JPH09113782A - Scanning lens mount structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To securely prevent mounting error with simple constitution by making a mount part allows a fitting device in a specific direction of a scanning lens and stop the fitting device in a direction different from the specific direction. SOLUTION: The refracting surfaces 140A and 140B of a 1st lens 141 are convex on a z-y plane on a photosensitive drum side 140A and concave on a polygon mirror side 140B. The refracting surfaces 140C and 140D of a 2nd lens 142 are convex on the z-y plane on a photosensitive drum side 140C and straight on a polygon mirror side 140D. Further, one end part of each lens is a convex cylindrical surface and the other is a concave cylindrical surface. Further, lens mount parts 143 and 144 have their internal surfaces formed in a convex cylindrical surface and a concave cylindrical surface in conformity with the lens shapes. If the lenses are fitted in wrong directions, the convex parts of the lenses 141 and 142 and the convex parts of the lens mount parts 143 and 144 interfere with each other so that the lenses may not be mounted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mounting structure of a scanning lens of an optical scanning device used in an image forming apparatus utilizing electrophotography such as a laser beam printer.

[0002]

2. Description of the Related Art In an image forming apparatus utilizing electrophotography, such as a laser beam printer, an optical scanning device is used to expose a photosensitive member to form a latent image.
In general, an optical scanning device uses a semiconductor laser to emit a laser beam modulated according to image information so as to scan (main scan) the surface of the photoconductor in a predetermined angular range. Simultaneously with the main scanning, the photoconductor is moved in the direction orthogonal to the scanning direction of the laser beam relative to the scanning line (sub-scanning) to form a two-dimensional latent image on the surface of the photoconductor.

Generally, an optical scanning device collimates a laser beam emitted from a semiconductor laser by a collimator lens, guides it to a deflector such as a polygon mirror through a cylindrical lens to scan-deflect it, and deflects the deflected beam to fθ. The scanning surface is irradiated with light through the lens.

[Problems to be solved by the invention]

In recent years, as the definition of the image forming apparatus has increased, the optical scanning apparatus has also been required to have high precision and high function. That is, as a lens used in an optical scanning device, a spherical lens that has a lens shape center coincident with the optical axis and is rotationally symmetric with respect to the optical axis has been generally used, but in recent years, an asymmetric lens is gradually used. It's starting to happen. In addition, there are many devices that use a plurality of lenses in combination to improve the characteristics of the lenses. When installing such a lens in the housing, if the order of arrangement in the mounting direction or the optical axis direction is wrong,
This will have a fatal adverse effect on the performance of the device.

Conventionally, a protrusion and a groove portion with which the protrusion engages are formed on the contact surfaces of the lens and the lens mounting portion on the housing, and the protrusion and the groove portion are engaged only when the lens is properly mounted. However, when the direction and order of the lenses are incorrect, rattling occurs between the lens and the lens mounting portion to prevent mistakes during mounting.

However, even if there is some rattling, if the lens fits in the mounting position of the housing, there is a case where the wrong mounting direction or order of the lens may not be noticed, and a countermeasure has been desired.

As described above, there is a demand for a mounting structure for a scanning lens in an optical scanning device, which has a simple structure and can reliably prevent a mounting error.

[0008]

Therefore, in the scanning lens mounting structure of the present invention, a long scanning lens extending in the same direction as the main scanning direction in which the beam scans the surface to be scanned, and the length of the scanning lens. And a mounting portion to which both ends in the lengthwise direction are fitted and mounted, the mounting portion allows fitting and mounting of the scanning lens in a predetermined direction, and the mounting direction is different from the predetermined direction. It is configured to have a shape that prevents fitting and mounting.

Both ends of the scanning lens are asymmetrical with respect to a main scanning plane including at least all of the chief rays of the scanning beam (across the main scanning plane), and at least the mounting lens has at least the scanning lens in the main scanning plane. When the lens is inserted in the opposite direction with respect to, the shape can be such that the fitting lens of the mounting lens is prevented from being mounted.

