JP2008304511A - Multibeam scanner and image forming apparatus equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remarkably improve easiness of maintenance of an apparatus having a plurality of light sources by approximately equalizing timing of replacing light sources by approximately equalizing the life of each light source. <P>SOLUTION: The multibeam scanner comprises: the plurality of light sources; a first optical system which condenses and combines the light beams emitted from the light emitting points of the respective light sources; a deflector which deflects the respective light beams from the optical system; a second optical system which focuses the light beams deflected and scanned with the deflector on a face to be scanned; and a synchronization detection means for deciding timing of the scanning start position on the face to be scanned, wherein a light source for synchronization detection used for detecting the synchronization among the plurality of light sources is used also for the scanning and exposing the face to be scanned, the light sources other than the light source for synchronization detection are used as the light sources for image forming for scanning and exposing the face to be scanned, and the number of the light emitting points of the light source for synchronization detection is smaller than that of the light emitting points of the light sources for image forming. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a multi-beam scanning apparatus including a plurality of light sources that emit at least one light beam and an image forming apparatus including the apparatus.

  For example, in the field of image forming apparatuses such as digital copying machines and laser printers, a multi-beam that emits a plurality of light beams for exposing and scanning the surface of a photosensitive drum or the like is provided in order to cope with a higher speed of image formation. Various image forming apparatuses using a beam scanning apparatus have been developed.

  This multi-beam scanning device includes a light source that emits a plurality of light beams, a polygon mirror that scans each emitted light beam in the main scanning direction, a scanning lens that guides each scanned light beam to an image carrier, etc. In recent years, a light source unit having two or more array light sources having a plurality of light emission points and combining and emitting a plurality of light beams emitted from each array light source is provided. Things that have been prepared are emerging.

  In a multi-beam scanning device, in order to obtain a good image quality by simultaneously recording image data for a plurality of lines using a plurality of light beams, the scanning start positions of the respective light beams in the main scanning direction are aligned. There is a need.

  For this purpose, a synchronization detection sensor is provided outside the effective scanning range and closer to the scanning start side than the surface to be scanned, and the synchronization detection light beam is emitted to the synchronization detection sensor and output from the synchronization detection sensor before the start of image formation. The image forming light beam is emitted after a predetermined time from the detected signal, thereby synchronizing the scanning start positions of the image forming light beams.

  However, the light emission time for synchronization detection is longer than that for the other image forming light beams by the time the light beam is emitted for synchronization detection. For this reason, the light source for synchronization detection has a shorter product life than other light sources for image formation and needs to be replaced earlier than other light sources for image formation. Since the timing of replacing a plurality of light sources varies, there is a problem that maintenance work is poor because it is necessary to frequently perform light source replacement work. In particular, in the case of an array light source in which a plurality of light emission points are arranged, when a light emission point selected from the plurality of light emission points is used for synchronization detection and the light emission point for synchronization detection reaches the end of its life, Even if the light emitting point is still available, there is a problem that the array light source itself must be replaced.

By the way, in Patent Document 1, in order to independently adjust a light beam interval when combining three light beams without using a beam splitter, a multi-beam is formed around the optical axis of a single light source semiconductor laser. Rotating the light source is disclosed. However, in the invention of Patent Document 1, only a single light source semiconductor laser is used as a light beam interval adjusting means, and there is no description that it is used as a synchronous detection light source that emits an image forming light beam. .
Japanese Unexamined Patent Publication No. 09-236763.

  Therefore, the technical problem to be solved by the present invention is to prevent deterioration of the image quality due to the change in the amount of light in the multi-beam scanning device including a plurality of light sources that emit at least one light beam, while preventing deterioration of the light sources. To provide a multi-beam scanning apparatus and an image forming apparatus equipped with the apparatus, in which the maintenance timing of the apparatus is greatly improved by making the light source replacement timing substantially the same by making the life of each light source substantially the same. It is.

