JP2006163058A - Optical scanning apparatus and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical scanning device capable of performing a small, inexpensive and clear optical scanning, and an image forming apparatus using the optical operation device.
A deflector that deflects light beams from a plurality of light source units, a first scanning optical system that includes at least one scanning optical element, and an opposite side of the first scanning optical system with the deflector interposed therebetween. And a second scanning optical system including at least one scanning optical element, and a detector that detects a light beam at least one of before scanning start and after scanning end of the scanning line, A plane perpendicular to the optical axis of the first scanning optical element located closest to the deflector among the scanning optical elements included in the first scanning optical system, and a scanning optical element included in the second scanning optical system Among these, the second scanning optical element located closest to the deflector is disposed in a region sandwiched by a plane perpendicular to the optical axis of the second scanning optical element.
[Selection] Figure 1

Description

  The present invention relates to an optical scanning device and an image forming apparatus.

  In recent years, there is an increasing demand for full color, high image quality, high speed, and low cost of image formation, and image forming apparatuses using an electrophotographic system using a plurality of colors have been put into practical use. In order to realize high speed as well as full color, a system having a plurality of image carriers that are scanning surfaces, for example, a quadruple tandem system including four image carriers has been put into practical use. According to this method, high-speed image formation is possible by simultaneously scanning scanning lines corresponding to four colors of cyan, magenta, yellow, and black. However, there is a limit to the accuracy of the optical components of the scanning optical system and the accuracy of assembly on the housing, and due to deformation of the optical element and changes in refractive index due to environmental fluctuations such as temperature and humidity in the device, It may happen that the full width magnification error of scanning lines, the timing of writing, etc. are relatively shifted. This causes image quality degradation such as main scanning dot position deviation and vertical streaking, and particularly main scanning dot position deviation appears as color misregistration in a color image, leading to degradation of color reproducibility and resolution.

  In addition, when scanning lines are written on a plurality of scanned surfaces, for example, the photosensitive surface, the cost is reduced by using a common deflector, and light is applied to both sides of the mirror-finished surface of this deflector. A counter scanning system that performs scanning has been put into practical use (see FIG. 2). In this method, as shown in FIG. 2, the start point and the end point when performing optical scanning on the surface to be scanned are opposite on both sides of the deflector. Therefore, in order to form a high-quality image even if each optical element causes a change in refractive index due to changes in the environment such as temperature and humidity and the writing magnification of each scanning line is different, There is a limit in detecting only the starting point. That is, it is necessary to detect the start point and the end point of each scanning line and to match the writing points corresponding to the respective colors.

  In addition, there is a one-side scanning method that performs all scanning on a plurality of scanned surfaces only on one side of the deflector in contrast to the above-described opposed scanning method, but in this case as well, in each scanning optical system, It is necessary to make the magnification error equal. To solve this problem, a method of synchronizing two points with respect to one scanning line is effective, but many detectors are required for this purpose. In a full-color optical scanning device, writing four scanning lines at the same time is important for speeding up, but for two-point synchronization, eight detectors twice as many are required, which increases the cost. is there. Furthermore, since detectors and detection optical systems have variations in accuracy at the manufacturing and mounting stages, and environmental conditions such as temperature and humidity in the optical scanning device are not uniform, the detectors and detection optical systems are When used separately for each detected light beam, the detection timing fluctuates and causes a relative difference, so that it is also a problem that an accurate scanning line position and writing magnification cannot be detected.

