shows the relationship between the angle between the optical axis of the semiconductor laser 25 and the optical axis of the photodiode 29 and the normal to the surface of the intermediate transfer belt 12 and the detection error, and FIG. 6 shows the laser beam on the intermediate transfer belt 12. The relationship between spot diameter and detection error of
Each is represented.

5 and 6, the angle between the optical axis of the semiconductor laser 25 and the optical axis of the photodiode 29 and the normal to the surface of the intermediate transfer belt 12 is 30 ° or less, and the laser beam It can be seen that if the spot diameter is 200 μm or less, highly accurate detection with a detection error of 5 μm or less can be performed.

As described above, according to the detection of the resist pattern in the present embodiment, high-speed detection can be performed with a low-cost device because there is no restriction on the accumulation time or the like using an expensive CCD. It becomes possible.

Also, a highly accurate detection can be performed on a resist pattern made of black toner on a black background, similarly to a resist pattern made of cyan toner, magenta toner, and yellow toner.

Although the detection of the resist pattern has been described above, it is also possible to detect the toner density of the pattern by detecting the output level of the amplifying means 30 as an analog value.

(Position shift correction calculation) The position shift correction is to perform a position shift correction calculation based on the result of detection of a resist pattern by the pattern detecting means 14.
The processing content will be described below.

FIGS. 7 and 8 show the pattern detecting means 14a.
9 and 10 show the output waveform of the pattern detecting means 1.
4b shows an output waveform.

(A) Sub-scanning position shift correction Regarding the sub-scanning position shift shown in FIG. 12A, the first pattern 21a of the image station 1d (black) and the first pattern 21a of the image station 1c (cyan) shown in FIG. An interval Y1 with the first pattern 22a is calculated. As shown in FIG. 7, the interval Y1 is the output signal Vo of the pattern detection means 14a.
Between the first rising edge and the third rising edge from the start of laser lighting of C
It is counted by a PU (not shown), and can be expressed by the following equation from the value T1 and the moving speed V of the intermediate transfer belt 12.

Y1 = T1 × V (1) Further, an interval X1 between the first pattern 21a and the second pattern 21b of the image station 1d (black) shown in FIG. 2 is calculated. As shown in FIG. 8, the interval X1 is determined by the CPU (not shown) in the displacement correcting means 15 between the first rising edge and the second rising edge from the start of laser emission of the output signal Vo of the pattern detecting means 14a. It can be expressed by the following equation from the counted value T4 and the moving speed V of the intermediate transfer belt 12.

X1 = T4 × V (2) The distance X between the first pattern 22a and the second pattern 22b of the image station 1c (cyan) shown in FIG.
2 is calculated. As shown in FIG. 8, the interval X2 is equal to 3 from the start of laser lighting of the output signal Vo of the pattern detecting means 14a.
The CPU (not shown) in the displacement correcting means 15 counts the interval between the fourth rising edge and the fourth rising edge, and calculates the value T5 and the moving speed V of the intermediate transfer belt 12.
Can be expressed by the following equation.

X2 = T5 × V (3) Further, the scanning start position of the image station 1d and the image station 1c are determined based on the intervals Y1, X1 and X2.
The distance S1 from the scan start position is calculated. The distance S1 can be represented by the following equation.

S1 = Y1 + X2 / 2−X1 / 2 (4) Similarly, the first pattern 21a and the image station 1
An interval Y2 with the first pattern 23a of b (magenta) is calculated. As shown in FIG. 7, the interval Y2 is determined by the CPU (not shown) in the displacement correcting means 15 between the first rising edge and the fifth rising edge from the start of laser lighting of the output signal Vo of the pattern detecting means 14a. It can be expressed by the following equation from the counted value T2 and the moving speed V of the intermediate transfer belt 12.

Y2 = T2 × V (5) Further, an interval X3 between the first pattern 23a and the second pattern 23b of the image station 1b (magenta) shown in FIG. 2 is calculated. As shown in FIG. 8, the interval X3 is determined by the CPU (not shown) in the displacement correcting means 15 between the fifth rising edge and the sixth rising edge from the start of laser lighting of the output signal Vo of the pattern detecting means 14a. It can be expressed by the following equation from the counted value T6 and the moving speed V of the intermediate transfer belt 12.

