JP2001166235A - Scanning optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a scanning optical device which can correct scanning lines formed with laser light transmitted through an fθ lens having power in a subscanning direction so that they form a certain shape. SOLUTION: The scanning optical device 1 is equipped with a scanning optical system 100 which forms scanning lines on a photosensitive drum 150 through an imaging optical system 130 by deflecting the laser light emitted by a light source part 110 through a polygon mirror 120 to make a scan. A 3rd lens 133 which constitutes the fθ lens 130 is a plastic lens which has power for converging the laser light mainly in the subscanning direction and is long in a main scanning direction, fixed to a lens frame 20 by pressing both its ends against the abutting surface on the opposite side by a leaf spring 29 from one side in the subscanning direction, and held while pressed against adjusting screws 32a to 32c at opposite positions from one side in the subscanning direction by leaf springs 31a to 31c arranged at equal intervals between them. The 3rd lens is deformed by varying the heights of the adjusting screws to correct the shape of the scanning lines.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a scanning optical device that scans spot light on a photosensitive drum surface by mechanically deflecting and scanning modulated light emitted from a laser with a rotary polygon mirror.

[0002]

2. Description of the Related Art Conventionally, an image forming device for writing provided in an image forming apparatus such as a copying machine, a printer, a facsimile printer or the like converts an electric signal of image information into modulated light using a laser or an LED element. By scanning the modulated light on a photoconductor using a scanning optical system, image information is recorded. Among these, as an image forming device using a semiconductor laser, an electrophotographic image forming apparatus provided with a scanning optical system including a semiconductor laser unit, a collimator lens, a cylindrical lens, a rotary polygon mirror, and an fθ lens, and a photosensitive drum. There is.

A scanning optical system using a semiconductor laser as a light source is used in a scanning optical device for monochrome printing, or a so-called tandem system in which a plurality of the above-described scanning optical system and a photosensitive drum are provided for each color component. Or a plurality of semiconductor laser units, and a plurality of light beams emitted from these semiconductor laser units are combined into one polygon mirror (rotating polygon mirror).
Is used in a so-called multi-beam type scanning optical apparatus that simultaneously performs deflection scanning and scans on a plurality of photosensitive drums, respectively. In a tandem scanning optical device that performs color printing by forming a beam light on the photosensitive drum for each color component, the photosensitive drum for each color component scans each color in one scanning line on printing paper. By printing in an overlapping manner, a color image is formed. At this time, by making the positions of the scanning lines in the sub-scanning direction relatively constant with respect to the plurality of photosensitive drums, it is possible to obtain a printing result without color shift.

In such a scanning optical system, a divergent laser beam emitted by a semiconductor laser is converted into a parallel light beam by a collimator lens, and is once converged only in a sub-scanning direction near a reflecting surface of a polygon mirror by a cylindrical lens, and has a uniform angular velocity. Is mechanically deflected and scanned by a polygon mirror rotating at high speed. The laser beam that has been deflected and scanned is converged in the main scanning direction and the sub-scanning direction by the fθ lens, and is imaged as a spot light on the photosensitive drum.
On the surface of the photosensitive drum, a scanning line is formed by the locus of the spot light, and exposure according to image information is performed.

In the above-described scanning optical system, a part of the lens constituting the fθ lens is made of plastic due to cost and workability, and is arranged at a position away from the deflector. For this reason, there is a case where the recording medium is formed to have a toric lens surface and to be long in the main scanning direction. In this case, since the plastic lens constituting the fθ lens is long, the lens itself may be curved and distorted in the sub-scanning direction. Therefore, conventionally, in order to prevent such a distortion from occurring in the plastic lens, the plastic lens is fixed to the housing by pressing the plastic lens from one side in the sub-scanning direction onto a contact surface of the housing with a plurality of leaf springs or the like. Configuration was adopted.

[0006]

However, if the lens having the power to converge the laser beam in the sub-scanning direction among the lenses constituting the fθ lens is a plastic lens that is long in the main scanning direction, this plastic lens is When pressed against the contact surface of the housing by a plurality of leaf springs from one side in the sub-scanning direction, a slight undulation originally on the contact surface affects this long plastic lens, and this plastic lens Causes slight distortion. For this reason, the scanning line formed on the photosensitive drum by the laser beam transmitted through the plastic lens may be curved (bowed) or distorted.

Further, in an image forming apparatus for color printing which is provided with a plurality of such scanning optical devices and corresponds to each of a plurality of photosensitive drums, the above-described distortion is generated in the scanning lines, so that the photosensitive element for each color component is formed. There is a problem that the shape of each scanning line cannot be made uniform with respect to the body drum, and a color shift exceeding an allowable range (several tens of μm) occurs in a printing result.

