JP2002350763A - Laser scanner and image forming device provided with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser scanner capable of reducing the deviation of a laser beam made incident on a beam converging device, and an image forming device equipped with the laser scanner. SOLUTION: A plane parallel plate 16 is turnably arranged between a collimator lens 21 and a wedge prism 17. The incident surface 16a and the radiation surface 16b of the plate 16 are inclined by a specified angle α to a subscanning direction. The laser beam C made incident from the incident surface 16a is diffracted while keeping specified width W, and radiated from the radiation surface 16b in a state where its height is deviated by specified height H. Therefore, the laser beam C is made incident on the vicinity of the center of the incident surface 4a of the beam converging device 4 by properly adjusting the turning amount of the plate 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser scanning device for scanning a laser beam and an image forming apparatus having the same.

[0002]

2. Description of the Related Art Conventionally, a digital copying machine having a laser diode for irradiating a laser beam based on a read image has been known. This type of digital copier is
For example, it has one laser diode, and the laser beam emitted from this laser diode passes through various optical members such as a beam compensator, a beam angle adjuster, a beam convergent, a polygon mirror, and an fθ lens, for example. Irradiated on the photoreceptor surface.

[0003] The beam compensator is for converting the diffused light emitted from the laser diode into parallel light. The laser beam converted into parallel light by the beam compensator is adjusted in its angle by passing through a beam angle adjuster, and then converged in a predetermined convergence direction by a beam converger,
The light is converged to one point on the reflection surface of the polygon mirror. The polygon mirror is rotated at a constant speed around its axis, and the laser beam is scanned by being reflected by the reflection surface of the polygon mirror that rotates at a constant speed. The laser beam scanned by the polygon mirror is converged in a predetermined convergence direction by the function of the fθ lens, and scans the surface of the photoconductor at a constant speed.

[0004]

However, a laser beam to be irradiated may be displaced with respect to a desired irradiation direction due to a deviation when the laser diode is mounted at a predetermined position or a deviation of an optical axis of the laser diode itself. Tilting may occur. When the laser beam is tilted, the position of the laser beam passing through the beam compensator is shifted, so that the laser beam cannot be incident near the center of the incident surface of the beam converging device.

In this case, the laser beam emitted from the beam converging device has a large inclination with respect to a desired irradiation direction, and the incident position of the laser beam on the fθ lens is largely shifted. Therefore, it is necessary to widen the allowable range of the deviation of the incident position of the laser beam in the fθ lens, and the production cost of the fθ lens increases. The present invention has been made under such a background, and an object of the present invention is to provide a laser scanning device capable of reducing a deviation of a laser beam incident on a beam converging device, and an image forming apparatus including the same.

[0006]

According to the first aspect of the present invention, there is provided an apparatus for scanning a laser beam, comprising: a laser diode for irradiating a laser beam; A laser beam emitted from a laser diode passes therethrough, and a beam compensator for converting the laser beam into parallel light, and a beam compensator disposed downstream of the beam compensator on the beam irradiation path and passing therethrough a predetermined laser beam. It has a beam converging device for converging to a position, and an incident surface and a radiation surface parallel to each other, and is rotatably disposed at any position in the optical path of the laser beam from the beam compensator to the beam converging device. A parallel plate that refracts the laser beam incident from the incident surface and emits the laser beam whose optical path is shifted from the radiation surface. A laser scanning apparatus according to claim.

[0007] For example, a polygon mirror is used to scan the laser beam. The laser beam that has passed through the beam converging device is converged in a predetermined convergence direction, and converged at one point on the reflection surface of the polygon mirror. The polygon mirror is designed to rotate at a constant speed around its axis,
The laser beam is scanned by being reflected by the reflecting surface of a polygon mirror that rotates at a constant speed. An fθ lens, for example, is disposed downstream of the beam irradiation path of the polygon mirror. The laser beam scanned by the polygon mirror is converged in a predetermined convergence direction by the function of the fθ lens, and scans a predetermined irradiation position at a constant speed.

According to the configuration of the present invention, by appropriately adjusting the amount of rotation of the parallel plate, the optical path of the laser beam passing through the parallel plate is shifted so that the laser beam is located near the center of the incident surface of the beam converging device. Can be incident. Therefore, the displacement of the laser beam incident on the beam converging device can be reduced. Also, since the inclination of the laser beam passing through the beam converging device can be reduced by making the laser beam incident near the center of the incident surface of the beam converging device, the laser beam should be made incident near the center of the incident surface of the fθ lens. Can be. As a result, the allowable range for the deviation of the incident position of the laser beam on the fθ lens can be narrowed, so that the production cost of the fθ lens can be reduced.

