JP2006039413A - Optical unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical unit composed by closing a case-shaped frame serving as an optical surface plate with a cover, in which a stable and highly accurate light beam scanning is performed. <P>SOLUTION: The cover and the frame are fixed interposing an elastic cushioning material by using a stepped screw having a step higher than the thickness of the cover or a screw to which a collar higher than the thickness of the cover is inserted, and the total of the thickness of the cover and the thickness of the cushioning material is larger than the height of the stepped part (collar) of the stepped screw. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technical field of an optical unit that performs light beam scanning, which is used for exposure of a photosensitive material in a digital photo printer.

  In various image recording apparatuses such as digital photo printers and electrophotographic printers, light that is deflected in a predetermined one-dimensional direction (main scanning direction) and incident on a predetermined recording position is modulated according to a recorded image An optical unit (light beam scanning unit) that performs beam scanning is used.

If it is an optical unit that records a color image on a color photosensitive material, it corresponds to each exposure of R (red) exposure, G (green) exposure, and B (blue) modulated according to the image to be recorded (image data). Three types of light beams are deflected in a predetermined main scanning direction by an optical deflector such as a polygon mirror, the scanning speed in the main scanning direction is made constant by an fθ lens, and predetermined recording (exposure) is performed by an optical path changing mirror or the like. Incident to the position.
In an image recording apparatus using such an optical unit, if the apparatus uses a photosensitive material that requires development processing, the photosensitive material is positioned in the recording position in the sub-scanning direction perpendicular to the main scanning direction. By scanning and conveying the photosensitive material, the photosensitive material is two-dimensionally scanned and exposed by the three light beams of R, G, and B modulated according to the recorded image to record the latent image, and the exposed photosensitive material is recorded. A predetermined development process is performed, and the image is output as a reproduced print.

  In the optical unit, various and many optical elements such as a light beam source, a mirror, a lens, an optical deflector, and a window member for passing the light beam are arranged. Foreign substances such as dust and dust are disposed on these optical elements. When the ink adheres, various problems such as deterioration in image quality occur.

For example, if foreign matter such as dust or dirt adheres to the scanning line of an fθ lens or mirror (so-called falling mirror or the like) arranged downstream of the optical deflector (downstream of the light beam traveling direction), the light beam As a result, light is reduced or the amount of light is reduced. As a result, streak unevenness extending in the sub-scanning direction occurs at the corresponding position in the main scanning direction.
In addition, regardless of whether the optical deflector is upstream or downstream, if dust or the like is deposited on the surface of the optical element that acts on the light beam and the reflectance or transmittance is reduced, the light amount of the light beam is reduced downstream of the optical element. This leads to a decrease in image quality such as insufficient density.
Furthermore, since an optical deflector such as a polygon mirror rotates (or swings) at a very high speed, if dust enters a sliding portion or the like, it may cause damage or failure.

In order to prevent dust and dirt from adhering to the optical element that causes such inconvenience, it is important to prevent dust and dirt from entering the unit.
For this reason, as shown in Patent Document 1 and Patent Document 2, an optical unit usually has a housing shape that is open on one side and a frame (housing) that also functions as an optical surface plate. By fixing various optical elements such as lens, optical path changing mirror, optical deflector, fθ lens, etc., and closing the release surface of the frame with a cover, the unit is hermetically sealed to ensure dust resistance. ing. The light beam exit and the like are closed with glass (seal glass / dust-proof glass) or the like, and the hermeticity in the unit is maintained.

Japanese Patent Laid-Open No. 11-133331 JP 2001-1117035 A

Here, it goes without saying that the cover and the frame need to be securely fastened in order to enhance the sealing property and ensure the dustproof property.
In addition, if the number of covers that block the opening surface of the frame increases, it will be disadvantageous in terms of hermeticity, that is, dustproofness, so in order to ensure high hermeticity, the number of covers should be reduced as much as possible. The release surface is preferably closed with a single cover.

However, in such an optical unit with improved sealing performance, an error occurs in the optical path of the light beam, and the light beam does not enter the proper position, resulting in image quality degradation and image recording position deviation caused by this. May cause problems.
For example, as described above, in an optical unit using three types of light beams corresponding to R, G, and B exposures, the optical path of one light beam is in the sub-scanning direction (with respect to the deflection direction (deflection surface)). If it fluctuates in the vertical (orthogonal) direction, the incident position on the photosensitive material will be shifted in the sub-scanning direction only for the light beam. As a result, image quality deterioration such as color misregistration and black blurring occurs, which is a serious problem.

