JP2001051214A - Light beam scanning device and image forming apparatus - Google Patents

Abstract

(57) [Problem] To enable a simple configuration to correct a magnification error of an image in a main scanning direction. A temperature sensor detects a temperature of an fθ lens. Correction data D for the detected temperature T
t is read from the correction amount storage unit 23 and sent to the write clock generation unit 18. Then, the write clock generator 18 generates a write clock frequency for the correction data Dt. The image magnification in the main scanning direction changes depending on the writing clock frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light beam scanning device used for optically writing an electrostatic latent image in an electrophotographic image forming process, and an electrophotographic image forming device provided with the light beam scanning device. .

[0002]

2. Description of the Related Art In an image forming apparatus using a light beam scanning device, a laser beam is modulated by image data, and a polygon mirror is rotated to scan at a constant angular velocity in a main scanning direction. The scanning on the photosensitive member is performed by correcting the scanning light at a constant speed.

However, in the conventional apparatus, especially when a plastic lens is used, the shape and the refractive index of the plastic lens change due to a change in environmental temperature, a change in the temperature inside the apparatus, and the like. For this reason, the scanning position on the image plane of the photoconductor changes, and a magnification error occurs in the main scanning direction, so that a high-quality image cannot be obtained. In an apparatus that forms an image of a plurality of colors using a plurality of laser beams and lenses, a color shift occurs due to a magnification error of each laser beam, and a high-quality image cannot be obtained.

[0004] From such a situation, changes in the environmental temperature,
Japanese Patent Application Laid-Open Nos. 9-58053 and 8-136838 disclose means for correcting a magnification error and a color shift of an image caused by a change in the temperature inside the apparatus.

In the technique disclosed in Japanese Patent Application Laid-Open No. 9-58053, a laser beam is detected at at least two points in each main scan of a plurality of laser beams, and each laser beam is detected by one laser beam detecting means. The number of counts by a predetermined clock from the detection to the detection by another laser beam detection means is measured, and according to the count number, the write modulation frequency of each laser beam is corrected,
Further, the timing from the synchronous position of each laser beam to image writing is corrected. This makes it possible to always obtain a high-quality image with the same magnification without being affected by a change in scanning speed due to a change in temperature, and to maintain the same magnification of an image by each laser beam. A high-quality image without color shift can be obtained.

According to the technique disclosed in Japanese Patent Application Laid-Open No. Hei 8-136838, a laser beam is detected between two points on a main scanning line.
The polygon motor driving the polygon mirror is controlled so that the deflection speed of the laser beam between the two detected points is constant. This makes it possible to automatically correct the magnification in the main scanning direction when the scanning optical system changes due to environmental fluctuation or the like.

[0007]

However, in any of the above prior arts, the laser beam is detected at two locations, the count number between them is measured by a predetermined clock, and the time difference is calculated. Two laser beam detection sensors and a time difference calculation unit are required. Since it is necessary to calculate the time difference in this way, in the conventional technology,
There is a problem that the configuration of the control system becomes complicated.

An object of the present invention is to enable a simple configuration to correct a magnification error of an image in the main scanning direction.

An object of the present invention is to improve the correction accuracy in the above case.

An object of the present invention is to make it possible to correct an image position shift in the main scanning direction.

An object of the present invention is to correct a color shift of an image by correcting a magnification error of the image in the main scanning direction.

[0012]

According to a first aspect of the present invention, there is provided a light emitting section for emitting a light beam modulated based on an image signal, a deflecting section for deflecting the light beam, and the deflected section. An optical system including an fθ lens that converts a light beam from a constant angular velocity scanning light to a constant velocity scanning light; and exposing and scanning the photosensitive member of an electrophotographic image forming apparatus with the light beam via the optical system. Thus, in a light beam scanning device for optically writing an electrostatic latent image on the photosensitive member, a temperature sensor for detecting a temperature of the light beam scanning device, and an electrostatic latent image on the photosensitive member based on the detected temperature. A light beam scanning device comprising: a first correction unit configured to correct a magnification error in a main scanning direction of an image.

Therefore, it is known that the occurrence of the magnification error of the image in the main scanning direction is largely caused by the temperature change of the light beam scanning device, and particularly caused by the temperature change of the plastic lens in the light beam scanning device. By detecting the temperature of the light beam scanning device, the magnification error of the image in the main scanning direction can be corrected with a simple configuration.

According to a second aspect of the present invention, in the light beam scanning device according to the first aspect, the temperature sensor detects a temperature of a plastic lens in the light beam scanning device.

Therefore, the magnification error of the image in the main scanning direction is corrected by detecting the temperature of the plastic lens, which is a main factor of the magnification error of the image in the main scanning direction, so that the magnification error of the image in the main scanning direction can be accurately detected. Can be corrected.

According to a third aspect of the present invention, in the light beam scanning device according to the second aspect, the plastic lens is the fθ lens.

Therefore, the temperature error of the fθ lens formed of a plastic lens, which is a main factor of the magnification error of the image in the main scanning direction, is detected to correct the magnification error of the image in the main scanning direction. Can be accurately corrected.