Further, both ends of the scanning lens have an asymmetrical shape with at least a surface orthogonal to the optical axis of the scanning lens interposed therebetween, and in the mounting portion, at least the scanning lens is orthogonal to the optical axis of the scanning lens. It is also possible to adopt a configuration having a shape that prevents the mounting lens from being fitted and mounted in the mounting portion when inserted in the opposite direction with respect to the surface.

Further, both ends of the scanning lens are asymmetrical with respect to a surface including at least the optical axis of the scanning lens and a surface orthogonal to the main scanning plane including all the chief rays of the scanning beam. In one case, the mounting portion is inserted in an opposite direction with respect to at least a plane where the scanning lens includes the optical axis of the scanning lens and is orthogonal to a main scanning plane including all the optical axes of the beams. In such a case, it is also possible to adopt a configuration having a shape that prevents fitting and mounting of the mounting lens to the mounting portion.

From another point of view, the scanning lens mounting structure of the present invention is a scanning lens mounting structure of an optical scanning device, and has a length extending in the same direction as the main scanning direction in which a beam scans on a surface to be scanned. The scanning lens has an elongate shape, and a pair of mounting portions to which both ends in the longitudinal direction of the scanning lens are fitted and mounted, and the scanning lens is composed of a plurality of lenses arranged along the optical axis thereof. At least one end of the plurality of lenses has a different shape for each lens, and the mounting portion corresponding to the end can mount all the lenses only when the plurality of lenses are correctly arranged. It is characterized by being configured as follows.

[0013]

1 is a diagram for explaining a scanning optical unit 100 to which the present invention is applied. The scanning optical unit 100 is used as a scanning optical system in an image forming apparatus utilizing electrophotography, such as a laser beam printer.

The scanning optical unit 100 includes a housing 2
00, a collimator unit 10 having a semiconductor laser and a collimator lens, a cylindrical lens 20, a polygon mirror 30 as a deflecting unit, and an fθ lens 40 are mounted.

Emitted from the scanning optical unit 100,
The scanning laser beam modulated according to the image information mainly scans the surface of the photosensitive drum 50 in a direction parallel to the rotation axis 51. The photosensitive drum 50 is rotated (sub-scanning) simultaneously with the main scanning, and as a result, a two-dimensional image is formed as a latent image on the surface of the photosensitive drum.

In the collimator unit 10, the laser beam emitted from the semiconductor laser is converted into parallel light by the collimator lens. The laser beam emitted from the collimator unit 10 enters a convex cylindrical lens 20 as an anamorphic optical system. The cylindrical lens 20 has no power in the main scanning direction (direction of the rotation shaft 51 of the photosensitive drum 50), but has power only in the sub scanning direction (direction perpendicular to the rotation shaft 51 of the photosensitive drum). The beam that has passed through the cylindrical lens 20 enters the polygon mirror 30. Note that the power of the cylindrical lens 20 in the sub-scanning direction causes the sub-scanning direction component of the laser beam to temporarily converge slightly before the reflecting surface 30R of the polygon mirror 30. The laser beam deflected by the polygon mirror 30 passes through the fθ lens 40 and scans and exposes the surface of the photosensitive drum 50.

FIG. 2 is a top view for explaining the mounting structure of the fθ lens 140 of the first embodiment. The upper side in the figure is the photosensitive drum 50 side, and the lower side in the figure is the polygon mirror 30 side. The fθ lens 140 of the first embodiment is the first lens 14
It has a first lens 142 and a second lens 142. The first lens 141 and the second lens 142 are provided in the housing 2
Pair of lens mounting portions 143, 144 formed on
In addition, the structure is such that the housing is fitted from above (in FIG. 2, the front side of the paper surface).

As shown in FIG. 2, the refracting surfaces 140A and 140B of the first lens 141 are convex on the photosensitive drum side 140A and concave on the polygon mirror 30 side 140B on the zy plane. Refractive surface 140C of second lens 142
And 140D are on the photosensitive drum side 14 on the zy plane.
0C is convex, and the polygon mirror side 140D is represented by a straight line. Further, both ends of each lens have a convex cylindrical surface on one side (right side in the drawing) and a concave cylindrical surface on the other side (left side in the drawing). In addition, the lens mounting portions 143 and 144
The inner surface of each of them is formed as a convex cylindrical surface and a concave cylindrical surface corresponding to the lens shape.

