JP2012008276A - Optical scanning device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical scanning device capable of sufficiently securing a space for synchronous detection even if a wider angle of view is achieved and further contributing to reducing a size of an image forming device.SOLUTION: An optical scanning device 1171 comprises a light source 1, an aperture 12 for shaping a luminous flux from the light source 1, a cylindrical lens 5 for condensing the luminous flux to a sub-scanning direction, a deflector 7 having a polygonal reflection surface, scanning optical systems 8 and 9 for guiding, to a photoreceptor 11 as a surface to be scanned, the luminous flux entering the deflector 7 to be deflection-scanned, and synchronization detection means 10 for performing a synchronization detection using the luminous flux reflected from the deflector 7 to the aperture 12. The synchronized light reflected from the polygon mirror 7 passes through the cylindrical lens 5 and then is reflected by an outer frame of the aperture 12 to reach synchronization detection means 21 via a condensing lens 20.

Description

  The present invention relates to an optical scanning apparatus, a copier having the optical scanning apparatus, a printer, a facsimile machine, a plotter, and an image forming apparatus such as a multifunction machine including at least one of them.

Electrophotographic image forming apparatuses used in laser printers, laser plotters, digital copiers, plain paper facsimiles, or multi-function machines of these are becoming more compact.
Accordingly, an optical scanning device having a short optical path to the photoconductor and a high angle of view is being provided. In order to realize an optical scanning device with a high angle of view, a configuration in which a light beam for synchronization detection in the synchronization detection unit is not passed through a scanning lens has been proposed (for example, see Patent Documents 1 and 2).

However, in the optical scanning device disclosed in Patent Document 1, the end portion of the scanning optical element is partially cut off to allow the synchronization detecting light beam to pass. Therefore, when the scanning field angle is increased, the optical scanning device synchronizes in the vicinity of the scanning optical element. Since the light beam passes, it is difficult to separate the scanning light beam and the synchronized light east.
Further, in the optical scanning device disclosed in Patent Document 2, the scanning optical element and the optical element for synchronization detection are separated from each other, and it is easy to separate the scanning light beam and the synchronization light beam. It is necessary to put an optical system for synchronization detection in a narrow layout between the incident optical system and the scanning optical system up to the detector, and there is a problem that the layout becomes difficult as the angle of view increases.

  The present invention has been made in view of such a current situation, and an optical scanning device capable of ensuring a sufficient space for synchronization detection even when the angle of view is increased and contributing to further downsizing of an image forming apparatus. Is the main purpose.

  In order to achieve the above object, according to a first aspect of the present invention, there is provided an optical scanning device comprising: a light source; an aperture for shaping a light beam from the light source; a deflector having a multi-surface reflecting surface; A scanning optical system that guides a light beam that is incident and deflected and scanned to a surface to be scanned, and synchronization detection means that performs synchronization detection with the light beam reflected from the deflector to the aperture.

According to a second aspect of the present invention, in the optical scanning device according to the first aspect, the frame shape of the aperture is such that the width in the main scanning direction of the portion corresponding to the synchronization detecting means is large. It is asymmetric with respect to a line extending substantially perpendicularly from the center in the main scanning direction.
According to a third aspect of the present invention, in the optical scanning device according to the first or second aspect, a portion of the aperture corresponding to the synchronization detection unit is based on a direction perpendicular to the optical axis. It is characterized by being arranged to be inclined in the main scanning direction so as to be separated from the detection means.

According to a fourth aspect of the present invention, in the optical scanning device according to any one of the first to third aspects, the reflectance of the aperture frame is different between the front and back surfaces, and the reflectance on the light source side is smaller than the reflectance on the deflector side. It is characterized by rate.
According to a fifth aspect of the invention, in the optical scanning device according to any one of the first to fourth aspects, the light source is a surface emitting laser.
According to a sixth aspect of the present invention, an optical scanning device that forms a latent image by irradiating a beam from a light source onto an image carrier that is a surface to be scanned is provided, and the latent image formed on the image carrier is developed as a developer. 6. An image forming apparatus that forms an image by forming a visible image and transferring the visible image directly or via an intermediate transfer member to a recording material, wherein the optical scanning device is defined in any one of claims 1 to 5. It is characterized by being an optical scanning device.