  An object of the present invention is to solve the above-described problems of the prior art, in which various optical elements are fixed to a housing-like frame serving as an optical surface plate, and the release surface (opening) of the frame is closed with a cover. In an optical unit that ensures (substantially) hermeticity inside the unit, a light beam can travel along a predetermined optical path and can be incident on an appropriate position of a scanning object such as a photosensitive material. It is an object of the present invention to provide an optical unit capable of recording a high-quality image without color misregistration when used in such a recording apparatus.

  To achieve the above object, the present invention provides an optical unit that deflects and emits a light beam in a predetermined main scanning direction, and includes a frame that acts as an optical surface plate in a casing shape having an opening, A cover for closing an opening of the frame; and an optical element disposed at a predetermined position in the frame, wherein the cover and the frame are fixed at least at a position higher than the thickness of the cover. Using a stepped screw or a screw inserted through a collar higher than the thickness of the cover, an elastic cushioning material disposed between the cover and the frame is used. Provided is an optical unit characterized in that the total of the thickness of the material is larger than the height of the stepped portion of the stepped screw and the collar.

  In such an optical unit of the present invention, it is preferable that the frame has an opening on the entire upper surface when the optical unit is properly installed, and the entire upper surface is closed by a single cover. Preferably, the cover and the frame are formed of different materials, and further, three light beams modulated according to the recorded image corresponding to each of red exposure, blue exposure and green exposure are used. Preferably, the optical paths of the respective light beams are different from each other in the main scanning direction and coincide with each other in a direction orthogonal to the main scanning direction.

According to the present invention having the above-described configuration, an optical unit (light beam scanning unit) that emits a light beam deflected in a predetermined direction (main scanning direction), and a light source is mounted on a housing-like frame serving as an optical surface plate By fixing optical elements such as various mirrors, lenses, optical deflectors, fθ lenses, etc., and closing the open surface of the frame with a cover to seal the inside of the unit (substantially), the inside of the unit, that is, the dust resistance of the optical element In the optical unit that secures the light beam, it is possible to prevent the light beam optical path from fluctuating due to environmental changes such as temperature and humidity, and to stably and accurately enter the light beam at a predetermined position of the scanning object such as a photosensitive material. .
Accordingly, the optical unit of the present invention is used for a color image recording apparatus such as a recording apparatus of a digital photo printer, for example, so that there is no color misregistration or uneven color regardless of the installation environment of the apparatus or its own heat generation. High-quality image recording can be performed stably.

  Hereinafter, the optical unit of the present invention will be described in detail based on the preferred embodiments shown in the accompanying drawings.

In FIG. 1, the conceptual diagram of an example of the optical unit 10 of this invention is shown.
The optical unit 10 has three light beams L (laser beams) corresponding to R (red) exposure, G (green) exposure, and B (blue) exposure modulated according to an image to be recorded (image data thereof). Is deflected in a predetermined one-dimensional direction (main scanning direction (arrow x direction in the figure)) and incident on a predetermined recording position (exposure position) E, thereby scanning exposure of the photosensitive material S (see FIG. 2). Thus, an image is recorded.
As an example, the optical unit 10 is a digital photo printer that creates a photographic print from image data obtained by photoelectrically reading an image taken on a photographic film, image data taken by a digital camera, or the like. This is used in a printer (printing device). In this printer, the photosensitive material S (printing paper) is scanned and conveyed in the direction perpendicular to the main scanning direction (sub-scanning direction (arrow y direction in the figure)) at the pre-recording position E, thereby deflecting in the main scanning direction. The photosensitive material is two-dimensionally scanned and exposed with the light beam thus recorded to record a latent image, and the photosensitive material on which the latent image is recorded is supplied to a development processing apparatus.

  In the illustrated example, the optical unit 10 includes a frame 12 that is a housing that one surface is released, a cover 14 that closes the release surface (upper surface) of the frame 12 (see FIG. 4 and indicated by a dotted line), and a frame 12. And various optical elements that are fixed to the head.

The frame 12 is a housing whose one surface (upper surface) is released and acts as an optical surface plate of the light beam scanning optical system in which various optical elements constituting the light beam scanning optical system are accommodated / fixed.
In the illustrated example, the frame 12 is made of an aluminum alloy as an example, and the inside thereof is substantially separated into a light source unit 16, a light deflecting unit 18, and an emitting unit 20 by partition walls 22 (22 a, 22 b and 22 c). . The partition wall 22a is partially cut away, and the transparent window member 28a is fixed here. Further, the partition wall 22c is also cut out except for the upper portion, and the transparent window member 28b is fixed here. .
The outer (side) wall of the frame 12 and the partition wall 22 are formed with screw holes 26 (17 in total) into which screws for fastening the frame 12 and the cover 14 are screwed.

