JPH08184775A - Scanning optical system - Google Patents

Abstract

PURPOSE: To prevent dust from entering into an optical housing by bringing the outer peripheral surface of a cover into close contact with the inner peripheral surface of a surrounding wall. CONSTITUTION: A placing surface 21b for placing the cover 32 is installed at the inside of the upper surface of the peripheral wall 21a of the optical housing 21, and also, the surrounding wall 21c for surrounding the outer peripheral surface of the cover 32 is installed at the outside. The surrounding wall 21c on the upwind side of a wind flowing in a direction B is made higher than the surface of the cover 32, and the surrounding wall on the downwind side is made lower than the surface of the cover 32. A pressure drop due to a labyrinth effect is generated on the upwind and downwind sides of the cover 32, then, the air and the dust hardly enter into the optical housing 21.

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 used in a laser beam printer, a laser facsimile, etc., for deflecting a laser beam and condensing it on a predetermined surface.

[0002]

2. Description of the Related Art In a conventional scanning optical device of this type, as shown in a schematic perspective view of FIG. 5, for example, a collimator lens 2, an aperture stop 3, and a collimator lens 2 are arranged in a traveling direction of a light beam from a laser light source 1.
The cylindrical lens 4 and the polygon mirror 5 are sequentially arranged, and the polygon mirror 5 is attached to the motor 6 and driven to rotate, whereby the light flux incident on the polygon mirror 5 is deflected and scanned. An fθ lens 7, a toric lens 8, and a photoconductor drum 9 are sequentially arranged in the traveling direction of the light beam deflected by the polygon mirror 5, and the light beam is focused on the photoconductor drum 9 and repeatedly scanned in the direction A. It is supposed to be done. A fixed mirror 10 is arranged at one scanning end of the light beam, and a sensor 12 for timing detection is arranged in the reflection direction of the fixed mirror 10 via a condenser lens 11. Then, among the optical systems arranged in this way, the optical system except the photosensitive drum 9 is built in an optical box (not shown).

In the conventional example thus constructed, the light flux emitted from the laser light source 1 is collimated by the collimator lens 2 and shaped into a shape corresponding to the aperture by the aperture diaphragm 3, and then the cylindrical lens 4 is formed. Is focused on the mirror surface of the polygon mirror 5. The light beam focused on the polygon mirror 5 is deflected and scanned by the motor 6, and is focused on the photosensitive drum 9 by the fθ lens 7 and the toric lens 8 as a minute spot image. At this time, the light beam deflected by the polygon mirror 5 is repeatedly scanned in the direction A at a constant speed by the fθ lens 7,
When there is a division error on the mirror surface of the polygon mirror 5, the scanning timing is deviated, so the sensor 12 detects the leading portion of the light beam and modulates the light beam in accordance with this timing.

In recent years, a scanning optical device which operates at high speed and with high accuracy has been strongly required, and the polygon mirror 5 is designed to rotate at high speed. Therefore, when the polygon mirror 5 rotates at a high speed, dust in the air often adheres to the mirror surface, the reflectance of the mirror surface decreases, and the density of the image formed on the photosensitive drum 9 decreases. Then, there is a problem that the image quality becomes poor.

In order to deal with such a problem, an optical box containing an optical system is covered with a cover (not shown),
Dust in the air is prevented from entering the inside of the optical box. This cover is made of a flexible synthetic resin material such as polypropylene and is fixed to the optical box by a snap fit.

[0006]

However, in the above-mentioned conventional example, since the cover is formed of the flexible synthetic resin material, even if the cover is fixed to the optical box by the snap fit, the space between the optical box and the cover is reduced. There is a gap in the air, and dust in the air enters the optical box and adheres to the optical system, which lowers the transmittance and reflectance of the optical system and reduces the image density, resulting in poor image quality. There is a point.

An object of the present invention is to solve the above-mentioned problems and to provide a scanning optical device capable of preventing dust from entering the inside of the optical box and improving the image quality.

