JP2009271426A - Optical scanning apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a more reliable optical scanning apparatus in which an erroneous detection of a synchronization signal is prevented by configuring the optical scanning apparatus such that a luminous flux from a light source which does not take the synchronization signal does not reach a photodetector for detecting the synchronization signal. <P>SOLUTION: The optical scanning apparatus includes: light source units 35K and 35M which are arranged in parallel in subscanning direction and emit laser light so as to be made incident on a same reflection face 22 of a rotating polygon mirror 21 at different angles with respect to the subscanning direction; a light receiving sensor 34 to which BD light 3'M which is deflected with the rotating polygon mirror 21 is condensed via a condenser lens 39, wherein when a photoreceptor is scanned with the laser light, the writing positions of the light source units 35K and 35M are controlled on the basis of the light signal received by the light receiving sensor 34, wherein a light shield member 36 is provided to shield the light receiving sensor 34 from non-BD light 3'K deflected with the rotating polygon mirror 21. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical scanning device used in an image forming apparatus such as a copying machine or a laser beam printer.

  2. Description of the Related Art Conventionally, an optical scanning device employing a so-called synchronous detection optical system (BD optical system) for determining a writing position of a scanning light beam in a main scanning direction on a photosensitive drum as an image carrier is known (for example, Patent Documents). 1).

  In the optical scanning device of Patent Document 1, a light beam emitted from one light source among a plurality of light sources is deflected and scanned by a deflector, and the light beam subjected to the deflection scan is received for synchronization detection via an imaging lens. It is comprised so that it may lead to an element. The other light sources (light sources that do not employ the BD optical system) are driven by delaying a relative time difference from the one light source (light source that employs the BD optical system). By omitting the BD optical system in this way, the entire apparatus can be configured easily.

Further, in the optical scanning device of Patent Document 1, a plurality of light sources includes two light sources arranged in parallel in the sub-scanning direction, and light beams emitted from the two light sources arranged in parallel in the sub-scanning direction are deflected. It is configured so that it is incident obliquely on the same reflecting surface of the vessel.
JP 2004-205640 A

  However, in the oblique incidence type optical scanning device as described above, a plurality of lasers from a plurality of light source means are required until the laser light deflected by the deflector reaches the synchronization detecting light receiving element from the deflector. The method of separating light becomes a problem.

  In other words, a sufficient separation distance in the sub-scanning direction is ensured between the laser light of the light source that takes the synchronization signal (light source that employs the BD optical system) and the laser light of the light source that does not take the synchronization signal (light source that does not employ the BD optical system). Difficult to do.

  For this reason, the laser light from the light source means that does not take the synchronization signal and the scattered light generated by the reflection of the laser light on the wall of the optical box or the optical component are incident on the light receiving element for synchronization detection, and erroneous detection is detected in synchronization detection There is concern about the generation.

  If erroneous detection of synchronization detection occurs, for example, the output position of the output image of the image forming apparatus may be printed out of the normal position, or rotation control of the deflector may be disabled.

  The present invention has been made in view of the circumstances as described above, and it is possible to prevent erroneous detection of a synchronization signal by configuring so that a light beam of a light source that does not take a synchronization signal does not reach a light receiving element for synchronization detection. An object of the present invention is to provide an optical scanning device with higher reliability.

In order to achieve the above object, the present invention provides:
A deflector having a reflecting surface for deflecting the light beam;
A first light source and a second light source, which are arranged in parallel in the sub-scanning direction and respectively emit a first light beam and a second light beam toward the deflector, wherein the first light beam and the second light beam are the deflector. A first light source and a second light source provided to be incident on the same reflecting surface at different angles with respect to the sub-scanning direction;
A light receiving sensor for condensing the first light flux deflected by the deflector via a condenser lens;
When the first light beam and the second light beam corresponding to the first light source and the second light source respectively scan the first light beam and the second light beam, the light received by the light receiving sensor. Control means for controlling a writing position of the first light source and the second light source based on a signal;
In an optical scanning device comprising:
A light shielding member is provided to block the second light beam deflected by the deflector from entering the light receiving sensor.

  According to the present invention, it is possible to provide a more reliable optical scanning device that can prevent erroneous detection of a synchronization signal.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed according to the configuration of the apparatus to which the invention is applied and various conditions. It is not intended to limit the scope to the following embodiments.

  The present invention relates to an image forming apparatus such as a laser beam printer or a digital copying machine using a semiconductor laser as a light source of an optical scanning device, and more particularly to prevention of erroneous detection of a synchronization signal.

  Example 1 will be described below.

(Description of image forming apparatus)
FIG. 2 is a schematic sectional view showing the color image forming apparatus 15 of the present embodiment.