Since the fθ lens 140 is long in the main scanning direction (Y-axis direction) and thin in the sub-scanning direction (direction perpendicular to the yz plane), the left and right sides are reversed. There is a risk that it will be installed. However, according to the configuration of the first embodiment, if the mounting direction is wrong, the convex portions of the lenses 141 and 142 interfere with the convex portions of the lens mounting portions 143 and 144, and the lens cannot be mounted. The left and right are not installed in reverse. Further, according to the above configuration, since the relationship between the refracting surface 140B and the refracting surface 140C is different from the relationship between the refracting surface 140D and the refracting surface 140A, the lenses 141 and 142 are interchanged in the order. Can be prevented from being attached to the lens attachment portions 143 and 144. That is, mounting of the lenses 141 and 142 in the state shown in FIG. 2 is allowed, and mounting in different states is prevented.

FIG. 3 is a top view for explaining the mounting structure of the fθ lens 240 of the second embodiment. As in the case of FIG.
The upper side in the figure is the photosensitive drum 50 side, and the lower side in the figure is the polygon mirror 30 side. Fθ lens 240 of the second embodiment
Has a first lens 241 and a second lens 242. The first lens 241 and the second lens 24
The reference numeral 2 has a structure that is fitted into a pair of lens mounting portions 243 and 244 formed in the housing 200 from above the housing (in FIG. 3, the front side of the drawing).

As shown in FIG. 3, the refracting surface of the first lens 241 and the refracting surface of the second lens 242 have the same shape as the lens 140 of the first embodiment shown in FIG. Both end portions of the lens 241 and the lens 242 and the lens mounting portions 243 and 244 have a shape inclined by a predetermined angle with respect to the optical axis in the yz section.

When the lens is attached upside down when the lens is attached,
The shapes of the end portions of the lenses 241, 242 and the lens mounting portion 24
The shape of 3, 244 does not match and the lens cannot be mounted. Therefore, according to the configuration of the second embodiment, the lens is not mounted upside down. Furthermore, the second
According to the configuration of the embodiment, as in the case of the first embodiment, the lenses 241 and 242 do not switch front and back (order in the z-axis direction) due to the shape of the refracting surface. That is, only in the state shown in FIG.
Wearing 2 is allowed.

FIG. 4 is a top view for explaining the mounting structure of the fθ lens 340 of the third embodiment. The upper side in the figure is the photosensitive drum 50 side, and the lower side in the figure is the polygon mirror 30 side. The fθ lens 340 of the third embodiment is the first lens 34.
It has a first and a second lens 342. The first lens 341 and the second lens 342 are the same as the housing 2
Pair of lens mounting portions 343, 344
Further, the structure is such that it is fitted from above the housing (in FIG. 4, the front side of the paper surface).

As shown in FIG. 4, the refracting surfaces 340A and 340B of the first lens 341 and the refracting surfaces 340C and 340D of the second lens 342 are the surfaces 340A and 340C on the photosensitive drum side on the zy plane. Are convex, and the surfaces 340B and 340D on the polygon mirror 30 side are concave. Further, the one end of each lens and the corresponding lens mounting portion have a predetermined shape that engages with each other when the lens is mounted, and is configured to prevent mistaken lens mounting.
In FIG. 4, a triangular medium protrusion 344P is formed on the inner surface of the lens mounting portion 344 on the polygon mirror side. Corresponding to this, the lens 342 on the polygon mirror side
A groove 342G that engages with the protrusion 344P is formed at the end of the. The projection 3 is formed on the scanning surface side of the end of the lens 342.
A triangular medium-shaped protrusion 342P similar to 44P is formed, and a groove 341G is formed on the surface of the end portion of the lens 341 on the polygon mirror side corresponding thereto. The surface of the lens 341 opposite to the surface on which the groove 341G is formed (the mounting portion 344).
The surface facing the inner surface of the polygon mirror side) is formed as a flat surface without protrusions, and the inner surface of the mounting portion on the polygon mirror side is also formed as a flat surface.

