JPH06281875A - Optical device for laser beam scanning - Google Patents

Abstract

PURPOSE:To provide an optical device for laser beam scanning capable of easily ascertaining the optical path of a laser beam deflected toward a photodetector. CONSTITUTION:An SOS sensor 8 is composed of a photodiode 13 and a transparent resin molding package 14 and mounted on a substrate 17. The substrate 17 is mounted into the mounting hole 15 of a unit case 11 while the SOS sensor 8 is located on the inner side of the substrate. An opening part 16, through which a laser beam transmitted through the transparent resin molding package 14 of the SOS sensor 8 is made to transmit, is provided on the substrate 17. By inserting proper paper P into the opening part 16, the optical path of the laser beam made incident on the SOS sensor 8 is traced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser beam scanning optical device, and more particularly, to a laser beam scanning optical device incorporated in a laser beam printer, a facsimile or the like, and provided with a light receiving element for detecting the image writing start position by the laser beam. Regarding

[0002]

2. Description of the Related Art Conventionally, a laser beam scanning optical device for forming an image of a laser beam generated from a light source such as a laser diode on a photosensitive drum via a deflector and an image forming optical system has an image writing start position. A light receiving element for detecting is detected. The light receiving element receives the laser beam deflected by the deflector. The output signal of the light receiving element that receives the laser beam is used as a horizontal synchronizing signal that determines the image writing start position.

By the way, generally, the optical path of the laser beam incident on the light receiving element is confirmed by visually observing the light receiving element from the laser beam incident side of the light receiving element.

[0004]

However, depending on the arrangement of the components such as the deflector and the imaging optical system that form the optical unit of the laser beam scanning optical device, and the shape of the unit case that accommodates these components, the light receiving element may be different. It may be difficult to view the light receiving element from the laser beam incident side.

Therefore, it is an object of the present invention to provide a laser beam scanning optical device capable of easily confirming the optical path of a laser beam deflected toward a light receiving element.

[0006]

In order to solve the above problems, the present invention provides a laser beam scanning optical device for deflecting a laser beam modulated according to image information by a deflector to form an image on a photosensitive member. A light receiving element for detecting an image writing start position that receives the laser beam deflected by the deflector, and is incident in the vicinity of the light receiving element so that the optical path of the laser beam deflected toward the light receiving element can be confirmed. The laser beam is emitted to the back of the light receiving element.

[0007]

According to the above construction, the laser beam modulated according to the image information is deflected by the deflector and imaged on the photoconductor. The light receiving element for detecting the image writing start position receives the laser beam deflected by the deflector. Since the laser beam incident near the light receiving element is emitted behind the light receiving element, the optical path of the laser beam deflected toward the light receiving element can be confirmed.

[0008]

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

FIG. 1 is a plan view showing the structure of a laser beam scanning optical device. 2 to 4 are a perspective view, a plan view, and a side sectional view of a main part of the laser beam scanning optical device, respectively.

The optical unit 100 includes a light source assembly 1 incorporating a laser diode light source and a collimator lens, a cylindrical lens 2, a polygon mirror 3, a toroidal lens 4, an fθ mirror 5, an SOS sensor 8, S.
Reflection mirror 6 for guiding the laser beam to the OS sensor 8
And a condenser lens 7 provided immediately before the SOS sensor 8 and these are housed in a unit case 11.

The SOS sensor 8 receives a laser beam and outputs an electric signal, and is composed of a photodiode 13 as a light receiving element and a transparent resin mold package 14 holding the photodiode 13. This transparent resin mold package 14 is the substrate 1
It is mounted on 7. In the unit case 11,
A mounting hole 15 for mounting the substrate 17 with the SOS sensor 8 inside is provided. The board 17 is
The SOS sensor 8 is inserted into the attachment hole 15 and is attached from the outside of the unit case 11. The substrate 17 is provided with an opening 16 for emitting the laser beam incident on the transparent resin mold package 14 of the SOS sensor 8 to the outside of the unit case 11. The condenser lens 7 has a hemispherical shape, and its focal length is set so that the laser beam is condensed behind the SOS sensor 8.

The laser diode light source is modulation-controlled based on image information input to a control unit (not shown), and a laser beam is emitted from the light source assembly 1 when turned on. This laser beam is converted into a convergent light beam by a collimator lens in the light source assembly 1 at a backward finite position. The laser beam emitted from the light source assembly 1 has its spot shape changed by the cylindrical lens 2 into a substantially linear shape whose longitudinal direction is parallel to the main scanning direction, and reaches the polygon mirror 3. The main scanning direction is the direction in which the laser beam is scanned by the rotation of the polygon mirror 3. The polygon mirror 3 is rotated by a motor (not shown) about the rotary shaft 12 in the direction of the arrow at a constant speed. Based on the rotation of the polygon mirror 3, the laser beam is deflected at a constant angular velocity within a plane perpendicular to the rotation axis 12 and is guided to the toroidal lens 4. The toroidal lens 4 has an entrance surface and an exit surface formed concentrically in the main scanning direction, has a constant power in the direction perpendicular to the deflecting surface, and corrects surface tilt of the polygon mirror 3 in combination with the cylindrical lens 2. . Further, the laser beam is reflected by the fθ mirror 5, passes through the slit 9 formed on the bottom surface of the unit case 11, and reaches a photosensitive drum (not shown). Image formation on the photosensitive drum is performed by main scanning by rotation of the polygon mirror 3 and sub-scanning by rotation of the photosensitive drum. fθ
The mirror 5 is fθ for correcting the main scanning speed of the laser beam.
In addition to having a function (distortion correction), it has a function of correcting the field curvature on the photosensitive drum.

