JPH0980342A - Optical scanning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively reduce or eliminate the effect of ghost light by a transparent parallel flat plate for dust protection by arranging the transparent parallel flat plate for dust protection, arranged between a scanning image forming lens and a surface to be scanned, slantingly to a subscanning correspondent direction. SOLUTION: The transparent parallel flat plate 3 for dust protection is provided at a partition part which partitions an optical scanning device side and an image formation part side and prevents suspended dust from the image formation part side from entering the optical scanning device side. At this time, this plate is provided at a tilt angle θs to the subscanning corresponding direction. Thus, the tilt angle θs of the transparent parallel flat plate 3 is properly set to make reflected light from the parallel flat plate 3 not return to the scanning image forming lens 2 or reduce a part returning to the scanning image forming lens 2. Consequently, the generation of ghost light can effectively be prevented or reduced.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an optical scanning device.

[0002]

2. Description of the Related Art An optical scanning device that optically scans a surface to be scanned by collecting a deflected light beam deflected by an optical deflector as a light spot on the surface to be scanned by a scanning imaging lens is a digital copying apparatus or an optical printer. , Is widely known in connection with facsimile recording devices and the like.

An optical scanning device generally forms an electrostatic latent image by optical scanning and develops the electrostatic latent image to obtain a recorded image. "Image forming part" is the part where the recorded image is obtained from the electrostatic latent image.
In the image forming unit, floating toner is generated,
The paper dust of the recording paper on which the toner image is fixed may float.

If these floating dusts enter the optical scanning device and adhere to the lens surface or the like, the optical scanning is hindered. Therefore, the optical scanning unit and the image forming unit are generally partitioned by some kind of partition, and the deflected light flux is partitioned. A transparent parallel flat plate for dust protection is provided in the part that is emitted from.

Conventionally, a dust-proof transparent parallel plate is used in a sub-scanning direction in a sub-scanning corresponding direction (a virtual optical path in which an optical path from a light source to a surface to be scanned is linearly developed along an optical axis of an 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 to do.

Therefore, a part of the deflected light flux transmitted through the scanning and imaging lens is reflected by the transparent parallel plate and returns to the scanning and imaging lens, is reflected by the lens surface of the scanning and imaging lens, and becomes "ghost light". It may reach the surface to be scanned and cause deterioration of the quality of the recorded image.

[0007]

In view of the above-mentioned circumstances, the present invention has an object to effectively reduce or prevent the influence of ghost light by the dust-proof transparent parallel plate.

[0008]

In the optical scanning device of the present invention, a deflected light beam deflected by an optical deflector is condensed as a light spot on a surface to be scanned by a scanning imaging lens to optically scan the surface to be scanned. The device is characterized by the following points (Claim 1).

That is, the dust-proof transparent parallel flat plate disposed between the scanning imaging lens and the surface to be scanned is "inclined from the sub-scanning corresponding direction".

As a result, among the deflected light beams incident on the transparent parallel plate from the scanning and imaging lens side, the light beams reflected on the transparent parallel plate travel in a direction different from the incident direction in the sub-scanning corresponding direction. Become.

The "transparent parallel plate" is made of, for example, parallel plate glass.

In the optical scanning device according to the second aspect, 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 auxiliary of the transparent parallel plate is defined. tilt angle in the scanning corresponding direction: [theta] s is the condition: and satisfies the ^{θs ≧ {tan ~ 1 (d} / L)} / 2.

According to a third aspect of the present invention, in the optical scanning device according to the first or second aspect, the light flux reflected by the transparent parallel plate and returned to the scanning imaging lens, the light flux reflected by the lens surface of the scanning imaging lens is reflected. A light-shielding device is provided to prevent the ghost light from reaching the surface to be scanned.

According to a fourth aspect of the present invention, in the optical scanning device according to the third aspect, the light shielding means is "a light shielding region formed on a transparent parallel plate".

According to a fifth aspect of the present invention, in the optical scanning device according to the third aspect, a transparent parallel plate is provided between an image forming portion including a photoconductor and the like and the optical scanning device, and the light shielding means is "transparent". It is composed of a light-shielding plate that constitutes a slit for transmitting a light beam in the arrangement portion of the parallel flat plates ”.