[0008]

A scanning optical device according to a first aspect of the present invention for achieving the above object is an optical box having an optical system for deflecting a light beam and condensing the light beam on a predetermined surface, and the optical box of the optical box. In a scanning optical device including a cover that covers an opening, a mounting surface for mounting the cover is provided on an upper surface of a peripheral wall of the optical box, and a surrounding wall that surrounds an outer peripheral surface of the cover is provided outside. The cover is fitted inside the surrounding wall.

The scanning optical device according to the second aspect of the present invention includes an optical box containing an optical system for deflecting a light beam and condensing it on a predetermined surface, a cover for covering an opening of the optical box, and the optical box. In a scanning optical device provided with a blower that blows air, a mounting surface for mounting the cover is provided inside on the upper surface of the peripheral wall of the optical box, and a surrounding wall that surrounds the outer peripheral surface of the cover is provided outside. The height of the surrounding wall is higher than the surface of the cover,
It is characterized in that it is high on the windward side and / or low on the leeward side.

[0010]

In the scanning optical device according to the first aspect of the present invention having the above-mentioned structure, the mounting surface for mounting the cover is provided on the inside of the upper surface of the optical box, and the surrounding wall surrounding the outer peripheral surface of the cover is provided on the outside. Since the cover is fitted on the inner side of the surrounding wall and placed on the placing surface, the outer peripheral surface of the cover closely adheres to the inner peripheral surface of the surrounding wall, and the adhesive force causes the lower surface of the cover to closely contact the placing surface.
It becomes difficult for dust to enter the inside of the optical box.

Further, in the scanning optical device according to the second invention,
On the upper surface of the optical box, the mounting surface for mounting the cover is provided inside, the surrounding wall surrounding the outer peripheral surface of the cover is provided outside, and the cover is mounted on the mounting surface inside the surrounding wall. If the height is higher on the windward side than the surface of the cover, a pressure drop occurs behind the inner peripheral surface of the enclosure, and if it is lower on the lee side, a pressure drop occurs behind the outer peripheral surface of the cover. hand,
It becomes difficult for dust to enter the inside of the optical box.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in FIGS. FIG. 1 is a perspective view of an embodiment, in which a semiconductor laser 23 and a collimator lens 24 which constitute a power supply unit 22 are attached to an optical box 21, and a laser beam L emitted from the semiconductor laser 23 travels in a traveling direction. The cylindrical lens 25 and the polygon mirror 26 are sequentially arranged. The polygon mirror 26 is attached to a motor (not shown), and the laser beam L is deflected and scanned by the driving force of this motor.

An imaging lens 27 and a folding mirror 28 are sequentially arranged in the traveling direction of the laser light flux L deflected and scanned by the polygon mirror 26, and a cover is provided in the traveling direction of the laser light flux L reflected by the folding mirror 28. A glass 29 is arranged, and the cover glass 29 closes a part of the opening of the optical box 21. A fixed mirror 30 is arranged at one scanning end of the laser light flux L deflected by the polygon mirror 5.
A sensor 31 for timing detection is arranged in the traveling direction of the laser light flux L reflected by.

These optical systems are arranged inside the optical box 21, and the upper opening of the optical box 21 is covered with a cover 32. A blower (not shown) is installed outside the optical box 21 covered with the cover 32 to cool the motor built in the optical box 21.

Here, as shown in the partially enlarged sectional views of FIGS. 2 and 3, the blower blows the air in the direction B with respect to the optical box 21. The peripheral wall 21 of the optical box 21
A mounting surface 21b for mounting the lower peripheral portion of the cover 32 is provided inside the upper surface of a. In addition, the peripheral wall 21
A windward side surrounding wall 21c and a leeward side surrounding wall 21d for surrounding the peripheral surface of the cover 32 are provided outside the upper surface of a. The cover 32 is formed of a synthetic resin material such as vinyl chloride, a metal material, or the like, and the size thereof is the enclosure walls 21c, 2
It is fitted inside 1d or has a slight gap d between the surrounding walls 21c and 21d. The mounting surface 21b is formed on the same plane, and the mounted cover 32 is joined to the mounting surface 21b in a planar manner. The cover 32 is mounted on the mounting surface 21b and then fixed by, for example, a snap fit or a screw.