Therefore, an object of the present invention is to solve the problem that a plastic lens having power in the sub-scanning direction and having a length in the main scanning direction among the lenses constituting the fθ lens is moved in one side in the sub-scanning direction by a plurality of leaf springs or the like. Each scan formed on the photosensitive drum for each color component by laser light transmitted through this plastic lens, while being fixed to the housing by being pressed against the contact surface on the opposite side from the side It is an object of the present invention to provide a scanning optical device capable of finely adjusting the shape of a line so as to have a relatively constant shape that does not cause color shift when multiple printing is performed on one scanning line on a printing sheet.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is directed to a main scanning device for converging a laser beam emitted from a light source and deflected and scanned by a deflector. A scanning optical device having a pair of flat edge surfaces substantially parallel to the direction and having a built-in scanning optical system including a plastic lens having a power to converge laser light in a sub-scanning direction orthogonal to the main scanning direction. In the case, a plurality of adjustment screws screwed into the housing and supporting one edge surface of the plastic lens at each end, and each of the adjustment screws sandwiching the plastic lens And a plurality of spring means for pressing the plastic lens toward each of the adjusting screws.

[0010] With this configuration, the height of the tip of the adjusting screw in the plastic lens and the vicinity of the portion sandwiched by the adjusting screw and the spring means disposed at a position facing the adjusting screw are small. By being adjusted, it is pushed or pushed back in the sub-scanning direction. Since there are the same number of adjustment screws as the number of places where the plastic lens is sandwiched between the adjustment screw and the spring means, fine-tuning the adjustment screw arbitrarily selected from the plurality of adjustment screws,
The part where the plastic lens is held by the unselected adjustment screw and spring means is not deformed, and only the part where the plastic lens is held by the selected adjustment screw and spring means and the vicinity thereof are minutely deformed in the sub-scanning direction. You.

Thus, for example, at least two scanning optical devices each having the above-described configuration are combined with each other.
When the scanning lines of each color are printed on the same line on the printing paper by the respective photosensitive drums corresponding to the color components of the colors, any one of the scanning lines is relatively the same as the remaining scanning lines. Even if slight color misregistration occurs due to the lack of the shape, the shape of the scanning line causing the color misregistration is changed by a laser beam in the sub-scanning direction in a scanning optical device that forms the scanning line. By deforming the shape of the plastic lens having the power to be converged in the sub-scanning direction, it is possible to correct the shape of the plastic lens so that it becomes the same as the shape of each of the other scanning lines.

Similarly, even when a plurality of scanning lines are formed side by side on the same photosensitive drum by a plurality of scanning optical devices having the above configuration, the shape of each scanning line can be made uniform.

In the scanning optical device according to the present invention, both ends of the plastic lens are sandwiched between the abutting surface provided in the housing and the spring means arranged at a position opposed to the abutting surface, so that the auxiliary lens is provided in the housing. Although it may be fixed in the scanning direction, when such an abutment surface is not provided, a portion sandwiched between the adjusting screw and the spring means is equally spaced between both ends of the plastic lens in the main scanning direction. It may be arranged. Further, the spring means may be a leaf spring or a coil spring.

The scanning optical device according to the present invention may be provided in each of the photosensitive drums corresponding to the four color components.
In this case, the four color components may be used for color printing as black, cyan, magenta, and yellow. Alternatively, a scanning optical device may be provided for each of the photosensitive drums corresponding to the three color components of cyan, magenta, and yellow.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a scanning optical device according to the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view of a scanning optical device 1 according to an embodiment of the present invention. FIG. 2 is a front view of the scanning optical device 1, and FIG. 3 is a longitudinal sectional view of the scanning optical device 1 taken along line AA shown in FIG.

As shown in FIG. 1, the scanning optical device 1 according to the embodiment has a scanning optical system 100 assembled in a housing including a housing 10 and a lens frame 20 held by the housing 10. ,It is configured.

The scanning optical system 100 includes a light source unit 110 that emits a parallel laser beam, a polygon mirror 120 that is a deflector that deflects the laser beam emitted by the light source unit 110 in the main scanning direction, and a polygon mirror 120. An fθ lens 130, which is an image forming optical system that forms a scanning line by forming an image of the deflected laser beam on the photosensitive drum 150.

The light source section 110 includes a semiconductor laser and a collimating lens for converting divergent light emitted from the semiconductor laser into parallel light. Light source unit 110 and polygon mirror 1
A cylindrical lens 115 having a power for converging the laser light only in the sub-scanning direction is provided between the cylindrical lens 115 and the lens 20.

The fθ lens 130 includes a first lens 131 and a second lens 132 fixed in the housing 10 and a third lens 133 fixed in the lens frame 20. The first lens 131 is a plastic lens that bears a function of correcting aberrations (for example, curvature of field in the main scanning direction, fθ characteristic error, and the like), and the second lens 132
Is a glass lens having a power to converge laser light mainly in the main scanning direction, and the third lens 133 is an anamorphic plastic lens having a power to converge laser light mainly in the sub-scanning direction.