According to a sixth aspect of the present invention, in the optical scanning device according to the first, second, third or fourth aspect, the light scanning device is unitized and the transparent parallel flat plate is unitized. It is characterized in that the transparent parallel plate mounting portion of the housing, which is provided in the ejection opening, is inclined from the sub-scanning corresponding direction.

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 the coupling lens and becomes a parallel light beam, a divergent light beam or a converging light beam and is incident on the optical deflector.

As the optical deflector, a polygon mirror or a rotation 2
A face mirror, a rotating single-sided mirror such as a "tenon-shaped mirror or a pyramidal mirror", and an oscillating mirror such as a galvanometer mirror can be used.

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 a long line image in the main scanning corresponding direction is formed on the deflection reflecting surface position of the optical deflector. You may make it image-form as.

As the scanning and imaging lens, an fθ lens can be preferably used when the optical deflector is a rotatable one such as a rotating polygon mirror, and when the optical deflector is an oscillating mirror, fs
An inθ lens is used. The main scanning speed can be made uniform by using such a scanning imaging lens.

As described above, in order to "correct the surface tilt", when the coupled light flux is formed 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, scanning image formation is performed. The lens has a function of making the position of the deflective reflection surface and the scanned surface position "geometrically-optically substantially conjugate" with respect to the sub-scanning corresponding direction in the sub-scanning corresponding direction.

In the invention according to claim 6, the transparent parallel flat plate for dust prevention is "a light beam emission opening in the housing".
The aperture for emitting light flux has a slit shape. Therefore, by making the portion other than this slit-shaped light beam emission opening a light-shielding property, "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 is It can be used as a “light-shielding device for preventing the ghost light from reaching the surface to be scanned”.

An optical deflector and a scanning image forming lens are provided in the housing. In addition to this, the coupled light beam is formed as a long line image in the main scanning corresponding direction at the deflecting reflection surface position of the optical deflector. A condensing optical system (cylinder mirror or cylinder lens) for causing the reflection, a folding mirror for bending the optical path of the deflected light beam, and the like can be provided.

Whether or not a housing is used,
A mirror member for bending the optical path is provided between the light source and the surface to be scanned.
It goes without saying that the above can be distributed.

In the optical scanning device according to any one of claims 1 to 6, the mirror member for bending the optical path is used as a folding mirror for bending the optical path of the deflected light beam, which is transparent to the scanning imaging lens. It can be arranged between parallel plates (Claim 7).

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, reference numeral 1 is a polygon mirror, reference numeral 2 is a scanning image forming lens, reference numeral 3 is a transparent parallel flat plate for dust protection, and reference numeral 4 is a photoconductive photoconductor.

A light beam from a light source side (not shown) is deflected by a polygon mirror 1 as an optical deflector, and is condensed as a light spot on a surface to be scanned by a scanning imaging lens 2,
The surface to be scanned is scanned.

The photoconductor 4 has its generatrix aligned with the main scanning line and its peripheral surface is in contact with the surface to be scanned, so that the light spot scans the photoconductor 4.

The dust-proof transparent parallel flat plate 3 is formed of "parallel flat plate glass" and has a strip shape which is long in a direction orthogonal to the drawing, and is provided in a partition portion for partitioning the optical scanning device side and the image forming portion side. Although the floating dust from the forming unit side is prevented from entering the optical scanning device side, as shown in the figure, it has an inclination angle in the sub-scanning corresponding direction: θs, that is, an inclination from the sub-scanning corresponding direction (vertical direction in the figure). Angle: inclined with θs (Claim 1).

Therefore, a part of the deflected light flux incident from the scanning and imaging lens 2 side is reflected by the transparent parallel plate 3, but the reflected light is incident in the sub-scanning corresponding direction as shown in the figure. Direction and angle: It will be reflected with an angle of 2θs.

Therefore, by appropriately setting the inclination angle θs of the transparent parallel plate 3, the reflected light from the transparent parallel plate 3 is prevented from returning to the scanning / imaging lens 2, or the portion returning to the scanning / imaging lens is adjusted. By reducing the amount, it becomes possible to effectively prevent or reduce the generation of ghost light.

FIG. 2 shows an example in which the inclination angle θs of the transparent parallel plate 3 is set so that 50% of the light reflected by the transparent parallel plate 3 returns to the scanning and imaging lens 2.

