JP2003270562A - Optical beam scanner and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To arbitrarily correct the positions of dots (pixels) in a horizontal scanning direction even if there is an environment fluctuation by temperature and to form high-grade images substantially free from color drifts. <P>SOLUTION: A controller 11 reads the correction data corresponding to the temperature detected by a temperature sensor 10 out of a memory 15, sets the data as a phase shift quantity in a shift quantity setting section 14 and forms a clock for dot writing for the purpose of performing a phase shift on the basis of the reference clock formed in a writing clock forming section 5 by a phase sift section 13. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to an image forming section of a printer, a copying machine, a facsimile machine or the like, and a light beam scanning device for optically writing an electrostatic latent image on a photoconductor of an electrophotographic system, and the same. The present invention relates to an image forming apparatus equipped with a light beam scanning device.

[0002]

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

However, in the conventional apparatus, particularly when the plastic lens is used, the shape and the refractive index of the plastic lens change due to the change of the ambient temperature or the change of the temperature inside the machine. For this reason, the scanning position on the image surface of the photoconductor changes, a magnification error occurs in the main scanning direction, and a high-quality image cannot be obtained. Further, in a color image forming apparatus that forms an image of a plurality of colors using a plurality of light beams and lenses, color shift occurs due to a magnification error of each light beam, and a high quality image cannot be obtained.

In order to deal with such a situation, Japanese Unexamined Patent Publication No.
Japanese Patent Application Laid-Open No. 58053 and Japanese Patent Application Laid-Open No. 8-136838 disclose a configuration for correcting an image magnification error and a color shift that occur due to a change in environmental temperature, a temperature change in the apparatus, or the like.

[0005]

However, in any of the methods described in both publications in the above-mentioned prior art,
Since the light beams are detected at two locations, the count number between them is measured by a predetermined clock, and the time difference is calculated, the two light beam detection sensors and the time difference calculation unit are naturally required. Further, although the full width in the main scanning direction can be corrected, the correction cannot be performed at an arbitrary position, so that the complete correction cannot be performed.

The object of the present invention is to solve the above-mentioned problems of the prior art, and the position of a dot (pixel) in the main scanning direction can be arbitrarily corrected even if there is an environmental change due to temperature, and color misregistration or the like is caused. An object of the present invention is to provide a light beam scanning device for performing high-quality image formation, and an image forming device equipped with the light beam scanning device.

[0007]

In order to achieve the above object, the invention according to claim 1 provides a light emitting section for emitting a light beam modulated on the basis of an image signal, and a deflecting section for deflecting the light beam. And an optical system including an fθ lens for converting the deflected light beam from the constant angular velocity scanning light to the constant velocity scanning light, and by exposing and scanning the photoconductor with the light beam through the optical system, In a light beam scanning device for optically writing an electrostatic latent image on the photoconductor, a temperature sensor for detecting a temperature inside the device, and main scanning of dots in the electrostatic latent image on the photoconductor based on the detected temperature. And a correction unit that corrects the positional deviation in the direction. With this configuration, it is possible to accurately correct the dot positional deviation even if the temperature environment inside the apparatus changes, thereby improving the image quality. Let It is possible.

According to a second aspect of the present invention, in the light beam scanning device according to the first aspect, the correction means is for generating a reference clock of a predetermined cycle and a reference clock generating means for shifting the phase of the reference clock. A shift amount setting means for setting the shift amount and a shift means for shifting the phase of the reference clock according to the shift amount setting means are provided, and the dot position shift is accurately corrected by this configuration. You can

According to a third aspect of the present invention, in the light beam scanning apparatus according to the second aspect, the shift amount setting means scans the photosensitive member with a shift amount for shifting the phase of the reference clock. It is characterized in that it is a correction amount for correcting the dot position deviation in the main scanning direction that occurs.

According to a fourth aspect of the present invention, in the light beam scanning device according to the third aspect, as the correction amount, at least correction data preset based on temperature data is stored in the storage means. With this configuration, the correction process can be performed quickly.

According to a fifth aspect of the present invention, in the light beam scanning apparatus according to the first aspect, the temperature sensor for detecting the temperature in the apparatus detects the temperature in the plastic lens provided in the apparatus. Characteristically, with this configuration, by performing correction processing based on the temperature in the plastic lens that is easily affected by temperature changes,
It is possible to more accurately correct the dot position deviation.

