JP2001091881A - Scanning optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a scanning optical device excellent in accuracy, rigidity, vibration characteristic, cost and environment maintenance. SOLUTION: As to this scanning optical device provided with a light source means, a first optical system guiding a light beam emitted from the light source means to a deflecting means, the deflecting means, a second optical system guiding a light beam deflected by the deflecting means to a surface to be scanned, a third optical system detecting the position of the light beam in a scanning direction, an optical base directly or indirectly holding at least the light source means, the first to the third optical systems, and the deflecting means, and a light shielding member attached to the optical base; the optical base is one thick plate, at least the part of the first to third optical systems, the light source means and the deflecting means are positioned and fixed on nearly the same plane surface being the one surface of the base.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning optical device for a semiconductor laser mounted on a laser beam printer (hereinafter abbreviated as "LBP"), and more particularly to an optical base for positioning and fixing an optical member and a deflecting member. And a positioning and fixing method.

[0002]

2. Description of the Related Art With the recent increase in speed and precision of LBP, demands for higher precision and higher reliability of optical scanning devices have been increasing. FIG. 9 is a conceptual diagram showing a general configuration example of a conventional optical scanning device. The laser beam emitted from the laser unit 1 passes through the optical function element 2, the collimator lens 3, and the cylindrical lens 4, and is incident on the reflection surface of the polygon mirror 501 that rotates at high speed integrally with the polygon mirror scanner motor 5. The laser beam deflected by the reflection surface of the polygon mirror 501 passes through the toric lens 6 and the fθ lens 7, and the light path is bent by the bending mirror 8 to be focused on a photosensitive drum (not shown).

Here, the optical function element 2 is used to detect the writing start position. The optical function element 2 is a diffraction grating, and guides the return light reflected by the polygon mirror 501 onto a BD sensor (not shown) including a photoelectric element such as a photodiode built in the laser unit 1. Since the polygon mirror 501 rotates at a high speed and at a constant speed integrally with the polygon scanner motor 5, a BD signal is output from the BD sensor at regular intervals and becomes a write start timing signal.

[0004] As shown in the figure, after the above-mentioned optical components and deflection components are positioned and fixed to the optical box 9, a lid (not shown) is connected so as to close the opening of the optical box 9, and the optical component and the deflection component are connected. The deflection component is shielded from external light and dust except for the opening window 901 from which the laser beam is emitted toward the photosensitive drum.

The optical box 9 has a function of positioning and fixing the optical parts and the deflecting parts with high accuracy, and at the same time, attenuating the vibration generated when the polygon mirror scanner motor 5 rotates at a high speed. Thereby, vibration of the bending mirror 8 and the lens is suppressed, and a good image with little dot displacement can be formed. The illustrated optical box 9 is a molded part, and many improvements have been made to its material and shape in order to achieve appropriate rigidity and attenuation characteristics. That is, as for the material, for example, about 30% of glass fiber is mixed into polycarbonate to increase rigidity. Further, the rib, the thickness, and the shape are optimized so that only a vibration mode having little effect on the image quality is excited.

[0006]

However, the above-described conventional configuration example has the following problems.

1) If glass fiber or the like is mixed into a molding material such as polycarbonate to increase the rigidity, the fluidity of the material deteriorates, the molding time becomes longer, and the molding dimensional accuracy also deteriorates.

2) There is a limit to increasing the rigidity for the reasons described in the preceding paragraph. Therefore, the vibration mode is controlled by optimizing the rib, the thickness, and the shape. However, the shape becomes complicated, the molding conditions such as temperature and pressure become complicated, and the molding time tends to be long.

3) Further, if the high speed and high precision of the LBP are advanced in the future, the printing performance of an optical box formed by molding may not be guaranteed.

An object of the present invention is to provide a scanning optical device which is excellent in accuracy, rigidity, vibration characteristics, cost and environmental protection.

[0011]

In order to solve the above-mentioned problems, in the present invention, the forming process of the optical box in the conventional example is abolished, and a thick sheet metal pressed product is obtained.