  In the illustrated frame 12, the light source unit 16 emits a light source 30R that emits a light beam Lr that performs R exposure, a light source 30B that emits a light beam Lb that performs B exposure, and a light beam Lg that performs G exposure. A light source 30G, an AOM (acousto-optic modulator) 32B that modulates the light beam Lb, an AOM 32G that modulates the light beam Lg, a mirror 34 that reflects each light beam L, and a light amount adjusting means that adjusts the light amount of the light beam Lr. 36R, a light amount adjusting unit 36B for adjusting the light amount of the light beam Lb, and a light amount adjusting unit 36G for adjusting the light amount of the light beam Lg are arranged.

In the illustrated example, the light source 30R of the light beam Lr and the light source 30B of the light beam Lb are both light sources using LD, and the light source 30G of the light beam Lb is a second harmonic formed by combining a laser light source and an SHG element. The light beam Lb is emitted by a wave.
The light beam Lr is modulated according to the image data by direct modulation for modulating and driving the light source 30R, and both the light beam Lb and the light beam Lg are modulated according to the image data by the AOM 32G and the AOM 32B.

A polygon mirror 40 and an fθ lens (scanning lens) 42 are disposed in the light deflection unit 18.
Further, a cylindrical lens 46, a cylindrical mirror 48, and a falling mirror 50 are arranged in the emitting unit 20. The positional relationship among the cylindrical lens 46, the cylindrical mirror 48, and the falling mirror 50 is as shown in FIG. 2. The cylindrical mirror 48 reflects the light beam L slightly obliquely upward, and then the falling mirror. 50 reflects the light beam downward, and the light beam L enters the recording position E. Further, the cylindrical lens 46 and the cylindrical mirror 48 constitute a surface tilt correction optical system of the polygon mirror 40.

In the optical unit 10 of the illustrated example, an optical sensor 54 for an image recording start synchronization signal (SOS (Start of scan)) on the photosensitive material S is disposed at the emitting portion 20 of the frame 12.
The optical sensor 54 is a line sensor extending in the vertical direction (that is, the sub-scanning direction).

In the optical unit 10 of the illustrated example, as shown in FIG. 3, an opening 58 for inserting the light receiving portion 56 of the optical sensor 54 and a bolt 60 for fixing the optical sensor 54 are provided on the outer wall of the frame 12. Four bolt holes 62 for insertion are formed through the wall.
The optical sensor 54 has four bolt holes 68 through which the bolts 60 are inserted.
Further, on the back surface of the optical sensor 54 (on the side opposite to the light receiving portion 56), two through holes 74 corresponding to the diameters of the bolts 60 are provided corresponding to the bolt holes 68 arranged vertically. Two sheet materials 72 are arranged. Note that one of the through holes 74 of the plate member 72 may be a slightly long hole for absorbing tolerance.

  In the illustrated example, a plate material 72 is disposed on the back surface of the photosensor 54 with the light receiving portion 56 of the photosensor 54 inserted from the opening 58 toward the inside of the frame 12, and the through hole 74 and the light of the plate material 72 are arranged. The optical sensor 50 is fixed to the frame 12 by inserting the bolt 60 through the washer 64 into the bolt hole 68 of the sensor 54 and fixing the bolt 60 to the bolt hole 62 with a bolt 60 and a nut (not shown).

Here, the bolt hole 68 of the optical sensor 54 is a long hole extending in the vertical direction. Therefore, in the optical unit 10, the position of the optical sensor 54 in the vertical direction (sub-scanning direction) can be adjusted from the outside without removing the cover 14 and releasing the frame 14.
Further, in the illustrated example, the bolt hole 68 which is a long hole is closed by two plate members 72, and the optical sensor 54 is fixed to the frame 12. Therefore, even if the bolt 60 is loosened to adjust the position of the optical sensor 54, it is possible to prevent dust and dirt from entering the frame 12 from the bolt holes 68 and 62.

The optical system installed in the frame 12 is basically a known light beam scanning optical system.
Specifically, the light beam Lr corresponding to the R exposure is modulated and emitted from the light source 30R according to the recorded image (R image data), reflected by the mirror 34, and light amount adjusted by the light amount adjusting unit 36R. The light passes through the window member 28a and enters the polygon mirror 40. The light beam Lb corresponding to the B exposure is emitted from the light source 30B, modulated by the AOM 30B in accordance with the recorded image (B image data), reflected by the mirror 34, and the light amount is adjusted by the light amount adjusting unit 36B. The light passes through the member 28 a and enters the polygon mirror 40. Further, the light beam Lg corresponding to the G exposure is emitted from the light source 30G, modulated by the AOM 30G in accordance with the recorded image (G image data), reflected by the mirror 34, and light amount adjusted by the light amount adjusting unit 36G. The light passes through the window member 28a and enters the polygon mirror 40.

