JP2000292729A - Optical scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical scanner capable of enhancing the quality of a formed image by improving the vibration proof ability of a reflection mirror. SOLUTION: This optical scanner has a condensing lens condensing a luminous flux emitted from a light source, a first image forming system condensing the luminous flux from the condensing lens and forming a linear image in the vicinity of the deflecting and reflecting surface of a deflector, a second image forming system performing scanning with the deflected luminous flux by the deflector on the surface to be scanned of an image carrier at a constant speed and condensing the luminous flux as a light spot, and the reflection mirror guiding the deflected luminous flux to the surface to be scanned; and is positioned and supported inside a housing. A scanning positional fluctuation preventing means 20 by vibration is provided for the mirror 7. A pressing member 9 having a resin long lens or a long mirror is arranged in a direction where the mirror 7 is smoothly curved. The supporting parts 10 and 14 of the mirror 7 are provided for the housing, receiving parts 16 and 18 are provided on both ends of the reflecting surface of the mirror 7 and the central part in a length direction, and the receiving parts are supported by the parts 10 and 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a digital copying machine,
The present invention relates to an optical scanning device applicable to a laser printer, an analog copier, a scanner, and the like, and more particularly, to a support structure of a folding mirror provided in the optical system.

[0002]

2. Description of the Related Art In optical scanning devices used in digital copiers, laser printers, analog copiers, scanners, and the like, there are restrictions on the space in which they can be arranged, so that the space between the light source and the image plane, particularly from the optical deflector, is limited. A folding mirror is arranged between the scanning surface and the optical path is folded or bent.
As an example of the mounting structure of the folding mirror in the conventional optical scanning device, both ends of the folding mirror are pressed by a plate spring against a support member formed integrally with the housing of the optical scanning device to determine the inclination of the reflection surface of the mirror. At the same time, it supports in the direction perpendicular to the reflection surface.

FIGS. 9 and 10 show examples of a mounting structure of a folding mirror in the above-mentioned conventional optical scanning device. FIG.
In FIG. 10, a pair of support members 73 and 74 stand up from the housing of the optical scanning device. Support member 7
One side surface of each of the mirrors 3 and 74 is a support surface of the folding mirror 71, and a leaf spring 75 as a pressing member is provided at both ends in the longitudinal direction of the folding mirror 71 from a side opposite to the reflection surface 72.
, And the reflection surfaces 72 on both ends in the length direction of the return mirror 71 are pressed against the support surfaces of the support members 73 and 74 by the elastic force of the leaf spring 75. The support surfaces of the support members 73 and 74 determine the inclination angle of the reflection surface 72 of the mirror 71, and the lower end of the mirror 71 is mounted on a pedestal 77 provided integrally with the housing. Positioning in the direction perpendicular to the mirror 71 is performed, and the mirror 71 is supported. The leaf spring 75 is attached to the housing by a screw 76.

[0004]

According to the above-mentioned conventional folding mirror mounting structure, the mechanical vibration of the optical scanning device itself, for example, the mechanical vibration caused by the rotational driving of an optical deflector composed of a polygon mirror or the like, or the optical scanning. The vibration of the drive system of a machine such as a copying machine equipped with the apparatus is transmitted to the return mirror 71, and the return mirror 71 vibrates. When the folding mirror 71 vibrates, the scanning position of the light beam is deviated from a target position corresponding to the vibration, and as a result, an image formed on the surface to be scanned of the image carrier is moved in a sub-scanning direction called banding. Band or linear density unevenness occurs,
The quality of the formed image may be impaired.

Therefore, as described in Japanese Patent No. 2806401, a pressing force is applied by a spring material in a direction perpendicular to the reflection surface of the folding mirror to press the folding mirror against the stopper, and the spring material and the folding mirror are combined. There has been proposed an image sensor in which the vibration of the return mirror is regulated by the frictional force generated between the mirror and the above-mentioned structure to eliminate the unevenness in the density of the formed image as described above. However, the invention described in the above publication has a drawback in that when the friction coefficient between the spring member and the folding mirror is small, the vibration reduction effect cannot be sufficiently obtained.