According to a fourth aspect of the present invention, in the light beam scanning device according to the first aspect, a plurality of the temperature sensors are provided in the light beam scanning device, and the first correction means is provided in the light beam scanning device. The correction is performed based on the average value of the temperatures detected by the plurality of temperature sensors.

Therefore, since the temperature of the light beam scanning device can be detected with high accuracy, it is possible to accurately correct the magnification error of the image in the main scanning direction.

According to a fifth aspect of the present invention, in the light beam scanning device according to any one of the first to fourth aspects, the second correction means for correcting the writing start position of the optical writing in the main scanning direction is provided. It is characterized by having.

Therefore, it is possible to correct the image position shift in the main scanning direction.

According to a sixth aspect of the present invention, there is provided the light beam scanning device according to any one of the first to fourth aspects, and the light beam scanning device performs the exposure scanning with the light beam emitted from the light beam scanning device. An image forming apparatus comprising: a photoconductor on which an electrostatic latent image is optically written; and a developing device for developing the electrostatic latent image with toner, and forms an image by an electrophotographic method.

Therefore, the same operation and effect as the invention according to any one of claims 1 to 4 can be obtained.

The invention described in claim 7 has a plurality of claim 1
5. The light beam scanning device according to any one of 1 to 4, wherein the plurality of light beams emitted by the plurality of light beam scanning devices are subjected to the exposure scanning to optically write the plurality of electrostatic latent images. One or more photoreceptors, and a developing device for developing the plurality of electrostatic latent images with toner to form a plurality of color toner images, and forming a color image by superimposing the plurality of color toner images. The image forming apparatus is an electrophotographic image forming apparatus.

Accordingly, the same operation and effect as those of the first aspect of the invention can be obtained, and the color shift of the image can be corrected.

According to an eighth aspect of the present invention, in the image forming apparatus according to the seventh aspect, the temperature sensor is provided only in any one of the plurality of light beam scanning devices, and The first correction means of the scanning device performs the correction based on the temperature detected by the temperature sensor provided in the single light beam scanning device.

Therefore, the manufacturing cost can be reduced.

According to a ninth aspect of the present invention, in the image forming apparatus of the seventh aspect, three or more light beam scanning devices are provided, and the temperature sensor is any one of the three or more light beam scanning devices. And the first correction unit of each of the light beam scanning devices performs the correction based on the temperature detected by the temperature sensor provided in each of the two light beam scanning devices. It is characterized by performing.

Therefore, the manufacturing cost can be reduced.

According to a tenth aspect of the present invention, there is provided a light beam scanning device according to any one of the first to fourth aspects, wherein the plurality of light beam scanning devices emit the light beam. A plurality of photosensitive members that are scanned and optically written to the plurality of electrostatic latent images, and a developing unit that develops the plurality of electrostatic latent images with toner to form a plurality of color toner images, The plurality of light beam scanning devices have the plurality of one polygon mirrors as the deflecting unit, and perform the counter-distribution scanning of the plurality of light beams around the polygon mirror. This is an image forming apparatus that forms a color image in which toner images are superimposed by an electrophotographic method.

Accordingly, the same operation and effect as those of the invention described in any one of the first to fourth aspects are exerted, whereby the color shift of the image can be corrected.

According to an eleventh aspect of the present invention, there is provided a light beam scanning device according to any one of the first to fourth aspects, and the exposure scanning is performed by a plurality of the light beams emitted by the light beam scanning device. A plurality of photoreceptors on which the plurality of electrostatic latent images are optically written, and a developing device for developing the plurality of electrostatic latent images with toner to form a plurality of color toner images; The light beam scanning device has a plurality of one polygon mirrors as the deflecting unit, and performs the counter-distribution scanning of the plurality of light beams around the polygon mirror. Provided at a plurality of locations of the beam scanning device, the first correction means corrects each of the magnification errors caused by the respective light beams based on temperatures detected by the plurality of temperature sensors so as to eliminate each of the magnification errors. Toner image The formation of the superposed color image is an image forming apparatus performed in electrophotography.

Therefore, the same operation and effect as those of the invention according to any one of the first to fourth aspects are exerted, whereby the color shift of the image can be corrected.

[0034]

[First Embodiment of the Invention] FIG.
FIG. 1 is a conceptual diagram showing a schematic configuration around a photoconductor of an image forming apparatus 1 according to a first embodiment of the present invention. As shown in FIG. 1, the image forming apparatus 1 includes a light beam scanning device 2. The light beam scanning device 2 includes an LD (Laser Diode) 20 (see FIG. 2), which is a light emitting unit that is turned on based on predetermined image data, and a laser beam emitted by the LD 20 is emitted by a collimating lens (not shown). A parallel light flux, passes through a cylinder lens (not shown), is deflected by a polygon mirror 4 which is a deflecting unit rotated by a polygon motor 3, and is composed of a plastic lens fθ.
The light passes through a lens 5, passes through a BTL (Barrel Toroidal Lens) 6, is reflected by a mirror 7, scans a photoreceptor 8, and optically writes an electrostatic latent image. Note that the fθ lens 5 is
The light beam deflected by the polygon mirror 4 is changed from constant angular velocity scanning light to constant velocity scanning light. BTL6
Performs focusing in the sub-scanning direction (condensing function and position correction in the sub-scanning direction (surface tilt, etc.)).

