JPH10161051A - Optical scanning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide constitution which can increase the degree of freedom of design of the optical scanning device which is so constituted as to correct a shift in image formation position on a photosensitive surface due to a surface tilt of a rotary mirror. SOLUTION: This an optical scanning device 10 which corrects the shift in the image formation position on the photosensitive surface due to the surface tilt of the rotary mirror 16 by imaging laser light 10 on the rotary mirror 16 and then converging the scanning laser light L2 emitted by it by a scanning condenser lens 33 in a vertical scanning direction; and the condenser lens 33 for synchronization converges signal light L4 for synchronization in the vertical scanning direction and a photodetector 32 detects the signal light L4 for synchronization which is thus converged. Therefore, the shift in the image formation position of the signal light L4 for synchronization due to the surface tilt of the rotary mirror 16 is corrected, so a reflecting mirror 31 for synchronization may be arranged in front of a cylindrical lens 182 (at a light-source side position).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device used for a laser printer or the like. More specifically, the present invention relates to a technique for detecting a synchronization signal light included in a scanning laser beam emitted from a rotating mirror.

[0002]

2. Description of the Related Art In an optical scanning apparatus used in an electrophotographic printing apparatus such as a laser printer or a copying machine, as shown in FIG.
It is called D. ) Is changed into a scanning laser beam L2 in the main scanning direction (the direction indicated by the arrow A) by the rotating mirror 16, and then on the photosensitive surface 221 of the photosensitive drum 22 via the imaging lens system 18. Is to lead to. Here, a collimator lens is provided between the light source 12 and the rotating mirror 16 for the purpose of preventing a shift of the image forming position of the scanning laser beam L2 on the photosensitive surface 221 due to the tilt of the rotating mirror 16. 141 and cylindrical lens 1
The imaging lens system 14 comprising the laser light L0
Is imaged on the reflecting surface 161 of the rotating mirror 16, and then a cylindrical lens 182 included in the imaging lens system 18 is formed.
The scanning laser light L2 is condensed in the sub-scanning direction (the direction indicated by the arrow B) by the (condensing lens for scanning).

[0003] In the optical scanning device configured as described above, a latent image is formed on the photosensitive surface 221 based on the light emitted from the light source 12, and a synchronizing signal for forming the latent image is generated by the light source 1.
2 is included in the emitted light. Therefore, in the conventional optical scanning device, the cylindrical lens 1 of the imaging lens system 18 is used.
The scanning laser light L0 on the photosensitive surface 221 side of
Is provided as a synchronization signal light, and a photodetector is provided for detecting the synchronization signal light reflected from the synchronization reflection mirror, and a synchronization signal is obtained from the detection result of the synchronization signal light. It is configured as follows.

[0004]

However, in the conventional optical scanning device, the signal light for synchronization reflected by the reflection mirror for synchronization is directly detected by the light receiving device.
From the viewpoint of preventing the shift of the imaging position of the signal light for synchronization due to the surface tilt of the lens, there is a design constraint that the reflection mirror for synchronization must be disposed after the cylindrical lens 182. .

Accordingly, an object of the present invention is to solve the above-mentioned problems, and after forming a laser beam on a reflecting surface of a rotating mirror, a scanning laser beam emitted from the rotating mirror is collected for scanning. In an optical scanning device of the type in which the light is condensed in the sub-scanning direction by an optical lens to correct the shift of the image forming position on the photosensitive surface due to the tilting of the rotating mirror, even in the stage preceding the condensing lens for scanning. It is an object of the present invention to provide a configuration in which a reflection mirror for synchronization can be arranged to increase the degree of freedom in design.

[0006]

According to the present invention, there is provided a light source for emitting laser light, a first imaging lens system for imaging the laser light emitted from the light source, and A rotating mirror that uses the laser light imaged by the first imaging lens system as a scanning laser light in the main scanning direction; and a second imaging lens system that forms the scanning laser light on a photosensitive surface. The scanning laser beam emitted from the rotating mirror is condensed in a sub-scanning direction by a scanning condenser lens included in the second imaging lens system, and the scanning laser beam emitted from the rotating mirror is tilted. In an optical scanning device that corrects a shift of an image-forming position on a surface, of the scanning laser light at a position closer to the light source than the condensing lens for scanning, in an intermediate position of an optical path from the rotating mirror to the photosensitive surface. Synchronization signal light included in specified direction A reflecting mirror for synchronization that reflects, and an image forming position of the synchronizing signal light caused by the tilting of the rotating mirror by condensing the synchronizing signal light reflected from the reflecting mirror in the sub-scanning direction. And a light receiver for detecting the signal light for synchronization collected by the focusing lens for synchronization.