X3 = T6 × V (6) Further, from the interval Y2, the interval X1, and the interval X3, the scanning start position of the image station 1d and the image station 1b are determined.
The distance S2 from the scan start position is calculated. The distance S2 can be expressed by the following equation.

S2 = Y2 + X3 / 2−X1 / 2 (7) Similarly, the first pattern 21a and the image station 1
An interval Y3 with the first pattern 24a of a (yellow) is calculated. As shown in FIG. 7, the interval Y3 is determined by the CPU (not shown) in the displacement correcting means 15 between the first rising edge and the seventh rising edge from the start of laser lighting of the output signal Vo of the pattern detecting means 14a. It can be expressed by the following equation from the counted value T3 and the moving speed V of the intermediate transfer belt 12.

Y3 = T3 × V (8) Further, an interval X4 between the first pattern 24a and the second pattern 24b of the image station 1b (yellow) shown in FIG. 2 is calculated. As shown in FIG. 8, the interval X4 is determined by the CPU (not shown) in the displacement correcting means 15 between the seventh rising edge and the eighth rising edge from the start of laser lighting of the output signal Vo of the pattern detecting means 14a. It can be expressed by the following equation from the counted value T7 and the moving speed V of the intermediate transfer belt 12.

X4 = T7 × V (9) Further, the scanning start position of the image station 1d and the image station 1a are determined based on the intervals Y3, X1 and X4.
The distance S3 from the scanning start position is calculated. The distance S3 can be represented by the following equation.

S3 = Y3 + X4 / 2−X1 / 2 (10) The sub-scanning position shift amount of each color is shifted by a difference between these distances S1, S2, and S3 and a predetermined design value Y. The calculation is performed by a CPU (not shown) in the correction means 15. Then, the position shift is corrected by adjusting the sub-scanning scan timing of each color based on the sub-scanning position shift amount obtained as described above.

(B) Correction of main scanning position shift The main scanning position shift shown in FIG. 12 (b) is a distance Z1 from the interval X1 obtained in the sub-scanning position shift correction to the scanning start position.
Is calculated. Distance Z1 can be expressed by the following equation.

[0089] Similarly, the distance Z2 from the interval X2 to the scanning start position
Is calculated. Distance Z2 can be expressed by the following equation.

[0090] Similarly, the distance Z3 from the interval X3 to the scanning start position
Is calculated. The distance Z3 can be expressed by the following equation.

[0091] Similarly, the distance Z4 from the interval X4 to the scanning start position
Is calculated. Distance Z4 can be expressed by the following equation.

[0092] Based on the difference between the distance Z1, the distance Z2, the distance Z3, and the distance Z4, the amount of main scanning positional deviation of each color is calculated by the positional deviation correcting unit 15.
The calculation is performed by a CPU (not shown). Then, the position shift is corrected by adjusting the main scan scan timing of each color based on the main scan position shift amount obtained as described above.

(C) Skew Error Correction The skew error shown in FIG.
1, distance S2, distance S3, distance S4, distance S5, distance S
6 can be calculated. Distance S
1, the distance S2, and the distance S3 are calculated by the equations (4), (7), (1).
0). In addition, distance S4, distance S5, distance S6
Can be obtained in the same manner as the distance S1, the distance S2, and the distance S3.

The third pattern 21c of the image station 1d (black) and the image station 1c shown in FIG.
An interval Y4 with the (cyan) third pattern 22c is calculated.

As shown in FIG. 9, the interval Y4 is set between the first rising edge and the third rising edge of the output signal Vo of the pattern detecting means 14b from the start of laser light emission by the CPU (not shown) in the displacement correcting means 15. ), And can be expressed by the following equation from the value T8 and the moving speed V of the intermediate transfer belt 12.