Means and actions / effects for solving the problem

In order to solve the above technical problem, according to the present invention,
Multiple light sources;
A first optical system that condenses and combines the light beams emitted from the light emitting points of the light sources;
A deflector for deflecting each light beam from the optical system;
A second optical system that forms an image of the light beam deflected and scanned by the deflector on the surface to be scanned;
A multi-beam scanning device comprising: synchronization detection means for determining the timing of the scanning start position on the surface to be scanned,
Among the plurality of light sources, a synchronization detection light source used for synchronization detection is also used for scanning exposure on the scanning surface, and light sources other than the synchronization detection light source perform scanning exposure on the scanning surface. Used as a light source for image formation,
A multi-beam scanning device is provided in which the number of light emitting points of the light source for synchronization detection is smaller than the number of light emitting points of the light source for image formation.

  In general, it is known that the lifetime of a light source becomes longer as the emission time until now is shorter. When a light emitting point emits light with the same light emission time and light emission amount, the more light emitting points included in a certain light source, that is, the more light emitting points integrated in the light source, The amount of heat generated increases, and the life of the light source is shortened. When the light source for synchronization detection is used for both synchronization detection and scanning exposure, light is emitted for a longer time than the light source for image formation by the amount of synchronization detection. As a result, the light source or the multi-beam scanning device has been replaced because the life of the synchronous detection light source is shorter than that of the image forming light source.

  On the other hand, according to the configuration of the present invention, the number of light emission points of the synchronization detection light source is smaller than the number of light emission points of the image forming light source, so that the light emission of the synchronization detection light source with a long light emission time is achieved. It is possible to suppress the deterioration of the points and prevent the deterioration of the image quality due to the light intensity deterioration. The life of the synchronization detection light source can be reduced to the same level as that of the image forming light source by covering the shortening of the lifetime of the light emission point of the synchronization detection light source due to the long-time emission. As a result, the replacement timing of the light source or the multi-beam scanning device is substantially aligned, so that the maintainability of the device is greatly improved.

  The light source for synchronization detection is a single light source having one light emitting point.

  Alternatively, the synchronization detection light source is an array light source having a plurality of light emitting points.

  The above-described multi-beam scanning apparatus is applied to an image forming apparatus that forms an image by scanning a plurality of light beams.

  Hereinafter, a multi-beam scanning device 1 of an image forming apparatus according to an embodiment of the present invention will be described in detail with reference to FIG.

  FIG. 1 is a schematic diagram of a multi-beam scanning apparatus 1 according to a first embodiment of the present invention incorporated in an image forming apparatus (for example, a copier, a printer, a facsimile, or a combination thereof). It is a top view. Since the image forming apparatus itself has a known configuration, the image forming apparatus will be briefly described and the multi-beam scanning apparatus 1 will be described in detail.

  First, the overall configuration of the image forming apparatus will be described.

  The image forming apparatus is a multi-beam digital copier having a plurality of light sources composed of laser diode elements (or semiconductor laser elements), and includes an image reading unit, an image signal processing unit, a memory unit unit, a control unit, a multi-beam. The scanning device 1 includes an image forming system, a paper feeding unit, a fixing unit, and the like.

  The image reading unit reads an original as image data, converts the read image data into an electric signal, and outputs the electric signal to the image signal processing unit. The image signal processing unit converts the electrical signal of the image data sent from the image reading unit into binarized data and stores it in the memory unit unit. The memory unit stores the image data corrected by the image signal processing unit in the image information memory in units of lines that are units of exposure scanning processing. Then, the image data is output to the control unit line by line according to the horizontal synchronization control by the control unit. Here, since a plurality of lines are simultaneously exposed and scanned using a plurality of laser beams in one horizontal synchronization period, data for a plurality of lines is output at a time.

