JP3856871B2 - Optical scanning device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical scanning device.
[0002]
[Prior art]
An optical scanning device for condensing a deflected light beam deflected by an optical deflector as a light spot on a surface to be scanned by a scanning imaging lens and optically scanning the surface to be scanned is a digital copying apparatus, an optical printer, or a facsimile recording apparatus. It is widely known in relation to etc.
[0003]
In general, an optical scanning device forms an electrostatic latent image by optical scanning, and develops the electrostatic latent image to obtain a recorded image. When a portion that obtains a recorded image from an electrostatic latent image is referred to as an “image forming unit”, floating toner is generated in the image forming unit, or paper dust of recording paper on which the toner image is fixed floats.
[0004]
If these floating dusts get mixed into the optical scanning device and adhere to the lens surface or the like, the optical scanning will be hindered. Therefore, the optical scanning unit and the image forming unit are generally partitioned by some partition, and the deflected light beam is emitted from the partition. The part is provided with a transparent parallel plate for dust prevention.
[0005]
Conventionally, the dust-proof transparent parallel plate is in a sub-scanning direction (parallel to the sub-scanning direction on a virtual optical path in which the optical path from the light source to the surface to be scanned is linearly developed along the optical axis of the optical system. The direction corresponding to the main scanning direction on the virtual optical path is referred to as the main scanning corresponding direction), and the surface is orthogonal to the virtual optical path. Had been deployed.
[0006]
For this reason, a part of the deflected light beam transmitted through the scanning imaging lens is reflected by the transparent parallel plate, returns to the scanning imaging lens, is reflected by the lens surface of the scanning imaging lens, and is scanned as “ghost light”. In some cases, the image quality of the recorded image is degraded.
[0007]
[Problems to be solved by the invention]
In view of the above-described circumstances, an object of the present invention is to effectively reduce or prevent the influence of ghost light by the dust-proof transparent parallel plate.
[0008]
[Means for Solving the Problems]
The optical scanning device of the present invention is a device for condensing the deflected light beam deflected by the optical deflector as a light spot on the surface to be scanned by the scanning imaging lens, and optically scanning the surface to be scanned. It is characterized (claim 1).
[0009]
In other words, the dust-proof transparent parallel plate disposed between the scanning imaging lens and the surface to be scanned is “tilted from the direction corresponding to the sub-scanning”.
[0010]
As a result, among the deflected light beams incident on the transparent parallel plate from the scanning imaging lens side, the light beam reflected by the transparent parallel plate travels in a direction different from the incident direction in the sub-scanning corresponding direction.
[0011]
The “transparent parallel plate” is made of, for example, parallel plate glass.
[0012]
According to the first aspect of the present invention, a transparent parallel plate is used as follows: “The deflected light beam is reflected by the transparent parallel plate and returned to the scanning imaging lens, and the light beam reflected by the lens surface of the scanning imaging lens is reflected as ghost light. In order to prevent reaching the scanning plane, it is tilted 2 to 10 degrees from the sub-scanning corresponding direction.
According to the second aspect of the present invention, the transparent parallel plate is disposed at an angle of 2 to 10 degrees with respect to the sub-scanning corresponding direction, is reflected by the transparent parallel plate and returns to the scanning imaging lens, and the lens surface of the scanning imaging lens A light shielding means for preventing the light beam reflected by the light from reaching the scanning surface as ghost light.
[0013]
The optical scanning device according to claim 3 is the optical scanning device according to claim 2, wherein the aperture of the scanning imaging lens in the sub-scanning corresponding direction is 2d, and the distance from the scanning imaging lens to the transparent parallel plate is L. When the angle of inclination of the transparent parallel plate in the sub-scanning corresponding direction: θs (2 to 10 degrees) is:
θs ≧ {tan ⁻¹ (d / L)} / 2
It is characterized by satisfying.
[0014]
According to a fourth aspect of the invention, in the optical scanning device according to the second or third aspect , the light shielding means is “a light shielding region formed on a transparent parallel plate”.