Y4 = T8 × V (15) Further, an interval X5 between the third pattern 21c and the fourth pattern 21b of the image station 1d (black) shown in FIG. 2 is calculated. As shown in FIG. 10, the interval X5 is determined by the CPU (not shown) in the displacement correcting means 15 between the first rising edge and the second rising edge from the start of laser lighting of the output signal Vo of the pattern detecting means 14b. It can be expressed by the following equation from the counted value T11 and the moving speed V of the intermediate transfer belt 12.

X5 = T11 × V (16) Further, the distance X between the third pattern 22c and the fourth pattern 22d of the image station 1c (cyan) shown in FIG.
6 is calculated. As shown in FIG. 10, the interval X6 is determined by the CPU (not shown) in the displacement correcting means 15 between the third rising edge and the fourth rising edge from the start of laser emission of the output signal Vo of the pattern detecting means 14b. It can be expressed by the following equation from the counted value T12 and the moving speed V of the intermediate transfer belt 12.

X6 = T12 × V (17) Further, the scanning end position of the image station 1d and the image station 1c are determined from the intervals Y4, X5 and X6.
The distance S4 from the scan end position is calculated. The distance S4 can be expressed by the following equation.

S4 = Y4 + X6 / 2−X5 / 2 (18) Similarly, the third pattern 21c and the image station 1
An interval Y5 with the third pattern 23c of b (magenta) is calculated. As shown in FIG. 9, the interval Y5 is determined by the CPU (not shown) in the displacement correcting means 15 between the first rising edge and the fifth rising edge from the start of laser emission of the output signal Vo of the pattern detecting means 14b. It can be expressed by the following equation from the counted value T9 and the moving speed V of the intermediate transfer belt 12.

Y5 = T9 × V (19) An interval X7 between the third pattern 23c and the fourth pattern 23d of the image station 1b (magenta) shown in FIG. 2 is calculated. As shown in FIG. 10, the interval X7 is determined by the CPU (not shown) in the displacement correcting means 15 between the fifth rising edge and the sixth rising edge from the start of laser lighting of the output signal Vo of the pattern detecting means 14b. It can be expressed by the following equation from the counted value T13 and the moving speed V of the intermediate transfer belt 12.

X7 = T13 × V (20) Further, the scanning end position of the image station 1d and the image station 1b are determined from the intervals Y5, X5 and X7.
The distance S5 from the scanning end position is calculated. The distance S5 can be expressed by the following equation.

S5 = Y5 + X7 / 2−X5 / 2 (21) Similarly, the third pattern 21c and the image station 1
An interval Y6 with the third pattern 24c of a (yellow) is calculated. As shown in FIG. 9, the interval Y6 is determined by the CPU (not shown) in the displacement correcting means 15 between the first rising edge and the seventh rising edge from the start of laser lighting of the output signal Vo of the pattern detecting means 14b. It can be expressed by the following equation from the counted value T10 and the moving speed V of the intermediate transfer belt 12.

Y6 = T10 × V (22) Further, an interval X8 between the third pattern 24c and the fourth pattern 24d of the image station 1b (yellow) shown in FIG. 2 is calculated. As shown in FIG. 10, the interval X4 is set between the seventh rising edge and the eighth rising edge from the start of laser lighting of the output signal Vo of the pattern detecting means 14a by the CPU (not shown) in the displacement correcting means 15. It can be expressed by the following equation from the counted value T14 and the moving speed V of the intermediate transfer belt 12.

X8 = T14 × V (23) Further, from the interval Y6, the interval X5 and the interval X8, the scanning end position of the image station 1d and the image station 1a
The distance S6 from the scan end position is calculated. The distance S6 can be expressed by the following equation.

S6 = Y6 + X8 / 2−X5 / 2 (24) Also, assuming that the time from the start of laser lighting to the first rising edge in the output signal Vo of the pattern detection means 14a is T0a, the laser lighting start point The distance S0a from to the scanning start position of the image station 1d is represented by the following equation.

S0a = T0a / V + X1 / 2 (25) On the other hand, assuming that the time from the start of laser lighting to the first rising edge in the output signal Vo of the pattern detecting means 14b is T0b, the image starts from the laser lighting start point. The distance S0b to the scanning end position of the station 1d is represented by the following equation.