  The multi-beam scanning device 1 emits a light beam while modulating a light beam in accordance with image data sent from the image memory via the control unit in accordance with horizontal synchronization control by the control unit, and outputs the surface of the photosensitive drum (that is, to be scanned). Surface) to form an electrostatic latent image on the photosensitive drum. A detailed description of the configuration and processing contents of the multi-beam scanning device 1 will be described later.

  The control unit is located between the memory unit unit and the multi-beam scanning device 1, reads image data sequentially from the memory unit unit, and exposes the photosensitive drum to the multi-beam scanning device 1 according to the read image data. Let it scan. At that time, exposure scanning timing adjustment processing is performed. In the image forming system, the charging charger first charges the rotationally driven photosensitive drum to a predetermined potential, and thereafter, when an electrostatic latent image is formed on the photosensitive drum by the multi-beam scanning device 1, Develops the electrostatic latent image on the photosensitive drum to generate a toner image. The transfer charger transfers the toner image on the photosensitive drum onto the recording paper. The cleaner scrapes off the toner remaining on the photosensitive drum after transferring the toner image onto the recording paper.

  In the paper feeding section, the recording paper stored in the paper feeding cassette is fed out one by one as the paper feeding roller rotates, and the fed recording paper is fed out toward the transfer charger. The fixing unit includes a pair of rollers, and fixes the toner image on the recording paper by a thermocompression process using these rollers.

  Next, the multi-beam scanning device 1 according to the first embodiment will be described with reference to FIG.

  Reference numeral 10 denotes a synchronization detection light source, which has a light emitting point (laser diode) smaller than a light emitting point of an image forming light source 20 to be described later, and emits, for example, one light beam S1 as shown in FIG. To do. That is, the synchronization detection light source 10 shown in FIG. 1 is a single light source having one light emitting point. The light beam S1 is used for both image formation and synchronous detection.

  Reference numeral 12 denotes a condensing optical system. The condensing optical system 12 forms an image of the collimator lens that collimates the diffused light emitted from the synchronization detection light source 10 and the light beam S1 from the synchronization detection light source 10 on the surface to be scanned, and the tilt angle. A cylindrical lens that corrects the inclination of the reflecting surface of the polygon mirror 40 is called.

An image forming light source 20 has a plurality of light emitting points (laser diodes) and emits two light beams R1 and R2 as shown in FIG. That is, the image forming light source 20 is an array light source in which two laser diodes are arranged so that the light emitting points are arranged at a predetermined angle with respect to the main scanning direction. The light beams R1 and R2 are used for scanning exposure (image formation).

  Reference numeral 22 denotes a condensing optical system. The condensing optical system 22 forms an image on the surface to be scanned and collimates the collimator lens that collimates the diffused light emitted from the image forming light source 20 and the light beams R1 and R2 from the image forming light source 20. It consists of a cylindrical lens that corrects the inclination of the reflecting surface of the polygon mirror 40 called a corner.

  Reference numeral 30 denotes a beam splitter as a combining optical element. The beam splitter 30 synthesizes each light beam by deflecting the light beam from the synchronization detection light source 10 at an angle of 90 degrees on the half mirror surface and transmitting the light beam from the image forming light source 20 as it is. These are emitted toward the polygon mirror 40. The condensing optical system 12 and the beam splitter 30 constitute a first optical system.

  Reference numeral 40 denotes a polygon mirror as a deflector having a plurality of deflection reflection surfaces (deflection surfaces made up of mirror surfaces). Light beams S1, R1, and R2 from the beam splitter 30 are reflected and scanned by a deflecting / reflecting surface that is rotationally driven at a high speed by a motor (not shown).

  Reference numeral 50 denotes a multi-beam scanning optical system (second optical system) having fθ characteristics. The multi-beam scanning optical system 50 includes a spherical lens having a negative refractive power and a toric lens having a positive refractive power. The multi-beam scanning optical system 50 is an optical system for moving the light beam deflected and reflected by the polygon mirror 40 on the photosensitive drum surface (scanned surface) at a constant speed.