The laser light emitted from the light source unit 110 as parallel light is reflected by the polygon mirror 120 as parallel light in the main scanning direction, and forms an image on the photosensitive drum 150 by the power of the fθ lens 130. Further, in the sub-scanning direction, an image is formed once in the vicinity of the polygon mirror 120 by the cylindrical lens 115, and is incident on the fθ lens 130 as diffused light, as shown in FIG.
An image is formed on the photosensitive drum 150 by the power of the fθ lens 130. In this way, the laser light is applied to the polygon mirror 1
By forming an image once in the vicinity of 20, it is possible to prevent the scanning position from shifting in the sub-scanning direction due to the inclination (surface tilt) of the reflection surface of the polygon mirror 120. The laser beam deflected at a constant angular speed with the rotation of the polygon mirror 120 is scanned at a constant speed on the photosensitive drum 150 by passing through the fθ lens 130.

Between the second lens 132 and the third lens 133 of the fθ lens 130, a light beam outside the effective scanning range on the photosensitive drum 150 is used as monitor light and the light receiving sensor 1
A folding mirror 140 that is turned toward 42 is arranged, and the monitor light reflected by the folding mirror 140 is condensed on the light receiving sensor 142 via the condensing lens 141 for monitor light. Condenser lens for monitor light 1
Reference numeral 41 denotes a cylindrical lens having a converging power in the sub-scanning direction in order to collect the monitor light separated without passing through the third lens 133 having a main converging power in the sub-scanning direction in the fθ lens 130 on the light receiving sensor 142. It is configured as a lens. From the light receiving sensor 142,
Each time the reflection surface of the polygon mirror 120 on which the laser light from the light source unit 110 is switched, a synchronization signal that determines the timing of the writing start position in the main scanning direction is output.

Next, the fθ lens 13 by the lens frame 20
0 holding structure of the third lens 133 and the third lens 1
33 will be described.

FIG. 4 is a perspective view of the front of the housing 10 and the lens frame 20 as viewed obliquely from above. FIG. 5 shows the lens frame 2
0 is an enlarged side view, and FIG. 6 is a cross-sectional perspective view of the back surface of the lens frame 20 viewed obliquely from above along the line AA shown in FIG.
FIG. 7 is an enlarged longitudinal sectional view of the lens frame 20 along the line AA. 8 is a sectional view of the lens frame 20 taken along the line BB shown in FIG. 7, and FIGS. 9 and 10 are sectional views of the lens frame 20 taken along the line BB shown in FIG. It is a partially enlarged view.

The casing 10 has an overall shape obtained by cutting off one of the side walls surrounding four sides of a thin box-shaped roughly formed bottom plate 15 with respect to a flat bottom plate 15 and forming an end surface thereof in a U-shape. Have. Hereinafter, this end face is referred to as the joining surface
Called. The direction perpendicular to the bottom plate 15 is referred to as “up and down direction”, and the side of the bottom plate 15 on which the side wall is formed is referred to as “up”. Further, a direction perpendicular to the up-down direction in the joining surface 10a is referred to as a “left-right direction”, and
The direction orthogonal to 0a is defined as the “optical axis direction”, and the bonding surface 10a
Is referred to as “rear”.

In the vicinity of the center of the front side wall of the casing 10 on the upper surface of the bottom plate 15, the polygon mirror 120 of the above-described scanning optical system 100 is disposed with its rotation axis directed perpendicular to the bottom plate 15. I have. This polygon mirror 1
The plane traversed by the laser light deflected by 20 is substantially parallel to the bottom plate 15. On the upper surface of the bottom plate 15, a first lens 131 and a second lens 132 of the fθ lens 130 are provided near the polygon mirror 120 between the polygon mirror 120 and the joint surface 10a. The first and second lenses 131 and 132 have their optical axes oriented along the bottom plate 15 to connect the rotation axis of the polygon mirror 120 and the center in the left-right direction of the joint surface 10a and to be orthogonal to the joint surface 10a. , Is located.
Therefore, the horizontal direction in the housing 10 corresponds to the main scanning direction in laser scanning, and the vertical direction generally corresponds to the sub-scanning direction.

As shown in FIGS. 2 and 4, rectangular parallelepiped protrusions 11b and 12b are formed at the lower left and right ends of the joint surface 10a so as to project perpendicularly from the joint surface 10a, respectively. Have been. These protrusions 11b,
The length of 12b in the up-down direction is formed smaller than the thickness of the bottom plate 15. In the joint surface 10a, screw holes 11a, 12a parallel to the optical axis direction are provided directly above the centers of the respective protruding portions 11b, 12b (at positions approximately one-fourth the height from the lower end of the joint surface 10a). Are formed respectively. The diameters of the heads of the screws 51 and 52 screwed into the screw holes 11a and 12a are the same as those of the above-described protrusions 11b and 1.
2b is slightly smaller than the length in the left-right direction.

The lens frame 20 for fixing the third lens 133 of the fθ lens 130 is joined to the joining surface 10a of the housing 10.

The lens frame 20 is formed in a substantially quadrangular prism shape elongated in the left-right direction.
A concave portion 25 for accommodating the third lens 133,
It is formed in a box shape as a whole. The opening edge of the concave portion 25 is formed on the front surface (the surface on the side of the joint surface 10a) of the lens frame 20, and the front surface is formed in a rectangular flat plane by the concave portion 25.
Is formed in a shape provided with a rectangular opening.