[0015]
According to a fifth aspect of the present invention, in the optical scanning device according to the second or third aspect , a transparent parallel plate is disposed between the image forming unit including the photosensitive member and the optical scanning device, and the light shielding means is “transparent parallel”. It is comprised by the light-shielding plate which comprises the slit for light beam transmission in the flat arrangement | positioning part. "
[0016]
According to a sixth aspect of the present invention, in the optical scanning device according to the first, second, third, fourth, or fifth aspect , the light beam is emitted from the optical scanning device housing in which the optical scanning device is unitized and the transparent parallel plate is unitized The transparent parallel plate mounting portion in the housing is inclined from the sub-scanning corresponding direction.
[0017]
As the light source of the optical scanning device, for example, “LD or LED” can be used. The light beam from the light source is coupled by a coupling lens and enters the optical deflector as a parallel light beam, a divergent light beam, or a convergent light beam.
[0018]
As the optical deflector, a polygon mirror, a rotating dihedral mirror, a rotating single-sided mirror such as a “tenon type mirror or pyramid mirror”, and a oscillating mirror such as a galvanometer mirror can be used.
[0019]
In order to correct so-called surface tilt in the optical deflector, the coupled light beam is condensed only in the sub-scanning corresponding direction, and is formed as a long line image in the main scanning-corresponding direction at the deflection reflecting surface position of the optical deflector. You may make it make it.
[0020]
As the scanning image forming lens, an fθ lens can be preferably used when the optical deflector is a rotating polygon mirror or the like, and when the optical deflector is an oscillating mirror, the fsin θ lens is used. Used. By using such a scanning imaging lens, the main scanning speed can be made constant.
[0021]
As described above, for “surface tilt correction”, when the coupled light beam is formed as a long line image in the main scanning correspondence direction at the position of the deflecting reflection surface of the optical deflector, the scanning imaging lens is With respect to the sub-scanning corresponding direction, the deflecting reflection surface position and the scanned surface position have a function of “substantially geometrically conjugate with respect to the sub-scanning corresponding direction”.
[0022]
In the invention described in claim 6, the transparent parallel flat plate for dust prevention is disposed in the “light-beam exit opening in the housing”, and the light-beam exit opening has a slit shape. Therefore, by making the portion other than the slit-shaped light beam exit opening light-shielding, “the light beam reflected by the transparent parallel plate and returned to the scanning imaging lens, and reflected by the lens surface of the scanning imaging lens, The light shielding means for preventing the ghost light from reaching the surface to be scanned can be used.
[0023]
An optical deflector and a scanning imaging lens are provided in the housing. In addition, the coupled light beam is imaged as a long line image in the direction corresponding to the main scanning at the position of the deflecting reflection surface of the optical deflector. A condensing optical system (cylinder mirror or cylinder lens), a folding mirror for bending the optical path of the deflected light beam, or the like can be provided.
[0024]
It goes without saying that one or more mirror members for bending the optical path may be disposed between the light source and the surface to be scanned, regardless of whether a housing is used.
[0025]
The optical scanning device according to any one of claims 1 to 6, wherein the optical path bending mirror member is a folding mirror for bending the optical path of the deflected light beam, and this is a scanning imaging lens, a transparent parallel plate, (Claim 7).
[0026]
DETAILED DESCRIPTION OF THE INVENTION
In FIG. 1, reference numeral 1 denotes a polygon mirror, reference numeral 2 denotes a scanning imaging lens, reference numeral 3 denotes a dust-proof transparent parallel plate, and reference numeral 4 denotes a photoconductive photoconductor.
[0027]
A light beam from a light source (not shown) is deflected by a polygon mirror 1 serving as an optical deflector, and is condensed as a light spot on a scanned surface by a scanning imaging lens 2 to scan the scanned surface.
[0028]
The photosensitive member 4 has its bus line aligned with the main scanning line, and its peripheral surface is in contact with the surface to be scanned. Therefore, the light spot scans the photosensitive member 4.