According to a sixth aspect of the present invention, 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 light beam for scanning at a constant angular velocity are provided. And an optical system including an fθ lens for converting light to a constant velocity scanning light, and an electrostatic latent image is optically written on the photoconductor by exposing and scanning the photoconductor with the light beam through the optical system. An image forming apparatus which is equipped with a light beam scanning device and which forms an image by visualizing an electrostatic latent image formed on the photoconductor with a developer, wherein the light beam scanning device is the light beam scanning device. The light beam scanning device according to any one of claims 1 to 3 is used, and even if the temperature environment inside the device changes, the dot position deviation in the electrostatic latent image on the photoconductor is accurately corrected by this configuration. To be able to It is possible to improve the image quality of the formed image.

According to a seventh aspect of the present invention, a light emitting section for emitting a light beam modulated based on an image signal, a deflecting section for deflecting the light beam, and a deflected light beam for scanning at a constant angular velocity are provided. And an optical system including an fθ lens for converting light to a constant velocity scanning light, and by exposing and scanning a plurality of photoconductors with a light beam through the optical system, electrostatic latent images are formed on the photoconductors. A light beam scanning device, comprising a plurality of light beam scanning devices for optical writing, wherein an electrostatic latent image formed on each photoconductor is visualized by a developer to form a color image. As a result, the light beam scanning device according to any one of claims 1 to 5 is used, and with this configuration, even if the temperature environment in the device changes, an electrostatic latent image on each photoconductor is formed. Accurate dot misalignment It is possible to positively, it is possible to improve the image quality of a color image.

According to an eighth aspect of the invention, in the image forming apparatus according to the seventh aspect, the dot position deviation in the main scanning direction in the electrostatic latent image on the photosensitive member is independently set for each color based on the detected temperature. This configuration makes it possible to suppress color misregistration of an image and improve the quality of a color image.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a light beam scanning device portion in an electrophotographic image forming apparatus for explaining a first embodiment of the present invention. An outline of the overall structure of the image forming apparatus is a light source and a light source. It consists of a light source driver, a light beam modulator, an image processor that processes image data, and a controller that controls each unit.

In FIG. 1, 1 is a laser diode (L
D), a light source consisting of a gas laser or a light emitting diode (LED), 2 is a light beam modulator, and in the case of a gas laser, an AOM (acousto-optic device) or the like is used and can be directly modulated. In the case of LD and LED, the driver and modulator are shared. The light source 1 and the modulator 2 constitute a light emitting unit. Reference numeral 3 is a personal computer (PC) or scanner, 4 is an image processor for performing various kinds of image data processing, 5 is a writing clock generation unit, 6 is a polygon mirror which is a deflection unit for deflecting the emitted light beam, and 7 is f.
Theta lens, 8 is a drum-shaped photosensitive member, 9 is a synchronous detector for scanning timing of the light beam, 10 is a temperature sensor provided in the plastic fθ lens 7 in this example, 11 is detection data of the temperature sensor 10. A controller that controls various parts by obtaining various data such as.

An image forming operation of the image forming apparatus having the above structure will be described.

Image data created by a personal computer (PC) 3 or image data read by an image scanner or the like is subjected to image data division and image processing by an image processor 4 and a light beam emitted from a light source 1. A pixel clock for modulating the signal is output from the write clock generation unit 5 to the modulator 2, and the photoconductor 8 is exposed by the light beam modulated according to the image data to form a latent image. That is, the light beam is deflected at a constant angular velocity by the polygon mirror 6, the correction for constant velocity deflection and the correction of surface tilt are performed by the fθ lens 7, and the photoconductor 8 is scanned in the main scanning direction to move as described above. Form an image. Although not shown, the latent image is visualized by a developer and transferred to a recording paper as is well known in the developing section to form an image.

Next, the correction of the dot position deviation at the time of writing on the photosensitive member, which is a feature of the present invention, will be described.

FIG. 2 is a block diagram showing the arrangement from the image processor 4 to the modulator 2 in FIG. 1, in which 12 is a buffer section of the image processor 4.
Reference numeral 3 is a reference clock phase shift unit, 14 is a shift amount setting unit, and 15 is a memory in which preset correction data (shift amount) is stored.

In FIG. 2, the phase shift unit 13 generates a write clock for performing a phase shift based on the reference clock generated by the write clock generation unit 5. The shift amount here is a correction amount for correcting the dot position deviation and can be set by the shift amount setting unit 14. In addition, the dot misregistration correction data corresponds to the temperature change from low temperature to high temperature based on the misalignment data on the image plane, and is calculated based on the data measured in advance and Corresponding data is stored in the memory 15.

In this way, the controller 11 reads the correction data corresponding to the detected temperature from the memory 15 according to the temperature detected by the temperature sensor 10, sets it as the phase shift amount in the shift amount setting unit 14, and performs the phase shift. The unit 13 generates a dot writing clock for performing the phase shift based on the reference clock generated by the writing clock generation unit 5.