The light beam transmitted through the scanning and imaging lens 2 is incident on the transparent parallel flat plate 3 as a light beam 7 to be condensed on the surface to be scanned, and a part thereof is reflected. The reflected light flux converges while advancing in the direction of the principal ray 8 and then diverges.

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 transparent. When reflected by the parallel plate 3, the direction of the principal ray 8 of the reflected light flux forms an angle of 2θs with respect to the incident direction. Therefore, the position where the principal ray 8 enters the scanning imaging lens 2 is in the sub-scanning corresponding direction. Is “L · tan2θs”.

The condition under which 50% of the light reflected by the transparent parallel plate 3 returns to the scanning / imaging lens 2, that is, the principal ray 8 of the reflected light flux returns to the edge portion of the aperture of the scanning / imaging lens 2 as shown in FIG. The condition is “L · tan2θs = d”, that is, “2θs =
tan ~ ¹ (d / L) ".

Therefore, if the inclination angle θs of the transparent parallel flat plate 3 is set to "{tan- ¹ (d / L)} / 2", the reflected light from the transparent parallel flat plate 3 returns to the scanning imaging lens 2. Rate 5
It can be reduced to 0%, and the condition: θs> {tan ~ ¹ (d / L)} /
When 2 is satisfied, the return rate can be reduced to 50% or less (claim 2).

Therefore, if the inclination angle of the transparent parallel plate 3 is set as large as possible, the return rate can be set to 0. However, if the inclination angle of θs becomes too large,
Aberration occurs in the scanning light flux, and the light spot shape changes from the desired shape. Therefore, the tilt angle of the transparent parallel plate 3:
The upper limit of θs is determined by the condition that the shape of the light spot maintains an appropriate shape.

Even if the "return rate" of the light reflected by the transparent parallel plate 3 to the scanning and imaging lens 2 is reduced to 50% or less, the effect as ghost light is effectively reduced. When the return rate is not 0, as shown in FIG. 2, the light flux returning to the scanning and imaging lens 2 is reflected by the lens surface and travels toward the surface to be scanned as ghost light 6.

Such ghost light 6 can be shielded against the surface to be scanned (photoreceptor 4) by using the light shielding member 5 as shown in FIG. 2 as the "light shielding means" (claim 3). ).

In FIG. 2, the light shielding member 5 is arranged between the transparent parallel flat plate 3 and the photosensitive member 4, and the normal scanning light beam passes through the opening (a slit shape long in the direction orthogonal to the drawing). The width and position of the opening are determined so as to block the ghost light 6.

As shown in FIG. 2, instead of independently providing the light blocking member 5 between the transparent parallel flat plate 3 and the photosensitive member 4, a light blocking means may be provided at the position of the transparent parallel flat plate 3. That is, as described above, the transparent parallel plate 3 is provided in the partition between the optical scanning device side and the image forming side, and prevents the floating dust from entering the optical scanning device side from the image forming portion side. Therefore, the position where the transparent parallel flat plate 3 is provided is originally the “partition portion”, and the transparent parallel flat plate 3 closes the “opening for passing the light flux for scanning” formed in the partition portion.

Therefore, it is also possible to form the partition portion itself with a light shielding material so that the width of the opening portion allows only the normal scanning light flux to pass therethrough and shields the ghost light 6.
That is, the transparent parallel plate 3 is arranged between the image forming portion including the photoconductor 4 and the optical scanning device, and a light shielding plate (aperture portion) constituting a slit for transmitting a light beam in the arrangement portion of the transparent parallel plate 3 ( A light shielding unit can be configured by the partition section (claim 5).

Alternatively, as shown in FIG. 3, the light-shielding region 9 (formed as a layer of a suitable light-shielding material on the surface of the transparent parallel plate 3) formed on the transparent parallel plate 3 serves as a light-shielding means, and the ghost light 6 Can be shielded from light (claim 4).

In FIG. 4, the optical scanning device is unitized, and the transparent parallel plate 3 is provided in the light beam emission 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, and by mounting the transparent parallel plate 3 on this portion as shown in the figure, The transparent parallel flat plate 3 can be arranged so as to be tilted in the sub-scanning corresponding direction.