[0029]
The dust-proof transparent parallel plate 3 is formed of “parallel plate glass”, is in the form of a strip that is long in a direction orthogonal to the drawing, and is provided in a partition that partitions the optical scanning device side from the image forming unit side. Is prevented from entering the optical scanning device side, as shown in the figure, with an inclination angle: θs in the sub-scanning corresponding direction, that is, an inclination angle: θs from the sub-scanning corresponding direction (vertical direction in the figure). (Claim 1).
[0030]
For this reason, a part of the deflected light beam incident from the scanning imaging lens 2 side is reflected by the transparent parallel plate 3, but the reflected light is incident on the incident direction and the angle in the sub-scanning corresponding direction as shown in the figure. : Reflected with an angle of 2θs.
[0031]
Therefore, by appropriately setting the inclination angle θs of the transparent parallel plate 3, the reflected light from the transparent parallel plate 3 does not return to the scanning imaging lens 2, or the portion returning to the scanning imaging lens decreases. Thus, it is possible to effectively prevent or reduce the generation of ghost light.
[0032]
FIG. 2 shows an example in which the angle of inclination: θs of the transparent parallel plate 3 is set so that 50% of the reflected light from the transparent parallel plate 3 returns to the scanning imaging lens 2.
[0033]
The light beam that has passed through the scanning imaging lens 2 is incident on the transparent parallel plate 3 as a light beam 7 that is condensed on the surface to be scanned and is partially reflected. The reflected light beam converges while traveling in the direction of the principal ray 8, and then travels while diverging.
[0034]
As shown in FIG. 1, when the aperture of the scanning imaging lens 2 in the sub-scanning corresponding direction is 2d and the distance from the scanning imaging lens to the transparent parallel plate is L, the principal ray of the deflected light beam is the transparent parallel plate 3. The direction of the principal ray 8 of the reflected light beam makes an angle of 2θs with respect to the incident direction, so that the position at which the principal ray 8 enters the scanning imaging lens 2 is “L” in the sub-scanning corresponding direction. “Tan 2θs”.
[0035]
The condition under which 50% of the reflected light from the transparent parallel plate 3 returns to the scanning imaging lens 2, that is, the condition that the principal ray 8 of the reflected light beam returns to the edge of the opening of the scanning imaging lens 2 as shown in FIG. "L · tan2θs = d" that is, ^{"2θs = tan ~ 1 (d /} L) ".
[0036]
Accordingly, if the tilt angle θs of the transparent parallel plate 3 is set to “{tan ⁻¹ (d / L)} / 2”, the return rate of the reflected light from the transparent parallel plate 3 to the scanning imaging lens 2 is 50. When the condition: θs> {tan ⁻¹ (d / L)} / 2 is satisfied, the return rate can be reduced to 50% or less ( claim 3 ).
[0037]
Accordingly, if the tilt angle: θs of the transparent parallel plate 3 is set as large as possible, the return rate can be set to 0. However, if the tilt angle: θs is too large, an aberration occurs in the scanning light beam and the light beam becomes light. The spot shape changes from the desired shape. Therefore, the upper limit of the inclination angle θs of the transparent parallel plate 3 is determined by the condition that the light spot shape maintains an appropriate shape.
[0038]
Even if the “return rate” of the reflected light from the transparent parallel plate 3 to the scanning imaging lens 2 is reduced to 50% or less, the influence as ghost light is effectively reduced. When the return rate is not 0, as shown in FIG. 2, the light beam returned to the scanning imaging lens 2 is reflected by the lens surface and travels to the surface to be scanned as ghost light 6.
[0039]
Such ghost light 6, by using a light-shielding member 5 as shown in FIG. 2 as "shading means" can be shielded against the surface to be scanned (photosensitive member 4) (Claim 2).