Generally, when the base material of the folding mirror is glass, the surface perpendicular to the reflection surface, that is, the side surface of the mirror,
It is often in a state of being cut without any special treatment, and when the base material of the mirror is a float glass, the surface opposite to the reflection surface, that is, the back surface has very flatness. high. Therefore, the coefficient of friction of the front and rear surfaces of the folding mirror is extremely small on both sides.
Therefore, the invention described in the above publication has a drawback that the spring material and the return mirror are easily slipped with each other, and the expected vibration reduction effect cannot be obtained.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems of the prior art, and an optical scanning device capable of improving the quality of an image formed by improving the vibration resistance of a folding mirror. The purpose is to provide.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a condensing lens for condensing a light beam emitted from a light source, and a condensing lens. A first image forming system for converging the light beam into a line image substantially parallel to the deflecting and reflecting surface near the deflecting and reflecting surface of the deflector, and the light beam deflected by the deflector on the scanned surface of the image carrier. A second imaging system for performing fast scanning and condensing the light as a light spot; and a folding mirror for guiding a light beam deflected by the deflector to the surface to be scanned, and is positioned and supported in the housing. The optical scanning device is characterized in that the scanning position fluctuation preventing means due to vibration is provided on the folding mirror.

The second imaging system has a long lens or a long mirror made of resin as in the second aspect of the present invention. It is desirable that a pressing member be provided in a direction for smoothly bending the folding mirror.

According to a third aspect of the present invention, the support portion of the folding mirror is provided in the housing, and the receiving portions are provided at both ends of the reflecting surface of the folding mirror and at the center in the longitudinal direction. It is desirable that the folding mirror is held by being supported by the support portion.

According to a fourth aspect of the present invention, the supporting portion for regulating the amount of bending of the scanning line due to the warpage in the longitudinal direction of the imaging optical system and the amount of bending of the return mirror corresponding to the scanning line direction is a housing. Is desirably provided.

It is desirable that the surface of the back surface, which is opposite to the reflection surface of the folding mirror and is in contact with the pressing member, has a large surface roughness.

As in the sixth aspect of the present invention, in the second aspect of the invention, the point of action of the pressing member is shifted in the length direction of the folding mirror from the housing-side supporting portion of the end reflecting surface of the folding mirror. It is desirable.

As in the invention according to claim 7, in the invention according to claim 6, when the length of the folding mirror is L and the amount of displacement of the point of action of the pressing member from the housing-side support portion is X, 2 It is more preferable to set the relation of ≦ 0.5 L / X ≦ 35.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an optical scanning device according to the present invention will be described below with reference to FIGS. First, an outline of an optical operation device to which the present invention is applied will be described. In FIG. 1, a coupling lens 2 composed of a condenser lens and a cylinder lens 3 are arranged on a path of a light beam emitted from a light source 1 composed of a semiconductor laser, for example, and a light deflector composed of a rotary polygon mirror is further provided in front thereof. The reflection surface of the container 4 is located. An fθ mirror 5 is disposed on the path of the deflected light by the deflector 4, and a long lens 6 is disposed on the path of the reflected light by the fθ mirror 5. A folding mirror 7 is arranged on the path of the light transmitted through the long lens 6, and the surface to be scanned of the image carrier 8 is located on the path of the light bent by the folding mirror 7. In this example, the image carrier 8 comprises a photosensitive drum. Optical components from the light source 1 to the return mirror 7 via the deflector 4 and the like are housed in a housing to constitute an optical scanning device unit, and this housing is incorporated in an apparatus body such as a digital copying machine or a printer. The luminous flux reflected by the folding mirror 7 passes through the protective glass fitted in the window of the housing, and reaches the image carrier 8 installed outside the housing.

In the example shown in FIG. 1, a light beam emitted from a light source 1 is condensed by a coupling lens 2, a light beam from the condensing lens is converged only in one direction by a cylinder lens 3, An image is formed near the reflecting surface as a line image substantially parallel to the deflecting reflecting surface. The cylinder lens 3 forms a first imaging system. The line image is reflected by the deflecting reflection surface, and is deflected in a predetermined angle range by rotating the deflector 4. The light beam deflected by the deflector 4 is
5 is returned by the fθ mirror 5, passes through the long lens 6, is bent in the optical path by the return mirror 7, and reaches the scanning surface of the image carrier 8. The fθ mirror 5 and the long lens 6 behind the deflector 4 constitute a second imaging system, and converge the line image on the surface to be scanned of the image carrier 8 as a light spot having a predetermined diameter. The fθ mirror 5 has an fθ function to make the scanning speed of the light beam on the scanned surface of the image carrier 8 uniform, and the long lens 6 together with the fθ mirror 5 has a light condensing function in the sub-scanning direction. It has a correction function.