Around the photoconductor 8, a charger 9 for charging the photoconductor 8, a developing device 10 for developing the electrostatic latent image on the photoconductor 8 with toner, and a toner image on the photoconductor 8 are fixed. A transfer unit 11 for transferring the image onto the recording paper, a cleaning unit 12 for removing the residual toner on the photoconductor 8, and a static eliminator 13 for eliminating the charge on the photoconductor 8 are arranged, which is a normal electrophotographic process. An image is formed on the recording paper by charging, exposing, developing, and transferring. Then, the image on the recording paper is fixed by a fixing device (not shown).

FIG. 2 is a block diagram showing the electrical connection of each part of the light beam scanning device 2. As shown in FIG.
A synchronous sensor 14 for detecting a laser beam before the image forming start position of the photoconductor 8 in the main scanning direction is provided.
The laser beam transmitted through the θ lens 5 is reflected by the mirror 15, condensed by the lens 16, and enters the synchronous sensor 14. This synchronization sensor 14 is for detecting a laser beam scanning synchronization signal which becomes a synchronization detection signal DETP.

When the laser beam scans, a synchronization detection signal DETP is output from the synchronization sensor 14 and sent to the phase synchronization clock generator 17. The write clock generator 18 has a function of determining a clock frequency for modulating the laser and generating the clock frequency. further,
Utilizing the fact that the image magnification in the main scanning direction changes depending on the clock frequency, a magnification correction function for changing the clock frequency based on the temperature detection result of the fθ lens 5 is also provided.

The clock WCLK whose magnification has been corrected and the synchronization detection signal DETP from the synchronization sensor 14 are sent to the phase synchronization clock generator 17 to generate a clock VCLK synchronized with the synchronization detection signal DETP, and to control the lighting of the laser.
It is sent to the D drive unit 19. In the LD drive section 19, the clock V
Lighting control of the LD 20 is performed according to a predetermined image signal synchronized with the clock CLK. Then, a laser beam is emitted from the LD 20, is deflected by the polygon mirror 4, passes through the fθ lens 5, and scans the photosensitive member 8. lens 5 is provided with a temperature sensor 21 for detecting the temperature, and the temperature data T is generated by sending the output of the temperature sensor to the temperature detection unit 22. Fθ is stored in the correction amount storage unit 23.
Frequency setting data of the clock WCLK for the temperature of the lens 5 is stored. This data is obtained from the displacement amount of the laser beam due to the temperature change of the fθ lens 5 shown in FIG. Temperature data T is stored in correction amount storage unit 2
3, the frequency setting data Dt of the clock WCLK corresponding to the temperature data T is output, sent to the write clock generator 18, and the clock W whose magnification is corrected.
CLK is generated. The phase-locked clock generator 1
7, the write clock generation unit 18, the correction amount storage unit 23, and the like can be realized as functions of a microcomputer that controls the image forming apparatus 1.

FIG. 4 shows a flowchart of the magnification correction processing. First, the temperature T of the fθ lens 5 is detected (step S1). Then, the correction data Dt for the temperature T is read from the correction amount storage unit 23 (step S2), and sent to the write clock generation unit 18. And write clock generator 1
In step 8, a write clock frequency for the correction data Dt is generated (step S3). Step S3 implements first correction means.

This operation flow is performed immediately before image formation. In continuous printing, since it is considered that a temperature change occurs during printing and the magnification changes, a correction operation is performed between sheets (between image formation and formation). Just do it.

Therefore, it is known that the occurrence of an image magnification error in the main scanning direction is largely caused by a change in the temperature of the light beam scanning device 2 and particularly by a change in the temperature of the plastic lens in the light beam scanning device 2. So
By detecting the temperature of the light beam scanning device 2, a magnification error of an image in the main scanning direction can be corrected with a simple configuration.

The position of the temperature sensor 21 need not be the fθ lens 5 if the light beam scanning device 2 is used, but the fθ lens 5 composed of a plastic lens which is a main factor of the magnification error of the image in the main scanning direction is used. If the temperature error is detected and the magnification error of the image in the main scanning direction is corrected, the magnification error of the image can be accurately corrected.

[Second Embodiment of the Invention] An image forming apparatus according to a second embodiment of the present invention will be described below.
The following description focuses on the differences, and the same reference numerals are used for common members and the like, and detailed description is omitted.

Image forming apparatus 1 according to Embodiment 2 of the present invention
However, the difference from the first embodiment of the present invention is the configuration of the light beam scanning device 2. FIG. 5 is a block diagram showing an electrical connection of each part of the light beam scanning device 2. The light beam scanning device 2 is different from the light beam scanning device 2 of the first embodiment in that the image magnification is corrected by controlling the rotation speed of the polygon motor 3. Other items are the same as those of the first embodiment.