[0040]
In FIG. 2, the light shielding member 5 is disposed between the transparent parallel plate 3 and the photoconductor 4, and the regular scanning light beam passes through an opening (a slit shape long in a direction perpendicular to the drawing). The width and position of the opening are determined so that the light 6 is shielded .
[0041]
As shown in FIG. 2, instead of providing the light shielding member 5 independently between the transparent parallel plate 3 and the photoconductor 4, a light shielding means may be provided at the position of the transparent parallel plate 3. That is, as described above, the transparent parallel plate 3 is provided in the partition portion between the optical scanning device side and the image forming side, and prevents floating dust from entering the optical scanning device side from the image forming portion side. Thus, the position where the transparent parallel plate 3 is provided is originally a “partition portion”, and the transparent parallel plate 3 blocks the “opening for allowing the scanning light beam to pass” formed in the partition portion.
[0042]
Therefore, the partition portion itself can be formed of a light shielding material, and the width of the opening can be made to allow only the regular scanning light beam to pass therethrough and shield the ghost light 6. That is, the transparent parallel plate 3 is disposed between the image forming unit including the photoconductor 4 and the optical scanning device, and the light shielding plate (slit opening) in the disposed portion of the transparent parallel plate 3 is configured as a light beam transmitting slit (the opening). The light shielding means can be constituted by the partition part.
[0043]
Alternatively, as shown in FIG. 3, the ghost light 6 is shielded by using a light shielding region 9 (formed on the surface of the transparent parallel plate 3 as a layer of an appropriate light shielding material) formed on the transparent parallel plate 3 as a light shielding means. (Claim 4).
[0044]
In FIG. 4, the optical scanning device is unitized, and the transparent parallel plate 3 is disposed in a light beam exit opening 5 ′ in the housing 11 of the unitized optical scanning device. The transparent parallel plate mounting portion (housing surface portion where the light beam emission opening 5 ′ is formed) in the housing 11 is inclined in the sub-scanning direction. By attaching the transparent parallel plate 3 to this portion as shown in the figure, The transparent parallel plate 3 can be inclined and arranged in the sub-scanning corresponding direction.
[0045]
In FIG. 4, reference numeral 1 ′ denotes a “drive motor” for the polygon mirror 1, and reference numeral 10 denotes a “cover” for closing the housing.
[0046]
As shown in FIG. 5, only the “surface of the portion to which the transparent parallel flat plate 3 is attached” of the housing 11 ′ is inclined (reference numeral 5 ″ indicates a light beam emission opening), and the outer wall of the housing is not inclined. Good. The transparent parallel flat plate 3 can be attached to the housing 11 ′ with an adhesive 13, for example.
[0047]
The embodiment described below with reference to FIGS. 6 to 9 is an embodiment of the invention described in claim 7.
[0048]
The embodiment shown in FIG. 6 is a modification of the embodiment shown in FIG. 1, and the same reference numerals as those in FIG. 1 are used to avoid confusion in order to avoid confusion. Is used.
[0049]
A folding mirror 13 provided between the scanning imaging lens 2 and the photoconductor 4 bends the optical path of the deflected light beam in the sub-scanning corresponding direction. The transparent parallel flat plate 3 is tilted from the sub-scanning corresponding direction with an inclination angle: θs. Therefore, the reflected light 8 reflected by the transparent parallel flat plate 3 has an incident direction and an angle of 2θs with respect to the sub-scanning corresponding direction. Since the light is reflected at an angle, the reflected light 8 from the transparent parallel plate 3 does not return to the scanning imaging lens 2 or is scanned and imaged by appropriately setting the tilt angle θs of the transparent parallel plate 3. By reducing the portion returning to the lens, it is possible to effectively prevent or reduce the generation of ghost light.
[0050]
FIG. 7 shows a modification of the embodiment of FIG. 2 is in the presence of a folding mirror 13 provided between the scanning imaging lens 2 and the transparent parallel plate 3. The inclination angle θs of the transparent parallel plate 3 is set so that 50% of the reflected light (indicated by a double arrow) 8 from the transparent parallel plate 3 returns to the scanning imaging lens 2.