On the other hand, of the laser beams that have passed through the toroidal lens 4, the laser beam reflected by the reflection mirror 6 enters the SOS sensor 8 via the condenser lens 7. The output signal of the photodiode 13 of the SOS sensor 8 that receives the laser beam is used as a horizontal synchronizing signal that determines the image writing start position.

On the other hand, the laser beam incident on the transparent resin mold package 14 of the SOS sensor 8 passes through the transparent resin mold package 14 and is emitted from the opening 16 of the substrate 17 to the outside of the unit case 11. The laser beam emitted to the outside of the unit case 11 is
The transparent resin mold package 14 has the opening 1 of the substrate 17.
Since it is larger than 6, it is injected outside the unit case 11 within the range of the size of the opening 16.

The optical path of the laser beam incident on the SOS sensor 8 is projected by inserting an appropriate paper P behind the focal point of the laser beam emitted from the opening 16 of the substrate 17. In the optical path of the laser beam projected on the paper P, the portion received by the photodiode 13 becomes a shadow. Regarding the moving direction of the laser beam projected on the paper P, the laser beam is actually the SOS sensor 8
This is the opposite direction of moving up.

By measuring the position of the laser beam projected on the paper P, it can be confirmed where the laser beam is incident on the center or the end of the photodiode 13. By checking the optical path of the laser beam, if the optical path of the laser beam is deviated, the mirror angle of the reflection mirror 6 is adjusted so that the laser beam is incident on the central portion of the photodiode 13, and the optical path of the laser beam is adjusted. Can be corrected.

The optical path of the laser beam incident on the SOS sensor 8 is not limited to paper, but a plastic plate may be used, or a wall may be irradiated.

The optical path of the laser beam incident on the SOS sensor 8 can be confirmed by blowing tobacco smoke or the like toward the opening 16.

The correction of the optical path deviation of the laser beam may be performed not by adjusting the mirror angle of the reflecting mirror 6 but by adjusting the mounting position of the SOS sensor 8.
Both the mirror angle of the reflection mirror 6 and the mounting position of the SOS sensor 8 may be adjusted.

In this embodiment, a hemispherical lens is used as the condenser lens 7, but it may be a cylindrical lens.

The shape of the opening 16 of the substrate 17 may be round, square, slit or the like. Further, the opening 16 is formed in the substrate 17.
Instead of providing the above, a transparent member may be provided at the position of the opening 16, and the laser beam may pass through this transparent member and be emitted to the outside of the unit case 11. Further, the substrate 17 itself may be a transparent member.

By forming the opening 16 in the substrate 17 in this way, the optical path of the laser beam incident on the SOS sensor 8 cannot be visually confirmed from the laser beam incident side of the SOS sensor 8 by arranging parts and units. Even with the shape of the case 11, the optical path of the laser beam incident on the SOS sensor 8 can be confirmed.

[0023]

As described above, according to the present invention, since the laser beam incident near the light receiving element is emitted behind the light receiving element, the optical path of the laser beam deflected toward the light receiving element can be easily confirmed.

[Brief description of drawings]

FIG. 1 is a plan view of a laser beam scanning optical device of this embodiment.

FIG. 2 is a perspective view of a main part of the laser beam scanning optical device according to the present embodiment.

FIG. 3 is a plan view of a main part of the laser beam scanning optical device according to the present embodiment.

FIG. 4 is a side sectional view of a main part of the laser beam scanning optical device according to the present embodiment.

[Explanation of symbols]

 1 Light Source Assembly 6 Reflection Mirror 7 Condensing Lens 8 SOS Sensor 11 Unit Case 13 Photodiode 14 Transparent Resin Mold Package 16 Opening

Claims (1)

[Claims] 1. A laser beam scanning optical device for deflecting a laser beam modulated according to image information by a deflector to form an image on a photoconductor, wherein image writing is performed by receiving the laser beam deflected by the deflector. A light receiving element for starting position detection is provided, and a laser beam incident near the light receiving element is emitted behind the light receiving element so that the optical path of the laser beam deflected toward the light receiving element can be confirmed. A laser beam scanning optical device characterized by being provided.