FIG. 3 is a timing chart showing the phase shift of the reference clock in this embodiment, and is a diagram showing the output pulse when the phase shift is performed with respect to the reference clock.

The phase shift shown in FIG. 3A is a case where the phase of the reference clock is advanced with the reference resolution.
The phase shift shown in (b) is when the phase is delayed. By advancing or delaying the phase of the reference clock in this way, the dot position can be corrected with high accuracy.

FIG. 4 is a conceptual diagram showing a dot position when an image is actually output in the case where the phase shift shown in FIG. 3 is performed. Then, the position shifts are performed by -1/2, -1/4, +1/4, and +1/2 in accordance with the temperature.

The image shown in FIG. 5B shows an example of a corrected image obtained by phase shifting the reference clock with respect to the current image shown in FIG.

FIG. 6 is a diagram showing an example of dot positional deviation in the main scanning direction in the present embodiment, which shows positional deviation from the reference position at each image height, and the positional deviation value is the temperature. It depends on For this reason, it becomes necessary to measure the displacement for each temperature. If the positional deviation data for each temperature is known, the correction data can be calculated.

FIG. 7 is a flow chart showing the correction processing in this embodiment.

The controller 11 first detects the temperature sensor 1
The temperature data of the fθ lens 7 detected at 0 is obtained (S
1), the correction data for the temperature is read from the memory 15 (S2). Then, the shift amount setting unit 14 sets the phase shift amount according to the correction data, and the phase shift unit 13 generates the write clock according to the phase shift amount (S3).

As described above, in the first embodiment, the electrostatic latent image formed by scanning the photoconductor 8 by detecting the temperature of the fθ lens 7 and shifting the phase of the reference clock based on the temperature. It is possible to correct the positional deviation of the dots in the image, which enables highly precise dot position control and improves the image quality.

In the first embodiment, the dot position deviation is corrected based on the temperature of the plastic fθ lens 7, which is easily affected by temperature. However, the ambient temperature in the apparatus or the temperature in the vicinity of other members is corrected. For example, it is conceivable to appropriately select the temperature detection target according to the device specifications and perform the dot position shift correction based on the detected temperature.

FIG. 8 is a block diagram showing a light beam scanning device portion in an electrophotographic color image forming apparatus for explaining the second embodiment of the present invention, and reference numeral 21 is described in the first embodiment. It has the same configuration as
Four light beam scanning devices for emitting laser beams 28 modulated corresponding to four colors of (black), C (cyan), M (magenta), and Y (yellow), and 22 are K,
It is a drum-shaped photoconductor on which latent images of images corresponding to four colors of C, M, and Y are formed. A charge coronatron 24 for charging the photoconductor is provided around each photoconductor 22, as is well known. ,
A developing device 25 for each color and a transfer coronatron 26 for transferring a developed image from the photoconductor 22 to the recording paper 23.
A cleaning device 27 for removing the residual developer is provided. Further, 29 is a recording paper 23 in the nip between each photoconductor 22 and the transfer coronatron 26.
Is a transport belt for transporting.

In FIG. 8, the light beam scanning device 21 is
A laser beam 28 modulated according to image data is applied to each photoconductor 22 to form a latent image, and the latent image is developed with toner by a developing device 25 for each color. The movement of the conveying belt 29 and the conveyed recording paper 23 pass through the nip between the photosensitive drum 29 and the transfer corotron 26, and yellow, magenta, cyan, and black are respectively applied to the recording paper 23 at the nip portions. Toner images are sequentially transferred. The recording paper 23 on which the four color toner images have been transferred in this manner is then fixed by a not-shown image fixing device, and is discharged onto a not-shown discharge tray.

Also in the light beam scanning device 21 in the second embodiment, the phase of the reference clock is shifted based on the temperature inside the device described in the first embodiment, thereby scanning each photoconductor 22. It is possible to correct the positional deviation of the dots of the electrostatic latent image that is formed, which enables highly precise dot position control and improves the color image quality.

In the color image forming apparatus having the structure shown in FIG. 8, high-speed image processing is possible because image processing for four colors is performed substantially in parallel in time, but on the other hand, 4 It is considered that color misregistration is likely to occur because writing of colors is performed by separate optical systems. Therefore, in the present embodiment, it is possible to effectively correct the color misregistration by correcting the dot misregistration as described above for each color of each photoconductor 22.