The light beams L (Lr, Lb, and Lg) deflected in the main scanning direction by the polygon mirror 40 are adjusted by the fθ lens 42 so that the scanning speed becomes uniform.
The light beam L that has passed through the fθ lens passes through the window portion 28b, passes through the cylindrical lens 16, is reflected by the cylindrical mirror 48, the optical path is adjusted, and surface tilt is corrected. Reflected downward and incident on the recording position E (photosensitive material S), a scanning line is defined.

  In the optical unit 10 shown in the figure, the three light beams L emitted from the respective light sources travel in the optical paths that are different in the main scanning direction and coincide with each other in the sub scanning direction. Incident at one point and deflected in the main scanning direction. Accordingly, each light beam L is incident on the recording position E at the same position in the sub-scanning direction but at a different position in the main-scanning direction to define a scanning line at the same position in the sub-scanning direction (non-multiplexed light). Beam scanning optics).

As described above, the upper surface (release surface) of the frame 12 to which the optical element is fixed is closed by the cover 14. Due to the blockage of the upper surface of the frame 12 by the cover 14, the inside of the optical unit 10 is (substantially) sealed, and the dust resistance of the inside, that is, the dust resistance of each optical element arranged in the frame 12 is ensured.
In the illustrated example, the cover 14 is formed with a window portion which is a through hole, and is closed by a filter 80 having sufficient dustproof performance. Therefore, the inside of the optical unit 10 is not completely sealed, is substantially sealed while maintaining a proper air permeability, and the inside (optical element) is also protected from dust (see FIG. 4 and the like).

4A is a top view of the cover 12, FIG. 4B is a side view (viewed in the direction of the arrow b), FIG. 4C is a back view of the cover 12 (lower surface = surface on the frame 12 side), Each is shown.
The cover 14 is a plate-shaped resin molded product, and on the back surface, a wall portion 82 is formed so as to slightly protrude downward (on the frame 12 side) so as to face the outer wall of the frame 12 and the partition wall 22. . In addition, through-holes 84 (17 in total) are formed in the wall portion 82 corresponding to the screw holes 26 of the frame 12.
Further, as indicated by a thick line in FIG. 4C, convex portions 86 slightly projecting downward from the wall portion 82 are provided in the entire area of both ends (both width direction end portions) of the wall portion 82 and around the through hole 84. (See FIG. 6) is formed.

A buffer material 90 made of an elastic member is disposed between the convex portions 86 of the wall portion 82. In the illustrated example, in order to further improve dust resistance, the cushioning material 90 is a single member having a shape corresponding to the entire region of the wall portion 82, that is, has a planar shape shown in FIG.
The buffer 12 is sandwiched between the outer wall of the frame 12 and the partition wall 22 and the wall portion 82 of the cover 14, and the frame 12 and the cover 14 are fastened (fixed), whereby the light source portion 16, the light deflection portion 18, and the emission portion. 20 parts are more preferably substantially separated, and the sealing inside the optical unit 10, that is, dustproofness is improved. This fastening method will be described in detail later.

  The material for forming the buffer material 90 is not particularly limited, and various materials having elasticity can be used. As an example, comb, urethane foam, silicone and the like are exemplified.

A cylindrical stopper 87 corresponding to the rotation axis of the polygon mirror 40 is formed on the optical scanning portion 18 (area corresponding thereto) on the back surface of the cover 14.
A normal optical unit has a stopper for preventing the polygon mirror 40 from coming off the rotation axis. However, when the rotation is stopped at a non-recording time or the rotation speed is reduced, an external impact is applied. The polygon mirror 40 and the stopper may collide and be damaged. By eliminating the stopper, such inconvenience can be avoided, but there is a possibility that the polygon mirror 40 may come off during transportation.
On the other hand, in the optical unit 10 shown in the drawing, the cover 14 is provided with a stopper 87 that prevents the polygon mirror 40 from coming off, thereby preventing the polygon mirror 40 from being damaged by the stopper, and at the same time the polygon mirror during transportation or the like. Is prevented from coming off.
The height of the stopper 87 may be determined as appropriate according to the amount by which the polygon mirror 40 is lifted and the distance from the polygon mirror 40 mounting position to the cover 14.

