JP2002250889A - Optical scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical scanner in which an adverse effect of heat generation upon an optical means, a polygon motor which rotates at a high speed, in particular, is decreased, and the distortion of an image is eliminated. SOLUTION: The optical scanner is so composed that a recording medium is exposed by being scanned with a beam information emitted from a light source via a first optical means, a polygonal mirror, and a second optical means. The optical scanner is characterized by the fact that respective members of the optical scanner are contained in an optical box having a shielding top lid and fixed at a prescribed positions inside the box, respectively, the polygonal mirror forms a polygon motor with a motor fixed coaxially with the polygonal mirror, the polygon motor is fixed in the optical box, the polygon motor is covered with a motor cover, the motor cover is in contact with the top lid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of guiding a light beam emitted from a light source corresponding to recording data to a deflector (hereinafter, sometimes referred to as a polygon mirror) via a first optical means. The present invention relates to an optical scanning device configured to perform scanning exposure on a recording medium via a second optical unit by rotation of the polygon mirror, and particularly to a technique for stabilizing the optical scanning device at high speed.

[0002]

2. Description of the Related Art After a light beam emitted from a light source corresponding to recording data is guided to a polygon mirror via first optical means made of glass, the polygon mirror is rotated (about 10,000 rotations / minute). There is generally known an optical scanning device configured to deflect the light beam and perform scanning exposure on a recording medium via second optical means made of glass or synthetic resin.

[0003] In the optical scanning device, the periphery of the polygon mirror is covered with a shielding member so as to prevent noise caused by the rotation of the polygon mirror. The opening area for reflected light is covered with transparent glass or synthetic resin.

[0004] On the other hand, there is a strong demand in the market for speeding up, miniaturizing, or reducing the cost of optical scanning devices.

[0005]

However, it has been found in the course of development by the present inventor that the conventional optical scanning device has many problems that are not particularly suitable for speeding up or downsizing.

For example, when the rotation speed of the polygon mirror is rotated at a high speed (20,000 to 30,000 rotations / minute), noise which does not cause much problem in the case of a low speed rotation as in the conventional apparatus is generated. .

Further, heat generated from a motor drive source for rotating the polygon mirror at high speed raises the temperature inside the housing-shaped device. In particular, the rotor of the motor for rotating the polygon mirror integrally therewith is made of various materials. Are combined, the distortions due to the different linear expansion coefficients are different from each other, so that the polygon mirror surface changes in planarity and the image quality is deteriorated. Further, at the time of high-speed rotation, the dynamic balance changes and the vibration of the motor itself increases. In addition, the temperature and humidity of the installation location must be strictly controlled, which not only causes problems such as securing safety and complicating handling, but also affects downsizing and cost reduction.

For example, the temperature rise in the optical scanning device when the high-speed rotation is continued is about 20 to 40 ° C. as compared with the temperature in the device in the conventional device, and the inside of the optical box, especially, the polygon mirror which is shielded Near 70 ° C or more and 75 ° C
To some degree.

In other words, even if an attempt is made to reduce the size of the apparatus, difficulties are involved due to the above-mentioned problems, and as a result, a reduction in the size and an inexpensive configuration cannot be adopted, and a recorded image of a desired image quality cannot be obtained. Problems arise.

The present invention has been made in view of the above problems, and a main object of the present invention is to provide an optical scanning device in which the adverse effect of heat generation on optical means is reduced as much as possible.

It is another object of the present invention to provide an optical scanning device in which generation of noise is reduced as much as possible.

[0012]

This object is achieved by any of the following technical means (1) to (5).

(1) After a light beam emitted from a light source corresponding to recording data is guided to a deflector via a first optical means, the recording medium is transmitted via a second optical means by rotation of the deflector. In the optical scanning device configured to perform the scanning exposure on the above, each member of the optical scanning device is housed in an optical box having a shielding upper lid and is fixed at a predetermined position inside,
The polygon mirror as the polarizer constitutes a polygon motor by a motor concentrically attached thereto, the polygon motor is fixed in the optical box, and the polygon motor is covered with a motor cover. Yes,
The optical scanning device, wherein the motor cover is in contact with the shielding upper lid.

(2) The optical scanning device according to item (1), wherein the motor cover is fixed to the motor base plate of the polygon motor or the optical box with screws.

(3) The upper surface of the motor cover is screwed and fixed to the shielding upper cover (1).
Or the optical scanning device according to item (2).

(4) The motor cover according to (1) or (2), wherein an upper surface portion of the motor cover is fixed to the shielding upper lid by a screw between the shielding upper lid and a heat conductive member. Optical scanning device.