  According to the present invention, since synchronization detection can be performed at a position away from the scanning lens near the light source, the degree of freedom in layout on the scanning start side can be increased, and sufficient space for synchronization detection can be provided even when the angle of view increases. Can be secured.

1 is a schematic configuration diagram of a laser printer as an image forming apparatus according to a first embodiment of the present invention. 1 is a schematic perspective view of an optical scanning device. It is a front view which shows an aperture, (a) is a figure which shows a prior art example, (b) is a figure which shows this invention. It is a general | schematic perspective view of the optical scanning device in 2nd Embodiment. It is a figure which shows the effect at the time of inclining an aperture in the main scanning direction, (a) is a figure when not inclining, (b) is a figure when it inclines. It is a front view which shows the light source of the optical scanning device in 3rd Embodiment.

Embodiments of the present invention will be described below with reference to the drawings.
First, an outline of a configuration of a laser printer as an image forming apparatus according to the present embodiment will be described with reference to FIG. The laser printer 1000 has a photoconductive photoconductor 1110 formed in a cylindrical shape as a carrier. Around the photoconductor 1110, a charging roller 1121, a developing device 1131, a transfer roller 1141, and a cleaning device 1151 are disposed as charging means. A corona charger can also be used as the charging means.
Further, an optical scanning device 1171 that performs optical scanning with the laser beam LB is provided, and exposure by optical writing is performed between the charging roller 1121 and the developing device 1131.

When image formation is performed, the photosensitive member 1110 is rotated at a constant speed in the clockwise direction, and the surface thereof is uniformly charged by the charging roller 1121, and is exposed to the exposure by the optical writing of the laser beam LB of the optical scanning device 1171. A latent image is formed.
The formed electrostatic latent image is a so-called negative latent image, and the image portion is exposed. This electrostatic latent image is reversely developed by the developing device 1131, and a toner image is formed on the image carrier 1110.
The paper feed cassette 1181 containing the transfer paper P as a recording material is detachable from the main body of the image forming apparatus 1000. When the paper feed cassette 1181 is mounted as shown in the drawing, the uppermost sheet of the stored transfer paper P is supplied. The transfer paper P fed by the paper roller 1201 is nipped between the registration roller pair 1191 at the leading end.

The registration roller pair 1191 feeds the transfer paper P to the transfer unit in time with the toner image on the image carrier 1110 moving to the transfer position.
The transferred transfer paper P is superimposed on the toner image at the transfer portion, and the toner image is electrostatically transferred by the action of the transfer roller 1141.
The transfer paper P to which the toner image has been transferred is sent to the fixing device 1161, where the toner image is fixed by the fixing device 1161, passes through the conveyance path 1211, and is discharged onto the tray 1231 by the discharge roller pair 1221.
The surface of the image carrier 1110 after the toner image has been transferred is cleaned by a cleaning device 1151 to remove residual toner, paper dust, and the like.

Details of the optical scanning device 1171 are shown in FIG.
In the figure, reference numeral 1 denotes a semiconductor laser as a light source, which is soldered to the substrate 2. Reference numeral 3 is a coupling lens, 5 is a cylindrical lens, 7 is a polygon mirror as a deflecting means (polyhedral mirror deflector), 8 is a scanning lens, 9 is an optical path bending mirror, 10 is a synchronization detecting means, and 11 is a surface to be scanned. , And 12 are apertures.
The synchronization detection means 10 includes a condenser lens 20 and a synchronization detection plate 21.
In the present embodiment, the rotation axis direction of the polygon mirror 7 will be described as the sub-scanning direction, and the sub-scanning direction and the direction orthogonal to the optical axis will be described as the main scanning direction.