As described above, in the optical unit 10, the upper surface (release surface) of the frame 12 on which the optical element is installed by sandwiching the cushioning material 90 between the outer wall of the frame 12 and the partition wall 22 and the wall portion 82 of the cover 14, By closing with the cover 14, the inside of the optical unit 10 is (substantially) sealed to ensure the dustproofness inside the frame 12.
Here, in the optical unit 10 of the present invention, as schematically shown in FIG. 6, the fastening (fixing) between the frame 12 and the cover 14 is higher than the thickness of the cover 14 and the cover 14- This is performed using a stepped screw 88 having a stepped portion 88a lower than the sum of the thickness and the thickness of the buffer material 90. In the optical unit of the present invention, by using such a fastening method, it is possible to stably perform high-quality image recording without color misregistration or the like.

In order to perform high-quality image recording without streak unevenness in the optical unit 10 that performs light beam scanning exposure, it is necessary to ensure dustproofness inside the unit and prevent adhesion of dust and dirt to the optical element. Is important as described above.
For this purpose, it is necessary to improve the sealing inside the unit by covering the release surface of the frame on which the optical element is installed with a cover. Further, in order to securely seal the inside of the unit and make the dust resistance more suitable, it is necessary to securely fasten the frame and the cover. Further, in order to further improve the sealing performance, it is preferable that the entire release surface of the frame is closed with a single cover as shown in the illustrated example.

However, in the optical unit 10 having improved sealing performance in this way, even if the optical element is properly installed on the frame 12, the optical path of the light beam L fluctuates and image quality deterioration such as color misregistration occurs. There are many cases.
As a result of repeated studies on the cause of the optical path variation of the light beam L, the present inventors have found that the temperature of the optical unit 10 is increased, the temperature of the optical unit 10 is increased due to heat generated by the light source, and the like. We found that this was caused by frame distortion due to environmental humidity changes (hereinafter referred to as environmental changes).

When the environmental change occurs in the optical unit 10, the frame 12 and the cover 14 are expanded / contracted (hereinafter referred to as expansion / contraction) according to the environmental change. Here, in the optical unit 10, the frame 12 and the cover 14 are often formed of different materials, such as the frame 12 is made of an aluminum alloy and the cover 14 is made of resin, as shown in the illustrated example.
Different forming materials have different amounts of expansion and contraction with respect to environmental changes. As a result, due to the difference in expansion and contraction between the cover 14 and the frame 12, the cover 14 is in a state where a large force is applied to the frame 12, and the frame 12 is slightly deformed by this force. That is, a slight distortion occurs in the frame 12 that is an optical surface plate.

If the frame 12 is distorted, even if the distortion is extremely small, an error occurs in the mounting angle of the optical element, and as a result, the optical path of the light beam fluctuates and enters an inappropriate position. Degradation of image quality will occur.
For example, if the mounting angle of the optical element changes and the optical path of one light beam L changes vertically with respect to the frame 12 (that is, the sub-scanning direction), only the light beam L from the predetermined recording position E to the sub-direction. The incident light enters the position that fluctuates in the scanning direction and defines a scanning line at a position different from the other light beams. As a result, image quality deterioration such as color misregistration and color blurring occurs.

In particular, the light source unit 16 is the most upstream in the traveling direction of the light beam L. When the angle variation of the light beam optical path occurs here, even if there is a very small variation in the light source unit 16, the optical path with the traveling of the light beam. The variation becomes large, and the light beam incident position varies greatly on the photosensitive material S. Moreover, the temperature of the light source unit 16 is likely to increase due to its own heat, and the frame 14 is easily distorted.
Further, in the non-multiplexed light beam scanning optical system in which the three light beams travel in different optical paths as in the illustrated example, the optical paths of the respective light beams are different, so that the sub-beams of the individual light beams due to the distortion of the frame 14 are obtained. Variations in the optical path in the scanning direction are likely to occur, and image quality degradation such as color shift is likely to occur.

Such distortion is more likely to occur as the frame 12 and the cover 14 are tightened more strongly in order to ensure dust resistance.
Further, as the cover 14 becomes larger, the force applied to the frame 12 by the cover 14 due to the difference in the amount of expansion / contraction increases. Therefore, a configuration in which the release surface of the frame 12 is closed with a single cover 14 as in the illustrated optical unit 10 is advantageous in terms of dust resistance, but is disadvantageous in terms of distortion of the frame 12 due to environmental changes. It is.