  In the figure, reference numerals 16a and 16b denote first and second optical scanning devices each having a configuration to be described later, and are optical scanning devices having approximately the same configuration.

  In the present embodiment, the laser beams 3C, 3Y, 3M, and 3K that are respectively light-modulated based on the image information are emitted from the optical scanning devices 16a and 16b, and the corresponding photoreceptors 1C and 1Y as image carriers. , 1M, and 1K surfaces are irradiated to form a latent image. Here, the photoconductor 1M constitutes a first image carrier, and the photoconductor 1K constitutes a second image carrier. The laser beam 3M constitutes a first light beam, and the laser light 3K constitutes a second light beam.

  The latent images are formed on the photoreceptors 1C, 1Y, 1M, and 1K, which are uniformly charged by the primary chargers 2C, 2Y, 2M, and 2K, respectively, and the developing devices 4C, 4Y, 4M, and 4K. Are visualized as developer images of cyan, yellow, magenta, and black, respectively. The visualized developer image is sequentially transferred onto the recording material 8 conveyed on the transfer belt 7 by the transfer rollers 5C, 5Y, 5M, and 5K, thereby forming a color image. .

  The recording material 8 is stacked on a feeding tray 9, and is fed one by one by a feeding roller 10, and is fed onto a transfer belt 7 by a registration roller 11 in synchronization with image writing timing.

  A cyan image, a yellow image, a magenta image, and a black image formed on the photoreceptors 1C, 1Y, 1M, and 1K surfaces while being accurately conveyed on the transfer belt 7 are sequentially formed on the recording material 8. The image is transferred to form a color image. The drive roller 12 feeds the transfer belt 7 with high accuracy and is connected to a drive motor (not shown) with little rotation unevenness.

  The color image formed on the recording material 8 is heat-fixed by the fixing device 13 and then conveyed by the discharge roller 14 and outputted outside the apparatus.

(Description of optical scanning device)
FIG. 1 is a schematic perspective view for explaining an internal configuration of an optical scanning device 16b (same configuration as 16a) of the present embodiment. FIG. 3 is a schematic cross-sectional view for explaining the optical path (incident optical system) until the light beam emitted from the light source reaches the rotary polygon mirror 21 as a deflector in the optical scanning device of the present embodiment.

  In the following description, the direction in which the light beam is deflected and scanned by the rotating polygon mirror 21 is referred to as a main scanning direction, which is a direction substantially orthogonal to the main scanning direction and substantially parallel to the rotation axis of the rotating polygon mirror 21. This direction is called the sub-scanning direction.

  Laser light 3 (3K, 3M) emitted from the semiconductor lasers 30K, 30M (see FIG. 3) is transmitted through the collimator lenses 31K, 31M (see FIGS. 3, 5) and the cylindrical lens 32, and then the same in the rotating polygon mirror 21. The light is condensed on the reflection surface 22. Here, the semiconductor lasers 30K and 30M are arranged in parallel in the sub-scanning direction (vertical direction in FIG. 3).

  The rotary polygon mirror 21 is rotationally driven at high speed by the scanner motor 23 and deflects the incident laser beams 3K and 3M in the same direction.

  The deflected laser beam 3K passes through the first fθ lens 20, is reflected by the reflection mirror 25, passes through the second fθ lens 24K, and is condensed and scanned on the photoreceptor 1K (see FIG. 2) by the reflection mirror 26. As a result, an electrostatic latent image is formed. The deflected laser light 3M passes through the first fθ lens 20, passes through the second fθ lens 24M, is reflected by the reflection mirror 27, and is condensed and scanned on the photoreceptor 1M (see FIG. 2). Thus, an electrostatic latent image is formed.

  Optical components such as the rotary polygon mirror 21, the scanner motor 23, the reflection mirrors 25, 26 and 27, and the fθ lenses 20 and 24 described above are contained in an optical box 29 made of resin.

  As shown in FIG. 3, light source devices 35 </ b> K and 35 </ b> M arranged in the sub-scanning direction are used as the laser light incident optical system to the rotary polygon mirror 21. Here, the light source device 35M corresponds to a first light source, and the light source device 35K corresponds to a second light source.

  The light source devices 35K and 35M convert the laser beams 3K and 3M emitted from the semiconductor lasers 30K and 30M into substantially parallel beams by the collimator lenses 31K and 31M, and are applied to the same reflecting surface 22 of the rotary polygon mirror 21 in the sub-scanning direction. The incident light is incident at different angles. That is, as shown in FIG. 3, the light source devices 35K and 35M are incident on the same reflection surface 22 at an angle ± θ with respect to the direction O orthogonal to the same reflection surface 22 of the rotary polygon mirror 21 in the sub-scanning direction. In addition, laser beams 3K and 3M are emitted.