In the specification of the present application, terms indicating the position and direction, such as the light source side, define the position and direction from the optical surface, and do not necessarily mean the structural position and direction.

In the present invention, after a laser beam is imaged on the reflection surface of the rotating mirror, the scanning laser beam emitted from the rotating mirror is condensed in the sub-scanning direction by a condensing lens for scanning, and the rotating mirror is rotated. Optical scanning device of the type that corrects the shift of the imaging position on the photosensitive surface due to the surface tilt of
The synchronizing condensing lens condenses the synchronizing signal light in the sub-scanning direction, and the light receiver detects the condensing synchronizing signal light. Therefore, even if the reflecting mirror for synchronization is not disposed after the condensing lens for scanning, it is possible to correct the shift of the imaging position of the signal light for synchronization due to the surface tilt of the rotating mirror. There is no hindrance for the photodetector to detect the synchronization signal light even if the surface falls. Therefore, at a position on the optical path from the rotating mirror to the photosensitive surface, the reflection mirror for synchronization can be arranged even before the scanning condenser lens (position on the light source side), so that the degree of freedom in design is high.

In the present invention, the synchronizing reflection mirror may include the synchronizing signal light included in the scanning laser light between the fθ lens included in the second imaging lens system and the scanning condenser lens. Is preferably reflected.

With this configuration, the synchronizing converging lens condenses the synchronizing signal light reflected from the synchronizing reflection mirror in the sub-scanning direction and causes the synchronizing signal light to fall due to the tilt of the rotating mirror. The one having an axisymmetric aspheric surface for correcting the deviation of the image forming position of the synchronization signal light can be used.

In the present invention, it is preferable that the image forming position on the rotating mirror and the light receiving position on the photodetector have a conjugate relationship. With this configuration, the synchronization signal light imaged in the form of a spot is detected by the light receiver, so that there is an advantage that the detection accuracy is high.

[0012]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view showing a schematic configuration of an optical scanning device to which the present invention is applied. In FIG. 1, an optical scanning device 10 is for a laser printer, and includes a light source 12 (LD) for emitting a laser beam L0 and a photosensitive drum 22. The optical scanning device 10 includes a first imaging lens system 14 and a rotating mirror 16 on an optical path from the light source 12 to the photosensitive drum 22.
(Polygon mirror), second imaging lens system 1 for forming an image on photosensitive drum 22 by fθ lens 181 and cylindrical lens 182 (condensing lens for scanning).
8, and the reflection mirror 20 are arranged in this order.
Here, the light source 12, the first imaging lens system 14, the rotating mirror 16, the second imaging lens system 18, and the reflection mirror 2
Numeral 0 is disposed substantially on the same plane as a whole, and the photosensitive drum 22 is disposed below the reflection mirror 20. As described above, the optical scanning device 10 has a configuration suitable for a small laser printer or the like because the optical components are three-dimensionally arranged.

In the optical scanning device 10, an LD which is a light source 12
From the laser light L0, and the laser light L0
To the imaging lens system 14. First imaging lens system 1
Reference numeral 4 denotes a collimator lens 141 and a cylindrical lens 142. After the collimator lens 141 converts the laser light L0 into a parallel light beam, the cylindrical lens 1
Reference numeral 42 forms an image of the laser beam L0 on the reflection surface 161 of the rotating mirror 16.

The rotating mirror 16 has six reflecting surfaces 161 and rotates around a rotation center axis 162. Accordingly, the rotating mirror 16 emits the laser light L0 formed on the reflection surface 161 as a scanning laser light L2 in the main scanning direction (the direction indicated by the arrow A). Here, the scanning laser light L2 is guided to the photosensitive surface 221 of the photosensitive drum 22 via the second imaging lens system 18 and the reflecting mirror 20, but the reflecting surface 161 of the rotating mirror 16 and the photosensitive surface 221 of the photosensitive drum 22 Are configured to have an optically conjugate relationship. Therefore, the scanning laser beam L2 is scanned in the main scanning direction indicated by the arrow A while forming an image in the form of a spot on the photosensitive surface 221 of the photosensitive drum 22. Further, even when the so-called tilting of the rotating mirror 16 occurs, the cylindrical lens 182 condenses the scanning laser beam L2 in the sub-scanning direction (the direction indicated by the arrow B), and the photosensitive surface caused by the tilting of the rotating mirror 16 The shift in the sub-scanning direction of the imaging position on the image 221 is corrected.