S0b = T0b / V + X5 / 2 (26) From the above, the skew error of the image station 1d is the difference between the distance S0a and the distance S0b, and the skew error of the image station 1c is (S0a + S1) and (S0b + S4). , The skew error of the image station 1b is (S0a +
Difference between (S2) and (S0b + S5), image station 1
The skew error of a is (S0a + S3) and (S0b + S
6) can be obtained by calculating the difference.

The position shift is corrected by adjusting the optical systems in the exposure means 6a, 6b, 6c, 6d of each color by an actuator (not shown) based on the skew error amount obtained as described above.

(D) Magnification Error Correction The magnification error shown in FIG. 12D can be obtained by calculating the scanning width of each image station. Scanning width W1 of image station 1d, image station 1
c, the scanning width W2 of the image station 1b,
The scanning width W4 of the image station 1a can be expressed by the following equations.

W1 = L2 + Z1 + Z5 (27) W2 = L2 + Z2 + Z6 (28) W3 = L2 + Z3 + Z7 (29) W4 = L2 + Z4 + Z8 (30) These scanning widths W1, W2, and scanning The magnification error amount of each color can be obtained from the difference between the width W3 and the scanning width W4.

The optical system (not shown) in each of the exposure means 6a, 6b, 6c, 6d for each color is adjusted by an actuator (not shown) based on the skew error amount obtained as described above. Is corrected.

(Embodiment 2) FIG. 11 is an explanatory diagram showing a configuration of a pattern detecting means of a color image forming apparatus according to Embodiment 2 of the present invention.

As shown in FIG. 11, the pattern detecting means 14 of this embodiment is different from the pattern detecting means 14 of the first embodiment shown in FIG.
6, a laser power control means 33 for varying the output level of the laser beam output from the semiconductor laser 25, an amplification variable means 32 for varying the amplification factor of the amplification means 30, and a comparison value for the comparison means 31. Is provided with comparison value varying means 34 for varying the value of.

First, Embodiment 2 will be described with reference to FIG. It should be noted that the generation of the resist pattern and the misregistration correction calculation are the same as in the first embodiment.

(Detection of resist pattern) First, when the laser beam driven by the laser drive circuit 26 and emitted from the semiconductor laser 25 hits the background portion (the portion on which the toner is not adhered) of the intermediate transfer belt 12, the intermediate transfer is performed. Since the background of the belt 12 is black but has gloss, the laser light is specularly reflected by about 5%, and the specularly reflected light is incident on the photodiode 29. Then, the specularly reflected light incident on the photodiode 29 is converted into a photocurrent proportional to the amount of light, is converted into a voltage proportional to the photocurrent by the amplifying unit 30, and is amplified.
Is obtained as (Laser beams 33a and 33f in FIG. 4).

Next, as shown in FIG. 2, the resist pattern 21a formed on the intermediate transfer belt 12 is transported to a position facing the pattern detecting means 14a, 14b, and when the resist pattern 21a starts to cover the laser beam, Most of the laser beam applied to the resist pattern 21a made of black toner is absorbed by the toner, and the rest is diffusely reflected (scattered) on the toner surface. Almost no incidence. Therefore, the photocurrent decreases, and the value of the output Vs of the amplifier 30 also decreases.

In the laser beams 33b and 33e of FIG. 4, when the resist pattern 21a covers half of the laser beams 33b and 33e, the amount of light incident on the photodiode 29 is smaller than that of the laser beams 33a and 33f. Since it is half, the output Vs of the amplifying means 30 becomes about 2.5V.
Further, in the laser beams 33c and 33d of FIG. 4, since the resist pattern 21a completely covers the laser beams 33c and 33d, almost no light is incident on the photodiode 29, so that the output Vs of the amplifying means 30 is about 1V. Becomes
Accordingly, the change in the ratio of the resist pattern 21a in the laser beams 33a to 33f as described above causes the change in FIG.
The output Vs of the amplifying means 30 shown in FIG.