That is, the correction amount storage unit 23 stores frequency setting data of the clock PCLK for controlling the rotation speed of the polygon motor 3 with respect to the temperature of the fθ lens 5. This data is obtained from the displacement amount of the laser beam due to the temperature change of the fθ lens 5 shown in FIG. By sending the temperature data T to the correction amount storage unit 23, the frequency setting data Dt of the clock PCLK for the temperature data T is output, sent to the clock generation unit 24, and the clock generation unit 24 generates the clock PCLK. The clock PCLK is sent to a polygon motor drive control unit 25 that controls the driving of the polygon motor 3, and the number of rotations of the polygon mirror 4 is controlled to correct the image magnification. Note that the clock generation unit 24 and the like can also be realized as functions of a microcomputer that controls the image forming apparatus 1.

FIG. 6 shows a flowchart of the magnification correction processing. First, the temperature T of the fθ lens 5 is detected (step S4). Then, the correction data Dt for the temperature T is read out from the correction amount storage unit 23 (step S5) and sent to the clock generation unit 24. Then, the clock generation unit 24 generates a rotation speed control frequency for the correction data Dt (step S6).

Third Embodiment Hereinafter, an image forming apparatus according to a third embodiment of the present invention will be described with reference to the first embodiment of the present invention.
The following description focuses on the differences, and the same reference numerals are used for common members and the like, and detailed description is omitted.

Image forming apparatus 1 according to Embodiment 3 of the present invention
However, the difference from the first embodiment of the present invention is the configuration of the light beam scanning device 2. FIG. 7 is a block diagram showing the electrical connection of each part of the light beam scanning device 2. This light beam scanning device 2 is different from the light beam scanning device 2 of the first embodiment of the invention in that a temperature sensor 2 for detecting the temperature of the fθ lens 5
The difference is that a plurality of 1s are provided. That is, in the present example, for example, there are three, left, right, and center. Temperature detector 22
Also has a function of an average value calculation unit for calculating the average value of the detected temperatures. Then, the calculated temperature data Ta is sent to the correction amount storage unit 23. Other items are the same as in the first embodiment of the invention.

FIG. 8 shows a flowchart of the magnification correction processing. First, the temperatures T1, T at the left, right, and center of the fθ lens 5
2, T3 are detected (step S7), and the temperatures T1, T
2. The average temperature Ta of T3 is calculated (step S8).
Then, the correction data Dt for the average temperature Ta is read from the correction amount storage unit 23 (step S9), and is sent to the write clock generation unit 18. And the write clock generator 18
, A write clock frequency for the correction data Dt is generated (step S3).

As described above, the temperatures T1, T2,
By detecting T3, calculating the average temperature Ta, and performing the magnification correction processing based on the average temperature Ta, the magnification error can be accurately corrected.

Fourth Embodiment FIG. 9 is a perspective view showing a schematic configuration of an image forming apparatus according to a fourth embodiment of the present invention. This image forming apparatus 26 is a four-drum type,
Four image forming units 27a, 27b, 27c and 27d are provided for forming a color image in which toner images of four colors (yellow, magenta, cyan and black) are superimposed. Each image forming unit 27a, 27b, 27c, 27d
Is an image forming apparatus 1 according to the first, second, or third embodiment of the invention.
The same reference numerals as those in FIG. 1 and the like denote the same members and the like, and a detailed description thereof will be omitted.

As shown in FIG. 9, the image forming apparatus 26
This is a configuration in which four sets of image forming units 27a, 27b, 27c, and 27d are sequentially arranged. An image of the first color is formed on the recording paper 29 conveyed by the transfer belt 28 in the direction of the arrow. By transferring the images in the order of the fourth color and the fourth color, a color image in which the four color images are superimposed can be formed on the recording paper 29. The transfer belt 28 is driven by a transport motor 30. Each image forming unit 27a,
When the magnification at 27b, 27c, 27d changes, the image position shifts in the main scanning direction. However, in the embodiment of the present invention, the occurrence of the image position shift can be suppressed by performing the magnification correction. .

[Fifth Embodiment] An image forming apparatus according to a fifth embodiment of the present invention is described below.
The following description focuses on the differences, and the same reference numerals are used for common members and the like, and detailed description is omitted.

Image forming apparatus 2 according to Embodiment 5 of the present invention
6 differs from Embodiment 4 of the invention in that the light beam scanning device 2 of each of the image forming units 27a, 27b, 27c, 27d
It is a structure of. FIG. 10 is a block diagram showing the electrical connection of each part of the plurality of light beam scanning devices 2. That is, in the image forming apparatus 26, only the fθ lens 5 in one light beam scanning device 2 among the plurality of light beam scanning devices 2 is provided with the temperature sensor 21 for detecting the temperature. Based on the temperature, the write clock WCLK is generated in each of the light beam scanning devices 2 to correct the image magnification. Although only two light beam scanning devices 2 are shown in FIG.
The other two light beam scanning devices 2 also receive the frequency setting data Dt of the clock WCLK from the single correction amount storage unit 23 and generate the clocks WCLK. In the case of the embodiment of the present invention, since the detected temperature is a representative value for correcting the image magnification of all the light beam scanning devices 2, the temperature difference between the light beam scanning devices 2, especially fθ
This is suitable when the temperature difference between the lenses 5 is not so large. As for the light beam scanning device 2 for detecting the temperature, it is preferable that the light beam scanning device 2 has a temperature difference as small as possible. For example, in the case of the image forming apparatus 26 shown in FIG. 9, the temperature is detected by one of the two central image forming units 27b and 27c. Therefore, it is not necessary to provide four temperature sensors 21 and temperature detection units 22 and the like, and only one is needed, so that the cost can be reduced as compared with the image forming apparatus 26 according to the fourth embodiment of the present invention. If only the temperature difference between the adjacent image forming units is small, especially the temperature difference of the fθ lens 5, there is provided a temperature sensor 21 in two non-adjacent image forming units, and the temperature sensor 21 is used depending on the detected temperature. Alternatively, the magnification of adjacent image forming units may be corrected. That is, two temperature sensors 21 and two temperature detectors 22 are provided, and thereby the image magnification of the four light beam scanning devices 2 is corrected.