Preferably, the beam converging device has a convex cylindrical lens surface on which a laser beam is incident. Preferably, the parallel plate is rotatable about a direction other than a direction perpendicular to the axis of the convex lens surface and the optical axis of the beam converging device. The parallel plate is rotatable about a direction perpendicular to the axis of the convex lens surface and the optical axis of the beam converging device, and a direction perpendicular to both the incident direction of the laser beam incident on the parallel plate. It is more preferable if it is.

According to a second aspect of the present invention, there is provided an image comprising a photoreceptor and a laser scanning device for writing an electrostatic latent image by scanning the photoreceptor with a laser beam. It is a forming device. According to this configuration, it is possible to provide an image forming apparatus including the laser scanning device having the effects of the first aspect of the invention.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A so-called multi-beam type digital copying machine according to an embodiment of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a schematic configuration diagram for explaining an image forming mode in a digital copying machine according to an embodiment of the present invention. This digital copying machine uses a laser beam C based on image data of a document read by a document reading unit (not shown) or image data read from an external personal computer connected to the digital copying machine.
Is provided with a laser scanning unit (LSU) 2 for scanning the surface of the photosensitive member 1 in the form of a drum.

The photosensitive member 1 is rotatably held around an axis A. After the surface of the photoconductor 1 is uniformly charged by the discharge of a main charger (not shown), a laser beam C is emitted from the laser scanning unit 2 to write an electrostatic latent image. Thereafter, an image based on the image data is transferred to a recording sheet by the operation of a developing device, a transfer device, and the like (not shown). Since the configurations of the main charger, the developing device, the transfer device, and the like are known, the description thereof is omitted here.

The laser scanning unit 2 includes a laser diode unit (LDU) 3. The laser diode unit 3 has, for example, two laser diodes 9, and a laser beam C based on the read image data is emitted from the two laser diodes 9 and aligned in a predetermined alignment direction. Irradiation from. The laser beam C emitted from the laser diode unit 3 enters a cylindrical lens (beam convergent) 4. The incident surface 4a of the cylindrical lens 4 is a convex lens surface having a convex cylindrical shape, and the laser beam C passing through the incident surface 4a is converged and enters the polygon mirror 5.

The polygon mirror 5 has, for example, a substantially regular hexagonal cross section, and its six outer surfaces form reflection surfaces 5a. A rotation axis of a polygon motor 6 is connected to the polygon mirror 5.
The polygon mirror 5 is configured to rotate at a constant speed around its axis B. By rotating the polygon mirror 5 in the direction of the arrow shown in FIG. 1 while irradiating the laser beam C from the laser diode unit 3 to the reflection surface 5a of the polygon mirror 5, the laser reflected by the reflection surface 5a of the polygon mirror 5 The beam C is scanned as shown by a two-dot chain line in FIG.

The laser beam C reflected by the reflection surface 5a of the polygon mirror 5 passes through the fθ lens 7 and is reflected by the reflection mirror 8, so that the laser beam is irradiated from the laser scanning unit 2 onto the surface of the photosensitive member 1. You. The laser beam C scanned by the polygon mirror 5 is applied to the fθ lens 7
Scans the surface of the photoreceptor 1 along the axis A at a constant speed. The direction along the axis A of the photoconductor 1 is the main scanning direction, and the scanning in the sub-scanning direction is achieved by rotating the photoconductor 1 around the axis A while irradiating the surface of the photoconductor 1 with the laser beam C. You.

In this embodiment, two lines of the electrostatic latent image are written on the surface of the photoconductor 1 at a time by scanning the surface of the photoconductor 1 with the laser beam C emitted from the two laser diodes 9. be able to. As a result, the time required for copying can be reduced, and the resolution in the main scanning direction and the sub-scanning direction can be increased. The sub-scanning direction is along the axis B of the polygon mirror 5, and for convenience, in the following description, the direction along the axis B of the polygon mirror 5 is referred to as the sub-scanning direction.

FIG. 2 is a plan view of the laser diode unit 3. In the following description, for convenience, the lower direction in FIG. The two laser diodes 9 are respectively mounted on different substrates 10. Printed wiring (not shown) is printed on the back surface of each substrate 10, and each laser diode 9 is connected to the connector 1
1 is controlled by a signal provided from a control unit (not shown) connected via the control unit 1.

A heat radiating plate 12 is mounted on the front surface of each substrate 10. The two substrates 10 have a common size and shape, and the two heat sinks 12 also have a common size and shape. Two substrates 10
And two corresponding heat dissipation plates 12 constitute two laser diode holding members 14 having a common size and shape in a state where they are attached to each other.
The laser diode holding member 14 includes a beam compensator 15,
It is attached to a rear plate 19a erected on the rear edge of a base 19 that holds the parallel flat plate 16, the beam angle adjuster 17, the beam combining member 18, and the like. Rear plate 19 of base 19
a, a through-hole 20 is formed at a position facing each laser diode 9, and the laser beams C emitted from each laser diode 9 are arranged in a line in a beam compensator 15, a parallel plate 16 and a beam The light passes through the angle adjuster 17 and enters the beam combining member 18.