In the second image forming system, a long optical component such as a long lens made of resin, a long mirror, or the like is mainly used for cost reasons. A long optical component made of a resin molded product is inferior in mechanical properties as compared with glass. In particular, warpage in the longitudinal direction occurs due to residual stress during molding, which may cause deterioration of optical characteristics such as bending of scanning lines. On the other hand, the warpage of a long optical component is determined by the cross-sectional shape in the sub-scanning direction and the molding conditions of the optical component. Can be made substantially constant.

Next, a description will be given of a more specific embodiment of the present invention in which means for preventing the scanning position from being fluctuated due to vibration is provided in the folding mirror. 2, 3 and 4,
In the housing 30 of the optical scanning device, the support portions 10 of the folding mirror 7 are raised in a pair with the housing 30 by integral molding. The distance between the two support portions 10 is almost the same as or slightly wider than the length of the folding mirror 7. The upper end edges of the two support portions 10 are bent at right angles in the direction facing each other to form a contact portion 101 with the folding mirror 7. The above housing 3
From 0, a supporting portion 14 whose upper end is bent like a hook rises integrally at a position corresponding to the longitudinal central portion of the folding mirror 7.

The folding mirror 7 is arranged between the two support portions 10 so as to communicate between the contact portions 101 and below the contact portion 101. Between the housing 30 and the folding mirror 7, a pair of two scanning position fluctuation preventing means 20 are arranged. The scanning position fluctuation preventing means 20 includes a leaf spring 9 as a pressing member. The leaf spring 9 is bent in a V-shape, and one end is a hook portion 92 bent outward at a substantially right angle. One side of the V-shaped leaf spring 9 is fixed to the housing 30 by appropriate means such as screwing, welding, bonding, and snap fitting. The other side of the leaf spring 9 rises obliquely upward and pushes the return mirror 7 obliquely upward by its elasticity.

The reflecting mirror 7 is turned on the reflecting surface 1 of the reflecting mirror 7 by the pushing force of the leaf spring 9 acting as a pressing force.
The receiving portions 16 at both ends in the length direction of the mirror 7 are pressed against the lower surface of the contact portion 101, and the reflection surface 17 of the folding mirror 7 is
The receiving portion 18 at the center in the length direction is pressed against the lower surface of the hook-shaped support portion 14. The inclination of the reflection surface 17 of the return mirror 7 is regulated by the lower surface of the contact portion 101, and the reflection surface 17 of the return mirror 7 faces obliquely upward in FIGS. Also, the reflection surface 17 of the folding mirror 7
And the displacement in the width direction is parallel to the folding mirror 7.
One side edge portion contacts the hook portion 92 of the leaf spring 9, and
When the other edge portion of the folding mirror 7 hits the support portion 14, the support portion 10 following the contact portion 101 is further provided.
Is regulated by hitting the vertical wall.
In addition, since the both end surfaces in the longitudinal direction of the folding mirror 7 are regulated by the support portions 10, the displacement of the folding mirror 7 in the longitudinal direction is regulated.

The position of the leaf spring 9 as a pressing member is as follows.
The point of action on the folding mirror 7 is shifted from the housing-side receiving portion 16 of the end reflecting surface of the folding mirror 7 to the inside in the length direction of the folding mirror 7. For this reason, as shown in FIG. 5, the leaf spring 9 pushes up the folding mirror 7 with the receiving portions 16 on the reflection surfaces 17 at both ends of the folding mirror 7 as a fulcrum, and the reflection mirror 17 is formed such that the reflection surface 17 is convex. Smoothly curved. The degree of this curvature depends on the position of the contact portion 101 that regulates the receiving portions 16 at both ends of the folding mirror 7, the position of the pair of leaf springs 9, and the position that regulates the receiving portion 18 at the center of the folding mirror 7. It depends on the position of the contact portion 14. As described above, by smoothly bending the folding mirror 7, the folding mirror 7 is held in a state where elastic force is given by its own elasticity, and the vibration resistance of the folding mirror 7 is improved. .

