JP3379241B2 - Optical scanning device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens fixing structure in an optical scanning device such as a digital copying machine or a printer. 2. Description of the Related Art Hitherto, as a fixing structure of an fθ lens of an optical scanning device, a number of fixing structures using screws or springs have been proposed. When the lens is fixed with screws, there is no risk of displacement due to vibration or impact, but there is a problem that the assemblability is very poor. That is, if the vertical direction is fixed, there is a problem that the horizontal position does not match, and if the horizontal direction is fixed, the vertical position does not match.
It was necessary to carefully fix both directions simultaneously. On the other hand, when the lens is fixed by a spring, the displacement can be easily eliminated by temporarily applying a force after assembly. [0003] Japanese Utility Model Publication No. 2-48813 discloses a lens fixing structure in which an elastic member for pressing the lens is attached to a rigid body straddling the side wall. In this structure, as shown in FIG. 3 of the above publication, the lens is pressed from above by a resilient member onto a protruding seat provided in the optical box. In such a structure, since the lens is supported by the elastic member, the position of the lens may be shifted when vibration, impact, or the like is applied, which is more pronounced when the lens is large and heavy. Will be noticeable. When the lens is shifted from a predetermined position, the lens is held at the shifted position and is not restored. As an improvement of the above conventional example, FIG.
The following lens fixing structure has been proposed. In this structure, each of the reference projections 19, 20, and 22, 23 on which the two lenses 6, 7 are mounted is provided on the optical housing 1, and the projection 1 is in contact with one surface of each lens.
8 and 21 are provided.
It is structured to be pressed by 5, 32. 33, 34
Is a screw for fixing the spring to the housing. Further, the lens is pressed downward by the spring 30 from above the lenses 6 and 7. According to such a structure, even if the lens moves due to vibration, impact, or the like, it can be restored to the original position by the force of the spring. In the conventional lens fixing structure shown in FIG. 4, for example, if the pressing force Fy of the spring 30 is too strong, when the horizontal position of the lens shifts,
Due to the frictional force between the lenses 6, 7 and the projections 19, 20 or 22, 23, there is a problem that they cannot return to their original positions. Similarly, if the springs 32, 35 are too strong, the vertical position will not return. Further, even when the spring force is balanced at the time of assembly, there is a possibility that the balance of the spring force may be lost due to aging or the like. Further, there is a problem that the number of parts is large and the number of assembling steps is also large. SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical scanning device that solves the above-described problems of the related art, has a simple structure, is easy to assemble, and has a lens fixing structure resistant to impact. According to the present invention, there is provided an optical scanning device comprising: a deflecting means for deflecting a light beam; a lens for forming an image of the light beam deflected by the deflecting means; and an optical housing. In the apparatus, there are a plurality of the lenses, and two of the lenses are provided.
An oblique cutout is provided in at least a part of the upper end of the mutually facing surfaces of the two lenses, and a projection is provided on the optical housing outside a position where the two lenses are to be fixed. A lens holding member that comes into contact with the cutout surfaces of the two lenses at the same time; and a pressing unit that presses the lens holding member downward. In the present invention, a notch is provided at the upper end of the opposing surfaces of the two lenses, and the notch is provided by a lens holding member.
Since the structure is such that the lenses are simultaneously pushed downward, the upper part of the lens as well as the lower part of the lens are supported in the horizontal direction by friction, and displacement due to vibration, impact, and the like is less likely to occur. Further, the pressing force in the horizontal direction and the pressing force in the vertical direction are always proportional, and even if the lens position temporarily shifts due to a strong impact or the like, the lens position is immediately restored to the original position. Lens displacement due to pressure imbalance does not occur. Also, the number of parts is small, and the assemblability is improved. FIG. 2 is a diagram showing an example of an optical system of a printer using an optical scanning device to which the present invention is applied. The optical housing 1 includes a polygon unit (not shown) having a laser light source unit 2, a mirror 4, and a polygon mirror 5, and a first f for focusing laser light on the photosensitive drum 2.
