JP2985279B2 - Optical scanning device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical scanning device used for a laser printer or the like.

2. Description of the Related Art Conventionally, in an optical scanning device used for a laser printer or the like, various optical components are collectively arranged on a base of the optical device. For example, a rotating polygon mirror device for driving a rotating polygon mirror by a motor, an imaging lens for introducing light from the rotating polygon mirror to form an image on the same plane on a base, and reflecting light from the imaging lens. Components such as a reflection mirror are housed therein, and these optical components are arranged by being regulated by respective positioning projections provided on the base.

The upper part of the base also prevents dust and toner from entering the optical device and adhering to the surfaces of lenses and mirrors and contaminating them, or preventing unnecessary light from entering from outside. For this purpose, a light-shielding cover is provided to cover the optical component (see Japanese Patent Application Laid-Open No. 64-46713).

[Problems to be Solved by the Invention] However, in the case where the rotary polygon mirror device and the imaging lens are mounted on the same plane on the base as described above, as shown in FIG. Since the motor flange portion P2 of the mirror device P1 and the positioning projection P4 of the imaging lens P3 interfere with each other, there is a problem that the imaging lens P3 cannot be mounted close to the rotating polygon mirror P5. For this reason, it was not possible to reduce the size of the imaging lens P3, so that the size of the optical device was increased, and it was difficult to reduce the cost.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to provide an optical scanning device in which a rotating polygon mirror and an imaging lens can be arranged close to each other.

Means for Solving the Problems In order to achieve this object, the present invention provides a deflecting means for deflecting and scanning a laser beam from a light source in a predetermined direction, and receiving the laser beam deflected by the deflecting means. An optical scanning device having an optical mechanism having an imaging lens system for converging light on a scanning body, comprising: a base on which the deflecting unit is arranged; and a light covering the deflecting unit arrangement side of the base and the optical mechanism. And at least one imaging lens is provided inside the cover and on the base such that a laser beam is input from the deflecting means in proximity to the deflecting means. The gist of the present invention is an optical scanning device characterized in that the optical scanning device is arranged on a surface facing the deflecting means arrangement side.

[Operation] In the optical scanning device of the present invention, a laser beam is emitted from a light source, the laser beam is deflected in a predetermined direction by a deflecting unit and scanned, and the deflected laser beam is applied to an object to be scanned by an imaging lens system. Collect light.

Then, by arranging at least one imaging lens on the inner surface of the cover and the surface opposite to the deflecting device arrangement side of the base so as to input the laser beam from the deflecting device, This makes it possible to arrange the imaging lens and the deflecting means close to each other.

[Embodiment] An overall configuration of an optical scanning device embodying the present invention will be described below with reference to FIG.

As shown in the figure, an optical scanning device 1 of the present embodiment scans a photosensitive drum 2 using a laser beam. As a configuration for this, a rotating polygon mirror device 5 is mounted on an optical bench 3. The optical system includes optical components such as an image lens (fθ lens) 7, a reflection mirror 9, and a second cylindrical lens 11, and a cover 13 is attached so as to cover these optical components.

The optical table 3 is made of unsaturated polyester filled with glass fiber and heated and compressed. The optical table 3 has a storage hole 15 for storing the rotary polygon mirror device 5 and a second cylindrical lens 11 fixed thereto. Fixing member 16, a rectangular opening 17 serving as a path of laser light to the second cylindrical lens 11, a fixing hole 18 for fixing the cover 13, and a screw hole
19 and are formed.

The rotary polygon mirror device 5 includes a laser diode 20 (FIG. 3).
Polygon mirror that deflects and reflects laser light emitted from
22, a motor 23 for rotating the rotary polygon mirror 22, and a motor flange portion 24 projecting onto the optical bench 3 to fix the device 5 to the optical bench 3.

As shown in FIG. 2, the fθ lens 7 is a half-moon-shaped convex lens in which one end of a circular lens is cut off the center of the circle, and is formed by a lens support portion 25 provided on the inner surface of the cover 13. Is attached to the cover 13 side in the vicinity of the rotary polygon mirror 22.

That is, inside the upper part of the cover 13, the lens supports 25a to 25d constituting the lens support portion 25 project downward so as to surround the four sides of the fθ lens 7, and a pair of the lens supports 25c and 25d Is set to a height that does not block the optical path of the laser light, and the other pair of lens supports 25a and 25b
The leaf springs 27a and 27b extending inward are screwed to the distal end.

Lens 7 is positioned so that the optical axis side of fθ lens 7 abuts against the inner surface of lens supports 25c and 25d in the direction of arrow X (FIG. 1), and the lens support in the direction of arrow Y. The outer peripheral portion of the fθ lens 7 abuts and is positioned on the inner side surfaces of 25a and 25b, and the outer peripheral portion of the fθ lens 7 abuts on the support surface 13a integrally formed with the cover 13 in the arrow Z direction. Then, it is pressed and fixed by the leaf springs 27a and 27b.

In addition, as shown in FIG.
a rectangular mirror for reflecting the laser beam from the θ lens 7 toward the photosensitive drum 2, and a side surface inclined at a predetermined angle
13b, that is, attached to the side surface 13b of the cover 13 which is formed to be inclined in advance so as to have an angle capable of performing such reflection.