The concave portion 2 on the front surface of the lens frame 20
The opening end of 5 is formed in a stepped shape with its peripheral edge cut slightly along the optical axis direction. Hereinafter, the front surface of the lens frame 20 is referred to as a joint surface 20a, and a surface facing the front at the periphery of the opening end of the concave portion 25 with a step difference from the joint surface 20a is
The leaf spring mounting surface 25a is used. And, this joining surface 20a
The lens frame 20 is joined to the casing 10 by bringing the joining surface 10a of the casing 10 into close contact with the casing 10.

The vertical length of the lens frame 20 is slightly shorter than the vertical length of the joint surface 10a.
To the same length as the length of the joining surface 10a in the left-right direction,
Is formed.

As shown in FIGS. 4 and 5, the lens frame 20 formed in a substantially quadrangular prism shape has an inverted convex shape when viewed from the rear as shown in FIGS. The grooves 21a and 22a having an inverted L-shaped cross section are formed. These grooves 21a and 22a are formed in a shape in which a portion from the lower end of each of the left and right side surfaces to a height of about ／ is cut off vertically from each of the left and right side surfaces to each of the right and left side surfaces. The depth of the cut is equal to the length of the protrusions 11b and 12b of the housing 10 in the left-right direction.

However, as shown in FIGS. 4 and 5, these grooves 21a and 22a are not formed over the entire area in the optical axis direction, and the protrusions 11b and 1b of the casing 10 extend from the joint surface 20a.
It is formed only at the rear, leaving only the same length as the protrusion amount of 2b. The portions where the grooves 21a and 22a are not formed (hereinafter, referred to as “projections 21c and 22c”) are formed in such a shape that the lower portions thereof are cut off by the vertical width of the protruding portions 11b and 12b of the housing 10. Have been. The length in the left-right direction of the lower end surfaces of these convex portions 21c, 22c is the same as the width in the left-right direction of the protruding portions 11b, 12b of the housing 10. Therefore, the lens frame 20 can be joined to the housing 10 in a state where the left and right side surfaces of the lens frame 20 and the housing 10 are flush with each other and the two joining surfaces 10a, 20a are joined. . At this time, the protruding portions 11b of the housing 10 are provided on the lower end surfaces of the convex portions 21c and 22c of the lens frame 20.
12b so that the upper end surfaces thereof are substantially in contact with each other.
By sandwiching the lower end of the lens frame 20 between b and 12b, the lens frame 20 can be easily positioned with respect to the housing 10 without any significant displacement in any of the left, right, up and down directions.

Each of the protrusions 21c and 22c has through holes 21d and 22d formed in parallel with the optical axis direction.
The through holes 21d and 22d are formed at positions that are coaxial with the screw holes 11a and 12a when the lens frame 20 is fitted into the housing 10. And each through hole 21
Screws 51 and 52 for fixing the lens frame 20 to the housing 10 are inserted through d and 22d, respectively.

As described above, the groove 2 is provided in the lens frame 20.
1a, 22a and the projections 21c, 22c are formed, so that the operator guides the tip of a driver or the like along the space formed by the grooves 21a, 22a so that the vicinity of the tip is close to the lens frame 20. Without interfering with any of them, the through holes 21d, 21d,
Screws 51 and 52 inserted into 22d can be turned.

Then, the screw holes 11a, 12a of the housing 10 are formed.
And the through holes 21d and 22d of the lens frame 20 are formed coaxially, so that the screws 51 and 52 are screwed into the respective through holes 21d and 2d.
By inserting the lens frame 20 into the screw holes 11a and 12a and screwing it into the screw holes 11a and 12a, the lens frame 20 is firmly fixed to the housing 10 without any positional displacement. Also, screw 5
By removing the lenses 1 and 52, the lens frame 20 can be easily removed from the housing 10.

The lens frame 20 that can be attached to and detached from the housing 10 has a holding mechanism for holding the third lens 133 of the fθ lens 130 in the recess 25 thereof.
The third lens 133 has a substantially rectangular parallelepiped shape that is long in the left-right direction as shown in a plan view by a two-dot chain line in FIG. 1 and a cross-sectional shape in FIG. It is formed as a simple edge surface. Also,
The inside of the third lens 133 is formed as a toric lens surface 133a by depressing the front surface and the rear surface in the shape of the lens surface. The concave portion 25 of the lens frame 20 is connected to the third lens 133 of the fθ lens 130.
Is formed to be slightly larger than the third lens 133 of the fθ lens 130 in order to house the inside.

The inner surface of the concave portion 25 facing forward is formed perpendicular to the optical axis direction.
A slit 80 parallel to the optical axis direction is formed to penetrate to the back of the lens frame 20. The slit 80 is formed to be long in the left-right direction, and allows a laser beam deflected and scanned in the left-right direction by the polygon mirror 120 to pass therethrough. Further, behind the slit 80, a window 90 made of a sheet glass which is long in the left-right direction is fixed to the lens frame 20 by a plate spring, and laser light passing through the slit 80 passes through the window 90. . The window 90 is arranged slightly inclined from a position perpendicular to the optical axis direction.