The θ lens 6 and the second fθ lens 7 are mounted. 8
Denotes an optical axis, and scans the photosensitive drum 2 according to the rotation of the polygon mirror 5. FIG. 1 shows an optical housing fθ with a part cut away.
It is a front view near a lens. The optical housing 1 has a first f
Three projections 22 and 23 for defining a horizontal reference plane for supporting the θ lens 6 and a projection 21 for positioning the lens 6 in the horizontal direction are provided. Similarly, projections 19, 20 and 18 are provided for supporting and positioning the second fθ lens 7. A columnar member 16 for supporting the upper bridge member 12 extends from both side surfaces of the housing 1. First
Lens 6 and second fθ lens 7 have a substantially rectangular cross section, and an oblique cutout 9 is provided at the upper end of the opposing surfaces of the two lenses. The angle of inclination of the notch may be such that the lens does not fall without the screws 14 and 15. However, the closer the angle is to the horizontal, the smaller the restoring force against the horizontal displacement. [0010] A lens pressing member 10 having a shape contacting both notched surfaces at the same time is disposed across the notched portions 9 of the two lenses.
The pressing spring 11 is pressed downward. Both surfaces of the lens holding member 10 and the cutout surface of the lens are machined so that a certain amount of frictional force is generated. The pressing spring 11 is fixed to the bridge member 12 and provides a restoring force against the vertical displacement of the lens, and generates a frictional force between the lens pressing member 10 and the cutout surface of the lens. A projecting portion 13 extends from the bridge member 12 above both lenses, and screws 14 and 15 provided on the projecting portion 13 are lightly in contact with the respective lenses. The screws 14 and 15 are for preventing the lens from being largely displaced by an impact or the like. FIG. 3 is a plan view showing a lens portion of the optical housing according to the present invention. Lens 6 is supported by three projections 22 and 23 and is in contact with positioning projection 21. The second fθ lens has three protrusions 19,
It is supported by 20 and is in contact with the positioning projection 18. The lens holding screws 14 and 15 are respectively arranged so as to hold substantially the centers of the three projections for vertical positioning. The pressing spring 11 has a substantially H shape, and is fixed to the bridge member 12 by, for example, an adhesive, a screw, a rivet, or the like. The bridge member 12 is fixed to a columnar member 16 extending from the side surface of the optical housing 1 with a screw 17. The bridge member 12
Although the projecting portions 13 extend from left to right, the width of the bridge member 12 may be configured to be wider than the interval between the screws 14 and 15 throughout. When assembling the optical housing, a force is temporarily applied in the horizontal direction after assembly to position the lens at a predetermined position, as in the conventional fixing method using a spring.
Thereafter, the screws 14 and 15 are lightly tightened and fixed so as not to distort the lens. In this state, when the lens attempts to move in the horizontal direction due to an impact, there is friction between the lens and the lens pressing member 10, so that the lens pressing member 10 is pressed in the horizontal direction by one of the lenses. 10 does not move because it has hit the other lens. Further, since the frictional force becomes extremely large against a sudden acceleration such as an impact, the frictional force and the holding spring 11 are increased.
It is difficult to push the lens holding member upward against the force of (1). Conversely, in the case of fine vibration, the frictional force is weakened, but in this case, if the lens is displaced from the original position, the lens is pressed by the lens pressing member 10 and returns to the original position. . FIG. 5 is a view schematically showing another embodiment of the present invention. FIG. 5A shows an example in which the lens pressing member 10 is pressed by a spring spring 40, and any other type, shape, and number of springs can be used. FIG.
(B) is an example in which the lens pressing member 10 is pressed by an arbitrary elastic member 12 such as rubber sandwiched between the lens pressing member 10 and the bridge member 12. FIG.