[Sixth Embodiment of the Invention] An image forming apparatus according to a sixth embodiment of the present invention will be described below.
The following description focuses on the differences, and the same reference numerals are used for common members and the like, and detailed description is omitted. FIG. 11 is a conceptual diagram showing a schematic configuration of an image forming apparatus according to Embodiment 6 of the present invention. The image forming apparatus 26 according to the sixth embodiment of the present invention is different from the fourth embodiment in place of the light beam scanning device 2 provided in each of the image forming units 27a, 27b, 27c, 27d. Is that a single light beam scanning device 31 is provided.

The light beam scanning device 31 uses one polygon mirror 4 to deflect and scan laser beams corresponding to different colors above and below the surface of the polygon mirror 4.
Further, the laser beams for four colors are scanned on the respective photoconductors 8 by performing counter-distribution scanning with the polygon mirror 4 as a center. Each laser beam of each color is deflected by a single polygon mirror 4, passes through each fθ lens 5, is turned back by each first mirror 32, each second mirror 33, passes through each BTL 6, and passes through each third mirror 34. To scan over each photoconductor 8.

FIG. 12 is a plan view of the light beam scanning device 31. A laser beam BK corresponding to black and a laser beam Y corresponding to yellow are emitted from the LD 20, pass through a CYL (cylinder lens) 35, enter the lower surface of the polygon mirror 4 by the reflection mirror 36, and rotate the polygon mirror 4. Then, the light is deflected, passes through the fθ lens 5, and is turned back by the first mirror 32. A laser beam C corresponding to cyan and a laser beam M corresponding to magenta are emitted from the LD 20, pass through the CYL 35, enter the upper surface of the polygon mirror 4, are deflected by rotation of the polygon mirror 4, and are deflected by the fθ lens 5 , And is turned back by the first mirror 32.

Synchronous sensor 14 for detecting laser beams Y, M, C, and BK before the image forming start position in the main scanning direction.
Are provided, and the laser beams Y, M, C, and BK passing through the fθ lens 5 are CYM (cylinder mirror) 37
Thus, the light is reflected and condensed and incident on the synchronous sensor 14. This synchronization sensor 14 is for detecting a laser beam scanning synchronization signal which becomes a synchronization detection signal. The laser beam BK and the laser beam C use a common CYM 37 and a synchronous sensor 14. The same applies to the laser beams Y and M. Since two laser beams are incident on the same synchronous sensor 14, the incident timings are different so that they can be detected. However, for each laser beam Y, M, C, BK,
A single synchronous sensor 14 may be provided.
As can be seen from FIG. 12, it can be seen that Y and M scan in the opposite directions with respect to BK and C.

FIG. 3 shows the amount of displacement of the laser beam in the main scanning direction after passing through the fθ lens 5 due to the temperature change of the light beam scanning device 31 (fθ lens 5). Assume that the temperature has risen to b with reference to the time of temperature a. Then f
Near the center of the θ lens 5, the position of the beam hardly changes even if the temperature rises. However, the closer to the end of the fθ lens 5, the more the laser beam shifts outward in the main scanning direction. FIG. 3 shows one half of the lens, and the same thing occurs on the opposite side with respect to the center in the main scanning direction.

Therefore, in the vicinity of the end of the image in the main scanning direction, the shift amount Y in the state of temperature b is smaller than that in the state of temperature a.
The image is magnified by twice as much as .times., And the difference "XY" between the vicinity of the synchronous sensor 14 and the vicinity of the end of the image becomes the amount of positional fluctuation in the main scanning direction.