Further, the height of each of the surrounding walls 21c and 21d is equal to or higher than the surface of the cover 32 on both the windward side and the leeward side, or is raised only on the windward side, or Only the leeward side is lowered. As a result, a pressure drop due to the so-called labyrinth effect occurs behind the windward side surrounding wall 21c and behind the leeward side cover 32, and the wind energy is weakened.

As shown in the partially enlarged sectional view of FIG. 4, when the height of the wall 21e on the windward side is made lower than that of the surface of the cover 32, the wind flows in the direction b and the air is blown into the optical box 21.
The optical box 2 from between the mounting surface 21b of the
It becomes easy to flow into 1. Therefore, it is most effective to make the height of the leeward wall 21c higher than the surface of the cover 32 and lower the height of the leeward wall 21d lower than the surface of the cover 32.

Since the scanning optical device according to the present embodiment is constructed as described above, the optical box 21 operates while being cooled by the blower, and the laser light flux L emitted from the semiconductor laser 23 of the power supply unit 22 is The collimator lens 24 forms a parallel light beam, and the cylindrical lens 25 linearly focuses the light beam on the polygon mirror 26. The laser light flux L focused on the polygon mirror 26 is deflected and scanned by the polygon mirror 26 rotationally driven by the motor, made into a light flux scanned at a constant speed by the imaging lens 27, reflected by the folding mirror 28, and covered. The light passes through the glass 29 and is condensed as a spot image on the rotating drum.

At this time, an electrostatic latent image is formed by the laser beam L focused on the rotating drum by the main scanning by the rotation of the polygon mirror 26 and the sub-scanning by the rotation of the rotating drum. Further, a part of the laser light flux L deflected by the polygon mirror 26 is reflected by the fixed mirror 30, and the scanning start signal is transmitted to the semiconductor laser 23 by the sensor 31. The timing is adjusted by this signal, and the write modulation of the semiconductor laser 23 is started.

As described above, while the laser light flux L is deflected and scanned, the wind blows in the direction B by the blower, and the optical box 2
1 is cooled. At this time, a pressure drop occurs due to the labyrinth effect behind the surrounding wall 21c on the windward side and behind the cover 32 on the leeward side, the energy of the wind there is lost, and an attempt is made to enter the inside of the optical box 21 through the gap d. The power of air becomes weak.

As described above, in the embodiment, when the cover 32 is fitted inside the surrounding walls 21c and 21d, the cover 32 is
The outer peripheral surface of the cover 32 adheres to the inner peripheral surfaces of the surrounding walls 21c and 21d.
It can be closely attached to 1b. Further, since the mounting surface 21b is provided so as to form the same plane, the cover 32 can be brought into flat contact with the mounting surface 21b, and the degree of adhesion between the cover 32 and the mounting surface 21b can be improved. You can When the cover 32 is formed of a metal plate, the flatness is improved and the influence of deformation at high temperature is reduced, so that the adhesion between the cover 32 and the mounting surface 21b can be further improved. Furthermore, when the height of the surrounding walls 21c and 21d is made higher than that of the cover 32, the close contact between the cover 32 and the surrounding walls 21c and 21d can be stabilized.

When the height of the leeward wall 21c is made higher than the surface of the cover 32, a pressure drop occurs behind the wall 21c, and the height of the leeward wall 21d is adjusted to the surface of the cover 32. If the pressure is lower than that, a pressure drop occurs behind the cover 32 on the leeward side, and the wall 21c on the windward side is generated.
When the temperature is raised and the surrounding wall 21d on the leeward side is lowered, a pressure drop occurs at both sides, so that air can be reduced from entering the gap d.