On the other hand, in the optical unit 10 of the present invention, the fastening of the frame 12 and the cover 14 for closing the frame 12 is performed by using a stepped screw (shoulder screw) 88 as schematically shown in FIG. While being used, the height of the stepped portion 88a of the stepped screw 88 is made larger than the thickness of the cover 14 (thickness including the wall portion 82 and the convex portion 86). In addition, the height of the stepped portion 88a of the stepped screw 88 is made smaller than the sum of the thickness of the cover 14 and the thickness of the cushioning material 90 (thickness before being sandwiched between the frame 12 and the cover 14). .
In this fastening method, instead of the stepped screw 88, a stepped screw 88 is used by inserting a screw into the collar using a normal screw and a collar (cylinder) corresponding to the stepped portion 88a. The fastening may be performed in the same state as that of the case.

Satisfying this condition and holding the cushioning material 90 between the outer wall of the frame 12 and the partition wall 22 and the wall portion 82 of the cover 14 as described above, the stepped screw 88 (the screw portion thereof) is passed through the through hole 84 of the cover 14. The cover 14 and the frame 12 are fastened by screwing 88b) into the screw holes 26 of the frame 12.
According to this fastening method, since the height of the stepped portion 88a of the stepped screw 88 is larger than the thickness of the cover 14, when the frame 12 and the cover 14 are fastened with the stepped screw 88, it is shown in FIG. Thus, the frame 12 and the cover 14 do not contact. In addition, since the height of the stepped portion 88a of the stepped screw 88 is smaller than the sum of the thickness of the cover 14 and the thickness of the cushioning material 90, the release surface of the frame 12 is formed by the cover 14 and the cushioning material 90 having elasticity. It can be reliably blocked.

Therefore, even if the frame 12 and the cover 14 expand and contract due to environmental changes, and the expansion and contraction amounts of the frame 12 and the cover 14 are different, the frame 12 and the cover 14 are not in direct contact with each other, Since the difference can be absorbed by the elasticity of the cushioning material 90, even when the release surface of the frame 12 is closed by one cover 14 as shown in the illustrated example, the cover 14 generates a force due to the difference in expansion / contraction amount. It is possible to prevent distortion of the frame 12 by preventing the frame 12 from being hung.
Moreover, even if the frame 12 and the cover 14 are not in contact, the release surface of the frame 12 can be reliably closed by the cover 14 and the cushioning material 90 having elasticity, so that the inside of the optical unit 10 is hermetically sealed. And good dust resistance can be ensured.
Therefore, according to the optical unit of the present invention, all light beams can be appropriately incident on the recording position E regardless of environmental changes, and stable and highly accurate light beam scanning can be performed to achieve high image quality. Images can be recorded stably.

Such fastening of the frame 12 and the cover 14 using the stepped screw 88 may be performed at all the fastening portions (screw fastening portions of the cover 14), or may be performed only at the selected fastening portion as appropriate. Also good.
In the case of a normal optical unit, the largest difference in expansion and contraction between the frame 12 and the cover 14 is the light source unit 16 that generates a large amount of heat. Therefore, at least the light source unit 16 is fastened using a stepped screw 88. It is preferable to use such a fixing method. In addition, the more fixing portions using such a fastening method using the stepped screw 88, the more suitably the distortion of the frame 14 can be prevented. Therefore, preferably, all the fastening portions are fastened by this method.

In the illustrated example, as a preferred embodiment, the diameter of the through hole 84 of the cover 14 is larger than the diameter of the stepped portion 88 a of the stepped screw 88.
By having such a configuration, the difference in expansion and contraction between the frame 12 and the cover 14 can be absorbed even by the difference in diameter between the through-hole 84 and the stepped portion 88a. Can be prevented.
The difference in diameter between the through hole 84 and the step portion 96a is not particularly limited, but when the longest pitch of the through hole 84 is x, “x × (linear expansion coefficient difference) × temperature difference + cover hole position. It is preferable that “degree + frame hole position degree”.
The longest pitch x of the through-holes 84 is the center distance between the through-holes 84 that are farthest from each other among all the through-holes 84 for screwing formed in the cover 14. The difference in coefficient of linear expansion is the difference in coefficient of linear expansion between the material forming the frame 12 and the cover 14. Further, the temperature difference is a difference between the assumed maximum temperature and the minimum temperature of the cover 14 in the usage state of the optical unit 10.
As before, it is preferable that at least the light source unit 16 is fastened so that there is a difference in diameter between the through hole 84 and the stepped portion, and the more fastening portions that have a difference in diameter between the throughhole 84 and the stepped portion 96a. Since the frame 14 can be preferably prevented from being distorted, the diameter of the through-hole 84 is set to the step of the stepped screw 96 except for the fastening portion which is used as a reference when positioning the frame 12 and the cover 14 is required. It is preferable to make it larger than the diameter of the part. When the reference is unnecessary, it is preferable to make the diameter of the through hole 84 larger than the diameter of the step portion of the stepped screw 96 at all positions.

