JPH09197320A - Laser exposure device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the vibration of a frame and an optical element without increasing the rigidity or weight of components by providing a vibration reduction member nearby a vibration position in a laser exposure device which is excited by an optical deflecting means. SOLUTION: A rib 10b for reinforcement is provided in the outer edge part of the frame and the vibration reduction member 21 formed in a plate shape on the top surface of the corner of the rib is fitted tightly to the plate-shaped corner part through a fitting member 21a by using an adhesive, etc. A resin material which is close in rigidity to an object position is used for the vibration reduction member 21 and the length, width, and thickness of the plate shape are so set that primary and secondary natural vibration frequencies are close to that at the object position. For operation, plural plate-shaped vibration reduction members 21 which are different in size are prepared, the corner parts are fitted to specific places through the fitting member 21a, and an observed member which has the largest vibration at operation time is selected and determined. This vibration reduction member 21 is thus provided to reduce the vibration at the position A of the frame 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser exposure device used in an image recording device such as a laser beam printer or a laser facsimile.

[0002]

2. Description of the Related Art Conventionally, a laser exposure apparatus of this type deflects and scans laser light modulated by an image signal by a mechanical optical deflecting means such as a polygon mirror rotating at high speed or a galvano mirror reciprocating at high speed. It is configured to irradiate a photosensitive member, which is a scanning target. One of the problems of a laser exposure apparatus that performs such scan recording is light and shade (so-called pitch unevenness) that occurs due to irregular intervals between scanning lines.
Vibration of the laser exposure apparatus is one of the causes. This vibration source is an optical deflector, and in the case of a polygon mirror, vibration occurs at the frequency of the rotation speed of the motor, and in the case of a galvanometer mirror, vibration occurs at the scanning frequency. This vibration is transmitted to each optical element via the exposure device frame to which the deflecting device is attached. When the natural frequency of the frame or the optical element of the exposure apparatus is close to this excitation frequency, it resonates to generate vibration and the laser beam also vibrates together.

When the frame of the laser exposure apparatus is made of resin, its rigidity tends to be lower than that of metal, so that vibration is likely to occur. Further, when changing the direction of the deflected and scanned laser beam, a mirror having a large aspect ratio, that is, a so-called long mirror is used, but the long mirror easily causes vibration. Further, the cylindrical lens for tilt angle correction provided near the object to be scanned is also a member having a large aspect ratio and easily vibrating.

In order to increase the rigidity of the frame of the laser exposure apparatus, a measure to increase the height of the reinforcing ribs of the frame is taken, but the higher the height, the more material is used, which is costly. In addition, the frame itself becomes large and the shape of the entire recording apparatus becomes large.

Further, in order to increase the rigidity of long components such as mirrors and cylindrical lenses, measures to make the components thicker are taken. The thicker this also becomes, the higher the cost becomes. Further, a reinforcing member may be provided in the thickness direction, but it is costly to sufficiently improve the effect.

[0006]

SUMMARY OF THE INVENTION The present invention is a laser exposure in which vibration of a frame or an optical element of a laser exposure apparatus excited by an optical deflector is reduced without increasing the rigidity or weight of the component. The purpose is to provide a device.

[0007]

SUMMARY OF THE INVENTION The above object is to provide a laser exposure apparatus for deflecting and scanning a laser beam by using a light deflecting means, which is provided in the vicinity of a vibrating portion in the laser exposure apparatus which is excited by the light deflecting means. And a vibration reducing member that reduces vibration of the vibrating portion by vibrating itself is provided.

The above-mentioned light deflecting means is a laser light polarizing means using a polygon mirror or a galvano mirror, and one fixed point of the vibration reducing member has the largest vibration amplitude of the vibrating portion. The preferred embodiment is near the site.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

The embodiment shown in FIG. 1 is a laser exposure apparatus for recording a color image, wherein FIG. 1 (a) is a plan view and FIG.
(B) shows a sectional view. In the figure, 11 is a semiconductor laser LD (laser diode) that emits laser light of each color of C (cyan), M (magenta), and Y (yellow).
The laser light emitted from each LD 11 is shaped into parallel light by a collimator lens 12 provided on the front surface thereof, and further passes through a cylindrical lens 13 to form a reflection mirror 1.
After being reflected at 4, the polygon mirror 15 which is an optical deflector
And is deflected one-dimensionally in the main scanning direction, and is adjusted by the fθ lens 16 so as to form an image at a predetermined position at a predetermined timing. The elongated mirrors 17 and 18 reflect the scanning light to form a cylindrical lens. After the surface tilt correction is performed by 19, the main scanning is performed on the recording medium P moving in the sub-scanning direction indicated by the arrow, and two-dimensional image exposure is performed.

It is such a laser light source. All the scanning optical systems including the LD 11 are fixed to the frame 10, and the frame 10 is firmly attached to the main body of the apparatus by the attachment portions 10a provided at three positions outside the frame. The polygon mirror 15, which is an optical deflector, rotates the polygon mirror at a rotation speed of 3000 rpm to 7500 rpm during laser exposure. Drive motors such as polygon mirrors are manufactured with careful attention to balance, but 50Hz to 125Hz
As a vibration source having a vibration frequency of, the frame 10 vibrates and is transmitted to each optical element via the frame 10.
When the natural frequency of the frame or the optical element is close to this excitation frequency, the light beam resonates, and the light beam also resonates, causing uneven pitch.