A scanning optical device according to the present invention comprises a light source means, a first optical system for guiding a light beam emitted from the light source means to a deflecting means, a deflecting means, and a light beam deflected by the deflecting means. A second optical system for guiding light on the surface to be scanned, a third optical system for detecting the position of the light beam in the scanning direction, at least the light source means, the first to third optical systems, and the deflection means; In a scanning optical device including an optical base for directly or indirectly holding, and a light shielding member coupled to the optical base, the optical base is a single thick plate, and the first to third optical bases are provided. At least a part of the optical system, the light source means, and the deflecting means are positioned and fixed on substantially the same plane on one surface of the optical base.

Further, in the scanning optical device according to the present invention, in the scanning optical device described above, the optical base has a plurality of convex portions or concave portions, and each of the plurality of convex portions or concave portions corresponds to the first to the first. At least a part of the optical system up to 3 and the light source means are placed or offset to make the first
The light source means is positioned with respect to at least a part of the optical systems of the first to third optical systems.

Further, in the scanning optical device according to the present invention, in the scanning optical device described above, the deflecting means is a spindle motor having a polygon mirror coupled to a rotating shaft, and the positioning of the polygon mirror in the optical base surface direction is performed. This is performed by fitting a part of the outer diameter of the spindle motor into a hole formed in the optical base.

Further, in the scanning optical device according to the present invention, in the scanning optical device described above, the deflecting means is a spindle motor having a polygon mirror coupled to a rotating shaft, and the spindle motor has a plurality of holes. A circuit board is fixed, and the optical base has a one-step or two-step projection. Positioning of the polygon mirror in the plane of the optical base is performed by aligning a plurality of holes of the spindle motor printed circuit board with the one step. Alternatively, it is performed by fitting to a two-step convex portion.

Further, in the scanning optical device according to the present invention, in the scanning optical device described above, the deflecting means is a spindle motor having a polygon mirror coupled to a rotating shaft, and the spindle motor has a plurality of holes. A circuit board is fixed, and a part of the plurality of protrusions or recesses is a one-step or two-step protrusion, and the positioning of the polygon mirror in the optical base surface direction is performed by using the plurality of spindle motor printed circuit boards. The hole is fitted in the one-step or two-step convex part.

Further, the scanning optical device according to the present invention is characterized in that, in the above-mentioned scanning optical device, the light source means is combined with the third optical system to be an integrated component.

In summary, the light source means, the deflecting means, the shape of the optical component, and the method of positioning and fixing to the optical base are improved, and the positioning and mounting portions to the optical base are set so as to be substantially coplanar. Thus, high-precision positioning and fixing can be achieved only by forming a concave portion, a convex portion, and a hole having a thickness equal to or less than the plate pressure on a thick sheet metal.

[Operation] In the above configuration, the rigidity increases because the optical base is a thick sheet metal. The natural frequency also moves to higher bands. Therefore, the optical base does not vibrate due to the vibration caused by the scanner motor, and deformation due to environmental change or the like does not occur, and a good image without dot displacement can be provided. Ideal for laser beam printers that require high speed and high accuracy. In addition, the light shielding and dust prevention measures are left to the lid member, but the cost does not increase much. On the other hand, the shape of the optical base is simplified, the number of processing steps is reduced, and the cost is reduced. Furthermore, because it is sheet metal,
Do not emit substances that are harmful to the environment.

[0020]

FIG. 1 shows a configuration example of a scanning optical device according to a first embodiment of the present invention. The difference from the conventional example is that the laser holder 1 for holding the laser unit 1 is provided on a thick plate optical base 10 which is pressed instead of the optical box 9.
01, the polygon mirror scanner motor 5, and other optical components are positioned and fixed. The figure is shown by trigonometry. As can be seen from the side view, each part is
Is fixed on substantially the same plane.