  Reference numeral 60 denotes an SOS (Start of Scan) sensor (photodiode) as synchronization detecting means. The SOS sensor 60 is located outside the effective scanning range when the light beam is scanned on the surface of the photosensitive drum (scanned surface), and is disposed on the scanning start side. The SOS sensor 60 is used to detect an image formation start position (writing position) in the main scanning direction in multi-beam scanning and generate a reference synchronization signal (beam detection signal). The timing of the scanning start position of image recording on the photosensitive drum surface (scanned surface) is adjusted by using the synchronization signal (beam detection signal).

  In FIG. 1 shown as the first embodiment, the synchronization detection light source 10 has one laser diode (light emitting point). From the synchronization detection light source 10, one light beam (SOS combined light beam) S1 is emitted. The light beam S1 for image formation and synchronization detection is used for both image formation and synchronization detection. The image forming light source 20 is an array light source having two laser diodes (light emitting points). The distance between the two laser diodes is, for example, 14 μm. Two light beams R 1 and R 2 are emitted from the image forming light source 20. The image forming light beams R1 and R2 are used for scanning exposure (image formation). As schematically shown in FIG. 4A, each light beam R1, S1, R2 from the multi-beam scanning device 1 is scanned on the surface to be scanned.

  As described above, a single light source having one laser diode (light emitting point) is used as the synchronization detection light source 10, and an array light source having two laser diodes (light emitting points) is used as the image forming light source 20. That is, by reducing the number of light emission points of the synchronization detection light source 10 to be smaller than the number of light emission points of the image forming light source 20, the synchronization detection light source 10 that is required to emit light for a long time has a sufficient capacity. The light emission in the state leads to a long life of the synchronization detection light source 10, and the life of the synchronization detection light source 10 can be made to be the same as that of the image forming light source 20. The maintenance is greatly improved.

  Next, the multi-beam scanning device 1 according to the second embodiment of the present invention will be described with reference to FIG. 2, but the basic configuration is the same as that of the first embodiment described above. The description will be omitted, and the difference will be mainly described. In both embodiments, the same or corresponding parts are denoted by the same reference numerals.

  Compared with the multi-beam scanning device 1 of the first embodiment, the image forming light source 20 is different.

  In FIG. 2 shown as the second embodiment, the synchronization detection light source 10 is a single light source having one laser diode (light emitting point). From the synchronization detection light source 10, one light beam S1 is emitted. The light beam for image formation and synchronization detection (SOS combined light beam) S1 is used for both image formation and synchronization detection. The image forming light source 20 is an array light source having four laser diodes. The interval between the four laser diodes is, for example, 14 μm. Four light beams R1, R2, R3, and R4 are emitted from the image forming light source 20. The image forming light beams R1, R2, R3, and R4 are used for scanning exposure (image formation). As schematically shown in FIG. 4B, each light beam R1, R2, S1, R3, R4 from the multi-beam scanning device 1 is scanned on the surface to be scanned.

  As described above, a single light source having one laser diode (light emitting point) is used as the synchronization detection light source 10, and an array light source having four laser diodes (light emitting points) is used as the image forming light source 20. That is, by reducing the number of light emission points of the synchronization detection light source 10 to be smaller than the number of light emission points of the image forming light source 20, the synchronization detection light source 10 that is required to emit light for a long time has a sufficient capacity. The light emission in the state leads to a long life of the synchronization detection light source 10, and the life of the synchronization detection light source 10 can be made to be the same as that of the image forming light source 20. The maintenance is greatly improved.

  Next, the multi-beam scanning device 1 according to the third embodiment of the present invention will be described with reference to FIG. 3, but the basic configuration is the same as that of the above-described second embodiment. The description will be omitted, and the difference will be mainly described. In both embodiments, the same or corresponding parts are denoted by the same reference numerals.