According to the present invention, a vibration reducing member is provided in the vicinity of a vibrating portion in a laser exposure apparatus which is deflected by light so as to reduce the vibration of the vibrating portion by vibrating itself. An example is shown in FIGS.

The embodiment shown in FIG. 2 is an embodiment in which a vibration reducing member 21 is provided for the purpose of reducing the vibration at the outer end of the frame 10 (the portion indicated by A in FIG. 1A). 2A shows a perspective view and FIG. 2B shows a side view. The outer end portion of the frame 10 shown by A in FIG. 1A has a free end shape in terms of material mechanics, and the outer end portion forming the outer edge has the maximum amplitude in comparison with other portions during operation. Vibration is observed. The vibration at point A is the vibration of the frame part where the polygon mirror that is the vibration source is attached,
Fluctuations or vibrations of the scanning light cause uneven pitch. Since the frame 10 of this embodiment uses a resin material, its rigidity is low and vibration is likely to occur. In this embodiment, reinforcing ribs 10b are provided on the outer edge of the frame, and plate-shaped vibration reducing members 21 are attached to the upper surfaces of the corners of the frame through the mounting portions 21a. It is firmly attached using an agent. The vibration-reducing member 21 is made of a resin material having a rigidity close to that of the target portion.
The next natural frequency is set to be close to the frequency of the target part. For the work, a plurality of plate-shaped vibration reducing members 21 having different sizes are prepared, the corners of the members are attached to predetermined positions via the attachment portions 21a, and the member in which the largest vibration is observed during operation is selected. It is also done by making a decision.
By providing such a vibration reduction member 21, while the vibration reduction member 21 is allowed to have a considerable vibration during operation, the vibration at the position A of the frame 10 is obviously reduced by mounting the vibration reduction member 21. Phenomenon such as pitch unevenness due to the vibration of the can no longer be recognized.

The embodiment shown in FIG. 3 is an embodiment in which a vibration reducing member 22 is provided in the vicinity of the central position of the elongated mirror 18 (the portion indicated by B in FIG. 1A) for the purpose of reducing vibration. 3A is a perspective view and FIG. 3B is a side view. The elongated mirror 18 is a rod-shaped glass member having a surface reflection coating, and both ends thereof are supported by supporting members 18a. Therefore, the elongated mirror 18 is supported at both ends, and when actuated, vibrates with the maximum amplitude with the central portion as a hara. Since the vibration of the mirror is magnified by the action of the optical lever, even a minute vibration greatly affects the recorded image. In this embodiment, the vibration reducing member 22 is provided at the center of the rear surface of the elongated mirror 18, and the vibration reducing member 22 in the form of a strip made of aluminum or the like is attached to the mounting portion 22a which supports the vicinity of the center. It is fixed. The primary or secondary natural frequency of the strip-shaped vibration reducing member 22 is set to be close to the frequency of the long mirror 18 during operation. For the work, a plurality of strip-shaped vibration reducing members 22 having different sizes are prepared, and the central portion thereof is attached to the central portion of the rear surface of the long mirror 18 via the mounting portion 22a. This is done by selecting and determining the members to be used.
By providing such a vibration reducing member 22, some vibration is recognized in the vibration reducing member 22 at the time of operation, but the vibration of the long mirror 18 is hardly recognized by mounting the vibration reducing member 22, and the long image is recorded in the long mirror. 1
The phenomenon such as pitch unevenness due to the vibration of No. 8 is not recognized at all.

The two embodiments have been described above.
The present invention is effective when a vibration reducing member is provided at a vibration portion due to resonance in the laser exposure apparatus. Further, although the example in which the polygon mirror is used as the light deflecting means has been described in the present embodiment, the present invention is also applied to a laser exposure apparatus having a mechanical light deflecting means using a galvano mirror.

[0016]

According to the present invention, vibration can be prevented in the long mirror in the laser exposure apparatus, the frame of the exposure apparatus, etc. without increasing the rigidity of the members, and thus it has been conventionally used to prevent the vibration. It is possible to reduce the amount of material, and it is possible to inexpensively provide a high-quality laser exposure apparatus that does not cause uneven pitch due to vibration.

[Brief description of drawings]

FIG. 1 is a plan view and a sectional view showing an embodiment of a laser exposure apparatus.

FIG. 2 is a perspective view and a side view showing an example of a vibration reducing member.

FIG. 3 is a perspective view and a side view showing another example of the vibration reducing member.

[Explanation of symbols]

 10 frame 11 LD 12 collimator lens 13,19 cylindrical lens 15 polygon mirror 16 fθ lens 17,18 long mirror 21,22 vibration reducing member 21a, 22a mounting portion (vibration reducing member)

Claims (3)

[Claims] 1. A laser exposure apparatus for deflecting and scanning a laser beam using an optical deflecting means, wherein the laser exposing apparatus is provided near a vibrating portion in the laser exposing apparatus which is excited by the optical deflecting means and vibrates itself. Thus, a laser exposure apparatus is provided with a vibration reducing member for reducing the vibration of the vibrating portion. 2. The laser exposure apparatus according to claim 1, wherein the light deflection means is a laser light polarization means of a polygon mirror or a galvanometer mirror. 3. The laser exposure apparatus according to claim 1, wherein one fixed point of the vibration reducing member is in the vicinity of a portion having the largest vibration amplitude of the vibrating portion.