As shown in FIG. 7A, the optical unit 10 of the illustrated example has a straight groove-shaped uneven portion 92 that is convex from the top surface and concave when viewed from the back surface. .
In the optical unit 10, by having such a concavo-convex portion 92, the force applied by the cover 14 to the frame 12 due to the difference in expansion and contraction between the frame 12 and the cover 14 due to the environmental change described above can be reduced. In addition, the synergistic effect of the frame 12 and the fastening of the cover 14 using the stepped screw 88 can more reliably prevent the frame 12 from being distorted and stably perform high-precision light beam scanning. Become.

  That is, since the cover 14 has such an uneven portion 92, the uneven portion 92 acts like a spring even if the expansion / contraction amount of the frame 12 and the cover 14 due to the environmental change is different. The difference can be absorbed by the uneven portion 92. Therefore, the force that the cover 14 applies to the frame 12 due to the difference in the amount of expansion / contraction can be greatly reduced, and only the cover 14 can be prevented from being deformed and distorting the frame 14.

There is no particular limitation on the formation location of the concavo-convex portion 92, and it may be appropriately formed in a portion where the cover 14 applies a large force to the frame 12 according to the configuration of the optical unit 10 or the like.
As described above, in the case of a normal optical unit, the largest difference in expansion and contraction between the frame 12 and the cover 14 is the light source part 16 that generates a large amount of heat. It is preferable to do this.

In the illustrated example, the concavo-convex portion 92 extends in the sub-scanning direction (arrow y direction), but the present invention is not limited to this and extends in the main scanning direction (arrow x direction). It may be a thing, or may extend in an oblique direction with respect to the main / sub-scanning direction.
That is, the extending direction of the concavo-convex portion 92 may be appropriately determined according to the expansion / contraction direction of the frame 12 and the cover 14, the direction of the force applied by the cover 14 to the frame 12, and the like.

The number of the uneven portions 92 is not limited to one in the illustrated example, and may include two uneven portions 92 (92a and 92b) as shown in FIG. As shown to C), it may have three uneven | corrugated | grooved parts 92 (92a, 92b, and 92c), and may also have four or more uneven | corrugated | grooved parts 92.
In addition, the concavo-convex portion is not limited to a linear shape as in the illustrated example, and may be a curved concavo-convex portion or a circular concavo-convex portion such as an arc shape or a parabolic shape, as shown in FIG. A plurality of circular and annular concavo-convex portions may be formed concentrically, and furthermore, the concavo-convex portions may be formed in a waveform. The circular concavo-convex portion can suitably prevent distortion of the cover 14 regardless of the direction in which the cover 14 and the frame 12 extend and contract.
Moreover, you may form in a cover suitably combining circular or annular uneven | corrugated | grooved part, uneven | corrugated | grooved parts, such as circular arc shape, and a linear uneven | corrugated part.

  Further, the size (length, height, width) of the concavo-convex portion 92 is not particularly limited, and the expansion / contraction difference depends on the size of the cover 14 and the magnitude and direction of the force that the cover 14 applies to the frame 12. The size that can sufficiently absorb the force applied to the frame 12 by the cover 14 due to the above may be determined as appropriate.

  That is, in the optical unit 10 of the present invention, the direction of expansion and contraction of the frame 12 and the cover 14 and the direction and magnitude of the force applied by the cover 14 to the frame 12 due to environmental changes are known through simulations and experiments. What is necessary is just to discover the uneven | corrugated | grooved part which has the spring property which can fully absorb the force applied to the flame | frame 12, by simulation, experiment, etc., and to form the uneven | corrugated | grooved part corresponding to this.

In the illustrated example, the concavo-convex portion 92 is convex on the upper surface and concave on the back (groove shape as viewed from the back surface of the cover 14), but the present invention is not limited to this, and is convex on the back surface. A concave / convex portion (groove shape when viewed from the upper surface of the cover 14) can be used on the upper surface.
Further, in the illustrated example, as a preferable aspect, the uneven portion 92 is formed on the cover 14. However, when the Young's modulus of the frame 12 is smaller than that of the cover 14, the light source and the optical element of the frame 12 are affected. Concavities and convexities may be formed in places that do not give the light, and concavities and convexities may be formed on both the frame 12 and the cover 14.