In the optical scanning device 10 configured as described above,
While scanning in the main scanning direction with the laser light imaged in the form of a spot on the photosensitive surface 221, the scanning position is moved to the photosensitive surface 221.
On the top, they are relatively shifted at a constant pitch in the sub-scanning direction. As a result, a latent image is formed on the photosensitive surface 221. In forming the latent image in this manner, the control of the feeding operation is performed by controlling the synchronization operation included in the scanning laser beam L2 at a timing such that the scanning laser beam L2 passes through the end portion of the scanning area. This is performed based on the detection result of the signal light.

For example, in the optical system of the optical scanning device 10 shown in FIG. 2, of the scanning laser beam L2 emitted from the rotating mirror 16, both ends of the scanning area of the laser beam reaching the photosensitive surface 221 are indicated by alternate long and short dash lines C1. , C2,
Further, the synchronization signal light L4 passes through a region between the one-dot chain line C2 and the one-dot chain line C3 shown on the side. Therefore, if the synchronization signal light L4 is detected and used as a laser beam for position detection in the sub-scanning direction, a latent image can be formed without deviation in synchronization of the scanning lines in the main scanning direction. In the optical system shown in FIG. 2, a reflection mirror 19 is provided on the optical path from the fθ lens 181 to the cylindrical lens 182.
1 and 192 are disposed, and these reflection mirrors 1
Numerals 91 and 192 deviate the optical path of the scanning laser light L0 reaching the photosensitive surface 221 in an out-of-plane direction toward FIG. 2, and this optical system is also substantially represented as shown in FIG.

In the optical system thus configured, a synchronization signal light detection system 30 for detecting the synchronization signal light L4.
Then, the synchronization signal light L4 is extracted from the scanning laser light L2 by using the synchronization reflection mirror 31 disposed at the position corresponding to the end portion (between the dashed lines C2 and C3) in the scanning region of the laser light. I do. Here, the synchronization reflection mirror 31
Is disposed at an intermediate position in the optical path from the rotating mirror 16 to the photosensitive surface 221. In the present embodiment, the last stage cylindrical lens included in the second imaging lens system 18 is required due to the requirement of a design surface such as miniaturization. 182, a light source side position, for example, fθ lens 181 and cylindrical lens 182
The synchronization reflection mirror 31 reflects the synchronization signal light L4 included in the scanning laser light L2 in a direction crossing the scanning region of the laser light.

The synchronization signal light detection system 30 includes a photodetector 32 at a position facing the synchronization reflection mirror 31 across the scanning region of the laser light in the direction in which the synchronization signal light L4 is reflected. Are arranged, and the signal light L4 for synchronization is detected by the light receiver 32. Here, the synchronization reflection mirror 31 reflects the synchronization signal light L4 in a direction crossing the scanning region of the laser beam, and the light receiver 32 detects the synchronization signal light L4 on the opposite side of the scanning region.

Further, the synchronizing signal light detection system 30 converges the synchronizing signal light L4 reflected from the synchronizing reflection mirror 31 in the sub-scanning direction at the preceding stage of the light receiver 32, and troubles the rotary mirror 16. A synchronizing condensing lens 33 that corrects the shift of the image forming position of the synchronizing signal light L4 due to this is disposed. That is, as shown in FIG. 3, the synchronizing condensing lens 33 is a lens having an axisymmetric aspheric surface R1 and an axisymmetric spherical surface R2. Of the imaging position of the synchronizing signal light L4 due to the tilt of the surface. Therefore, the light receiver 32 detects the synchronization signal light L4 condensed by the synchronization condenser lens 33. That is, unlike the scanning laser light L0 that reaches the photosensitive surface 221, the synchronization signal light L4 passes through the synchronization condenser lens 33 instead of passing through the cylindrical lens 182, so that the tilt of the rotating mirror 16 is corrected. Receiver 3 after being focused
2 is detected.