[0037]

As described above, according to the present invention,
By correcting the misalignment of the dots in the electrostatic latent image on the photoconductor in the main scanning direction based on the temperature detected by the temperature sensor that detects the temperature inside the device, the temperature environment at each part inside the device changes. Since the dot positional deviation can be corrected accurately, the image quality can be improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a light beam scanning device portion in an electrophotographic image forming apparatus for explaining a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration from the image processor in FIG. 1 to sending the image data to a modulator.

FIG. 3 is a timing chart showing the phase shift of the reference clock in the present embodiment, showing the output pulse when the phase shift is performed with respect to the reference clock.

FIG. 4 is a conceptual diagram showing dot positions when an image is actually output when the phase shift shown in FIG. 3 is performed.

FIG. 5 is an explanatory diagram showing an example of an image when the phase shift of the reference clock is performed on the current image.

FIG. 6 is a diagram showing an example of dot position shift in the main scanning direction according to the present embodiment.

FIG. 7 is a flowchart showing a correction process according to this embodiment.

FIG. 8 is a configuration diagram showing a light beam scanning device portion in an electrophotographic color image forming apparatus for explaining a second embodiment of the present invention.

[Explanation of symbols]

1 light source 2 modulator 4 image processor 5 Write clock generator 6 polygon mirror 7 fθ lens 8,22 photoconductor 9 Sync detector 10 Temperature sensor 11 Controller 13 Phase shift unit 14 Shift amount setting section 15 memory 21 Light beam scanning device

Continued front page    F term (reference) 2C362 BA86 BB28 CA22 CA39 CB13                 2H045 AA01 CA82 CA98 CA99 DA41                 5C051 AA02 CA07 DB09 DB22 DB24                       DB30 DB33 DE04 EA01                 5C072 AA03 BA12 DA02 DA04 HA02                       HA06 HA09 HA13 HB01 QA14                       XA05                 5C074 AA10 BB03 CC22 CC26 DD09                       DD15 DD24 EE03 FF15 GG03                       GG04

Claims (8)

[Claims] 1. A light emitting section for emitting a light beam modulated based on an image signal, and a deflecting section for deflecting the light beam,
And an optical system including an fθ lens that converts the deflected light beam from the uniform angular velocity scanning light into the constant velocity scanning light, and by exposing and scanning the photoconductor with the light beam via the optical system, In a light beam scanning device for optically writing an electrostatic latent image on a photoconductor, a temperature sensor for detecting the temperature inside the device and a main scanning direction of dots in the electrostatic latent image on the photoconductor based on the detected temperature. And a correction means for correcting the positional deviation in the light beam scanning device. 2. The correction means includes a reference clock generation means for generating a reference clock having a predetermined cycle, a shift amount setting means for setting a shift amount for shifting the phase of the reference clock, and the shift amount setting means. 2. The light beam scanning device according to claim 1, further comprising a shift unit that shifts the phase of the reference clock in accordance with the above. 3. The shift amount for shifting the phase of the reference clock in the shift amount setting means,
The light beam scanning device according to claim 2, wherein the light beam scanning device is a correction amount for correcting a dot position shift in the main scanning direction caused by scanning on the photoconductor. 4. The light beam scanning device according to claim 3, wherein as the correction amount, correction data set in advance based on at least temperature data is stored in a storage means. 5. The light beam scanning device according to claim 1, wherein the temperature sensor for detecting a temperature inside the device detects a temperature in a plastic lens provided inside the device. 6. A light emitting section for emitting a light beam modulated based on an image signal, and a deflecting section for deflecting the light beam,
And an optical system including an fθ lens that converts the deflected light beam from the uniform angular velocity scanning light into the constant velocity scanning light, and by exposing and scanning the photoconductor with the light beam via the optical system, In an image forming apparatus which is equipped with a light beam scanning device for optically writing an electrostatic latent image on a photoconductor, and which forms an image by visualizing the electrostatic latent image formed on the photoconductor with a developer, An image forming apparatus comprising the light beam scanning device according to claim 1 as the light beam scanning device. 7. A light emitting section which emits a light beam modulated based on an image signal, and a deflecting section which deflects the light beam,
And an optical system including an fθ lens for converting the deflected light beam from the uniform angular velocity scanning light to the constant velocity scanning light, and by exposing and scanning a plurality of photoconductors with the light beam via the optical system. , A plurality of light beam scanning devices for optically writing an electrostatic latent image on each of the photoconductors are mounted, and a color image is formed by visualizing the electrostatic latent image formed on each of the photoconductors with a developer. An image forming apparatus that uses the light beam scanning device according to claim 1 as the light beam scanning device. 8. The image according to claim 7, wherein the dot position deviation in the main scanning direction in the electrostatic latent image on the photoconductor can be independently corrected for each color based on the detected temperature. Forming equipment.