(5) The optical scanning device according to item (1), wherein the motor cover is fixed to the shielding upper lid via an adhesive between the motor cover and the shielding upper lid.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a front view of the optical scanning device, FIG. 2 is a plan view of the optical scanning device, and FIG. 3 is a sectional view of an example of a polygon motor used in the embodiment of the present invention, that is, attached to an optical box. FIG. 4 is a cross-sectional view showing a state in which an upper surface portion of a motor cover screwed to a base of a polygon motor in contact with a shielding upper cover, and FIG. 4 is a cross-sectional view of another example of a polygon motor used in the embodiment of the present invention. FIG. 7 is a cross-sectional view showing a state in which the lower portion of the motor cover is screwed to the base of the polygon motor attached to the optical box and the upper surface of the motor cover is screwed and fastened to the shielding upper lid and is in contact therewith. FIG. 5 is a sectional view of another example of the polygon motor used in the embodiment of the present invention, that is, the lower portion of the motor cover is screwed to the base of the polygon motor attached to the optical box and the motor is rotated. FIG. 6 is a cross-sectional view showing a state in which the upper surface of the cover is screwed and fastened to the shielding upper lid via a heat conductive member and is in contact therewith. FIG. 6 is a view showing still another example of the polygon motor used in the embodiment of the present invention. FIG. 4 is a cross-sectional view, that is, a cross-sectional view showing a state in which the motor cover is fastened to the shielding upper lid via an adhesive.

As shown in FIGS. 1 and 2, the optical scanning device according to the present invention has a housing shape in which a shielding upper lid 2 is assembled on an optical box 1 having a window frame 112 and a slit 114 formed thereon. And an optical unit for guiding a light beam corresponding to the recording data to the recording medium and performing scanning exposure. As shown in FIG. 2, the optical box 1 is made of polycarbonate resin (PC resin) in a shape reinforced by several ribs 101 indicated by dotted lines. However, it is desirable that the shielding cover 2 is made of a metal having good thermal conductivity such as an Al alloy.

Reference numeral 3 denotes a laser light source, and reference numeral 4 denotes first optical means, which has a collimator lens 40 and a first cylindrical lens 41 as main components.

Although the collimator lens 40 and the first cylindrical lens 41 in the embodiment are formed of glass, they may be formed of plastic.

Reference numeral 5 denotes a deflector (hereinafter, referred to as a polygon mirror 5) comprising a polygonal polygon mirror. The deflector 5 deflects a light beam 8 emitted from the laser light source 3 and passed through the first optical means 4. It is provided so as to be rotatable around the drive shaft center 501.

As shown in the sectional view of FIG. 3, the motor is concentrically integrated with the rotor of the DC motor so as to rotate about a fixed drive shaft 501 provided on a motor base plate 202 which is a magnetic field generator of the DC motor. Are provided, and a polygon motor 200 capable of rotating at high speed is formed. The polygon motor 200 will be described in some detail.

The polygon mirror 5 as an optical deflector of this embodiment is incorporated in, for example, the optical scanning device shown in the sectional views of FIGS. Is deflected by the rotation of the motor, and is incorporated in the polygon motor 200 and its motor base plate 202
Is fixed to the optical box 1 side.

The polygon motor 200 is constructed as described above. The polygon motor 200 is further covered with a motor cover 201 for the purpose of preventing dust and noise, and the upper surface portion 201a of the motor cover 201 is in contact with the shielding upper cover 2. are doing. It is desirable that at least a portion of the motor cover 201 that comes into contact with the shielding upper lid 2 is made of a metal having high thermal conductivity. As shown in FIG. 3, the manner of contact between the upper surface portion 201a and the shielding upper cover 2 is that the bottom of the motor cover 201 is fixed to the motor base plate 202 or the bottom of the optical box 1 (not shown) so that the upper surface portion 201a is 4 and the motor cover 201 as shown in FIG.
The upper surface 201a of the motor cover 201 is also screwed to the shielding upper lid 2 via the heat conducting member 241 as shown in FIG. FIGS. 6A and 6B show a case where the motor cover 201 is stopped and brought into contact with the motor base plate 202 or the case where the bottom of the motor cover 201 is not stopped by the bottom of the motor base plate 202 or the optical box 1 in FIGS. As described above, the upper surface portion 201a of the motor cover 201 is in contact with the shielding upper lid 2 by being adhered with the heat conductive adhesive, and the motor cover 201
May not be stopped by the motor base plate 202 or the bottom of the optical box 1 (not shown).