According to the above construction, when the lenses 341 and 342 are mounted with the vertical direction (direction perpendicular to the zy plane) reversed, the projection 342P at the end of the second lens 342 is mounted. The second lens 342 cannot be mounted because it interferes with the portion 344. Also, lens 3
If the lenses 41 and 342 are mounted out of order in the z-axis direction, even if the lens refracting surface 34
Even if the shapes of 0A and 340D do not interfere with each other, the second lens 342 cannot be attached because the protrusion 342P at the end of the second lens 342 interferes with the attachment portion 344. That is, the mounting of the lenses 341 and 342 is allowed only in the state shown in FIG.

FIG. 5 is a top view showing the mounting structure of the fθ lens 440 of the fourth embodiment. The upper part of the figure is the photosensitive drum 5.
It is the 0 side, and the lower side in the figure is the polygon mirror 30 side.
The lens 440 is composed of a first lens 441 and a second lens 442, and both ends thereof are fitted in the mounting portions 443 and 444.

As shown in FIG. 5, lenses 441 and 442 are provided.
Both ends have different shapes and thickness. That is, the end portion 441A of the first lens 441 has a shape in which the surface on the scanning surface side and the surface on the polygon mirror side are inclined by a predetermined amount with respect to the y axis on the yz plane. The other end 44
In 1B, the surface on the scanning surface side and the surface on the polygon mirror side are
Both are parallel to the y-axis on the y-z plane. On the other hand, in the end portion 442A of the second lens 442, the surface on the scanning surface side is
On the yz plane, the shape is inclined by a predetermined amount with respect to the y axis, and the surface on the polygon mirror side is parallel to the y axis.
On the other hand, in the other end 442B, the surface on the scanning surface side and the surface on the polygon mirror side are both parallel to the y axis on the yz plane. Corresponding to the shape of the lens end portion described above, the shapes of the lens mounting portions 443 and 444 are not symmetrical with respect to the optical axis, and the inner surface of the mounting portion 444, which faces the scanning surface side surface of the end portion 441A of the lens 441, is: On the yz plane, the shape is inclined by a predetermined amount with respect to the y axis.

FIG. 6 is a top view showing the mounting structure of the fθ lens 540 of the fifth embodiment. The upper part of the figure is the photosensitive drum 5.
It is the 0 side, and the lower side in the figure is the polygon mirror 30 side.
The lens 540 includes a first lens 541 and a second lens 542, and both ends thereof are fitted in the mounting portions 543 and 544.

As shown in FIG. 6, the end portion 5 of the lens 541 is
41A and the end 542A of the lens 542 are provided with protrusions 541P and 542P in the y-axis direction.
The lens mounting portion 544 has a groove portion 544A into which the protrusions 541P and 542P of the lenses 541 and 542 are fitted.
And 544B are formed. In addition, the protrusion 541
P is provided on the side surface of the end portion 541A near the polygon mirror side, and the raised portion 542P is provided on the side surface of the end portion 542A near the scanning surface side.

With the above arrangement, when the order of the lenses 541 and 542 in the front-rear direction (the order in the z-axis direction) is switched, the positional relationship between the protrusions 541P and 542P does not match the positions of the grooves 544A and 544B. Therefore, the lenses 541 and 542 cannot be mounted. Therefore, they are not mounted in a state in which the order of both is interchanged. If the lens is mounted upside down when the lens is mounted, the protrusion 54 of the mounting portion 543
Since the grooves are not formed at the positions corresponding to 1P and 542P, the lenses 541 and 542 cannot be mounted again. Therefore, even with the configuration of the fifth embodiment,
The lens is never installed upside down.