As a prior art example, there is a “light beam scanning device” that can obtain a clear multicolor image by correcting a shift in magnification error of each of a plurality of imaging optical systems at low cost (for example, see Patent Document 1). ). In this invention, two-point synchronization detection is performed by the opposed scanning method, but each station has a synchronization detection means. The synchronization detection means on the writing start side and the synchronization detection means on the writing end side are commonly used. Not.
As another prior art example, there is an “optical scanning optical system” that performs two-point synchronization detection and uses both the writing start-side synchronization detecting means and the writing end-side synchronization detecting means ( For example, see Patent Document 2). This patent document 2 does not disclose an optical scanning device having a plurality of scanning optical systems.
Japanese Patent Laid-Open No. 10-307269 JP 2001-133714 A

  Regarding the cost reduction in realizing the two-point synchronization, the invention described in Patent Document 1 has been proposed. In this method, by using both one-point synchronization and two-point synchronization, the magnification error fluctuation can be reduced at low cost. However, although this method reduces the number of detectors and can correct the scanning line at a lower cost than the conventional method, it still requires a large number of detectors, which limits the downsizing of the optical scanning device. there were.

  In response to this demand for miniaturization, for example, in the invention described in Patent Document 2, by providing an optical means for guiding the light beam toward the optical scanning start position to the optical detector at the peripheral rib portion of the scanning optical element, A method for reducing the size and correcting the color misregistration is cited. However, as demands for higher image quality, lower cost, and smaller size increase, two-point synchronization is detected in as many scanning optical systems as possible to detect and correct scanning line magnification error and main scanning position deviation. However, it has been a challenge to realize clear full-color image formation at a low space and at a low price.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical scanning device that can perform small-sized, inexpensive, and clear optical scanning, and an image forming apparatus using the optical scanning device.

  To achieve this object, the invention described in claim 1 is directed to a deflector for deflecting light beams from a plurality of light source units, a first scanning optical system including at least one scanning optical element, and a first scanning. The second scanning optical system, which is located on the opposite side of the optical system with the deflector interposed therebetween and includes at least one scanning optical element, emits a light beam at least one of before and after scanning of the scanning line. A detector that detects the light and a detection optical system that guides the light beam to the detector; the first scanning optical system and the second scanning optical system scan the light beam deflected by the deflector, and different scanned surfaces Is a first scanning optical element at a position closest to the deflector among the scanning optical elements included in the first scanning optical system. Included in the second scanning optical system and a plane perpendicular to the optical axis of Characterized in that it is arranged with a plane perpendicular to the optical axis of the second scanning optical element located closest to the deflector of 査光 optical element, the region between the.

  According to a second aspect of the present invention, in the first aspect of the invention, the detector detects at least two scanning lines, and a light beam forming at least one of the two detected scanning lines is placed with a time difference. And detecting twice or more.

  According to a third aspect of the present invention, in the first or second aspect of the invention, an arbitrary light beam guided to the detector is guided near a plane parallel to both the rotation axis of the deflector and the scanning line. Features.

  The invention described in claim 4 is characterized in that, in the invention described in claim 3, an arbitrary light beam guided to the detector is guided in the vicinity of an extension line of the rotating shaft of the deflector.

  According to a fifth aspect of the present invention, in at least one of a deflector that deflects light beams from a plurality of light source units, a scanning optical system that includes at least one scanning optical element, and before and after the scanning line is scanned. A scanning optical system having a detector that detects the light beam and a detection optical system that guides the light beam to the detector; the scanning optical system scans the light beam deflected by the deflector; The detector detects at least two scanning lines, and detects a light beam forming at least one scanning line out of the two detected scanning lines with a time difference twice or more. It is characterized by doing.

  The invention described in claim 6 is the invention described in any one of claims 1 to 5, wherein the detector is arranged on a side different from the side having the surface to be scanned across the deflector. And

  According to a seventh aspect of the present invention, in at least one of a deflector that deflects light beams from a plurality of light source units, a scanning optical system that includes at least one scanning optical element, and before and after the scanning line is scanned. It has a detector that detects the light beam and a detection optical system that guides the light beam to the detector, and all the deflection angles of the light beam are within a range of 180 degrees with the center of the deflector as the axis, An optical scanning device that scans a plurality of different image carriers to form a plurality of scanning lines, and includes a straight line A passing through the rotation center of each of the plurality of image carriers, and a scanning optical element included in the scanning optical system. Among them, the angle formed by the optical axis C of the scanning optical element closest to the deflector is zero or more, and the detector is arranged in a range sandwiched between the straight line A and the optical axis C.