At the four corners of the inner surface where the slits 80 are formed in the concave portion 25, as shown in FIGS. 6 and 7, the lens receiving seats 26 formed in a flat plate shape are provided, respectively. A lens seat 26 'having the same shape is provided at the upper and lower ends of the center in the left-right direction. These six lens receivers 26, 26 'have their front surfaces (hereinafter, the respective front surfaces of the lens receivers 26, 26' are referred to as "applying surfaces 26a") on the same plane perpendicular to the optical axis direction. The four corners of the rear surface of the third lens 133 and the upper and lower surfaces of the center of the rear surface in the left-right direction are respectively applied to the abutting surfaces 26a.

The leaf springs 27a to 27c for pressing the upper and lower edges of the front surface of the third lens 133 are located above and below the leaf spring mounting surface 25a formed on the periphery of the opening end of the recess 25. 27e and leaf springs 27f to 27
j is attached. These leaf springs 27a to 27
j has an overall shape formed by joining one side of a rectangular flat plate to the long side of a strip-shaped flat plate whose longer side is longer than the one side to form a substantially L-shaped flat plate, and the center of the rectangular flat plate A pad for preventing the third lens 133 from being damaged is provided on a surface of the strip-shaped flat plate where the through hole is formed and which comes into contact with the third lens 133. These leaf springs 27a to 27j
Is fixed on the leaf spring mounting surface 25a by a set screw. Therefore, the amount of the step between the joining surface 20a and the leaf spring mounting surface 25a is determined by the fact that when the leaf springs 27a to 27j are screwed to the leaf spring mounting surface 25a with set screws, these leaf springs 27a to 27j and the set screw Are not protruded forward from the joint surface 20a.

The leaf springs 27a to 27e for pressing the upper edge of the third lens 133 and the leaf spring 27f for pressing the lower edge are provided.
27j are arranged such that the portions provided with the pads are equally spaced between the left and right ends of the front surface of the third lens 133. Also, leaf springs (27a, 27
f) (27b, 27g) (27c, 27h) (27d,
27i) (27e, 27j) are formed so as to be vertically symmetrical with respect to a plane that bisects the recess 25 in the vertical direction. The upper and lower symmetrical leaf springs 27a to 27j form a pair, and press the third lens 133 from the front surface thereof toward the contact surface 26a of the lens receiving seats 26 and 26 '. It is fixed in the optical axis direction in the concave portion 25 of 20.

The inner surface of the concave portion 25 facing upward (hereinafter referred to as the floor surface) is formed perpendicular to the vertical direction, and is formed into a strip-shaped plate on both left and right ends of the floor surface. Lens seats 28, 28 are provided. The lens receivers 28 are arranged such that their upper surfaces are included in the same plane perpendicular to the vertical direction (hereinafter, referred to as “horizontal plane”). The left and right ends of the lower edge are attached respectively. Hereinafter, the upper surfaces of the lens seats 28 will be referred to as contact surfaces 28a.

Further, the upper surface of the third lens 133 is pressed toward the lens seats 28 near the left and right ends above the leaf spring mounting surface 25a formed on the periphery of the opening end of the concave portion 25. Are attached. Each of the leaf springs 29, 29 is formed in a shape obtained by bending a strip-shaped flat plate at a substantially right angle along the short side direction. Each of the leaf springs 29, 29 is formed such that the length from the fold line to the tip of one of the two end pieces that are substantially perpendicular to each other is longer than that of the other end piece.
A through hole for inserting a set screw is formed in an end piece having a shorter length from the fold line to the tip. Hereinafter, the end piece whose length from the fold line to the tip is long is referred to as a pressing side piece.

As shown in FIG. 7, these leaf springs 29, 29 are fixed on the leaf spring mounting surface 25a by set screws, and their pressing side pieces are formed on the upper surface of the recess 25 (the lower part of the inner surface). (Inner surface facing toward the rear) in the optical axis direction. The leaf springs 29 press the left and right ends of the upper edge surface of the third lens 133 toward the contact surfaces 28a from above, so that the third lens 133 is It is fixed in the vertical direction in the recess 25.

Incidentally, reference numeral 133c in FIG.
This shows so-called burrs that are solidified at an injection port (lens gate) when a plastic material is injected into a mold for manufacturing the third lens 133 of the lens 130 and solidified. Reference numeral 133b denotes a handle 133b protruding downward from the center of the lower edge surface of the third lens 133,
The handle 133b is formed integrally with the third lens 133. The handle 133b is formed in a rectangular parallelepiped shape, and is provided on the lens seat 2 on the floor surface of the concave portion 25 of the lens frame 20.
It is inserted into a through hole 23 formed perpendicularly to the floor surface at the middle between 8, 28. The through-hole 23 penetrates from the floor surface to the lower surface of the lens frame 20 and has a rectangular cross-sectional shape.
The width of the handle 133b of the third lens 133 in the left-right direction is formed. As described above, since the left-right width of the through hole 23 and the left-right width of the handle 133b are equal, the center of the third lens 133 in the left-right direction is the lens frame 2.
0 can be easily adjusted to the center in the left-right direction. Then, when the third lens 133 is placed on the contact surface 28a of the lens receiving seat 28, 28, a flathead screwdriver or the like is inserted into the through hole 23 from the lower surface of the lens frame 20, and the handle 133b of the third lens 133 is inserted. Of the third lens 133 to the lens seats 26 and 26 '.
Can be applied to the contact surface 26a.