FIG. 7 shows a lens mounting structure 6 of the sixth embodiment.
FIG. 40 is a front view showing 40 in the z-axis direction. Holding portions 643 and 644 that hold both ends of the lens 640L in the longitudinal direction are formed on the housing 200. Lens 64
On the upper surface 200B of the housing on which 0L is placed, a groove portion 200G is formed at a position displaced from the center in the longitudinal direction toward the end portion side. When the lens is attached, the protrusion 640P formed on the lower surface of the lens 640L is inserted into the groove 200G. Further, a tapered portion 640T is formed on the lower surface of the lens 640L in the longitudinal direction, and the lens 640L is mounted in contact with the inclined portions 643T and 644T provided on the lens holding portion.

With the above configuration, when the lens 640L is mounted in the x-axis direction in the opposite direction, the lens 64
The end portion of 0L and the inclined portion 64 of the lens mounting portions 643 and 644
Since 3T and 644T interfere with each other, the lens 640L cannot be mounted. If the lens 640L is mounted in the y-axis direction in the opposite direction, the projection 6
Since the groove into which 40P is to be inserted is not formed on the housing upper surface 200B, the lens 640L cannot be completely mounted. Therefore, it is possible to prevent the lens 640L from being mounted in the wrong direction.

FIG. 8 shows a lens mounting structure 7 of the seventh embodiment.
FIG. 40 is a front view showing 40 in the z-axis direction. Holding portions 743 and 744 for holding both ends of the lens 740L in the longitudinal direction are formed on the housing 200. Lens 74
On the upper surface 200B of the housing on which 0L is placed, a protrusion 200P is formed at a position displaced from the center in the longitudinal direction toward the end side. When the lens is attached, the protrusion 200P is inserted into the groove 740G formed on the lower surface of the end of the lens 740L.

With the above structure, when the lens 740L is mounted in the opposite direction in the x-axis direction in the drawing, the upper surface of the lens 740L having no groove and the protrusion 200P are formed.
Therefore, the lens 740L cannot be mounted because of interference between and. Further, when the lens 740L is mounted in the opposite direction in the y-axis direction in the figure, the position of the groove into which the protrusion 200P should be inserted does not correspond, and thus the lens 740L cannot be mounted completely. Therefore, even with the configuration of the seventh example, it is possible to prevent the lens 740L from being mounted in the wrong direction.

FIG. 9 shows a lens mounting structure 84 of the eighth embodiment.
It is the side view seen from the y-axis direction which shows 0. Lens 84
Lens mounting portions 843 and 844 holding 0L at both ends are formed on the housing 200. FIG. 9 shows the mounting part 8
43 shows an xz section of 43. As shown in FIG. 9, the bottom surface 843B and one side surface 843V of the mounting portion 843 extend in the z-axis and x-axis directions, respectively. Extends to. On the other hand, the mounting portion 84
The other side surface 843T of the lens 3 and the lens 8 that abuts on this side surface
The side surface 840T of 40L is inclined at a predetermined angle with respect to the x-axis. That is, the lens 840L is the lens mounting portion 8
In the portion held by 43, the thickness in the z-axis direction is large in the upper part of the drawing, and the thickness in the z-axis direction is small in the lower part of the drawing.

With the above structure, when the lens 840L is mounted in the opposite direction in the x-axis direction, the inclined portion 84
3T and the side surface 840V of the lens interfere with each other and the lens 840
I cannot attach L correctly. In addition, when the lens 840L is mounted in the opposite direction in the z-axis direction in the figure, the inclined portion 843T and the lens side surface 840V and the inclined portion 840T and the contact surface 843V interfere with each other.
After all, the lens 840L cannot be mounted.

According to the scanning lens mounting structure of the present invention, when the long fθ lens is incorporated into the housing, mounting of the lens in a direction other than the predetermined direction is prevented, so that the lens is mounted in the wrong direction. Can be prevented. In particular, since the lens is prevented from being mounted in the opposite direction in at least two directions out of the three directions of the optical axis direction, the lengthwise direction, and the direction perpendicular to the both directions, f can be easily and accurately determined.
The θ lens can be attached to the housing.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an optical scanning device to which the present invention is applied.