FIG. 3 is a cross-sectional side view of the laser diode unit 3, in which the laser diode holding member 14, the rear plate 19a and the like are omitted. 2 and 3
, The beam compensator 15 is for making incident diffused light parallel light, and has a collimator lens 21 therein. The collimator lens 21
For example, the incident surface 2 composed of a plane orthogonal to the laser beam C
1a and a radiation surface 21b composed of a convex cylindrical convex lens surface facing the incident surface 21a.

The parallel flat plate 16 has a pair of main surfaces 1 facing each other.
6A and 16B are plate-shaped lenses formed so as to be parallel to each other, and one of a pair of main surfaces 16A and 16B forms an incident surface 16A and the other forms a radiation surface 16B. The parallel flat plate 16 is held by a support shaft 23 fixed to a support plate 22 erected on a base 19. The support shaft 23 extends in a direction orthogonal to the two laser beams C, and the parallel flat plate 16 is, as shown by an arrow in FIG.
It is rotatable around the support shaft 23. The direction perpendicular to both laser beams C is defined as either a direction perpendicular to the axis of the incident surface 4a of the cylindrical lens 4 and the optical axis of the cylindrical lens 4 or an incident direction of the laser beam C incident on the parallel plate 16. Are also orthogonal directions.

The laser beam C emitted from the laser diode 9 passes through a collimator lens 21 to be converted into parallel light, and then passes through a parallel flat plate 16 tilted by a predetermined angle, thereby increasing the height (beam) from the base 19. Change). The beam height of the laser beam C can be set to a desired height by adjusting the inclination angle of the parallel plate 16. The parallel flat plate 16 is not limited to the above-described direction. If the parallel flat plate 16 can rotate around a direction other than a direction perpendicular to the axis of the incident surface 4 a of the cylindrical lens 4 and the optical axis of the cylindrical lens 4, the The beam height can be changed.

The beam angle adjuster 17 is for adjusting the angle of the incident laser beam C, and has a wedge prism 24 provided therein. The wedge prism 24 has, for example, a flat entrance surface 24a, respectively.
And a radiation surface 24b are formed in a non-parallel manner to each other, and are held rotatably around the axis of the passing laser beam C. Laser beam C from parallel plate 16
The beam passes through the wedge prism 24, the angle of which is adjusted, and enters the beam combining member 18. By adjusting the angle of the laser beam C by each wedge prism 24, the two laser beams C
The distance between can be adjusted.

The beam synthesizing member 18 is constituted by, for example, a prism having a substantially quadrangular prism shape, and has two reflecting surfaces 18a and 18b for reflecting the laser beam C emitted from each laser diode 9. Each reflective surface 18
a, 18b are 45 ° with respect to the incident laser beam C
The laser beam C, which is inclined and is incident on each of the reflecting surfaces 18a and 18b, is reflected at 90 ° with respect to the respective incident directions, and is directed toward the reflecting surface 5a of the polygon mirror 5.

One of the reflecting surfaces 18a and 18b totally reflects the incident laser beam C, while the other reflecting surface 18b reflects half of the incident laser beam C. It is a half mirror surface that transmits and reflects the other half. The laser beam C reflected by the reflecting surface 18a transmits through the reflecting surface 18b and is reflected by the reflecting surface 18a.
Irradiated with the laser beam C reflected by b, aligned in the sub-scanning direction. FIG. 4 is an illustrative view for explaining a change of the laser beam C in the sub-scanning direction. The laser beam C emitted by the laser diode 9 is a diffused light, and the laser beam C incident on the incident surface 21a of the collimator lens 21 is sub-scanned by the function of the radiation surface 21b formed of a convex cylindrical convex lens surface. The light becomes parallel light having a predetermined width W in the direction.

The plane of incidence 16a and the plane of emission 16b of the parallel plate 16 are inclined by a predetermined angle α with respect to the sub-scanning direction. The laser beam C incident from the incident surface 16a is
The light is refracted with the predetermined width W, and is emitted from the radiation surface 16b with the beam height shifted by the predetermined height H. The laser beam C incident on the parallel plate 16 is emitted substantially parallel to the incident direction. Laser beam C from parallel plate 16
Is incident on the incident surface 24a of the wedge prism 24, and is emitted while being tilted from the radiation surface 24b inclined with respect to the incident surface 24a. The laser beam C from the wedge prism 24 is reflected at the reflection surface 1 of the beam combining member 18 at the same angle.
The light is reflected by 8a and 18b and enters the incident surface 4a of the cylindrical lens 4.