  The invention described in claim 8 is characterized in that, in the invention described in any one of claims 1 to 7, the detection optical system guides a plurality of light beams to the detector through one lens.

  The invention according to claim 9 is the invention according to any one of claims 1 to 8, wherein the light source unit modulates the intensity of the emitted light based on the signal detected by the detector. And

  A tenth aspect of the invention includes the optical scanning device according to any one of the first to ninth aspects.

  According to the present invention, for example, in each scanning line, in the opposed scanning system, the scanning optical element closest to the deflector guides the light beam for detecting the scan line to the area surrounding the deflector. A plurality of scanning lines can be detected in a concentrated manner, and the optical scanning device can be downsized.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings.

  An optical scanning apparatus according to an embodiment of the present invention will be described with reference to FIG. As shown in FIG. 1, the horizontal direction is the optical axis direction of the scanning optical element, and the vertical direction is the sub-scanning direction of the scanning optical system. Light beams emitted from a plurality of light source units (not shown) are deflected with one deflector 1 in common, and are respectively scanned by scanning optical systems a1, a2, 21 to 25 located on both sides of the deflector. This is an optical scanning device that scans a surface to be scanned 3 and forms a plurality of scanning lines. This optical scanning device includes a detector 5 that detects at least one of a start point and an end point of a scanning line, and a detection optical system 4 that guides a light beam to the detector 5, and the light source unit is detected by the detector 5. The intensity of light can be modulated based on the received signal. At this time, the light beam guided to the detector 5 passes through the approximate center of the scanning optical element a1 located closest to the deflector 1 and is perpendicular to the optical axis of the scanning optical element a1 and the deflector 1 a1 And is guided to a region that passes through the approximate center of the scanning optical element a2 located closest to the deflector and is sandwiched between a plane perpendicular to the optical axis of the scanning optical element a2.

  The detector 5 detects at least two scan lines, and detects at least one scan line more than once with a time difference. At this time, the predetermined light beam guided to the deflector 1 is guided near a plane parallel to both the rotation axis of the deflector 1 and the scanning line, and near the extension line of the rotation axis of the deflector 1. Led. At this time, the detector 5 may be arranged on the side different from the scanned surface 3 with the deflector 1 interposed therebetween.

  FIG. 3 shows an optical scanning device that deflects light beams from a plurality of light source units (not shown) through a common deflector 301 and performs scanning by scanning optical elements 311 and 312. In this optical scanning device, a plurality of different scanning lines 303 are formed on a plurality of image carriers 306, and a light beam is applied to a detector 305 that detects at least one of a start point and an end point of the scanning line 303 and a detector 305. The light source unit is capable of modulating the intensity of light based on a signal detected by the detector 5, and includes a straight line A passing through the rotation centers of the plurality of image carriers 306, and a deflector 301. The detector 5 is arranged in a range that is sandwiched between the optical axis C of the scanning optical element 311 located at the closest position. The detection optical system 4 that guides the light beam to the detector is configured to guide a plurality of light beams to the detector 5 using only one lens 307 as a common lens.

Next, Example 1 of the optical scanning device according to the embodiment of the present invention will be described.
As shown in FIG. 1, in the optical scanning device of the present embodiment, for example, a semiconductor laser can be used as a light source unit (not shown) capable of modulating the light intensity. In the example shown in FIG. 1, scanning is performed with one light source for scanning one surface to be scanned, but an optical scanning device that simultaneously scans using a plurality of laser beams may be used, and the present invention limits the number of light sources. It is not something to do. In this optical scanning device, a light beam from a light source is formed as a long line image in the main scanning direction in the vicinity of the deflection reflection surface of the deflector 1 by a coupling optical system (not shown). The light beam formed as a line image is deflected at a constant angular velocity by the deflector 1. This light beam is scanned by the scanning optical systems a 1, 2, 24, 25 and guided to the surface to be scanned 3. The scanning optical systems a 1, 2, 24, and 25 are for condensing a light beam on the surface to be scanned 3 and scanning the surface to be scanned 3 at a constant velocity. The scanning beam is formed on the surface to be scanned 3 at a substantially constant speed.