  Compared to the multi-beam scanning device 1 of the second embodiment, the synchronization detection light source 10 is different.

  In FIG. 3 shown as the third embodiment, the synchronization detection light source 10 is an array light source having two laser diodes (light emitting points). Two light beams S 1 and S 2 are emitted from the synchronization detection light source 10. The light beam for image formation and synchronization detection (SOS combined light beam) S1 is used for both image formation and synchronization detection. The other light beam, that is, the image-forming light beam S2 is used for scanning exposure (image formation). The image forming light source 20 is an array light source having four laser diodes. The interval between the four laser diodes is, for example, 14 μm. Four light beams R1, R2, R3, and R4 are emitted from the image forming light source 20. The image forming light beams R1, R2, R3, and R4 are used for scanning exposure (image formation). As schematically shown in FIG. 4C, the light beams R1, S1, R2, R3, S2, and R4 from the multi-beam scanning device 1 are scanned on the surface to be scanned.

  As described above, an array light source having two laser diodes (light emitting points) is used as the synchronization detection light source 10, one of which is used as the image formation and synchronization detection light beam S1, and the other as the image formation light beam S2. And using an array light source having four laser diodes (light emitting points) as the image forming light source 20, that is, the number of light emitting points of the synchronization detecting light source 10 is equal to the number of light emitting points of the image forming light source 20. By reducing the number of light sources, the synchronization detection light source 10 that is required to emit light for a long time is allowed to emit light with sufficient capacity, leading to a long life of the synchronization detection light source 10, and the life of the synchronization detection light source 10 Can be made substantially the same as the lifetime of the light source 20 for image formation, and the maintainability of the multi-beam scanning apparatus 1 and the image forming apparatus is greatly improved.

  Next, the multi-beam scanning device 1 according to the fourth embodiment of the present invention will be described with reference to FIG. 5, but the basic configuration is the same as that of the first embodiment described above. The description will be omitted, and the difference will be mainly described. In both embodiments, the same or corresponding parts are denoted by the same reference numerals.

  Compared with the multi-beam scanning device 1 of the first embodiment, the configuration of the first optical system from the light source to the polygon mirror 40 is different.

  In FIG. 5 shown as the fourth embodiment, the synchronization detection light source 10 is composed of one light source, and a condensing optical system 12 including a collimator lens and a cylindrical lens is disposed in front of the synchronization detection light source 10. It is arranged. The image forming light source 20 includes three separate light sources, and a condensing optical system 22 including a collimator lens and a cylindrical lens is disposed in front of each image forming light source 20. . Then, a laminated mirror body 32 is used instead of the beam splitter 30 as a combining optical element. The laminated mirror body 32 is formed by laminating a plurality of mirrors at different angles, and deflects the light beam S1 from the synchronization detection light source 10 and the light beams R1, R2, and R3 from the image forming light source 20 at a predetermined angle. The light beams S1, R1, R2, and R3 are emitted toward the polygon mirror 40.

  The synchronization detection light source 10 is a single light source having one laser diode (light emitting point). From the synchronization detection light source 10, one light beam S1 is emitted. The light beam for image formation and synchronization detection (SOS combined light beam) S1 is used for both image formation and synchronization detection.

  Of the three image forming light sources 20, the first image forming light source 20 is a single light source having one laser diode. From the image forming light source 20, one light beam R1 is emitted. Of the three image forming light sources 20, the second image forming light source 20 is an array light source having two laser diodes. The distance between the two laser diodes is, for example, 14 μm. Two light beams R 1 and R 2 are emitted from the image forming light source 20. Of the three image forming light sources 20, the third image forming light source 20 is an array light source having three laser diodes. The interval between the three laser diodes is, for example, 14 μm. Three light beams R1, R2, and R3 are emitted from the image forming light source 20. A total of six light beams of the image forming light beams R1, R2, and R3 are used for scanning exposure (image formation).