A laser beam emitted from a semiconductor laser (not shown) having a BD sensor built-in with the optical functional element 2 fixed to the laser holder 101 is coupled to the laser holder 101.
After the position is adjusted, the collimator lens 3 becomes a parallel light beam or a convergent light beam by the fixed collimator lens 3 and passes through the cylindrical lens 4. The polygon mirror 501, which rotates together with the polygon mirror scanner motor 5, deflects the reflected light beam in the plane of the drawing. The laser beam converted into a parallel beam or a convergent beam by the toric lens 6 is converted by the fθ lens 7
The convergence is adjusted so that the focal position is linear on the surface of the photosensitive drum, and the light is reflected by the bending mirror 8 and condensed in the direction indicated by the one-dot chain arrow in the figure. The reflectivity of the bending mirror 8 varies depending on the deflection angle. Thereby, the polygon mirror 5
The final correction is applied to the dependency of the reflectance of No. 01 on the incident angle and the dependency of the absorptance of the optical molded lens on the deflection so that the laser spot power on the photosensitive drum becomes constant.

FIG. 3 is a diagram for explaining the concept of a method of positioning components. The hatched portions are the members to be positioned. Base 1
Positioning is performed by forming, for example, a cylindrical half-bump convex portion with high precision. FIG. 3 (a) shows the positioning in the height direction using the top flat portion of the half blanking convex portion, and FIG. 3 (b) shows the use of the side surface of the half blanking convex portion for high precision in a plane parallel to the base surface. Enable positioning.

Next, a method of attaching each component to the base 10 will be described. FIG. 2 shows a component shape of the thick plate optical base 10 (hereinafter, referred to as “base”). The figure is actual size, and the base 10
Is made by precision pressing a 5 mm thick aluminum plate. Numerals 1001 to 1003 denote convex portions for positioning and fixing the laser holder 101. A hole is formed in the laser holder 101 side and fitted, so that the positioning and fixing can be performed with high accuracy in the direction perpendicular to the paper surface and in the direction in which the optical axis does not shift. A hole 1003a for fixing the laser holder 101 with a screw is provided at the center of the half-blanked projection 1003.

Numerals 1004 to 1006 denote one-stage and two-stage half-bumps for positioning and fixing the cylindrical lens 4.
A method of positioning and fixing the cylindrical lens 4 will be described with reference to FIG. The position in the direction perpendicular to the plane of FIG. 1 is determined by the amount of protrusion of the half-blanked projections 1004 to 1006, and is determined by high-precision pressing. The deviation from the optical axis is caused by
It depends on the variation of the protrusion amount of 1006 and the positional accuracy of the two-step protrusions 1004a and 1005a on the paper surface, and is based on the high-precision press working. After the cylindrical lens 4 is positioned and fixed, the adhesive 11 is filled and fixed in the holes 4a and 4b of the cylindrical lens 4 as shown in the figure. The fixing method of the laser holder 101 described above is the same as that of the cylindrical lens 4, but is fixed by a set screw instead of an adhesive.

Reference numeral 1007 in FIG. 2 denotes a through hole into which the outer diameter or a part of the outer diameter of the polygon mirror scanner motor 5 is inserted. FIG. 5 shows a cross-sectional view at the time of insertion. In the figure, the hole 1007 is fitted with the outer diameter of the polygon scanner motor 5, and as a result, the polygon mirror 501 is positioned in the plane of FIG. 1, and at the same time, the deviation of the rotation axis from the ideal axis is suppressed. As shown, the motor PCB (printed circuit board) 502 collides with the half-blanked protrusions 1008 to 1010 in FIG. 2 and the position in the direction perpendicular to the paper is determined with high accuracy. In addition, holes for screwing the motor PCB 502 are provided at the center of each of the half-bent projections 1008 to 1010.
In the embodiment, the positioning in the paper plane of FIG. 1 is performed by the outer diameter of the motor and the through hole 1007.
08-1010 with one or two-step convex shape
By assuring the positioning accuracy of the B502 with high accuracy, the polygon mirror 501 is connected via the motor PCB502.
May be positioned.