FIG. 13 shows an image position shift in the main scanning direction due to magnification correction. In the embodiment of the present invention, since each laser beam is subjected to counter-distribution scanning with the polygon mirror 4 as the center, the change in the magnification of the image described with reference to FIG. Appears as an image position shift. A magenta image (M) and a cyan image (C) will be described as examples. The scanning directions of the two colors on the photoconductor 8 are opposite. In FIG. 13, the images of the respective colors are shown vertically separated for easy understanding, but they are assumed to actually overlap. And the export of the M image is on the left,
The C image is written on the right side. Further, the magnification and the writing start position are changed by the same amount for the M image and the C image, and the end of the image to be formed in the main scanning direction is assumed to correspond to the vicinity of the end of the image in the main scanning direction in FIG. The M image and the C image at the temperature a match the magnification and the main scanning position. Then, when the temperature rises to b, as described with reference to FIG. 3, for the M image, the image spreads (enlarges) by “Y × 2”, and the main scanning writing position shifts to the right by “XY”. For the C image, the image is 'Y × 2'
And the main-scanning writing position is shifted to the left by 'XY'. As a result, in the M image and the C image, a positional shift in the main scanning direction occurs by '((XY) × 2) + (Y × 2)'. Therefore, magnification correction is performed by the above method. Then, it can be seen that the enlarged image can be corrected for the M image and the C image, but the write start position in the main scanning direction cannot be completely corrected, resulting in a displacement of p.

Hereinafter, a method for correcting the write start position in the main scanning direction will be described. FIG. 14 shows the light beam scanning device 3
1 shows a block diagram of an electrical connection.
Only the elements necessary for optically writing an image for each color are shown.

As shown in FIG. 14, a synchronous sensor 14 for detecting a laser beam before an image forming start position in the main scanning direction is provided, and the laser beam transmitted through the fθ lens 5 is reflected and condensed by the CYM 37. , And enters the synchronous sensor 14. This synchronization sensor 14 is for detecting a laser beam scanning synchronization signal which becomes a synchronization detection signal. When the laser beam scans, the synchronization sensor 14 outputs a synchronization detection signal DE.
The TP is output and sent to the synchronization detection signal delay unit 38.
lens 5 is provided with a temperature sensor 21 for detecting the temperature, and the temperature data T is generated by sending the output of the temperature sensor 21 to the temperature detection unit 22. The correction amount storage unit 23 stores frequency setting data of the clock WCLK with respect to the temperature of the fθ lens 5 and image position deviation correction data. This data is obtained from the displacement amount of the laser beam due to the temperature change of the fθ lens 5 shown in FIG. By sending the temperature data T to the correction amount storage unit 23, the frequency setting data of the clock WCLK and the image position shift correction data Dt for the temperature data T are output and sent to the magnification / position shift control unit 39.

FIG. 15 is a block diagram of the magnification / position deviation control unit 39. The magnification / position deviation control unit 39 determines the clock frequency for modulating the laser by the clock generation unit 40, It has a function to generate.
Further, utilizing the fact that the image magnification in the main scanning direction changes according to the clock frequency, based on the correction data Dt,
It also has a magnification correction function for changing the clock frequency.
Further, in order to correct the image position shift occurring after the magnification correction by the position shift correction data calculation unit 41, the correction data D
The position shift correction data a and b are calculated from t and the generated clock WCLK. The correction data Dt includes the frequency setting data of the clock WCLK and the image misalignment correction data. For example, if the correction data Dt is a 2-bit serial data, the upper bit is the clock WCLK.
The frequency setting data of CLK and the lower bits may be divided like image position deviation correction data. The correction data D
If t is 16 bits wide, the upper 8 bits are clock W
The frequency setting data of the CLK and the lower 8 bits may be divided as image position deviation correction data. The displacement data a and b are calculated from the compensation data Dt and the clock WCLK. The compensation data Dt is the displacement amount with respect to the temperature, for example, A (mm) at the temperature Ta, and B at the temperature Tb.
(Mm).
It is necessary to convert the shape according to the first correction method, for example, how many pixels A (mm) corresponds to. Therefore, even with the same correction data Dt, the displacement correction data a and b differ depending on the light beam scanning device 31. And when converting, W
Since a positional shift amount of one cycle or less of CLK may be calculated, a shift amount that is an integral multiple of one cycle of WCLK is data a, and a shift amount of one cycle or less is data b.

Then, as shown in FIG. 14, the clock WCLK whose magnification has been corrected is supplied to the phase-locked clock generator 17.
The position shift correction data a is sent to the main scanning write position control unit 42, and the position shift correction data b is sent to the synchronization detection signal delay unit 3
Send to 8.

The synchronization detection signal delay section 38 delays the synchronization detection signal DETP from the synchronization sensor 14 in accordance with the position shift correction data b. Then, the synchronization detection signal DDETP delayed by a shift amount of one cycle or less of WCLK is sent to the phase synchronization clock generation unit 17, and the clock WCLK becomes the clock VCLK synchronized with DDETP, and the LD driving unit 19 that controls the lighting of the laser and It is sent to the main scanning writing position control unit 42.

The main-scanning writing position control unit 42 controls the timing of the image signal sent to the LD driving unit 19 in units of one cycle of VCLK based on the position shift correction data a and the clock VCLK.

The LD drive section 19 controls the lighting of the LD 20 according to an image signal synchronized with the clock VCLK. Then, a laser beam is emitted from the LD 20, is deflected by the polygon mirror 4, passes through the fθ lens 5, and scans the photosensitive member 8.

The functions of the correction amount storage section 23, the magnification / position shift control section 39, the synchronization detection signal delay section 38, the phase synchronization clock generation section 17, and the main scanning writing position control section 42 control the image forming apparatus 1. Microcomputer.