In the optical unit 10, electric wires and signal lines for driving each light source 30, AOM 32, polygon mirror, and the like are bundled and taken out as a harness.
The harness is taken out from the take-out portion 100 and the take-out portion 102 formed in the cover 14 (see FIG. 8). The extraction part 100 (extraction part 102) is formed so as to be concave from the front surface to the back surface side of the cover 14, and a semi-cylindrical guide part 100a (102a) whose end is spherically closed, and the guide part 100a It is comprised from the through-hole 100b (102b) formed through the cover 14 so that the non-blocking end side may be contact | connected.
The harness passes through the through hole 100b, is inserted and guided in the guide portion 100a, and is taken out to the outside.

Here, no matter how well the frame 12 and the cover 14 are sealed, if there is a gap between the through hole 100b and the harness, sufficient dustproofness cannot be ensured. Dust or the like will enter.
In the illustrated optical unit 10, in order to avoid such inconvenience, as shown schematically in FIG. 8, an elastic buffer member 108 is wound around the harness, and the through hole 100 d is completely formed by the buffer member 108. The dustproof property inside the optical unit 10 is ensured by closing it.
As the buffer member 108, various elastic materials such as a foamed urethane sheet and a rubber sheet can be used.

The optical unit of the present invention has been described in detail above. However, the present invention is not limited to the above-described embodiments, and various improvements and modifications may be made without departing from the scope of the present invention. It is.
For example, the optical unit in the illustrated example is a non-multiplexing light beam scanning optical system, but the present invention is not limited to this, and a multiplexing system that combines light beams using a dichroic mirror or the like is used. It may be a light beam scanning optical system. Or it is not limited to what records a color image using three types of light beams, It may be an optical unit of a light beam scanning optical system which records a monochrome image with one light beam, Further, it may be an optical unit for reading various images by light beam scanning instead of image recording.

It is a schematic perspective view at the time of releasing the cover of an example of the optical unit of the present invention. It is a schematic perspective view for demonstrating the optical system of the optical unit shown in FIG. It is a disassembled schematic perspective view for demonstrating attachment of the SOS sensor of the optical unit shown in FIG. (A) is a top view of the cover of the optical unit shown in FIG. 1, (B) is the front view, and (C) is the back view. It is a top view of the buffer material of the optical unit shown in FIG. It is a conceptual diagram for demonstrating the fastening method of the flame | frame and cover in the optical unit shown in FIG. (A) is a schematic perspective view of the cover of the optical unit shown in FIG. 1, (B), (C) and (D) are schematic perspective views of another example of the cover of the optical unit of the present invention. It is a conceptual diagram for demonstrating the dust-proof method of the harness extraction part in the optical unit shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical unit 12 Frame 14 Cover 16 Light source part 18 Light deflection part 20 Output part 22 Partition 26 Screw hole 28 Window member 30R, 30G, 30B Light source 32B, 32G AOM
34 Mirror 36R, 36G, 36B Consideration adjusting means 40 Polygon mirror 42 fθ lens 46 Cylindrical lens 48 Cylindrical mirror 50 Falling mirror 54 Optical sensor 56 Light receiving portion 58 Opening portion 60 Bolt 62, 68 Bolt hole 64 Washer 72 Plate member 74 Through hole 80 Filter 82 Wall portion 84 Through hole 86 Convex portion 87 Retaining stopper 88 Stepped screw 90 Buffer material 92 Concavity and convexity 100 Extraction portion

Claims (4)

An optical unit that deflects and emits a light beam in a predetermined main scanning direction,
A frame having an opening and acting as an optical surface plate, a cover for closing the opening of the frame, and an optical element disposed at a predetermined position in the frame;
Fixing the cover and the frame in at least one place using a stepped screw having a step higher than the thickness of the cover or a screw inserted through a collar higher than the thickness of the cover, The thickness of the cover and the thickness of the cushioning material is greater than the height of the stepped portion of the stepped screw and the collar. Optical unit.   2. The optical unit according to claim 1, wherein the entire upper surface of the frame is an opening in a state where the optical unit is properly installed, and the entire upper surface is closed by a single cover.   The optical unit according to claim 1, wherein the cover and the frame are formed of different materials. Three light beams that are modulated according to the recorded image, corresponding to each of red exposure, blue exposure, and green exposure, are emitted.
4. The optical unit according to claim 1, wherein optical paths of the respective light beams are different from each other in the main scanning direction and coincide with each other in a direction orthogonal to the main scanning direction.

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