In FIG. 2, 1011 to 1019 and 1020 to 1
027 denotes a toric lens 6 and an fθ lens 7, respectively.
Is a half-bumped convex portion for positioning and fixing the position. The protrusion amount and shape are different. Since the positioning and fixing method is the same for both, the toric lens 6 will be described. FIG.
7 shows a state in which the toric lens 6 is positioned and fixed on the base. The half-hollow protrusions 1011 and 1019 position the paper in the vertical direction, and the half-hollow protrusions 1014 and 1015 position the central protrusion 6a of the toric lens 6 in the horizontal direction. Further, the position and the inclination in the direction perpendicular to the paper surface are determined by the protrusion amounts of the half-blanked convex portions 1012, 1018, and 1016. The processing accuracy required from the optical design can be sufficiently satisfied by processing the protrusion amount of the half-blanked convex portion, the accuracy of the flat portion, and the position in the paper surface with high accuracy.

The half-bent protrusions 1013 and 1017 have a smaller protrusion amount than the other protrusions. The shape is also oblong. This is a device for applying and fixing the adhesive 21 between the bottom surface of the toric lens 6 and the half-bent protrusions 1013 and 1017 as shown in the figure. The filling position of the adhesive is limited, and the amount of distortion given to the plastic lens by the curing of the adhesive becomes constant. As a result, stable lens characteristics are obtained.

Finally, a method for positioning and fixing the bending mirror 8 will be described. The folding mirror can be omitted depending on the arrangement of the scanner unit in the printer. As shown in FIG. 4, the projections 1029, 10
Form 30. In particular, the surfaces 1030a and 1030b holding the bending mirror 8 are precisely pressed. Further, the direction parallel to the surfaces 1030a and 1030b is positioned at the corner of the half blanking convex portion 1031. Apply adhesive 31 to surface 10
The recess between 30a and 1030b is filled and fixed.

The lid member 12 shown in FIG. 8 is connected to the optical base from the near side of FIG. 1 to contribute to light shielding and countermeasures against dust. 12
a and 12b are cylindrical projections, and the holes 103 shown in FIG.
2 and 1033 to determine the relative position with respect to the optical base 10. 12c is a through hole, a set screw and a screw hole 103.
At 4, the lid 12 is fixed. Furthermore, the lid 12 is formed using the projections 12d, 12e, 12f, and 12g having spring properties.
Is fixed to the optical base 10 by patching.

Reference numerals 12h to 12k denote walls for blocking stray light of the laser beam and preventing wind speed generated by high-speed rotation of the polygon mirror 501 from catching dust and adhering to the surface of the polygon mirror 501. In the conventional example, the optical box plays the role, but the function is transferred to the lid 12.

[0031]

As described above, according to the present invention,
Abolished the optical box by molding in the conventional example,
The optical base was made by precision pressing of thick sheet metal. The laser unit, polygon mirror scanner motor, and plastic lens positioning / fixing method enable high-precision positioning required from optical design by forming a high-precision half-blanking convex portion and pressing and positioning. . That is, the laser unit, the polygon mirror scanner motor, the toric lens and the fθ lens are positioned and fixed on substantially the same plane parallel to the optical base surface.

Further, the laser unit is a composite element which incorporates an optical functional element and incorporates a BD sensor to detect a writing start timing signal, and is configured to be positioned and fixed to an optical base via a laser holder. Further, a structure such as a wall that blocks external light and stray light and a wall that prevents intrusion of dust is provided in the lid.

In the above configuration, the rigidity increases because the optical base is a thick sheet metal. The natural frequency also moves to a higher band. Therefore, the optical base does not vibrate due to the vibration caused by the scanner motor, and deformation due to environmental change or the like does not occur, and a good image without dot displacement can be provided. Ideal for laser beam printers that require high speed and high accuracy. Also, the light shielding and dust prevention measures are left to the lid member, but the cost of the lid member does not increase so much, but the shape of the optical base is simplified, the number of processing steps is reduced, and the cost is reduced. Furthermore, because it is sheet metal,
Do not emit substances that are harmful to the environment.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a scanning optical device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an optical base constituting the scanning optical device according to the embodiment of the present invention.