In FIG. 4, reference numeral 1'indicates a "driving motor" for the polygon mirror 1, and reference numeral 10 indicates a "cover" for closing the housing.

As shown in FIG. 5, only the "surface of the portion to which the transparent parallel 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. You may Housing 1
The transparent parallel plate 3 can be attached to the 1'by an adhesive 13, for example.

The embodiment described below with reference to FIGS. 6 to 9 is an embodiment of the invention described in claim 7.

The embodiment shown in FIG. 6 is a modification of the embodiment shown in FIG. 1. In order to avoid complication, what is considered to have no possibility of confusion is as shown in FIG. The same code is used.

The folding mirror 13 provided between the scanning imaging lens 2 and the photosensitive member 4 bends the optical path of the deflected light beam in the sub-scanning corresponding direction. The transparent parallel plate 3 is tilted with a tilt angle of θs from the sub-scanning corresponding direction,
Therefore, the reflected light 8 reflected by the transparent parallel plate 3
Is reflected at an angle of 2θs with the incident direction with respect to the sub-scanning corresponding direction, so the inclination angle of the transparent parallel plate 3 is:
By appropriately setting θs, the reflected light 8 from the transparent parallel plate 3 is prevented from returning to the scanning imaging lens 2 or the portion returning to the scanning imaging lens is reduced, thereby generating ghost light. Can be effectively prevented or reduced.

FIG. 7 shows a modification of the embodiment shown in FIG.
The difference from the configuration of FIG. 2 lies 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 double arrow) 8 by the transparent parallel plate 3 returns to the scanning imaging lens 2.

The light beam which has passed through the scanning and imaging lens 2 is incident on the transparent parallel flat plate 3 as a light beam 7 to be condensed on the surface to be scanned, through the folding mirror 13 and on the way of condensing, and a part thereof is reflected. It The reflected light flux converges while advancing in the direction of the principal ray 8 and then diverges.

As in the embodiment of FIG. 2, the scanning imaging lens 2 has a diameter of 2d in the sub-scanning corresponding direction, and the distance from the scanning imaging lens 2 to the transparent parallel plate via the folding mirror 13 on the optical axis. Is L, the condition for returning 50% of the light reflected by the transparent parallel plate 3 to the scanning imaging lens 2 is “2θs = t.
an ~ ¹ (d / L) ".

[0053] Therefore, the inclination angle of the transparent parallel flat plate 3: By setting θs to ^{"{tan ~ 1 (d / L} )} / 2 ", a return to the scanning imaging lens 2 of the reflected light by the transparent parallel flat plate 3 Rate 5
It can be reduced to 0%, and the condition: θs> {tan ~ ¹ (d / L)} /
By satisfying the condition 2, the return rate can be reduced to 50% or less.

The inclination angle θs of the transparent parallel flat plate 3 is set to an upper limit under the condition that the light spot shape is kept in the proper shape, as described in the embodiment of FIG. Become.

The light flux returned to the scanning and imaging lens 2 is reflected by the lens surface and travels as ghost light 6 toward the surface to be scanned.
The ghost light 6 can be shielded from the surface to be scanned (photoconductor 4) by using the light shielding member 5 as shown in FIG.

The light shielding member 5 is composed of the transparent parallel plate 3 and the photosensitive member 4.
And the normal scanning light flux passes through the opening (long slit in the direction orthogonal to the drawing), but the width and position of the opening are adjusted so as to block the ghost light 6. It is set.

Needless to say, as described in the embodiment of FIG. 2, the light shielding means can be provided at the position of the transparent parallel plate 3.

FIG. 8 shows a modification of the embodiment shown in FIG. 3. The difference from the embodiment shown in FIG. 3 is that the fold-back provided on the optical path between the scanning imaging lens 2 and the transparent parallel plate 3. There is a mirror 13. Similar to the embodiment of FIG. 3, the light-shielding region 9 formed on the transparent parallel plate 3 serves as the light-shielding means,
The ghost light 6 is blocked.

FIG. 9 shows a modification of the embodiment shown in FIG. 4. As in the embodiment shown in FIG. 4, the optical scanning device is unitized, and the transparent parallel flat plate 3 is the unitized optical scanning device. Luminous flux exit opening 5 '''in the housing 110
The folding mirror 13 that is provided in the housing 110 and bends the optical path of the deflected light flux is also provided in the housing 110.