In the case where the fθ mirror 5 and the long lens 6 shown in FIG. 1 are made of a resin molded product as described above, a warp occurs in the longitudinal direction due to the inside during molding. The amount of bending of the scanning line on the surface to be scanned of the image carrier 8 or the deviation of the scanning line direction may occur. Further, the amount and the direction of the warpage of the optical component due to such resin molding are substantially constant depending on the shape of the surface of the optical component in the sub-scanning direction and the molding conditions. Therefore, the positions of the contact portion 101 and the support portion 14 that regulate the bending amount of the folding mirror 7 may be appropriately set, and the bending amount of the folding mirror may be regulated according to the bending amount of the scanning line or the deviation of the scanning line direction. . This makes it possible to cancel the bending of the scanning line and the deviation in the scanning line direction.

The folding mirror 7 is generally made of glass-based float glass. In terms of vibration resistance, it is advantageous to increase the thickness of the return mirror 7, but if a mirror of 10 mm or more is used, a large cost is required for the cutting process. Therefore, float glass of 5 mm or less is usually used. The back surface opposite to the reflection surface 17 is provided with a surface roughness and a coefficient of friction about twice or more that of a normal smooth surface by sanding treatment or the like. Therefore, the frictional force between the folding mirror 7 and the leaf spring 9 increases, the relative movement between the housing and the folding mirror 7 decreases, and it is possible to contribute to an improvement in vibration resistance.

FIG. 6 schematically shows the force acting on the folding mirror 7 supported as described above. The pressing force of the two leaf springs 9 as the pressing members is set appropriately by simulation. This indicates that it is possible to smoothly bend convexly upward. FIG. 7 shows an example in which the height positional relationship between the contact part 101 and the support part 14 is reversed from that in FIG. 6, and the folding mirror 7 is made convex downward. As described above, by changing the height position of the support portion 14 corresponding to the central portion in the longitudinal direction of the folding mirror 7, the folding mirror 7 can be bent in one direction or the opposite direction, and thereby the second mirror can be curved. Scanning line bending caused by the imaging system can be cancelled. Actually, since the scanning line bending caused by the second imaging system is substantially constant, it is not necessary to change the warping direction of the folding mirror 7 for each optical scanning device.

Assuming that the length of the folding mirror 7 is L and the amount of deviation of the point of action of the leaf spring 7 as a pressing member from the contact portion 101 of the housing-side support portion 10 is X, the ratio between L and X is FIG. 8 shows the results of a subjective evaluation of the banding level while changing. In outputting images for evaluation, the same optical scanning device was used for all components except for the presence or absence of sanding treatment on the back surface of the folding mirror. In addition, in this subjective evaluation, 1 m, which is considered to be the most visually noticeable,
Banding at a pitch of about m was evaluated by a plurality of persons on a 7-point scale. The vertical axis in FIG. 8 indicates the average point. Four or more evaluation points were regarded as good images, and less than four points were regarded as bad images. As apparent from FIG. 8, in the case where the back surface of the folding mirror is subjected to sanding treatment, the vibration resistance is improved by setting the relation of 2 ≦ L / 2X ≦ 35, that is, the relation of 2 ≦ 0.5L / X ≦ 35. It turns out that it becomes favorable.

[0026]

According to the first aspect of the present invention, there is provided a light source, a condenser lens, a first image forming system, a deflector, a second image forming system, and a folding mirror for guiding a deflected light beam to a surface to be scanned. In the optical scanning device, the means for preventing the scanning position from being fluctuated due to vibration is provided on the return mirror, so that the vibration resistance of the return mirror can be improved, and the quality of the formed image can be improved.

According to the second aspect of the present invention, in the first aspect of the present invention, the second imaging system has a long lens or a long mirror made of resin, and the vibration resistance of the folding mirror is improved. The pressing member is provided in a direction to smoothly bend the folding mirror in order to improve the folding mirror, so that the folding mirror is held in a state where elasticity is given by its own elasticity, and the folding mirror is folded. The vibration resistance of the mirror is improved.

According to the third aspect of the present invention, in the first aspect of the present invention, the supporting portion of the folding mirror is provided on the housing, and the receiving portions are provided at both ends of the reflecting surface of the folding mirror and at the center in the longitudinal direction. Since the receiving portion is supported by the supporting portion to hold the return mirror, the return mirror is held at both ends and the center in the length direction, and the scanning position fluctuation preventing means due to vibration is provided. And the vibration resistance of the return mirror is improved.

According to the fourth aspect of the present invention, in the first aspect of the present invention, the bending amount of the scanning line caused by the warpage in the longitudinal direction of the imaging optical system and the bending of the return mirror corresponding to the scanning line direction. Since the supporting portion for regulating the amount is provided in the housing, the bending of the scanning line and the deviation in the scanning line direction are canceled, and the quality of the formed image can be improved.