The divergent light beam emitted from the semiconductor laser 1 is converted by the coupling lens 3 into a weak convergent light beam, a parallel light beam, or a weak divergent light beam. The beam exiting the coupling lens 3 passes through the aperture 12 for stabilizing the beam diameter on the surface to be scanned, enters the cylindrical lens 5, and is condensed in the sub-scanning direction by the action of the cylindrical lens 5, A line image that is long in the main scanning direction is formed near the deflecting and reflecting surface of the polygon mirror 7.
The light beam from the light source side is emitted to the scanning imaging optical system side of the polygon mirror 7.
The polygon mirror 7 is rotated around the rotation axis in the rotation direction (clockwise direction) shown in the figure by the drive motor 15.
The scanning lens 8 and the optical path bending mirror 9 guide the light beam deflected by the polygon mirror 7 to the photoconductor 11 to form a light spot. In the present embodiment, the polygon mirror 7 is clockwise, and the photoconductor 11 is scanned from the back of the paper toward the front.

Next, the synchronization detection method in this embodiment will be described.
In the present embodiment, synchronization detection is performed using a light beam reflected from the polygon mirror 7 toward the light source. The aperture 12 includes an opening 12a through which a light beam passes, and a frame 12b as an aperture body that holds the opening 12a.
The frame 12b is formed of a high brightness aluminum plate. The light source side (surface) of the aperture 12 is painted in black so as not to reflect the incident beam from the light source side.
If the incident beam is reflected by the aperture 12 toward the light source during optical scanning of the photoconductor 11, there is a problem that the amount of the light beam incident on the photoconductor 11 changes as noise. Further, the polygon mirror 7 side (back surface) of the aperture 12 is not painted, and the light beam from the polygon mirror 7 side is reflected.
That is, the aperture 12 is
The condition is that the reflectance on the light source side is smaller than the reflectance on the polygon mirror side.
The aperture 12 may be formed of a non-reflective member, and a reflective film may be formed on the back side (polygon mirror 7 side) so as to satisfy the above conditions.

The synchronization detection is performed in a state in which the polygon mirror 7 is rotated by 1 ° from the timing of reflection from the polygon mirror 7 to the light source before optical scanning is performed by the scanning lens 8. The synchronous light reflected from the polygon mirror 7 passes through the cylindrical lens 5, is reflected by the outer frame portion of the aperture 12 (the portion on the scanning lens side where the opening 12 a of the frame 12 b does not exist), and is detected synchronously through the condenser lens 20. It reaches the plate 21.
As shown in FIG. 3B, in the shape of the frame 12b of the aperture 12 in the present embodiment, the width in the main scanning direction of the portion corresponding to the synchronization detecting means 10 is large. That is, as compared to the conventional one in which the opening 12a as shown in FIG. It is shifted to one side in the scanning direction and is asymmetric.
In other words, the length of the frame 12b in the aperture 12 in the main scanning direction is increased only on the scanning lens 8 side. As a result, the light beam is reliably reflected to the synchronization detection plate 21.
Accordingly, the aperture 12 can have both a function of shaping the light beam emitted from the light source and a function as a reflection surface of the synchronization detection light.
Further, by shortening the portion of the frame 12b opposite to the scanning lens 8, unnecessary space can be omitted, and the optical scanning device can be miniaturized.

  With the above configuration, since the synchronization detection is performed at a position distant from the scanning lens 8 in terms of layout, the scanning lens 8 and the synchronization detection plate 21 are less likely to interfere with each other even when the scanning field angle is increased. Further, since the incident optical system and the synchronous optical system can be shared up to the aperture 12, the degree of freedom in layout is higher than when a completely independent synchronous optical system is arranged between the incident optical system and the scanning optical system. Miniaturization can be achieved.

In this embodiment, the synchronization detection is performed at the timing when the polygon mirror 7 is rotated toward the scanning lens 8 from the timing at which the light beam returns from the polygon mirror 7 to the light source. .
As described above, since the synchronization detection can be performed at a position away from the scanning lens near the light source, the layout freedom on the scanning start side is increased, so that the scanning lens can have a high angle of view and the writing unit can be made compact. .