The transparent parallel plate mounting portion (housing surface portion where the light beam emission opening 5 '''is formed) of the housing 110 is inclined in the sub-scanning direction. The transparent parallel plate 3 can be arranged by inclining from the direction corresponding to the sub-scanning by mounting. As in the embodiment shown in FIG. 4, adjusting the tilt angle of the transparent parallel plate 3 prevents the reflected light from the transparent parallel plate 3 from returning to the scanning imaging lens 2 or returns to the scanning imaging lens. The amount can be small.

In FIG. 9, reference numeral 1'indicates a "driving motor" for the polygon mirror 1 and reference numeral 10 indicates a "cover" for closing the housing, as in FIG. The transparent parallel plate 3 is attached to the housing 110 by, for example,
It can be performed with an adhesive or the like.

In each of the above-described embodiments, the "inclination angle of the transparent parallel plate" is preferably about 2 to 10 degrees in consideration of the influence of aberration caused by the inclination.

[0063]

According to the optical scanning device of the present invention, the returning light beam is scanned and imaged by effectively reducing or preventing the light beam reflected by the dust-proof transparent parallel plate from returning to the scanning and imaging lens. It is possible to effectively reduce or prevent the influence of light reflected by the lens as ghost light on optical scanning.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an embodiment of the invention according to claim 1;

FIG. 2 is a diagram for explaining an embodiment of the invention described in claims 2, 3 and 5.

FIG. 3 is a diagram for explaining an embodiment of the invention according to claim 4;

FIG. 4 is a diagram for explaining an embodiment of the invention according to claim 6;

FIG. 5 is a diagram for explaining another example of the embodiment of the invention according to claim 6;

FIG. 6 is a diagram for explaining an embodiment of the invention according to claim 7;

FIG. 7 is a diagram for explaining another embodiment of the invention according to claim 7;

FIG. 8 is a diagram for explaining another embodiment of the invention according to claim 7;

FIG. 9 is a diagram for explaining another example of the embodiment of the invention described in claim 7;

[Explanation of symbols]

 1 Polygon mirror 2 Scanning imaging lens 3 Dust-proof transparent parallel plate 4 Photoreceptor

Claims (7)

[Claims] 1. An optical scanning device for converging a deflected light beam deflected by an optical deflector as a light spot on a surface to be scanned by a scanning and imaging lens to optically scan the surface to be scanned. An optical scanning device characterized in that a transparent parallel plate for dust prevention disposed between the scanning surface and the scanning surface is inclined with respect to the sub-scanning corresponding direction. 2. An optical scanning device according to claim 1, wherein 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 transparent parallel plate. Angle in the direction corresponding to sub-scanning: θs
But the ^{condition: θs ≧ {tan ~ 1 (} d / L)} / 2 optical scanning apparatus which satisfies the. 3. The optical scanning device according to claim 1, wherein the light is reflected by a transparent parallel plate and returned to the scanning imaging lens,
An optical scanning device comprising a light-shielding device for preventing the light flux reflected by the lens surface of the scanning imaging lens from reaching the surface to be scanned as ghost light. 4. The optical scanning device according to claim 3, wherein the light shielding means is a light shielding region formed on a transparent parallel plate. 5. The optical scanning device according to claim 3, wherein a transparent parallel plate is provided between an image forming section including a photoconductor and the like and the optical scanning device, and the transparent parallel plate is provided for transmitting a light beam in the placement section. An optical scanning device, characterized in that a light shielding means is constituted by a light shielding plate which constitutes a slit. 6. The optical scanning device according to claim 1, 2 or 3 or 4, wherein the optical scanning device is unitized, and a transparent parallel flat plate is provided in an opening for luminous flux emission in a housing of the optical scanning device. The optical scanning device is characterized in that the transparent parallel plate mounting portion of the housing is inclined from the sub-scanning corresponding direction. 7. The optical scanning device according to claim 1, 2 or 3 or 4 or 5 or 6, wherein a folding mirror for bending the optical path of the deflected light beam is provided between the scanning imaging lens and the transparent parallel plate. An optical scanning device characterized in that