Further, since the upper and lower edge surfaces of the third lens 133 are formed with draft angles for extracting the third lens 133 from the mold for molding, the upper and lower edge surfaces are aligned with the optical axis. It is not formed to be a plane parallel to the direction. For this reason, the left and right ends of the lower surface of the third lens 133 are, as shown in FIGS.
The third lens 1 is provided on contact surfaces 28a, 28a on the upper surfaces of the lenses 8, 28.
When the lower edge surface of the third lens 133 is applied to the third lens 133,
Wedge-shaped projection 1 so that the optical axis is parallel to the optical axis direction.
33d and 133d are formed. This protrusion 13
3d and 133d are provided only on the left and right ends of the lower surface of the third lens 133, have the same left and right widths as the contact surface 28a, respectively, and are integrally formed with the third lens 133.

As described above, the third of the fθ lens 130
The concave portion 25 having a mechanism for fixing the lens 133
Has adjustment screws 32a to 32c on the floor and leaf springs 31a to 31c near the upper surface.

Each of the adjusting screws 32a to 32c has a flat upper end and a cross-shaped hole (+) or a slot (-) (not shown) formed at the lower end, and can be twisted by a driver or the like. It is formed as follows. Recess 25
Three screw holes 20 b, 20 b, 20 b which are vertically parallel from the floor surface to the lower surface of the lens frame 20 penetrate between the lens seats 28, 28 on the floor surface. The holes 20b, 20b, 20b are arranged in a line in the left-right direction at substantially equal intervals in the vicinity of the inner surface of the recess 25 in which the slit 80 is formed. However, recess 25
Because the through hole 23 is arranged at the center of the floor surface of
The screw hole 20b arranged at the center is arranged offset to the left so as not to interfere with the through hole 23. Each of the adjusting screws 32a to 32c is screwed into each of the screw holes 20b, 20b, and 20b from the lower surface of the lens frame 20 and assembled. The upper end surfaces of the adjusting screws 32a to 32c protrude from the floor surface. They are arranged at approximately the same height as the contact surfaces 28a, 28a.

The adjustment screws 32a to 32c provided on the lens frame 20 can finely adjust the height of the upper end surfaces of the adjustment screws 32a to 32c from outside the lens frame 20. The upper ends of the adjusting screws 32a to 32c are arranged such that the third lens 133 has the left and right ends at the abutment surfaces 28a,
When it is fixed in the concave portion 25 by being sandwiched between 28a and the leaf springs 29, 29, it comes into contact with the lower edge surface of the third lens 133.

Further, between the leaf springs 29, 29, leaf springs 31a to 31c are arranged at substantially equal intervals. Like the leaf spring 29, the leaf springs 31a to 31c are formed by bending a strip-shaped flat plate at a substantially right angle along the short side direction.
And is fixed on the leaf spring mounting surface 25a by a set screw, and their pressing side pieces are
5 is directed rearward in the optical axis direction substantially along the upper surface (the inner surface facing downward among the inner surfaces).

The vicinity of the tip of the pressing side piece of each of the leaf springs 31a to 31c bent in the optical axis direction is located at a position vertically opposed to the adjusting screws 32a to 32c provided on the floor surface of the recess 25. , Is located. Accordingly, since the adjusting screw 32b is offset to the left due to the through hole 23, the leaf spring 31b is also adjusted to the adjusting screw 3b.
2b, it is arranged to be offset from the center to the left.

The third lens 1 of the fθ lens 130
The left and right ends of 33 are leaf springs 29, 29 and abutment surface 28.
a and 28a, the third
The left and right ends of the lens 133 are held by being sandwiched from above and below by the leaf spring 31a and the adjusting screw 32a, the leaf spring 31b and the adjusting screw 32b, and the leaf spring 31c and the adjusting screw 32c.

As described above, the optical axis of the third lens 133 of the fθ lens 130 fixed in the lens frame 20 is adjusted when the lens frame 20 is fixed to the housing 10.
1 and 2 of the fθ lens 130 fixed to the upper surface of
They are arranged coaxially with the optical axes of the lenses 131 and 132. The laser light deflected in the left-right direction by the rotation of the polygon mirror 120 provided in the housing 10 is f
After sequentially transmitting through the first to third lenses 131 to 133 of the θ lens 130, a scanning line is formed on the surface of the photosensitive drum 150.

As described above, the third of the fθ lens 130
Since the lens 133 is made of plastic, it has a property of having a large coefficient of thermal expansion and being easily curved as compared with a glass lens.
Therefore, since the third lens 133 is not bent, the adjusting screw 32a is provided in addition to the both ends of the third lens 133.
-32c and the leaf springs 31a-31c hold the middle between the three points, whereby the third lens 133 can be prevented from bending.