A second embodiment will be described based on FIGS. 4 and 5. Note that the same parts as those in the above embodiment are denoted by the same reference numerals, and unless otherwise specified, description of the configuration and functions already described is omitted, and only the main part will be described (the same applies to other embodiments below).
As shown in FIG. 4, in this embodiment, the aperture 12 is arranged to be inclined in the main scanning direction. That is, in the above embodiment, the aperture 12 is disposed substantially parallel to the light source substrate 2, but is disposed at an angle θ in the main scanning direction.
In other words, with respect to a direction perpendicular to the optical axis, the portion corresponding to the synchronization detection unit 10 is disposed so as to be inclined in the main scanning direction so as to be separated from the synchronization detection unit 10.

  By adopting such a configuration, as shown in FIG. 5B, the angle difference between the light beam emitted from the light source 1 and the light beam returned to the aperture 12 and used for synchronization detection becomes large. Therefore, (θ1 <θ2) is facilitated. Further, since the angle difference becomes large, there is an effect that the degree of freedom in layout is increased, such that the synchronization detection plate 21 does not have to be disposed in the vicinity of the cylindrical lens 5.

FIG. 6 shows a third embodiment.
In this embodiment, a surface emitting laser is used as a light source. By using a surface emitting laser as the light source, secondary integration of the light source is easy, and since the number of beams can be increased, high-density and high-speed writing can be performed.
An example of a surface emitting laser is shown in FIG. As shown in FIG. 6 as an example, the light source has a two-dimensional array 100 in which 40 light emitting units are two-dimensionally arranged and formed on one substrate. These 40 light emitting units are arranged at regular intervals when all the light emitting units are orthogonally projected onto a virtual line extending in the sub-scanning corresponding direction (here, the same as the Z-axis direction). The “light emitting portion interval” refers to the distance between the centers of two light emitting portions.

Each light emitting unit is a vertical cavity surface emitting laser having an oscillation wavelength of 780 nm. That is, the two-dimensional array 100 is a surface emitting laser array having 40 light emitting units.
The polarization state of the light beam emitted from each light emitting unit is linearly polarized light, and the polarization direction thereof is parallel to the sub-scanning corresponding direction. Further, the divergence angle (FFP) in a steady state (light output is stable) of the light emitted from each light emitting unit is 7 degrees (deg) in both the main scanning corresponding direction and the sub scanning corresponding direction. .
The light source is arranged so that the light beam is emitted in the + W direction.

DESCRIPTION OF SYMBOLS 1 Semiconductor laser as a light source 7 Polygon mirror as a deflector 10 Synchronous detection means 11 Photoconductor as scanning surface 12 Aperture 12a Frame 100 Surface emitting laser 1171 Optical scanning device P Recording material

Japanese Patent No. 3768840 JP 10-48554 A

Claims (6)

  A light source, an aperture for shaping a light beam from the light source, a deflector having a multi-surface reflecting surface, a scanning optical system for guiding a light beam incident on the deflector and deflected and scanned to the surface to be scanned, and the deflector An optical scanning device comprising: synchronization detection means for performing synchronization detection using a light beam reflected from the aperture to the aperture. The optical scanning device according to claim 1,
The frame shape of the aperture is asymmetric with respect to a line extending substantially perpendicularly from the center of the aperture in the main scanning direction, with the width corresponding to the synchronization detecting means being large in the main scanning direction. An optical scanning device. The optical scanning device according to claim 1 or 2,
The light is characterized in that the aperture is inclined with respect to a main scanning direction so that a portion corresponding to the synchronization detection unit is separated from the synchronization detection unit with respect to a direction perpendicular to the optical axis. Scanning device. In the optical scanning device according to any one of claims 1 to 3,
The reflectance of the aperture frame is different between the front and back,
An optical scanning device characterized in that the reflectance on the light source side <the reflectance on the deflector side. In the optical scanning device according to any one of claims 1 to 4,
An optical scanning device, wherein the light source is a surface emitting laser. An optical scanning device for forming a latent image by irradiating a beam from a light source onto an image carrier that is a surface to be scanned, and developing the latent image formed on the image carrier with a developer, In an image forming apparatus for forming an image by transferring to a recording material directly or via an intermediate transfer member,
An image forming apparatus, wherein the optical scanning device is the optical scanning device according to claim 1.

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