FIG. 16 is a timing chart of the write start position correction in the main scanning direction. The rising edge of DETP serves as a writing reference in the main scanning direction. It is assumed that writing starts from the edge at a position where the writing clock VCLK corresponds to three clocks. In this case, the synchronization detection signal delay unit 38 does not delay DETP, and DETP = DDE
It becomes TP. / LGATE is a gate signal in the main scanning direction, and image data is sent to the LD drive unit 19 at L level (the upper diagram in FIG. 16).

Here, it is assumed that the magnification / position shift control unit 39 corrects the magnification and further delays the writing start position in the main scanning direction by one clock cycle +＋ １ cycle. Then, DETP is delayed by 1/4 cycle of VCLK by the synchronization detection signal delay unit 38,
The signal DDETP is sent to the phase synchronous clock generator 17. Further, in the main scanning writing position control unit 42,
The timing of / LGATE is delayed by one cycle of VCLK. As a result, as shown in FIG.
Delay 3 clocks from ETP / LGATE
After correction (lower diagram in FIG. 16), / LGATE is enabled with a delay of 4 clocks + 1/4 clock, that is, the positional deviation is corrected by 1 clock + 1/4 clock. Will be.

FIG. 17 shows a flowchart of the processing of magnification correction and main scanning position correction. First, the temperature T of the fθ lens 5 is detected (step S11). Then, the correction data Dt for the temperature T is read from the correction amount storage unit 23 and sent to the magnification / position shift control unit 39 (step S1).
2). Then, the magnification / position shift control unit 39 first generates a write clock frequency for the correction data Dt (step S13). Next, based on the correction data Dt and the generated clock WCLK, the positional deviation correction data a and b are obtained.
Is calculated (step S14). Then, the writing position in the main scanning direction is corrected from the correction data a and b (step S15). Step S15 implements a second correction unit.

This operation flow is performed immediately before image formation. During continuous printing, it is considered that a temperature change occurs during printing and a change in magnification and position shift occurs, so the interval between sheets (between image formation and formation). The correction operation may be performed.

As described above, the light beam scanning device 3
According to 1, it is also possible to correct an image position shift in the main scanning direction.

[0075]

According to the first aspect of the present invention, the occurrence of an image magnification error in the main scanning direction is largely caused by a change in the temperature of the light beam scanning device. By detecting the temperature of the light beam scanning device,
With a simple configuration, a magnification error of an image in the main scanning direction can be corrected.

According to a second aspect of the present invention, in the light beam scanning device according to the first aspect, the temperature of the plastic lens, which is a main factor of the magnification error of the image in the main scanning direction, is detected and the image in the main scanning direction is detected. Is corrected, the magnification error of the image in the main scanning direction can be accurately corrected.

According to a third aspect of the present invention, in the light beam scanning device according to the second aspect, f is constituted by a plastic lens which is a main factor of a magnification error of an image in the main scanning direction.
Since the magnification error of the image in the main scanning direction is corrected by detecting the temperature of the θ lens, the magnification error of the image in the main scanning direction can be accurately corrected.

According to a fourth aspect of the present invention, in the light beam scanning device according to the first aspect, since the temperature of the light beam scanning device can be accurately detected, a magnification error of an image in the main scanning direction is accurately corrected. be able to.

According to a fifth aspect of the present invention, in the light beam scanning device according to any one of the first to fourth aspects, it is possible to correct an image position shift in the main scanning direction.

The invention described in claim 6 has the same operation and effect as the invention described in any one of claims 1 to 4.

The invention described in claim 7 has the same operation and effect as the invention described in any one of claims 1 to 4, whereby color shift of an image can be corrected.

According to the invention of claim 8, in the image forming apparatus of claim 7, the manufacturing cost can be reduced.

According to the ninth aspect, in the image forming apparatus according to the seventh aspect, the manufacturing cost can be reduced.

The tenth aspect of the present invention relates to the first to fourth aspects.
Has the same operation and effect as the invention according to any one of the above,
Thereby, the color shift of the image can be corrected.

The invention described in claim 11 is the invention according to claims 1-4.
Has the same operation and effect as the invention according to any one of the above,
Thereby, the color shift of the image can be corrected.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram illustrating a schematic configuration around a photoconductor of an image forming apparatus according to a first embodiment of the present invention;

FIG. 2 is a block diagram showing an electrical connection of each part of a light beam scanning device of the image forming apparatus.

FIG. 3 is a graph illustrating an image position shift amount due to a temperature change of an fθ lens of the light beam scanning device.

FIG. 4 is a flowchart of a magnification correction process of the image forming apparatus.

FIG. 5 is a block diagram illustrating electrical connections of respective units of a light beam scanning device of the image forming apparatus according to the second embodiment of the present invention;

FIG. 6 is a flowchart of a magnification correction process of the image forming apparatus.

FIG. 7 is a block diagram showing electrical connections of respective parts of a light beam scanning device of an image forming apparatus according to Embodiment 3 of the present invention.

FIG. 8 is a flowchart of a magnification correction process of the image forming apparatus.