Further, since the upper ends of the adjusting screws 32a to 32c are not slightly aligned, the third lens 1
33, and the third lens 133
Because of the slight curvature and minute distortion inherent to the whole, or the slight deviation of the refractive index of the third lens 133,
The scanning line formed on the photoconductor drum 150 by the laser beam transmitted through the third lens 133 is necessarily bent (bowed) or distorted.

The curving or distortion generated in the scanning line due to the curving or distortion of the third lens 133 is caused by adjusting the adjusting screws 32a to 32c in the lens frame 20 having the structure for holding the third lens 133. It can be removed by adjusting.

For example, in one scanning line, 1
In the case where the area around / 4 is curved downward, the adjustment screw 32a, which is disposed in the third lens 133 and located in the vicinity of about 1/4 from the left side, is pushed upward by an appropriate amount, so that the downwardly convex curved projection is formed. The horizontal direction and the vertical direction of the third lens 133 correspond to the main scanning direction and the sub-scanning direction on the surface of the photosensitive drum 150.

In one scanning line, 1 /
In the case where the area around 4 is curvedly projected upward, the third lens 1
At 33, the adjusting screw 32c, which is disposed in the vicinity of about 1/4 from the right side, is pulled back by an appropriate amount, and the upward pressure of the leaf spring 31c presses the third lens 133 to reduce the upwardly convex curved deformation to reduce its curved protrusion. Can be modified.

As described above, by finely adjusting each of the adjusting screws 32a to 32c, the scanning line formed on the photosensitive drum 150 by the laser beam transmitted through the third lens 133 causes the curved line of the third lens 133, The curvature protrusion and distortion in the sub-scanning direction caused by the distortion can be corrected, and the shape can be adjusted.

The scanning optical apparatus 1 of the present embodiment described above is manufactured as one optical unit having a set of scanning optical systems 100, and is incorporated in a plurality of image forming apparatuses such as a copying machine and a color printer. Used. Hereinafter, an example of an image forming apparatus in which the scanning optical device of the present embodiment is combined with each of a plurality of photosensitive drums will be described.

FIG. 11 is a schematic configuration diagram of an image forming apparatus 200 incorporating the scanning optical devices 1a to 1d according to the embodiment of the present invention. The image forming apparatus 200 shown in FIG.
Scanning optical devices 1a to 1d are provided for the photoconductor drums 150a to 150d corresponding to the respective color components of black, cyan, magenta, and yellow, and are used to form a color image by performing multiplex printing on one print sheet 300. is there.

Each of the scanning optical devices 1a to 1d has the same configuration as the scanning optical device 1 shown in FIG. 1, and includes a scanning optical system including a light source unit, a polygon mirror, and an fθ lens each including a housing and a lens frame. Provided in the housing. From the light source units provided in these scanning optical devices 1a to 1d, laser beams corresponding to the color components of the respective photosensitive drums 150a to 150d are respectively emitted, and the respective laser beams are deflected by respective polygon mirrors. Fθ lens.

The method of providing a plurality of combinations of the scanning optical system and the photosensitive drums 150a to 150d for each color component as in this embodiment is called a tandem system, and the scanning optical system for each color component is independent. The scanning line of each color component is formed on each of the photosensitive drums 150a to 150d by deflecting and scanning the laser beam.

The scanning optical devices 1a to 1d of the present embodiment are similar to those shown in FIG.
As shown in the figure, four of the four are arranged in parallel inside the image forming apparatus 200. Laser light emitted from each of the scanning optical devices 1a to 1d to the right in FIG. 11 is directed downward at substantially right angles by mirrors 160a to 160d, respectively, and the photosensitive members of the respective color components arranged in parallel in the sheet supply / discharge direction. The light enters the body drums 150a to 150d, respectively. Thereby, each of the photosensitive drums 150a to 150d
, A scanning line is formed by each laser beam, and image information for each color component is exposed.

The printing paper 300 fed by the feeding roller 180 is sequentially transferred to each of the photosensitive drums 150a to 150a.
Passes through each lower end of 50d. Each photoconductor drum 150
a to 150d, the toner of each color adhered (developed) according to the pixel information (electrostatic latent image) on the surface,
transfer charger 1 disposed opposite to the lower surface of each of a to 150d
70a-170d charge wires 175a-175d
Is transferred onto the printing paper 300 one after another by the corona discharge. The printing paper 300 to which the respective color toners have been transferred is sent to the fixing device 190. The fixing device 190 includes a heat roller 191 containing a halogen lamp 192 and a press roller 1.
93, the printing paper 300 is heated and pressed against, so that the unfixed toner of each color is fixed on the printing paper 300. At the same time, the printing paper 300 on which the toner of each color is fixed
Is discharged out of the image forming apparatus 200 by the rotation of the rollers 191 and 193 of the fixing device 190.