Further, by comparing the output Vs of the amplifying means 30 with a predetermined reference potential (2.5 V in this case),
The output Vo of the comparing means 31 shown in FIG. 4 can be obtained, and the resist pattern 21a can be detected.

Also, for the cyan, magenta, and yellow resist patterns, which are the color toners, part of the irradiated laser light is absorbed by the toner, and the rest is diffusely reflected (scattered) on the toner surface. It hardly occurs, and it is possible to detect the resist pattern as in the case of the black toner.

Here, when the optical axis of the semiconductor laser 25 or the photodiode 29 is displaced, or when the output is reduced due to the deterioration of the semiconductor laser 25, the detection value Vs on the background of the intermediate transfer belt 12 is reduced and the reference value is reduced. Potential V
r may be lower than this, and in such a state, it is impossible to detect the resist pattern.

Therefore, when the optical axis of the semiconductor laser 25 or the photodiode 29 is displaced, or when the output of the semiconductor laser 25 is reduced and the resist pattern cannot be detected, the laser power control is performed. The output of the semiconductor laser 25 is increased by the means 33 to increase the detection value Vs on the background of the intermediate transfer belt 12, the amplification rate is increased by the amplification rate varying means 32, and the reference potential Vr is decreased by the comparison value varying means 34. This makes it possible to detect the resist pattern.

As described above, in the first and second embodiments, the transfer / conveying means has been described in the color image forming apparatus using the intermediate transfer belt 12. However, the direct paper transfer method using the paper conveying belt is used. Can be applied to the color image forming apparatus.

[0123]

As described above, according to the present invention, it is possible to obtain an effective effect that it is possible to detect a resist pattern at high speed and with high accuracy with a low-cost structure and accurately correct positional deviation. Can be

As a result, an effective effect that an image with high print quality can be obtained is obtained.

Further, according to the present invention, since a black toner on a black background can be detected with high accuracy, a color image forming apparatus having high printing quality can be obtained without selecting a combination of the background and the toner color. An effective effect that can be obtained is obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of a color image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an arrangement of a registration pattern and a pattern detection unit on an intermediate transfer belt in a transfer unit of the color image forming apparatus according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram illustrating a configuration of a pattern detection unit of the color image forming apparatus according to the first embodiment of the present invention.

FIG. 4 is an explanatory diagram illustrating a relationship between a resist pattern, a laser beam, and a signal in a pattern detection unit in the color image forming apparatus according to the first embodiment of the present invention.

FIG. 5 is a graph showing the relationship between the angle between the optical axis of the semiconductor laser and the optical axis of the photodiode of the color image forming apparatus according to the first embodiment of the present invention and the normal to the surface of the intermediate transfer belt, and the detection error.

FIG. 6 is a graph illustrating a relationship between a spot diameter of a laser beam on an intermediate transfer belt and a detection error of the color image forming apparatus according to the first embodiment of the present invention.

FIG. 7 is a waveform diagram showing an output signal of one of the pattern detection units in the color image forming apparatus according to the first embodiment of the present invention.

FIG. 8 is a waveform chart showing an output signal of one of the pattern detection units in the color image forming apparatus according to the first embodiment of the present invention.

FIG. 9 is a waveform diagram showing an output signal of the other pattern detection unit in the color image forming apparatus according to the first embodiment of the present invention.

FIG. 10 is a waveform chart showing an output signal of the other pattern detection unit in the color image forming apparatus according to the first embodiment of the present invention.

FIG. 11 is an explanatory diagram illustrating a configuration of a pattern detecting unit of the color image forming apparatus according to the second embodiment of the present invention.

FIG. 12 is an explanatory diagram showing types of displacement of a transferred image.

FIG. 13 is an explanatory view showing a configuration of a conventional resist pattern detecting means.

FIG. 14 is an explanatory view showing a conventional arrangement of a resist pattern on an intermediate transfer belt and a pattern detection unit.

FIG. 15 is an explanatory diagram showing a conventional arrangement of a resist pattern on an intermediate transfer belt, a pattern detection unit, and an output signal of the pattern detection unit.