  The optical scanning apparatus according to the present embodiment employs a so-called counter scanning method in which light beams emitted from a plurality of light sources are scanned with the deflector 1 facing both sides. In order to detect the scanning line, the light beam directed to each surface to be scanned is guided to the detector 5 by the detection optical system 4, but as shown in FIG. 1, it passes through the respective centers of the scanning optical elements a1 and a2 and each of them. Guided to a region sandwiched between planes perpendicular to the optical axis. Further, all the light beams are incident on the detector 5 to detect the start point and the end point thereof. Therefore, in this embodiment, the detector is made common to each scanning optical system, and information on the writing magnification of all the scanning lines and the main scanning position deviation can be obtained. Therefore, the light intensity from the light source unit is modulated. As a result, it is possible to correct the writing magnification of all the scanning lines and the main scanning position deviation, reduce the number of detectors, and reduce the cost. Further, since the detector and the detection optical system can be disposed in the vicinity of the scanning optical system, the optical scanning device can be reduced in size.

Next, Example 2 of the optical scanning device according to the embodiment of the present invention will be described with reference to FIG.
In the optical scanning apparatus of this embodiment, all scanning lines are formed using the scanning lenses 311 and 312 in common. A plurality of light beams from a plurality of light sources (not shown) capable of modulating light intensity are coupled by a coupling optical system (not shown), and as a line image long in the main scanning direction in the vicinity of the deflection reflection surface of the deflector 301. A plurality of light beams are imaged and deflected at a constant angular velocity by using the deflector 301 in common. The plurality of light beams are scanned by the scanning lenses 311 and 312, folded by the folding mirror 307, and guided to the plurality of image carriers 306 that are the scanned surfaces. The scanning lenses 311 and 312 are for condensing the luminous flux on the surface to be scanned 303 and scanning the plurality of image carriers 306 at a constant speed, and deflecting at a constant angular speed by the deflector 301. The emitted light beam is scanned on the image carrier 306 at a substantially constant speed.

  A straight line A connecting the rotation centers of the plurality of image carriers 306 has an angle formed with the optical axis C of the scanning lens 311 larger than zero, and is away from the deflector in the optical axis C direction as shown in FIG. However, the straight line A is inclined with respect to the optical axis C so that the image carrier is closer to the optical axis C.

  In order to detect the scanning line, the light beam traveling toward each surface to be scanned is guided to the detector 305 by the detection optical system 304, but the detector 5 falls within the range where the straight line A and the optical axis C are sandwiched as shown in FIG. Is arranged. Therefore, according to the present embodiment, the optical path lengths of the respective scanning optical systems can be made the same without being folded by a folding mirror or the like, so that the number of components of the optical element can be reduced. In addition, the optical scanning device and the optical scanning device can be obtained by bringing the image carrier closer to the scanning optical system as compared with the prior art, and bringing the detector closer to the scanning optical system and placing it between the image carrier and the optical scanning device. The image forming apparatus using can be downsized.

Next, an image forming apparatus according to an embodiment of the present invention will be described with reference to FIG.
The photoconductive photoreceptors 42a to 42d rotate at a constant speed in the clockwise direction as indicated by arrows in FIG. The surfaces of the photoreceptors 42a to 42d are uniformly charged by the charging device 45, and are exposed by the multi-beam scanning method by the optical scanning device 41 of the present invention as described above.