The second cylindrical lens 11 is arranged in alignment with the opening 17 and guides the laser beam from the reflection mirror 9 to the photosensitive drum 2, and is a rectangular lens slidable in its own longitudinal direction.

The cover 13 for covering the above-described optical component is a light-shielding cover made of a thermoplastic resin containing glass fiber, and includes the lens support portion 25 on the upper inside thereof, and the reflection mirror 9 is attached to the inclined side surface 13b. Have been. And, by the screw 30 which is positioned by the fixing protrusion 26 engaging with the fixing hole 18 and passed through the screw holes 19 and 28,
It is fixed to the optical table 3.

Next, the operation of the optical scanning device 1 according to the present embodiment having the above configuration will be described with reference to FIG.

First, an LED driver (not shown) based on the image information signal
The laser light emitted from the laser diode 20 as a light source is converted into a parallel light beam by a collimator lens 32, passes through a first cylindrical lens 33, and is rotated by a constant high speed. It is incident on 22a.

When the rotating polygon mirror 22 rotates, the reflected laser beam is deflected within a predetermined angle range for each mirror surface 22a. The same angle range is repeatedly scanned.

The laser beam reflected by the rotary polygon mirror 22 passes through the fθ lens 7 as an imaging lens so that the peripheral surface of the photosensitive drum 2 as an object to be scanned performs image-forming scanning at a constant speed on a straight line. I do. Next, the light is reflected by the reflecting mirror 9 in a direction perpendicular to the incident direction, and is reflected by the second cylindrical lens 11.
To reach.

Then, laser light is incident on the peripheral surface of the photosensitive drum 2 from the second cylindrical lens 11 to perform main scanning, and at the same time, rotation of the photosensitive drum 2 performs sub-scanning.

The synchronization signal that determines the write start position of this main scan is
The laser light at a predetermined position before the start of writing in the deflection range transmitted through the fθ lens 7 is reflected by the synchronization detecting mirror 35 and is incident on the optical sensor 36 which is a photoelectric element for synchronization detection, and is obtained from its detection output. .

As described above, the optical scanning device 1 of the present embodiment includes the cover 13
The fθ lens 7 is attached to the inside of the upper part by the lens support 25. This allows the motor flange
The fθ lens 7 can be arranged very close to the rotating polygon mirror 22 so as to receive the laser beam reflected by the mirror surface 22a without being disturbed by the mirror 24. Therefore, the whole apparatus can be formed compactly, and furthermore, an inexpensive f
Even when the θ lens 7 is used, a sufficient scanning angle can be obtained, so that significant cost reduction can be achieved.

In addition, since the fθ lens 7 is fixed by using the lens supports 25a to 25d and the leaf springs 27a and 27b arranged in a square shape, it is possible to use a half-moon shaped lens with a part cut, and as a result, The mounting of the fθ lens 7 is easy, and the mounting accuracy is improved. Also, as in the conventional case, fθ
Since it is not necessary to remove the portion of the lens 7 other than the portion scanned by the laser beam and process it into a strip shape, there is no need to increase the processing accuracy of one side to be cut, and there is an advantage that the processing cost is reduced.

Further, since the reflection mirror 9 is directly fixed to the cover 13, it is possible to obtain the optical scanning device 1 with high precision without assembling and adjusting the reflection angle of the laser light.

Further, by fixing the cover 13 to the optical table 3 using the positioning member 26 and the screw holes 19 and 28,
It is possible to effectively prevent dust and toner from entering inside and adhere to and contaminate the surfaces of lenses and mirrors, and prevent unnecessary light rays from entering from outside.

[Effects of the Invention] As is clear from the above, according to the present invention, by providing the imaging lens on the cover that covers the optical component, the imaging lens can be brought closer to the rotating polygon mirror. As a result, a sufficient scanning angle can be obtained with a small-diameter imaging lens, so that the entire optical scanning device can be reduced in size, and the number of manufacturing steps does not increase. Can be.

[Brief description of the drawings]

FIG. 1 is a schematic structural view showing the optical scanning device of the embodiment in a cut-away manner, FIG. 2 (A) is a front view showing a fixed state of the fθ lens, FIG. 2 (B) is its bottom view, and FIG. FIG. 4 is an explanatory view showing an optical path of a laser beam, and FIG. 4 is a front view showing a conventional example with a part cut away. DESCRIPTION OF SYMBOLS 1 ... Optical scanning device 3 ... Optical bench 7 ... ftheta lens 22 ... Rotating polygon mirror 24 ... Motor flange part 25 ... Lens support part

Claims (1)

(57) [Claims] 1. An optical mechanism comprising: a deflecting means for deflecting a laser beam from a light source in a predetermined direction for scanning, and an imaging lens system for condensing the laser light deflected by the deflecting means on an object to be scanned. An optical scanning device comprising: a base on which the deflecting unit is disposed; and a cover for shielding light by covering the deflecting unit arrangement side of the base and the optical mechanism, and further comprising at least one image forming unit. A lens is disposed inside the cover and on a surface of the base opposite to the side on which the deflecting means is arranged, so that a laser beam from the deflecting means is input near the deflecting means. Optical scanning device.