FIG. 3 is a diagram illustrating a method of positioning an attachment member on an optical base according to an embodiment of the present invention.

FIG. 4 is a diagram illustrating a method for positioning and fixing a bending mirror according to an embodiment of the present invention.

FIG. 5 is a diagram illustrating a method for positioning and fixing a polygon mirror scanner motor according to an embodiment of the present invention.

FIG. 6 is a diagram illustrating a method for positioning and fixing a toric lens according to an embodiment of the present invention.

FIG. 7 is a diagram illustrating a method for positioning and fixing a cylindrical lens according to an embodiment of the present invention.

FIG. 8 is a diagram illustrating a configuration of a lid member and a positioning and fixing method according to the embodiment of the present invention.

FIG. 9 is a plan view illustrating a conventional general scanning optical device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser unit 2 Optical function element 3 Collimator lens 4 Cylindrical lens 5 Polygon mirror scanner motor 501 Polygon mirror 6 Toric lens 7 fθ lens 8 Bending mirror 9 Optical box 10 Optical base 11, 21, 31 Adhesive 12 Lid member

Continued on front page F-term (reference) 2C362 AA43 AA45 BA83 BA86 BA89 BA90 DA03 DA41 2H045 AA01 BA02 CA03 CA63 CB22 DA02 DA04 DA44 5C072 AA03 BA02 BA04 BA20 DA04 DA21 HA02 HA08 HA13 HA20 XA05

Claims (6)

[Claims] 1. A light source means, a first optical system for guiding a light beam emitted from the light source means to a deflecting means, a deflecting means, and a light beam deflected by the deflecting means on a surface to be scanned. A second optical system that emits light, a third optical system that detects the position of a light beam in the scanning direction, and at least the light source unit, the first to third optical systems, and the deflection unit are directly or indirectly connected. In a scanning optical device including an optical base to be held and a light shielding member coupled to the optical base, the optical base is a single thick plate, and at least one of the first to third optical systems is provided. A scanning optical device, wherein the unit, the light source unit, and the deflection unit are positioned and fixed on substantially the same plane on one surface of the optical base. 2. The optical base includes a plurality of convex portions or concave portions, and each of the plurality of convex portions or concave portions includes at least a part of the first to third optical systems and the light source unit. 2. The scanning optical apparatus according to claim 1, wherein at least a part of the first to third optical systems and the light source unit are positioned by being placed or shifted. 3. The optical system according to claim 1, wherein the deflecting means is a spindle motor having a polygon mirror coupled to a rotating shaft, and positioning the polygon mirror in the plane of the optical base includes adjusting a part of the outer diameter of the spindle motor to the optical base. 3. The scanning optical device according to claim 1, wherein the scanning is performed by fitting into a hole formed in the scanning optical device. 4. The deflecting means is a spindle motor in which a polygon mirror is coupled to a rotating shaft, a spindle motor printed circuit board having a plurality of holes is fixed to the spindle motor, and the optical base is one stage or It is provided with a two-step projection, and positioning of the polygon mirror in the optical base surface direction is performed by fitting a plurality of holes of the spindle motor printed circuit board into the one-step or two-step projection. The scanning optical device according to claim 1, wherein: 5. The deflecting means is a spindle motor in which a polygon mirror is coupled to a rotating shaft. A spindle motor printed circuit board having a plurality of holes is fixed to the spindle motor. The portion is a one-step or two-step projection, and the positioning of the polygon mirror in the optical base surface direction is performed by fitting a plurality of holes of the spindle motor printed circuit board into the one-step or two-step projection. The scanning optical device according to claim 2, wherein the scanning is performed by: 6. The light source device according to claim 1, wherein the light source unit is combined with the third optical system to form an integrated component.