By appropriately adjusting the beam height and angle of the laser beam C with the parallel plate 16 and the wedge prism 24, the laser beam C can be made to enter the vicinity of the center of the entrance surface 4a of the cylindrical lens 4.
Therefore, the displacement of the laser beam C incident on the cylindrical lens 4 can be reduced. Cylindrical lens 4
Laser beam C having a predetermined width W incident on the incident surface 4a
Are converged in the sub-scanning direction and converge to one point on the reflection surface 5a of the polygon mirror 5. Reflection surface 5 of polygon mirror 5
The laser beam C reflected at a spreads at the same angle as the converged angle and enters the incident surface 7a of the fθ lens 7.

The laser beam C is applied to the cylindrical lens 4
Of the laser beam C passing through the cylindrical lens 4 in the sub-scanning direction can be reduced by making the laser beam C incident near the center of the incident surface 4a of the fθ lens 7 near the center of the incident surface 7a of the fθ lens 7. Can be incident. As a result, the allowable range for the shift of the incident position of the laser beam C on the fθ lens 7 can be narrowed, so that the production cost of the fθ lens 7 can be reduced.

The adjustment of the optical axis of the laser beam C is performed, for example, from the laser diode unit 3 to the cylindrical lens 4.
This is performed by arranging a CCD camera in the optical path of the laser beam C up to and adjusting the beam height and angle of the laser beam C by the parallel plate 16 and the wedge prism 24 while monitoring the laser beam C. The present invention is not limited to the contents of the above embodiments, and various modifications can be made within the scope of the claims.

For example, the parallel plate 16 is not limited to the configuration disposed between the collimator lens 21 and the wedge prism 24. If the parallel plate 16 is located between the collimator lens 21 and the cylindrical lens 4, for example, the wedge prism 24 and the beam combining The configuration may be arranged between the beam combining member 18 and the cylindrical lens 4. The parallel plate is limited to a plate-shaped parallel plate 16 formed such that a pair of main surfaces 16a and 16b facing each other are parallel to each other as long as the member has an incident surface and a radiation surface which are parallel to each other. Not something.

The photosensitive member 1 is not limited to a drum-like member, but may be, for example, a belt-like member. The digital copying machine is not limited to the two-beam type, and may be a type capable of writing an electrostatic latent image for a plurality of lines on the surface of the photoconductor at a time with a plurality of laser beams of three or more beams. Although a digital copying machine has been described as an embodiment of the present invention, the present invention is not limited to a digital copying machine but can be applied to an image forming apparatus such as a facsimile or a printer.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an image forming mode in a digital copying machine according to an embodiment of the present invention.

FIG. 2 is a plan view of a laser diode unit.

FIG. 3 is a sectional side view of the laser diode unit.

FIG. 4 is an illustrative view for explaining a change in a sub-scanning direction of a laser beam;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Laser scanning unit 4 Cylindrical lens (beam converging device) 9 Laser diode 15 Beam compensator 16 Parallel plate 16a Incident surface 16b Radiation surface C Laser beam

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masanori Kiyama 1-2-28 Tamazo, Chuo-ku, Osaka-shi, Osaka Inside Kyocera Mita Co., Ltd. (72) Inventor Keiichi Funaki 1-2-2 Tamazo, Chuo-ku, Osaka-shi, Osaka No. 28 Inside Kyocera Mita Co., Ltd. (72) Yoshinobu Yoneima, Inventor 1-2-2 Tamatsuzo, Chuo-ku, Osaka City, Osaka Prefecture No. 28 Inside Kyocera Mita Co., Ltd. (72) Eiji Tatsumi 1-2-1, Tamazo, Chuo-ku, Osaka City, Osaka No. 28 Kyocera Mita Co., Ltd. (72) Inventor Hideki Sugimura 1-2-28 Tamatsukuri, Chuo-ku, Osaka City, Osaka Prefecture F-term in Kyocera Mita Co., Ltd. BA22 BA33 CA63 CB13 DA02 DA41 2H076 AB05 AB06 AB18 EA24

Claims (2)

[Claims] 1. An apparatus for scanning a laser beam, comprising: a laser diode for irradiating the laser beam; and a laser beam emitted from the laser diode, so that the laser beam is turned into parallel light. A beam compensator, which is arranged downstream of the beam compensator on the beam irradiation path and converges a passing laser beam to a predetermined position, and has an incident surface and a radiation surface parallel to each other, The laser beam from the beam compensator to the beam converging device is rotatably disposed at any position in the optical path of the laser beam, refracts the laser beam incident from the incident surface, and emits the laser beam whose optical path is shifted. And a parallel plate radiating from a surface. 2. An image forming apparatus, comprising: a photoconductor; and a laser scanning device according to claim 1, which scans the photoconductor with a laser beam to write an electrostatic latent image.