As a result, the polygon motor 200 is covered with the motor cover 201 to maintain a dustproof state, and the high temperature state in the motor cover 201 is exhausted by the motor cover 201 having good thermal conductivity and the shielding upper cover 2 to remove the heat. , The distortion of the mirror reflection surface of the polygon motor 200 is improved, and the image quality of the formed image can be greatly improved.

Specifically, the optical box 1 and the motor cover 20
1 and the shielding lid 2 have a space temperature of 20 to
According to the present invention, it is possible to keep the temperature, which may rise from nearly 40 ° C. and reach a maximum of about 75 ° C., to 55 ° C. or less, and the material of each member constituting the polygon mirror 5 and the rotor of the polygon motor 200 ( In particular, the distortion of the polygon mirror 5 due to the difference in the linear expansion coefficient) was drastically reduced, and the image quality of the output image could be greatly improved.

Also, even during high-speed rotation, the distortion of the above-described members is eliminated, so that the dynamic balance of the rotor constituting the polygon mirror 5 is not lost, and noise generation is not noticeable.

Thus, the light beam having no distortion formed on the polygon mirror 5 is projected to the second optical means. Reference numeral 6 denotes an fθ lens, and reference numeral 7 denotes a second cylindrical lens, which is fixed in position inside the optical box 1 via appropriate means.

The fθ lens 6 and the second cylindrical lens 7 are main elements constituting the second optical means. The fθ lens 6 and the second cylindrical lens 7 form a light beam 8 deflected by the polygon mirror 5 on a recording medium 9 such as a photosensitive member. It is designed to function as an image lens.

[0032]

According to the optical scanning device of the present invention, a rise in the temperature of the polygon mirror caused by heat generated during high-speed rotation of the polygon motor is avoided, the distortion of the mirror surface of the polygon mirror is greatly reduced, and the image distortion of the formed image is almost eliminated. Can be
High-speed image processing by an optical scanning device can be performed stably at a relatively low cost without taking up space by providing an expensive cooling device.

Further, the dynamic balance at the time of high-speed rotation was maintained in a stable state, and noise generation was greatly reduced.

[Brief description of the drawings]

FIG. 1 is a front view of an optical scanning device.

FIG. 2 is a plan view of the optical scanning device.

FIG. 3 is a cross-sectional view of an example of a polygon motor used in the embodiment of the present invention.

FIG. 4 is a sectional view of another example of the polygon motor used in the embodiment of the present invention.

FIG. 5 is a sectional view of another example of the polygon motor used in the embodiment of the present invention.

FIG. 6 is a sectional view of still another example of the polygon motor used in the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical box 2 Shielding top lid 5 Polygon mirror 8 Light beam 200 Polygon motor 201 Motor cover 201a Upper surface part of motor cover 202 Motor base plate 241 Heat conduction member

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme coat ゛ (Reference) H04N 1/113 H04N 1/04 104A F-term (Reference) 2C362 BA90 DA12 DA33 2H045 AA33 AA59 CB22 DA04 DA41 5C051 AA02 CA07 DA01 DB02 DB24 DB30 DB35 DC04 DC07 DD02 EA08 5C072 AA03 BA12 DA02 DA04 HA02 HA09 HA13

Claims (5)

[Claims] 1. A light beam emitted from a light source corresponding to recording data is guided to a deflector via a first optical unit, and then, by rotation of the deflector, a light beam on a recording medium is transmitted via a second optical unit. In the optical scanning device configured to perform scanning exposure, each member of the optical scanning device is housed in an optical box having a shielding upper lid and fixed at a predetermined position inside, and the polygon mirror as the polarizer is A polygon motor is constituted by a motor concentrically attached to the polygon motor, the polygon motor is fixed in the optical box, and the polygon motor is covered with a motor cover. An optical scanning device, wherein the optical scanning device is in contact with the optical scanning device. 2. The optical scanning device according to claim 1, wherein the motor cover is fixed to the motor base plate of the polygon motor or the optical box with screws. 3. The optical scanning device according to claim 1, wherein an upper surface of the motor cover is fixedly screwed to the shielding upper cover. 4. The optical scanning device according to claim 1, wherein an upper surface portion of the motor cover is fixed to the shielding upper cover with a screw between the upper surface of the motor cover and the shielding upper lid via a heat conductive member. . 5. The optical scanning device according to claim 1, wherein the motor cover is fixed to the shielding upper cover via an adhesive between the motor cover and the shielding upper lid.