Therefore, in the above-described embodiment, the degree of contact between the cover 32 and the optical box 21 can be improved, and the pressure of the air flowing through the contact between the cover 32 and the optical box 21 can be lowered. It is possible to prevent dust from entering the inside of the optical box 21. For this reason, the transmittance and reflectance of the optical system can be favorably maintained, and the image quality can be improved without lowering the image density.

In this embodiment, the opening of the optical box 21 is sealed with the cover glass 29, but the gap between the imaging lens 27 and the cover 32 is sealed with an elastic body such as Moltoprene (trade name). For example, polygon mirror 2
Since the space around 6 is sealed, it is not necessary to seal the opening of the optical box 21 with the cover glass 29.
Further, the cover 32 is fixed by snap fitting or screws, but if the cover 32 is attached to the mounting surface 21b with double-sided tape, the degree of sealing of the optical box 21 can be further improved. Although the imaging lens 27 is composed of one sheet, it may be composed of two or more sheets.

[0025]

As described above, in the scanning optical device according to the first and second aspects of the present invention, it is possible to prevent dust from entering the inside of the optical box, so that it is possible to prevent dust from adhering to the optical system. The amount can be reduced, the transmittance and reflectance of the optical system can be favorably maintained, and the image quality can be improved without lowering the image density.

In particular, in the scanning optical apparatus according to the first aspect of the present invention, the mounting surface for mounting the cover on the upper surface of the optical box is provided inside, and the surrounding wall surrounding the outer peripheral surface of the cover is provided outside, and the cover surrounding the cover. Since it is fitted inside the cover, the outer peripheral surface of the cover can be brought into close contact with the inner peripheral surface of the surrounding wall, and the adhesive force can bring the outer peripheral lower surface of the cover into close contact with the mounting surface, so that dust does not adhere to the optical box. It is possible to prevent it from entering the inside.

Further, in the scanning optical device according to the second aspect of the present invention, the mounting surface for mounting the cover on the upper surface of the optical box is provided inside, the surrounding wall surrounding the outer peripheral surface of the cover is provided outside, and the cover is attached to the surrounding wall. Since it is placed on the inner mounting surface, if the height of the enclosure is higher on the windward side than the surface of the cover, a pressure drop will occur behind the enclosure, and if it is lower on the lee side, the cover will be lowered. It is possible to prevent a dust from entering the inside of the optical box due to a pressure drop behind the optical box.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of an embodiment.

FIG. 2 is a partially enlarged sectional view.

FIG. 3 is a partially enlarged sectional view.

FIG. 4 is an operation explanatory view.

FIG. 5 is a perspective view of a conventional optical system.

[Explanation of symbols]

 21 optical box 21a peripheral wall 21b mounting surface 21c, 21d, 21e enclosure wall 26 polygon mirror 32 cover

Claims (5)

[Claims] 1. A scanning optical device comprising an optical box having an optical system for deflecting a light beam and condensing the light beam on a predetermined surface, and a cover for covering an opening of the optical box, wherein an upper surface of a peripheral wall of the optical box. The scanning optical device is characterized in that a mounting surface on which the cover is mounted is provided inside, and a surrounding wall surrounding the outer peripheral surface of the cover is provided outside, and the cover is fitted inside the surrounding wall. 2. The scanning optical device according to claim 1, wherein the mounting surface is formed in the same plane. 3. The scanning optical device according to claim 1, wherein the cover is made of a metal material. 4. The scanning optical device according to claim 1, wherein the height of the surrounding wall is higher than the surface of the cover. 5. Scanning optics comprising an optical box containing an optical system for deflecting a light beam and condensing it on a predetermined surface, a cover for covering an opening of the optical box, and a blower for blowing air on the optical box. In the device, a mounting surface on which the cover is mounted is provided on the upper surface of the peripheral wall of the optical box, and a surrounding wall that surrounds the outer peripheral surface of the cover is provided outside, and the height of the surrounding wall is the surface of the cover. The scanning optical device is characterized in that it is higher on the windward side and / or lower on the leeward side.