  As described above, a single light source having one laser diode (light emitting point) is used as the synchronization detection light source 10, and an array light source having two laser diodes (light emitting points) and two lasers are used as the image forming light source 20. Using an array light source having a diode (light emitting point) and a single light source having one laser diode (light emitting point), that is, the number of light emitting points of the synchronization detection light source 10 is set to the light emitting point of the image forming light source 20. By reducing the number to less than the number, the synchronization detection light source 10 that is required to emit light for a long time is allowed to emit light with sufficient capacity, leading to a longer life of the synchronization detection light source 10. The service life of the multi-beam scanning device 1 and the image forming apparatus can be greatly improved.

  Note that the above embodiment is merely an example, and various modifications are possible as long as the number of light emitting points of the synchronization detection light source 10 is less than the number of light emitting points of the image forming light source 20. Deformation can be performed. For example, an array light source having three laser diodes (light emitting points) can be used as the synchronization detection light source 10, and an array light source having four laser diodes (light emitting points) can be used as the image forming light source 20. Furthermore, an array light source having two laser diodes (light emitting points) is used as the synchronization detection light source 10, and an array light source having three laser diodes (light emitting points) and two laser diodes (light emitting points) are used as the image forming light source 20. An array light source having a light emission point) and an array light source having two laser diodes (light emission points) can be used.

1 is a schematic top view of a multi-beam scanning device according to a first embodiment of the present invention used in an image forming apparatus. It is typical explanatory drawing of the light beam from the multi-beam scanning apparatus which concerns on 2nd embodiment of this invention. It is typical explanatory drawing of the light beam from the multi-beam scanning apparatus which concerns on 3rd embodiment of this invention. It is a figure which shows typically a mode when the light beam from the multi-beam scanning apparatus which concerns on this invention is scanned on a to-be-scanned surface. (A) is a case where there are two light beams from the light source for image formation and one light beam from the light source for synchronization detection. (B) is a case where there are four light beams from the light source for image formation and one light beam from the light source for synchronization detection. (C) is a case where there are four light beams from the light source for image formation and two light beams from the light source for synchronization detection. It is a typical top view of the multi-beam scanning device concerning a 4th embodiment of the present invention.

Explanation of symbols

1: Multi-beam scanning device 10: Synchronous detection light source 12: Condensing optical system 20: Image forming light source 22: Condensing optical system 30: Beam splitter (combining optical element)
32: Laminated mirror body (synthetic optical element)
40: Polygon mirror (deflector)
50: Multi-beam scanning optical system (second optical system)
60: SOS sensor (synchronous detection means)
S1: Light beam for image formation and synchronization detection (SOS combined light beam)
S2: Image forming light beam R1: Image forming light beam R2: Image forming light beam R3: Image forming light beam R4: Image forming light beam

Claims (4)

Multiple light sources;
A first optical system that condenses and combines the light beams emitted from the light emitting points of the light sources;
A deflector for deflecting each light beam from the optical system;
A second optical system that forms an image of the light beam deflected and scanned by the deflector on the surface to be scanned;
A multi-beam scanning device comprising: synchronization detection means for determining the timing of the scanning start position on the surface to be scanned,
Among the plurality of light sources, a synchronization detection light source used for synchronization detection is also used for scanning exposure on the scanning surface, and light sources other than the synchronization detection light source perform scanning exposure on the scanning surface. Used as a light source for image formation,
The multi-beam scanning device characterized in that the number of light emitting points of the light source for synchronization detection is smaller than the number of light emitting points of the light source for image formation.   The multi-beam scanning device according to claim 1, wherein the synchronization detection light source is a single light source having one light emitting point.   The multi-beam scanning device according to claim 1, wherein the synchronization detection light source is an array light source having a plurality of light emitting points. An image forming apparatus that forms an image by scanning a plurality of light beams,
An image forming apparatus using the multi-beam scanning device according to claim 1 as a scanning device that scans the plurality of light beams.

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