The laser light is emitted from the light source devices 35K and 35M toward the same reflecting surface 22 at different angles with respect to the sub-scanning direction, so that the following configuration is possible. That is, the light source devices 35K and 35M irradiate a laser beam on a position close to the same reflecting surface 22 of the rotary polygon mirror 21, and further separate the deflected laser beam so as to be guided to the corresponding photoreceptor. Can be configured.

  In addition, there is a concern that the increase in the oblique incident angle θ may increase the degree that the position error (exit / exit of the surface) of the reflecting surface leads to the amount of image formation position deviation on the photosensitive member. For this reason, in this embodiment, the angle θ is set to 3 degrees or less.

  Note that the upper opening of the optical box 29 of this embodiment is closed by the cover member 19 as shown in FIG.

(Description of synchronization detection optical system)
Next, the synchronization detection optical system (BD (beam detector) optical system) will be described with reference to FIGS.

  FIG. 4 is a schematic perspective view for explaining the configuration of the synchronization detection optical system of the present embodiment. FIG. 5 is a schematic perspective view showing a state in which the optical scanning device is cut in the sub-scanning direction in order to explain the synchronization detection optical system of the present embodiment.

  Among the laser beams 3 ′ (3′K, 3′M) reflected by the rotating polygon mirror 21, the laser beam 3′M is a condensing lens disposed between the rotating polygon mirror 21 and the light receiving sensor. It is guided to the light receiving sensor 34 via 39. Here, the light receiving sensor 34 is a light receiving element for synchronization detection, and a condenser lens (hereinafter referred to as BD lens) 39 is an imaging member for synchronization detection. The laser light reflected by the rotary polygon mirror 21 and guided to the light receiving sensor 34 for synchronization detection is hereinafter referred to as BD light 3'M.

  Then, when the laser beams 3K and 3M are scanned onto the photoconductors 1K and 1M by the light source devices 35K and 35M, the control means provided in the optical scanning device 16b is based on the signal of the light received by the light receiving sensor 34. The writing positions of the light source devices 35K and 35M are controlled. As a result, the writing position in the main scanning direction of the image by the laser light on the photosensitive member can always be matched, and the writing position in the output image of the image forming apparatus can always be matched.

  Here, in the optical scanning device 16b of the present embodiment, the synchronization detection optical system is provided only for the light source device 35M. In the other light source device 35K, a method of driving by delaying a relative time difference from the light source device 35M by the control means of the optical scanning device 16b is employed.

  Thus, the BD light 3'M forms a synchronization detection optical system that determines the writing timing of the scanning light beam that is scanned in the main scanning direction on the photoconductors 1K and 1M.

(About shading member)
As shown in FIGS. 4 and 5, laser light (hereinafter referred to as non-BD light) 3′K emitted from the light source device 35 </ b> K that does not include the synchronization detection optical system and reflected by the rotary polygon mirror 21 is scattered by the BD lens 39. There is concern over the generation of light 103K.

  Therefore, in the present embodiment, a light shielding member 36 that blocks the scattered light 103K is provided between the rotary polygon mirror 21 and the light receiving sensor 34. By blocking the scattered light 103K by such a light shielding member 36, it is possible to prevent the scattered light 103K from reaching the light receiving sensor 34.

  As described above, according to this embodiment, it is possible to prevent erroneous detection of a synchronization signal due to the non-BD light 3′K entering the light receiving sensor 34 for synchronization detection, and a more reliable optical system. A scanning device and an image forming apparatus can be provided.

  Here, in the light blocking member 36 of the present embodiment, the target to be blocked is not limited to the scattered light 103K generated by the BD lens 39, but stray light generated by a wall or the like provided inside the optical box 29. It may be. In addition, one or more light shielding members 36 may be disposed so as to be optimized at positions where stray light other than the BD light 3'M can be prevented from entering the light receiving sensor 34.

  Next, Example 2 will be described with reference to FIGS.

  FIG. 6 is a schematic perspective view for explaining the configuration of the synchronization detection optical system of the present embodiment. FIG. 7 is a schematic perspective view showing a state in which the optical scanning device is cut in the sub-scanning direction in order to explain the synchronization detection optical system of the present embodiment. In the present embodiment, the different components from the first embodiment will be described, and the description of the same components as those in the first embodiment will be omitted.

  In this embodiment, the light blocking member 37 that blocks the non-BD light 3 ′ K of the light source device 35 </ b> K that does not include the synchronization detection optical system is disposed between the rotary polygon mirror 21 and the BD lens 39. Here, it is more preferable that the light shielding member 37 is disposed in the vicinity of the BD lens 39 among the rotary polygon mirror 21 and the BD lens 39.