FIG. 9 is a perspective view illustrating a schematic configuration of an image forming apparatus according to Embodiment 4 of the present invention;

FIG. 10 is a block diagram showing electrical connections of respective parts of a light beam scanning device of an image forming apparatus according to Embodiment 5 of the present invention.

FIG. 11 is a conceptual diagram showing a schematic configuration of an image forming apparatus according to Embodiment 6 of the present invention.

FIG. 12 is a plan view of a light beam scanning device of the image forming apparatus.

FIG. 13 is an explanatory diagram illustrating an image position shift in the main scanning direction due to magnification correction.

FIG. 14 is a block diagram showing electrical connections of respective parts of a light beam scanning device of an image forming apparatus according to Embodiment 5 of the present invention.

FIG. 15 is a block diagram showing a configuration of a magnification / position shift control unit of the light beam scanning device.

FIG. 16 is a timing chart of a write start position correction in the main scanning direction of the image forming apparatus.

FIG. 17 is a flowchart of a magnification correction process of the image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Light beam scanning device 4 Deflection part, polygon mirror 5 fθ lens 8 Photoconductor 10 Developing device 20 Light emitting unit 21 Temperature sensor 26 Image forming device 31 Light beam scanning device

Claims (11)

[Claims] 1. A light emitting unit for emitting a light beam modulated based on an image signal, a deflecting unit for deflecting the light beam, and converting the deflected light beam from uniform angular velocity scanning light to uniform velocity scanning light. F
an optical system including a θ lens, and by exposing and scanning the photosensitive member of the electrophotographic image forming apparatus with the light beam through the optical system, an electrostatic latent image is formed on the photosensitive member. In a light beam scanning device for writing, a first temperature sensor for detecting a temperature of the light beam scanning device, and a first error correcting a magnification error of an electrostatic latent image on the photoconductor in a main scanning direction based on the detected temperature. A light beam scanning device comprising a correction unit. 2. The light beam scanning device according to claim 1, wherein the temperature sensor detects a temperature of a plastic lens in the light beam scanning device. 3. The light beam scanning device according to claim 2, wherein the plastic lens is the fθ lens. 4. A method according to claim 1, wherein a plurality of said temperature sensors are provided in said light beam scanning device, and said first correction means performs said correction based on an average value of the temperatures detected by said plurality of temperature sensors. The light beam scanning device according to claim 1, wherein: 5. The light beam scanning device according to claim 1, further comprising a second correction unit configured to correct a writing start position of the optical writing in a main scanning direction. 6. The light beam scanning device according to claim 1, wherein the exposure scanning is performed by the light beam emitted by the light beam scanning device, and optical writing of the electrostatic latent image is performed. An image forming apparatus comprising: a photosensitive member to be developed; and a developing device for developing the electrostatic latent image with toner, and forms an image by an electrophotographic method. 7. A plurality of light beam scanning devices according to claim 1, wherein the plurality of light beams emitted from the plurality of light beam scanning devices are subjected to the exposure scanning and the plurality of light beam scanning devices. One or more photoreceptors on which an electrostatic latent image is optically written; and a developing device for developing the plurality of electrostatic latent images with toner to form a plurality of color toner images; An image forming apparatus characterized in that a color image formed by superimposing images is formed by an electrophotographic method. 8. The light beam scanning device according to claim 1, wherein the temperature sensor is provided only in any one of the plurality of light beam scanning devices, and the first correction means of each of the light beam scanning devices is the single light beam scanning device. The image forming apparatus according to claim 7, wherein the correction is performed based on a temperature detected by the temperature sensor provided in the apparatus. 9. The light beam scanning device is provided with three or more, and the temperature sensor is provided only in any two of the three or more light beam scanning devices. 8. The image forming apparatus according to claim 7, wherein the first correction unit performs the correction based on a temperature detected by the temperature sensors provided in the two light beam scanning devices. 10. A plurality of light beam scanning devices according to claim 1, wherein the plurality of light beams emitted from the plurality of light beam scanning devices are subjected to the exposure scanning and the plurality of light beam scanning devices. A plurality of photoreceptors on which an electrostatic latent image is optically written; and a developing device for developing the plurality of electrostatic latent images with toner to form a plurality of color toner images; Has a plurality of polygon mirrors as the deflecting unit, and scans the plurality of light beams facing each other with the polygon mirror as a center. An image forming apparatus that forms an image by an electrophotographic method. 11. A plurality of the light beam scanning devices according to claim 1, wherein the plurality of light beams emitted from the light beam scanning device are subjected to the exposure scanning and the plurality of the electrostatic light beams are scanned. A plurality of photoreceptors on which a latent image is optically written; and a developing device for developing the plurality of electrostatic latent images with toner to form a plurality of color toner images. A plurality of polygon mirrors are provided as the deflecting unit, and the plurality of light beams are counter-distributedly scanned around the polygon mirror, and the temperature sensors are provided at a plurality of locations of the light beam scanning device. A color correction unit configured to correct the magnification error caused by each of the light beams based on temperatures detected by the plurality of temperature sensors so as to eliminate each of the magnification errors, and to superimpose the plurality of color toner images. An image forming apparatus that forms an image by an electrophotographic method.