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Beam-spot position compensation method, optical scanning device, and multi-color image forming device

Inactive Publication Date: 2005-09-01
RICOH KK
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0014] An object of the present invention is to provide a beam-spot position compensation method which enables the compensation of the sparseness or denseness of the beam-spot position spacing with good accuracy and simple algorithm.
[0016] Another object of the present invention is to provide a multi-color image forming device which is capable of providing a color image with good image quality and few color deviations. In order to achieve the above-mentioned object, the present invention provides a beam-spot position compensation method for use in an optical scanning device which scans a surface of a photosensitive medium by a light beam emitted by a light source, the beam-spot position compensation method comprising the steps of: defining a plurality of sections by dividing a scanning region on the scanned surface; adjusting an emission timing of the light beam for every section so that a spacing between beam-spot positions corresponding to pixels of start and end of each section is changed by a predetermined amount; and compensating the sparseness or denseness of beam-spot position spacings of the plurality of sections in the whole scanning region.

Problems solved by technology

However, there is the limitation in the compensation of the scanning speed using the fθ lens.
Furthermore, the sparseness or denseness of the beam-spot position spacing is increased according to the manufacture error of the fθ lens.
If the sparseness or denseness of the beam-spot position spacing occurs, the distortion of the image arises, which causes the degradation of image quality.
Moreover, the color image forming device uses two or more fθ lenses, and, due to the manufacture error of the fθ lens and others, the sparseness or denseness of the beam-spot position spacing which is varied for each of the colors arises, and consequently the color deviation arises.
Generally, the pixel clock control unit for the frequency modulation method is complicated in the structure, and there is the problem that when the width of the frequency modulation becomes very small, it is difficult to perform the pixel clock control suitably, and the compensation of the beam-spot position with high accuracy cannot be performed.
Moreover, there is the problem that the algorithm for obtaining the compensation data needed for performing the compensation is very complicated.

Method used

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  • Beam-spot position compensation method, optical scanning device, and multi-color image forming device
  • Beam-spot position compensation method, optical scanning device, and multi-color image forming device
  • Beam-spot position compensation method, optical scanning device, and multi-color image forming device

Examples

Experimental program
Comparison scheme
Effect test

example 1

[0486] The curve 17A (before mirror rotation) shows the position error on the design by the scanning / focusing optical system in the optical scanner made as an experiment to FIG. 59.

[0487] This position error (position deviation from the ideal image quantity of the optical spot shown with the axis of ordinate) is the position error peculiar to the scanning / focusing optical system. The effective scanning region is ±150 mm, i.e., 300 mm, and the image quantity by the side of the optical scanning start is +. The inclination of the scanning line occurred in the initial state, and posture adjustment of the reflection mirror near the scanned surface is performed to compensate this.

[0488] As shown in FIG. 60A, the reflection mirror MR is counterclockwise rotated only for the 2.627 minutes around the rotation shaft AX by the side of the edge A by the side of the optical scanning start. The incident angle of the sub-scanning direction to the reflection mirror MR of the deflected light beam ...

example 2

[0497] The optical scanner of the trial production is made to generate deflection of the scanning line, the mirror is incurvated by return deflection of this scanning line, and it compensated. The curve 19A (before mirror deflection) in FIG. 61 is the position error (before compensating the deflection of the scanning line) peculiar to the scanning / focusing optical system.

[0498] As shown in FIG. 62A and FIG. 62B, the center section B1 is pressed to the both ends A1 and C1 of Mirror MR by return, and bending is given. In the sub-scanning direction, the incident angle of the light beam to this reflection mirror MR is 17.65 degrees, as shown in FIG. 62B.

[0499] The surface of the reflection mirror MR is concave with a radius of curvature of 12 m by the curve. The amount of curves is −260 micrometers to 220 mm width of +110 mm to −110 mm of the effective scanning region. FIG. 66 shows the concrete numeric values similar to FIG. 64.

[0500] The position deviation before mirror deflection ...

example 3

[0503] In the Example 3, the scanning line which writes in, the color, for example, the black components image, of a certain reference, is made into the reference scanning line supposing the full color image formation, and the position error of the optical spot in the optical scanner is compensated by making the position error of the optical spot in this reference scanning line into the reference position error.

[0504] After an appropriate time, rotation of the mirror compensated the inclination of the scanning line by return, and the position error of the main scanning direction of the optical spot originated and generated in this compensation is compensated again.

[0505] The reflection mirror is the thing of the 34.5 incident angles like what is shown in FIG. 60 A-FIG. 60C.

[0506] This is counterclockwise rotated around the revolving shaft AX for the 3 minutes, 297-micrometer variation rate is carried out by the optical scanning termination side to the effective scanning region wi...

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Abstract

In a beam-spot position compensation method for use in an optical scanning device which scans a surface of a photosensitive medium by a light beam emitted by a light source, a plurality of sections are defined by dividing a scanning region on the scanned surface. An emission timing of the light beam for every section is adjusted so that a spacing between beam-spot positions corresponding to pixels of start and end of each section is changed by a predetermined amount. The sparseness or denseness of beam-spot position spacings of the plurality of sections in the whole scanning region is compensated.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of The Invention [0002] The present invention relates to a beam-spot position compensation method for image forming device, such as digital copier, laser printer or laser facsimile, and relates to an optical scanning device and a multi-color image forming device using the beam-spot position compensation method. [0003] 2. Description of The Related Art [0004] Generally, the optical scanning device is widely known in connection with the laser printer or the like. The optical scanning device is provided in which the light beam from the light source is deflected by the optical deflector, it is focused on the scanned surface by the scanning / focusing optical system including the fθ lens, so that the optical spot is formed on the scanned surface, and the optical scanning of the scanned surface is carried out using this optical spot. The scanned surface is, for example, the photoconductive surface of the photoconductor or the like. [0005] The opti...

Claims

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Application Information

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IPC IPC(8): G02B26/08G02B26/12
CPCG02B26/123
Inventor IMAI, SHIGEAKINAKAJIMA, TOMOHIRO
Owner RICOH KK
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