According to the fifth aspect of the present invention, in the second aspect of the present invention, the surface roughness of the back surface which is opposite to the reflection surface of the folding mirror and is in contact with the pressing member is large. Therefore, the frictional force between the folding mirror and the pressing member increases, the relative movement between the housing and the folding mirror decreases, and the vibration resistance can be improved.

According to the sixth aspect of the present invention, in the second aspect of the invention, the point of action of the pressing member is shifted in the length direction of the folding mirror from the housing-side supporting portion of the end reflecting surface of the folding mirror. Therefore, the folding mirror is held at its both ends, the center in the longitudinal direction, and the middle thereof, and the pressing member functions as a scanning position fluctuation preventing means due to vibration. Vibration is further improved.

According to the seventh aspect of the present invention, in the sixth aspect of the present invention, when the length of the folding mirror is L and the amount of shift of the point of action of the pressing member from the housing-side support portion is X, 2 ≦ 0.5 L / X ≦ 35, the length L of the folding mirror, which can obtain good vibration resistance, and the shift amount X of the point of action of the pressing member from the housing-side support portion. And a better image can be formed.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of an optical scanning device according to the present invention.

FIG. 2 is a perspective view showing a configuration example of a main part of the optical scanning device according to the present invention, as viewed obliquely from the back.

FIG. 3 is a cross-sectional view of one end of the main part.

FIG. 4 is a sectional view of a central portion of the main part.

FIG. 5 is a rear view of a central part of the main part.

FIG. 6 is a schematic diagram showing a relationship between a fulcrum and a working point of the folding mirror in the embodiment.

FIG. 7 is a schematic diagram illustrating a relationship between a fulcrum and a working point of a folding mirror according to another embodiment.

FIG. 8 is a diagram showing the relationship between the image evaluation point and the ratio of the length L of the return mirror and the displacement X of the point of action of the pressing member from the housing-side support portion in the embodiment.

FIG. 9 is a perspective view showing an example of a folding mirror holding structure in a conventional optical scanning device.

FIG. 10 is a right side view of the conventional folding mirror holding structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source 2 Condensing lens 3 1st imaging system 4 Deflector 5 f (theta) mirror which comprises a 2nd imaging system 6 Long lens which comprises a 2nd imaging system 7 Folding mirror 9 Leaf spring as a pressing member 10 Holding Unit 16 receiving unit 18 receiving unit 20 scanning position fluctuation preventing means 30 housing

Claims (7)

[Claims] 1. A condensing lens for condensing a light beam emitted from a light source, and a first lens for condensing the light beam from the condensing lens into a line image substantially parallel to the deflecting reflection surface near a deflecting reflection surface of a deflector. An image system, a second imaging system that scans the light beam deflected by the deflector on the surface to be scanned of the image carrier at a constant speed and condenses the light beam as a light spot, and converts the light beam deflected by the deflector to A folding mirror for guiding to the surface to be scanned,
An optical scanning device positioned and supported in a housing, wherein a means for preventing a change in scanning position due to vibration is provided on a folding mirror. The second imaging system has a long lens or a long mirror made of a resin, and has a direction in which the folding mirror is smoothly curved in order to improve the vibration resistance of the folding mirror. The optical scanning device according to claim 1, further comprising a pressing member. 3. A supporting portion of the folding mirror is provided on the housing, and receiving portions are provided at both ends of the reflecting surface of the folding mirror and at the center in the longitudinal direction, and the receiving portions are supported by the supporting portion. 2. The optical scanning device according to claim 1, wherein a folding mirror is held. 4. A supporting portion for regulating the amount of bending of a scanning line caused by warpage in the longitudinal direction of an imaging optical system and the amount of bending of a return mirror in accordance with the scanning line direction is provided in a housing. The optical scanning device according to claim 1. 5. The optical scanning device according to claim 2, wherein the surface of the back surface that is opposite to the reflection surface of the folding mirror and that contacts the pressing member has a large surface roughness. 6. The optical scanning device according to claim 2, wherein the action point of the pressing member is shifted from the housing-side support portion of the end reflecting surface of the folding mirror in the length direction of the folding mirror. 7. The relationship of 2 ≦ 0.5 L / X ≦ 35, where L is the length of the folding mirror and X is the amount of displacement of the point of action of the pressing member from the housing-side support portion.
The optical scanning device according to claim 1.