  The photosensitive member 42 on which the electrostatic latent image is written by this exposure is visualized as a toner image by the developing device 43, and the toner images visualized on the plurality of photosensitive members 42a to 42d by the transfer unit 46 are formed as one image. In this manner, the images are sequentially transferred onto the intermediate transfer belt 48 to form a superimposed full color image. This full-color image is transferred to the sheet-like recording medium S by another transfer unit 49 and fixed by the fixing unit 47 to complete image formation, and is discharged outside the apparatus.

  The photosensitive member 42 is removed by the cleaning means 44 from the toner and paper dust remaining without being completely transferred. Thereafter, it is charged again by the charging means 45. By using the optical scanning device 41 as in the embodiment, it is possible to perform good optical scanning with low cost and space saving, and to perform good image formation.

  As described above, according to the optical scanning device of the embodiment of the present invention, for example, in the scanning method with each scanning line facing the scanning line, the scanning optical element closest to the deflector surrounds the area surrounding the deflector. By guiding the light beam for detecting the light, a plurality of scanning lines can be detected in a concentrated manner, and the optical scanning device can be downsized.

  Further, according to the optical scanning device of the embodiment of the present invention, two or more scanning lines can be detected using only one detector, and the number of parts can be reduced. Furthermore, since at least one scanning line is detected at two points with a time difference, the main scanning position information of the scanning line can be obtained with high accuracy, and the influence of the variation in accuracy of the multiple detectors in question can be affected. It can be avoided as much as possible. By modulating the light based on this signal, it is possible to satisfactorily correct color reproducibility and resolution degradation in a full-color image. As a result, an inexpensive image with high image quality can be provided.

  In addition, according to the optical scanning device of the embodiment of the present invention, it is easy for the light beams directed to the respective scanned surfaces in the opposed scanning method to equalize the distance from each optical element to the detector. Can be easily shared, the number of parts is reduced, and a cheaper optical scanning device can be provided.

  Further, according to the optical scanning device of the embodiment of the present invention, the arrangement of the synchronization detection optical system is not expanded in the main scanning direction, so that the optical scanning device can be further downsized.

  Further, according to the optical scanning device of the embodiment of the present invention, only one scanning line can be detected by only one detector, and moreover, a plurality of detectors with a time difference between at least one scanning line. Since the detection is performed once, it is possible to reduce the number of detectors necessary for performing the main scanning position shift of the scanning line and the writing magnification error with higher accuracy, and it is possible to provide an inexpensive optical scanning device.

  Further, according to the optical scanning device of the embodiment of the present invention, the synchronization optical system can be provided without extending the distance between the surface to be scanned and the scanning optical system, so that the optical scanning device can be downsized.

  Further, according to the optical scanning device of the embodiment of the present invention, the image carrier and the optical scanning are entirely performed by arranging the optical axis C of the scanning optical system and the straight line A connecting the rotation axis of the image carrier to be inclined. The distance to the device can be shortened. In addition, by arranging a two-point synchronization detector in the area between C and A, a space-saving optical scanning device can be realized even if a synchronization detection optical system and a photodetector are used.

  In addition, according to the optical scanning device of the embodiment of the present invention, the lens for condensing the synchronous light beam, which has been used individually with respect to the conventional light beam, is shared, so that the detection optical system of the optical scanning device can be used. The number of parts can be reduced, and the difference in detection timing of a plurality of scanning lines can be reduced by using a common detection optical system, so that an optical scanning device capable of performing optical scanning with low cost and high accuracy can be realized.

  Further, according to the image forming apparatus which is an embodiment of the present invention, it is possible to realize good image formation by using the optical scanning device.

  As mentioned above, although the Example of this invention was described, it is not limited to the said Example, A various deformation | transformation is possible in the range which does not deviate from the summary.

  The present invention can be applied to an image forming apparatus such as a laser printer, a color copying machine, and a facsimile.