As described above, the optical scanning device 10 according to the present embodiment
Then, on the reflection surface 161 of the rotating mirror 16, the laser light L0
Is formed, the scanning laser beam L2 emitted from the rotating mirror 16 is condensed in the sub-scanning direction by the cylindrical lens 182, and the image forming position on the photosensitive surface 221 due to the tilt of the rotating mirror 16 is formed. And the synchronizing condenser lens 33 condenses the synchronizing signal light L4 in the sub-scanning direction, and the condensing synchronizing signal light L4
Is detected by the light receiver 32. Therefore, the reflecting mirror for synchronization 3
1 is not disposed downstream of the cylindrical lens 182, the synchronization signal light L
4 can be corrected. Therefore,
Even if the rotating mirror 16 is tilted, there is no problem in that the light receiver 32 normally detects the synchronization signal light L4. Therefore, the synchronization reflection mirror 31 can be disposed at a position before the cylindrical lens 182 (position on the light source side) at an intermediate position of the optical path from the rotating mirror 16 to the photosensitive surface 221, so that the degree of design freedom is high.

[0022]

As described above, according to the present invention, after forming a laser beam on the reflection surface of the rotating mirror, the scanning laser beam emitted from the rotating mirror is sub-scanned by the scanning condenser lens. In an optical scanning device that corrects the imaging position on the photosensitive surface due to the tilting of the rotating mirror by focusing in the direction, the focusing lens for synchronization focuses the signal light for synchronization in the sub-scanning direction. It is characterized in that the photodetector detects light and the signal light for synchronization collected in this way. Therefore,
According to the present invention, it is possible to correct the deviation of the imaging position of the signal light for synchronization due to the surface tilt of the rotating mirror without disposing the reflection mirror for synchronization at the subsequent stage of the condensing lens for scanning. Even if the rotating mirror is tilted, there is no hindrance for the light receiver to detect the synchronization signal light. Therefore, the degree of freedom in design is high, for example, the reflection mirror for synchronization can be arranged even before the scanning condenser lens (position on the light source side).

[Brief description of the drawings]

FIG. 1 is a perspective view showing a schematic configuration of an optical scanning device for a laser printer.

FIG. 2 is a plan view showing the arrangement of a reflection mirror for synchronization, a condenser lens for synchronization, and a light receiver for detecting the signal light for synchronization in the optical scanning device for a laser printer according to the embodiment of the present invention; FIG.

FIG. 3 is a sectional view of a synchronizing condenser lens used in the optical scanning device shown in FIG. 2;

[Explanation of symbols]

 Reference Signs List 10 optical scanning device 12 light source 14 first imaging lens system 141 collimator lens 142 cylindrical lens 16 rotating mirror 161 reflecting surface 18 second imaging lens system 181 fθ lens 182 cylindrical lens (condensing lens for scanning) 20 reflecting mirror Reference Signs List 22 photosensitive drum 221 photosensitive surface 30 signal light detection system for synchronization 31 reflection mirror for synchronization 32 light receiver 33 focusing mirror for synchronization L0 laser light L2 scanning laser light L4 synchronization signal light R1 axisymmetric aspherical surface

Claims (4)

[Claims] 1. A light source for emitting laser light, a first imaging lens system that forms an image of the laser light emitted from the light source, and a laser light that is imaged by the first imaging lens system. A rotating mirror for scanning laser light in the main scanning direction, and a second imaging lens system for forming an image of the scanning laser light on a photosensitive surface, and a scanning lens included in the second imaging lens system. An optical scanning device that condenses the scanning laser beam emitted from the rotating mirror in a sub-scanning direction by a condenser lens and corrects a shift of an image forming position on the photosensitive surface due to a tilt of the rotating mirror; A synchronization reflection for reflecting a synchronization signal light included in the scanning laser light in a predetermined direction at a position closer to a light source than the scanning condenser lens, in a middle position of an optical path from the rotating mirror to the photosensitive surface. A mirror and the reflecting mirror for synchronization A synchronizing condensing lens that converges the reflected synchronizing signal light in the sub-scanning direction and corrects a shift in an imaging position of the synchronizing signal light caused by a surface tilt of the rotating mirror; A light receiver for detecting the synchronization signal light condensed by the light condensing lens. 2. The synchronization reflection mirror according to claim 1, wherein the synchronization reflection mirror includes the scanning laser light between an fθ lens included in the second imaging lens system and the scanning condenser lens. An optical scanning device, which reflects signal light for use. 3. The synchronizing condensing lens according to claim 1, wherein the synchronizing condensing lens condenses the synchronizing signal light reflected from the synchronizing reflection mirror in a sub-scanning direction and tilts the rotating mirror. An optical scanning device having an axisymmetric aspheric surface for correcting a shift of an image forming position of the synchronization signal light caused by the above. 4. The method according to claim 1, wherein
An optical scanning device, wherein an image forming position on the rotating mirror and a light receiving position on the photodetector have a conjugate relationship.