  The light blocking member 37 arranged in this way can prevent the non-BD light 3 ′ K from entering the BD lens 39. Therefore, the possibility of generating scattered light (corresponding to the scattered light 103K shown in FIG. 5) by the BD lens 39 can be eliminated, and erroneous detection of synchronous detection due to the scattered light can be prevented.

  Here, as described above, when the oblique incident angle ± θ (see FIG. 3) of the laser beam to the rotary polygon mirror 21 is set to be approximately ± 3 degrees or less, the BD light 3′M and the non-BD light 3 There is a case where it is difficult to separate each other's rays because the ray distance with 'K is close.

  However, in this embodiment, a light shielding member 37 is provided in the vicinity of the BD lens 39 as a place where a sufficient separation distance (separation distance) L between the BD light 3′M and the non-BD light 3′K can be secured. Therefore, the non-BD light 3′K can be shielded more reliably. Further, even when the arrangement accuracy and component accuracy of the light shielding member 37 are loosened, or even when the height of the BD light 3′M is shifted due to environmental fluctuations, etc., the BD light 3′M is blocked by the light shielding member 37. Can be prevented.

  The light blocking member 37 has an inclination θ ′ with respect to the optical axis of the non-BD light 3′M. Thus, after the non-BD light 3′K is reflected by the light shielding member 37, it reaches the image region via the rotary polygon mirror 21, the imaging lens (the fθ lens (see FIG. 1) described above), and the like. Can be prevented.

  As described above, according to this embodiment, it is possible to provide an inexpensive and more reliable optical scanning device and image forming apparatus.

  Here, the light blocking member 37 may be provided integrally with the optical box 29, but is not limited thereto. This will be described below.

  8 and 9 are schematic perspective views showing modifications of the light shielding member.

  That is, the light blocking member 37 may be provided integrally with the BD lens 39 (see FIG. 8). Further, a sheet metal member 38 may be applied as a light shielding member, and the sheet metal member 38 may be fixed to the optical box 29 by an arbitrary fixing means 40 such as a screw or an adhesive (see FIG. 9). In the case where the light blocking member 37 is provided integrally with the BD lens 39, the light blocking member 37 may be formed by two-color molding or the like so that the light blocking member 37 is formed of a member that does not transmit the non-BD light 3'K.

  Furthermore, it is preferable that the size of the BD lens 39 is set to be small enough to prevent non-BD light from entering the BD lens 39.

1 is a schematic perspective view showing an optical scanning device of Example 1. FIG. FIG. 2 is a schematic cross-sectional view illustrating a color image forming apparatus using the optical scanning device according to the first embodiment. FIG. 3 is a schematic cross-sectional view illustrating an incident optical system of the optical scanning device according to the first embodiment. FIG. 3 is a schematic perspective view illustrating a synchronization detection optical system of the optical scanning device according to the first embodiment. FIG. 3 is a schematic perspective view illustrating a state in which the optical scanning device is cut in the sub-scanning direction in order to explain the synchronization detection optical system according to the first embodiment. FIG. 6 is a schematic perspective view illustrating a synchronization detection optical system of an optical scanning device according to a second embodiment. FIG. 9 is a schematic perspective view illustrating a state in which the optical scanning device is cut in the sub-scanning direction in order to explain the synchronization detection optical system according to the second embodiment. The schematic perspective view which shows the modification of a light shielding member. The schematic perspective view which shows the modification of a light shielding member.

Explanation of symbols

1K, 1M Photoconductor 3K, 3M Laser light 3′K, 3′M Laser light reflected by rotating polygon mirror 21 Rotating polygon mirror 22 Same reflecting surface 34 Light receiving sensor 35K, 35M Light source device 36 Light shielding member 39 Condensing lens

Claims (2)

A deflector having a reflecting surface for deflecting the light beam;
A first light source and a second light source, which are arranged in parallel in the sub-scanning direction and respectively emit a first light beam and a second light beam toward the deflector, wherein the first light beam and the second light beam are the deflector. A first light source and a second light source provided to be incident on the same reflecting surface at different angles with respect to the sub-scanning direction;
A light receiving sensor for condensing the first light flux deflected by the deflector via a condenser lens;
By the light received by the light receiving sensor when the first light beam and the second light beam are scanned on the first image carrier and the second image carrier respectively corresponding to the first light source and the second light source. Control means for controlling a writing position of the first light source and the second light source based on a signal;
In an optical scanning device comprising:
An optical scanning device characterized in that a light shielding member is provided to block the second light beam deflected by the deflector from entering the light receiving sensor.   The optical scanning device according to claim 1, wherein the light shielding member is provided between the deflector and the condenser lens.

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