(C) is an example in which the lens pressing member 10 is directly pressed by the screw 42. In this case, the lens pressing member 1
0, the stress due to the elastic deformation of the bridge member 12 and the like acts instead of the force of the spring. FIG. 5D shows an elastic member 4 such as rubber.
3 is an example of directly pressing the lens. In this case, the shape or presence or absence of the cutout portion of the lens does not matter much. FIG. 5E shows an example in which the lens pressing member 44 is formed by an elastic member such as a leaf spring. In this example, the lens pressing member 44 is supported by the screw 45. However, if the lens pressing member 44 is formed in a shape such that the lens pressing member 44 comes into contact with the bridge member 12, the screw 45
May be omitted. Although the embodiment has been described above, the present invention may be modified as follows. Lens holding member 1
The contact between the 0 and the notch of the lens may not be a surface,
For example, it may be a line or a point. That is, the cutout surface of the lens and the inclined surface of the lens holding member 10 may not be flat, and one or both surfaces of the lens or the lens holding member may be spherical, cylindrical, or mountain-shaped projections having a triangular cross section, or It may be a cylindrical depression or the like. In the embodiment, the screw 14 fixing the upper part of the lens,
15 is not always necessary, and may be replaced by another configuration, for example, a member extending from the bridge member 12 and constituting the abutting surface. [0015] Even if the lens has three or more lenses,
If two lens blocks are formed by bonding, the present invention can be applied as it is. Further, other lenses may be present before, after, or in the middle of the lenses 6 and 7 of the embodiment. In the embodiment, the holding spring 11 does not need to be fixed to the bridge member 12, but is provided only with a structure such as a fitting pin or a dent that regulates the position of the spring 11 in a plane parallel to the bridge member 12. May be. The lens fixing structure of the present invention can also be applied to fix one lens, in which case, instead of the second lens,
A member having a notch may be used, or the other end of the lens holding member 10 may be rotatably supported. As described above, in the present invention,
A notch is provided at the upper end of the opposing surfaces of the two lenses,
Since the two lenses are simultaneously pressed downward by the lens pressing member, the upper portion of the lens is supported in the horizontal direction by friction as well as the lower portion of the lens, and displacement due to vibration, impact, and the like is less likely to occur. Further, the pressing force in the horizontal direction and the pressing force in the vertical direction are always proportional, and even if the lens position temporarily shifts due to a strong impact or the like, the lens position is immediately restored to the original position. Lens displacement due to pressure imbalance does not occur. Also, the number of parts is small, and the assemblability is improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view of the vicinity of an fθ lens with a part of an optical housing cut away. FIG. 2 is a diagram illustrating an example of an optical system of a printer using an optical scanning device to which the present invention is applied. FIG. 3 is a plan view showing a lens portion of an optical housing according to the present invention. FIG. 4 is a front view showing the vicinity of an fθ lens of a conventional optical housing. FIG. 5 is a diagram schematically showing another embodiment of the present invention. [Description of Signs] 1 ... optical housing, 2 ... photosensitive drum, 3 ... laser light source unit,
4 mirror, 5 polygon mirror, 6 first fθ lens, 7 second fθ lens, 8 optical axis, 9 notch, 10 lens holding member, 11 pressing spring, 12
... bridge member, 13 ... overhang, 14, 15 ... screw, 16 ... columnar member, 18, 21 ... positioning projection

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02B 7/00 G02B 7/02 G02B 7/18

Claims (1)

(57) [Claim 1] In an optical scanning device having a deflecting unit for deflecting a light beam, a lens for forming an image of the light beam deflected by the deflecting unit, and an optical housing. There are a plurality of the lenses, and at least a part of the upper end of the mutually facing surfaces of the two lenses is provided with an oblique cutout, and the two lenses are provided in the optical housing. A projection is provided outside the position to be fixed, and further, a lens pressing member that simultaneously contacts the cutout surfaces of the two lenses,
An optical scanning device comprising: pressing means for pressing a lens pressing member downward.