FIG. 16 is an explanatory diagram showing a conventional arrangement of a resist pattern on an intermediate transfer belt, a pattern detection unit, and an output signal of the pattern detection unit.

[Explanation of symbols]

 1a, 1b, 1c, 1d Image station 2a, 2b, 2c, 2d Photoconductor drum (photoconductor) 4a, 4b, 4c, 4d Developing means 6a, 6b, 6c, 6d Exposure means 7 Transfer means 9a, 9b, 9c, 9d Exposure light 12 Intermediate transfer belt (transfer material) 13 Resist pattern generation means 14 Pattern detection means 15 Position shift correction means 21a, 21b, 21c, 21d Resist patterns 22a, 22b, 22c, 22d Resist patterns 23a, 23b, 23c, 23d Resist pattern 24a, 24b, 24c, 24d Resist pattern 25 Semiconductor laser 27 Lens 28 Lens 29 Photodiode (photosensor) 30 Amplifying means 31 Comparison means 32 Amplification rate variable means 34 Comparison value variable means 33 Laser power control means

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Kazuhiko Soeda, Inventor Kazuma 1006 Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. Terms (reference) 2H030 AA01 AB02 AD12 BB16 BB23 BB42 BB44 BB56

Claims (12)

[Claims] A plurality of image stations provided with a photoreceptor on which a latent image is formed and a developing unit for developing the latent image formed on the photoreceptor as a toner image corresponding to a development color; A plurality of exposure means for irradiating each of the photoconductors with light to form a latent image; and sequentially transferring and superimposing toner images of respective colors formed by the plurality of image stations on a transfer material. Transfer means for forming a composite image on the resist pattern, a resist pattern generating means for generating a resist pattern in the plurality of exposure means, and forming a predetermined resist pattern in the image station provided corresponding to the exposure means, A semiconductor laser for irradiating the resist pattern with laser light and a photosensor for detecting reflected light from the transfer means are developed and transferred onto the transfer means. A color image forming apparatus comprising: a pattern detecting unit that detects the detected resist pattern; and a position shift correcting unit that corrects a position shift based on a result detected by the pattern detecting unit. 2. The apparatus according to claim 1, wherein said pattern detecting means includes at least one of a lens for optically stopping laser light output from said semiconductor laser and a lens for optically stopping light incident on said photosensor. Claim 1.
The color image forming apparatus as described in the above. 3. The color image forming apparatus according to claim 1, wherein said pattern detecting means includes a comparing means for outputting a comparison result between an output of said photosensor and a predetermined comparison value. 4. The color image forming apparatus according to claim 3, wherein said pattern detecting means includes a comparison value changing means for changing a value of a comparison value with respect to an output of said photosensor. 5. The color image according to claim 1, wherein said pattern detecting means includes an amplifying means for amplifying an output of said photosensor and sending it to said comparing means. Forming equipment. 6. The color image forming apparatus according to claim 5, wherein said pattern detection means includes an amplification rate variable means for changing an amplification rate of said amplification means. 7. The color image forming apparatus according to claim 1, wherein said pattern detecting means includes laser power control means for controlling an output value of said semiconductor laser. 8. The method according to claim 1, wherein said pattern detecting means comprises: an angle formed by an optical axis of said semiconductor laser and a normal to said transfer means surface; and an angle formed by an optical axis of said photosensor and a normal to said transfer means surface. The color image forming apparatus according to any one of claims 1 to 7, wherein 9. The color image forming apparatus according to claim 8, wherein an angle formed by an optical axis of said semiconductor laser and a normal to a surface of said transfer means is 30 ° or less. 10. The color image forming apparatus according to claim 1, wherein a beam diameter of a laser beam output from the semiconductor laser is 200 μm or less on the transfer unit. . 11. The color image forming apparatus according to claim 1, wherein said photosensor is divided and installed at two positions in a width direction of said transfer means. 12. The color image forming apparatus according to claim 1, wherein a toner density is detected by said pattern detecting means.