[0051]
The light beam that has passed through the scanning imaging lens 2 is incident on the transparent parallel plate 3 as a light beam 7 that is condensed on the surface to be scanned, via the folding mirror 13, and is partially reflected. The reflected light beam converges while traveling in the direction of the principal ray 8, and then travels while diverging.
[0052]
As in the embodiment of FIG. 2, the aperture of the scanning imaging lens 2 in the sub-scanning corresponding direction is 2d, and the distance on the optical axis from the scanning imaging lens 2 to the transparent parallel plate via the folding mirror 13 is L. to time, the conditions 50% of the reflected light by the transparent parallel plate 3 returns to the scanning imaging lens 2 is ^{"2θs = tan ~ 1 (d /} L) ".
[0053]
Therefore, the inclination angle of the transparent parallel flat plate 3: By setting θs to ^{"{tan ~ 1 (d / L} )} / 2 ", the return rate of the scanning imaging lens 2 of the reflected light by the transparent parallel flat plate 3 50 % in can be reduced, conditions: [theta] s> by satisfying ^{{tan ~ 1 (d / L} )} / 2, can be reduced the rate of return to 50% or less.
[0054]
The upper limit of the inclination angle θs of the transparent parallel flat plate 3 is determined by the condition that the light spot shape maintains an appropriate shape in the same manner as described with reference to the embodiment of FIG.
[0055]
The light beam returned to the scanning imaging lens 2 is reflected by the lens surface and travels as the ghost light 6 toward the scanning surface. The ghost light 6 is obtained by using a light shielding member 5 as shown in FIG. The light can be shielded against the surface to be scanned (photosensitive member 4).
[0056]
The light shielding member 5 is disposed between the transparent parallel plate 3 and the photosensitive member 4, and allows the normal scanning light beam to pass through an opening (a slit shape long in a direction perpendicular to the drawing), but the ghost light 6 is shielded. Thus, the width and position of the opening are determined.
[0057]
Needless to say, the light shielding means can be provided at the position of the transparent parallel plate 3 as described in the embodiment of FIG.
[0058]
FIG. 8 shows a modification of the embodiment shown in FIG. 3, and the difference from the embodiment of FIG. 3 is that the folding mirror 13 provided on the optical path between the scanning imaging lens 2 and the transparent parallel plate 3 is different. Is in existence.
As in the embodiment of FIG. 3, the ghost light 6 is shielded by using the light shielding region 9 formed on the transparent parallel plate 3 as a light shielding means.
[0059]
FIG. 9 is a modification of the embodiment of FIG. 4. As in the embodiment of FIG. 4, the optical scanning device is unitized, and the transparent parallel plate 3 is in the housing 110 of the unitized optical scanning device. A folding mirror 13 is also provided in the housing 110, which is disposed in the light beam exit opening 5 ′ ″ and bends the optical path of the deflected light beam.
[0060]
The transparent parallel plate mounting portion (the housing surface portion where the light beam emission opening 5 ′ ″ is formed) in the housing 110 is inclined in the sub-scanning direction, and the transparent parallel plate 3 is mounted on this portion as shown in the figure. Thus, the transparent parallel flat plate 3 can be arranged to be inclined from the sub-scanning corresponding direction.
As in the embodiment shown in FIG. 4, the reflected light from the transparent parallel plate 3 does not return to the scanning imaging lens 2 or returns to the scanning imaging lens by adjusting the inclination angle of the transparent parallel plate 3. The amount can be reduced.
[0061]
In FIG. 9, reference numeral 1 ′ denotes a “drive motor” for the polygon mirror 1 and reference numeral 10 denotes a “cover” for closing the housing, as in FIG. The transparent parallel flat plate 3 can be attached to the housing 110 with, for example, an adhesive.
[0062]
In each of the above embodiments, the “inclination angle of the transparent parallel plate” is appropriately about 2 to 10 degrees in consideration of the influence of aberration caused by the inclination.