FIG. 2 is a top view showing the configuration of the lens unit according to the first example.

FIG. 3 is a top view showing the configuration of a lens unit according to a second example.

FIG. 4 is a top view showing the configuration of a lens unit according to a third example.

FIG. 5 is a top view showing the configuration of a lens unit according to a fourth example.

FIG. 6 is a top view showing the configuration of a lens unit according to a fifth example.

FIG. 7 is a front view showing the configuration of a lens unit according to a sixth example.

FIG. 8 is a front view showing the configuration of a lens unit according to a seventh example.

FIG. 9 is a side view showing the configuration of a lens unit according to an eighth example.

[Explanation of symbols]

 10 Collimator Unit 20 Lens Unit 21 Cylindrical Lens 22 Slit Plate 30 Polygon Mirror 40 fθ Lens 50 Photosensitive Drum 122 Slit Plate

Claims (7)

[Claims] 1. A scanning lens mounting structure of an optical scanning device, comprising: a long-shaped scanning lens extending in the same direction as a main scanning direction in which a beam is scanned on a surface to be scanned; A mounting part to which both ends are fitted and mounted, wherein the mounting part allows the scanning lens to be fitted and mounted in a predetermined orientation, and the fitting and mounting in an orientation different from the predetermined orientation. A structure for mounting a scanning lens, characterized in that 2. Both ends of the scanning lens are asymmetrical with respect to a main scanning plane including at least all the principal rays of the scanning beam, and at least the mounting lens has at least the scanning lens with respect to the main scanning plane. The scanning lens mounting structure according to claim 1, wherein the scanning lens mounting structure has a shape that prevents the mounting lens from being fitted and mounted in the mounting portion when inserted in a direction different from the predetermined direction. . 3. The both ends of the scanning lens have an asymmetrical shape with at least a plane orthogonal to the optical axis of the scanning lens sandwiched therebetween, and in the mounting portion, at least the scanning lens has an optical axis of the scanning lens. Claim 1 or 2 is characterized in that it has a shape that prevents fitting of the mounting lens to the mounting portion when inserted in a direction different from the predetermined direction with respect to an orthogonal surface. The scanning lens mounting structure according to [1]. 4. Both ends of the scanning lens have an asymmetrical shape with a surface including at least an optical axis of the scanning lens and a surface orthogonal to a main scanning plane including all principal rays of the scanning beam interposed therebetween. And the mounting portion is different from the predetermined orientation with respect to at least the surface where the scanning lens includes the optical axis of the scanning lens and which is orthogonal to the main scanning plane including all the optical axes of the beams. The scanning lens mounting structure according to claim 1, wherein the scanning lens mounting structure has a shape that prevents the mounting lens from being fitted and mounted in the mounting portion when inserted in an orientation. 5. A direction other than a predetermined direction in at least two directions of an optical axis direction of the scanning lens, the main scanning direction, and a direction orthogonal to both the optical axis direction and the main scanning direction. The scanning lens mounting structure according to claim 1, wherein the scanning lens is prevented from being mounted. 6. A scanning lens mounting structure of an optical scanning device, comprising: a long-shaped scanning lens extending in the same direction as a main scanning direction in which a beam scans on a surface to be scanned; The scanning lens includes a plurality of lenses arranged along the optical axis, and at least one end of each of the plurality of lenses is a lens. 2. The scanning lens mounting structure, wherein the scanning lens mounting structure has different shapes, and the mounting portion corresponding to the end portion is configured so that all the lenses can be mounted only when the plurality of lenses are correctly arranged. 7. A scanning lens mounting structure of an optical scanning device, comprising: an elongated scanning lens extending in the same direction as a main scanning direction in which a beam is scanned on a surface to be scanned; The scanning lens is mounted in a predetermined direction. The scanning lens is mounted in a predetermined direction. The scanning lens is mounted in a predetermined direction. Only in this case, the scanning lens mounting structure is characterized in that both ends of the scanning lens are respectively fitted and mounted in the mounting portions.