It is a figure which shows the structure of the optical scanning device which is embodiment of this invention. It is a figure which shows the structure of the conventional optical scanning apparatus of a counter scanning system. It is a figure which shows the structure of the optical scanning device which is Example 2 of this invention. 1 is a diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Deflector 3 Scanned surface 4 Detection optical system 5 Detector a1, a2, 21, 22, 23, 24, 25 Scanning optical system 41 Optical scanning device 42a, 42b, 42c, 42d Photoconductor 43 Developing device 44 Cleaning means 45 Charging devices 46, 49 Transfer means 47 Fixing means S Sheet-like recording medium 200 Light source 201 Deflectors 202a, 202b, 202c, 202d Scanning optical element 301 Deflector 303 Scanning line 304 Detection optical system 305 Detector 306 Image carrier 307 Lens ( Folding mirror)
311 and 312 Scanning optical element (lens)

Claims (10)

A deflector for deflecting light beams from a plurality of light source units;
A first scanning optical system comprising at least one scanning optical element;
A second scanning optical system that is located on the opposite side of the first scanning optical system across the deflector and includes at least one scanning optical element;
A detector for detecting the luminous flux at least one of before and after the scanning of the scanning line;
A detection optical system for guiding a light beam to the detector,
An optical scanning device in which the first scanning optical system and the second scanning optical system scan a light beam deflected by the deflector and scan different scanned surfaces to form a plurality of scanning lines,
The detector includes a plane perpendicular to the optical axis of the first scanning optical element located closest to the deflector among the scanning optical elements included in the first scanning optical system, and the second scanning optical An optical scanning device arranged in a region sandwiched between a scanning optical element included in the system and a plane perpendicular to the optical axis of the second scanning optical element closest to the deflector.   The detector detects at least two scanning lines, and detects a light beam forming at least one scanning line out of the two detected scanning lines at least twice with a time difference. The optical scanning device described.   3. The optical scanning device according to claim 1, wherein an arbitrary light beam guided to the detector is guided near a plane parallel to both the rotation axis of the deflector and the scanning line.   4. The optical scanning device according to claim 3, wherein an arbitrary light beam guided to the detector is guided in the vicinity of an extension line of a rotation axis of the deflector. A deflector for deflecting light beams from a plurality of light source units;
A scanning optical system comprising at least one scanning optical element;
A detector for detecting the luminous flux at least one of before and after the scanning of the scanning line;
A detection optical system for guiding a light beam to the detector,
An optical scanning device in which the scanning optical system scans a light beam deflected by the deflector and scans different scanned surfaces to form a plurality of scanning lines,
The detector detects at least two scanning lines, and detects a light beam forming at least one scanning line out of the two detected scanning lines with a time difference twice or more. apparatus.   6. The optical scanning device according to claim 1, wherein the detector is disposed on a side different from the side on which the scanning surface is located with the deflector interposed therebetween. A deflector for deflecting light beams from a plurality of light source units;
A scanning optical system comprising at least one scanning optical element;
A detector for detecting the luminous flux at least one of before and after the scanning of the scanning line;
A detection optical system for guiding a light beam to the detector,
All of the deflection angles of the luminous flux are within a range of 180 degrees with the center of the deflector as an axis, and an optical scanning device that scans a plurality of different image carriers to form a plurality of scanning lines. There,
An angle formed between a straight line A passing through the rotation center of each of the plurality of image carriers and an optical axis C of the scanning optical element closest to the deflector among the scanning optical elements included in the scanning optical system is Is greater than or equal to zero,
The optical scanning device, wherein the detector is arranged in a range sandwiched between the straight line A and the optical axis C.   The optical scanning device according to claim 1, wherein the detection optical system guides a plurality of light beams to the detector through a single lens.   9. The optical scanning device according to claim 1, wherein the light source unit modulates the intensity of emitted light based on a signal detected by the detector. 10.   An image forming apparatus comprising the optical scanning device according to claim 1.

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