[0063]
【The invention's effect】
According to the optical scanning device of the present invention, by effectively reducing or preventing the light beam reflected by the dust-proof transparent parallel plate from returning to the scanning imaging lens, the returning light beam is reflected by the scanning imaging lens. It is possible to effectively reduce or prevent the ghost light from affecting the optical scanning.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining an embodiment of the invention as set forth in claim 1;
FIG. 2 is a diagram for explaining an embodiment of the invention as set forth in claims 2, 3, and 5.
FIG. 3 is a view for explaining an embodiment of the invention as set forth in claim 4;
FIG. 4 is a diagram for explaining an embodiment of the invention as set forth in claim 6;
FIG. 5 is a view for explaining another example of the embodiment of the invention as set forth in claim 6;
FIG. 6 is a view for explaining an embodiment of the invention as set forth in claim 7;
FIG. 7 is a view for explaining another embodiment of the invention described in claim 7;
FIG. 8 is a view for explaining another embodiment of the invention as set forth in claim 7;
FIG. 9 is a view for explaining another example of the embodiment of the invention described in claim 7;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Polygon mirror 2 Scan imaging lens 3 Dust-proof transparent parallel plate 4 Photoconductor

Claims (7)

In an optical scanning device that condenses a deflected light beam deflected by an optical deflector as a light spot on a scanned surface by a scanning imaging lens and optically scans the scanned surface,
A dust-proof transparent parallel plate disposed between the scanning imaging lens and the surface to be scanned is returned to the scanning imaging lens when the deflected light beam is reflected by the transparent parallel plate, and is returned by the lens surface of the scanning imaging lens. An optical scanning device characterized in that the reflected light beam is disposed at an angle of 2 to 10 degrees from the sub-scanning corresponding direction in order to prevent the reflected light beam from reaching the scanning surface as ghost light. In an optical scanning device that condenses a deflected light beam deflected by an optical deflector as a light spot on a scanned surface by a scanning imaging lens and optically scans the scanned surface,
A dust-proof transparent parallel plate disposed between the scanning imaging lens and the surface to be scanned is disposed at an angle of 2 to 10 degrees from the sub-scanning corresponding direction;
A light shielding means for preventing the deflected light beam from being reflected by the transparent parallel plate and returning to the scanning imaging lens and preventing the light beam reflected by the lens surface of the scanning imaging lens from reaching the scanned surface as ghost light. An optical scanning device comprising: The optical scanning device according to claim 2.
When the aperture of the scanning imaging lens in the sub-scanning corresponding direction is 2d and the distance from the scanning imaging lens to the transparent parallel plate is L,
The inclination angle: θs in the direction corresponding to the sub-scanning of the transparent parallel plate is the condition:
θs ≧ {tan ⁻¹ (d / L)} / 2
An optical scanning device characterized by satisfying The optical scanning device according to claim 2 or 3,
An optical scanning device, wherein the light shielding means is a light shielding region formed on a transparent parallel plate. The optical scanning device according to claim 2 or 3,
A transparent parallel plate is disposed between the image forming unit including the photoconductor and the optical scanning device,
An optical scanning device characterized in that a light shielding means is constituted by a light shielding plate which constitutes a slit for transmitting a light beam in an arrangement part of a transparent parallel plate. The optical scanning device according to claim 1, 2, 3, 4 or 5,
The optical scanning device is unitized,
An optical scanning device characterized in that a transparent parallel flat plate is disposed in a light beam emission opening in a housing of the optical scanning device in which the transparent parallel flat plate is unitized, and the transparent parallel flat plate mounting portion in the housing is inclined from the sub-scanning corresponding direction. The optical scanning device according to claim 1, 2, 3, 4, 5, or 6.
An optical scanning device characterized in that a folding mirror for bending the optical path of the deflected light beam is disposed between the scanning imaging lens and the transparent parallel plate.

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