At this time, since the scanning lines of each color component to be multiplexed on one scanning line on the printing paper 300 are drawn at the adjusted positions on the respective photosensitive drums 150a to 150d, each scanning line is drawn. The scanning line is the printing paper 300
Are printed without any color shift on the same scanning line. These photosensitive drums 150a to 150d
In addition to the exposure process units formed by the scanning optical devices 1a to 1d, device units such as a main charger, a developing device, a cleaning device, and a static eliminator for executing each process of charging, developing, cleaning, and static elimination are provided around the device. Is placed,
Here, illustration is omitted.

In such an image forming apparatus 200,
If the scanning lines of each color component to be multiplexed to be printed on one scanning line are slightly irregularly printed due to curving or distortion, the image formed on the printing paper may have uneven color, and the image may be uniform. Color images cannot be obtained.

However, since the scanning optical device 1 shown in FIG. 1 is incorporated in the image forming apparatus 200,
The shape of each scanning line can be made relatively uniform with respect to the plurality of photosensitive drums 150a to 150d, and a printing result without color shift can be obtained.

In addition, even if the scanning lines themselves are slightly curved or distorted to the extent that they are inconspicuous, no color shift occurs if the scanning lines of the respective color components are relatively uniform in shape. Therefore, even if all the scanning lines cannot be aligned in a straight line shape, and even if one of the scanning lines is extremely slightly curved, the shape of the other scanning lines is adjusted according to the shape of the scanning line. By aligning them, it is possible to obtain a print result free from color misregistration.

<Operation of the Embodiment> As described above, the scanning optical device 1 according to the embodiment of the present invention has the third lens 133 whose left and right ends are fixed by the leaf springs 29, 29 and the contact surfaces 28a, 28a. , The middle of the left and right ends of the third lens 133 is sandwiched and held from above and below by the leaf spring 31a and the adjusting screw 32a, the leaf spring 31b and the adjusting screw 32b, the leaf spring 31c and the adjusting screw 32c,
By slightly changing the adjusting screws 32a to 32c, a part of the third lens 133 can be slightly deformed in the sub-scanning direction.

Therefore, the scanning optical device 1 can finely adjust the main body of the third lens 133 to change the shape of the scanning line formed by the laser beam transmitted through the third lens 133.
It can be finely modified to any shape.

[0072]

As described above, according to the scanning optical apparatus of the present invention, among the lenses constituting the fθ lens, a plurality of plastic lenses having power in the sub scanning direction and elongated in the main scanning direction are provided. While being fixed to the housing by being pressed against the abutting surface on the opposite side from the one side in the sub-scanning direction by a leaf spring or the like, the light of each color component is exposed by the laser light transmitted through this plastic lens. Fine adjustment can be made so that each scanning line formed on the body drum has a relatively constant shape without causing color shift when multiple printing is performed on one scanning line on printing paper.

[Brief description of the drawings]

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

FIG. 2 is a front view of the scanning optical device according to the embodiment of the present invention.

FIG. 3 is a longitudinal sectional view of the scanning optical device taken along line AA shown in FIG.

FIG. 4 is a perspective view of the front of the housing and the lens frame according to the embodiment of the present invention as viewed obliquely from above.

FIG. 5 is an enlarged side view of a lens frame according to the embodiment of the present example.

FIG. 6 is a cross-sectional perspective view of the rear surface of the lens frame taken along line AA shown in FIG. 1 as viewed obliquely from above.

FIG. 7 is an enlarged vertical sectional view of the lens frame taken along line AA shown in FIG. 1;

8 is a sectional view of the lens frame taken along line BB shown in FIG. 7;

9 is a partially enlarged view of a cross section of the lens frame taken along line BB shown in FIG.

FIG. 10 is a partially enlarged view of a cross section of the lens frame taken along line BB shown in FIG. 7;

FIG. 11 is a schematic configuration diagram of an image forming apparatus incorporating a scanning optical device according to an embodiment of the present invention.

[Explanation of symbols]

 1 to 1d scanning optical device 10 housing 10a joining surface 20 lens frame 20a joining surface 25 concave portion 28 lens seat 28a contact surface 29 leaf spring 31a to 31c leaf spring 32a to 32c adjusting screw 100 scanning optical system 110 light source section 120 polygon Mirror 130 fθ lens 131 first lens 132 second lens 133 third lens 140 folding mirror 150 to 150d photoconductor drum

[Procedure amendment]

[Submission Date] October 25, 2000 (2000.10.
25)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction contents]

Thus, for example, at least two scanning optical devices each having the above-described configuration are combined with each other.
When scanning lines of each color are printed on the same line of the printing paper by each photosensitive drum corresponding to the color component of more than one color, any one of the scanning lines is relative to the remaining scanning lines. Even if a slight color shift occurs due to not having the same shape, the shape of the scanning line causing the color shift is changed by the laser light in the sub-scanning direction in the scanning optical device that forms the scanning line. By deforming the shape in the sub-scanning direction of the plastic lens having the power to converge, the shape can be corrected so as to be the same as the shape of each of the other scanning lines.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction contents]

The laser light emitted from the light source unit 110 as parallel light is reflected by the polygon mirror 120 as parallel light in the main scanning direction, and is converged on the photosensitive drum 150 by the converging power of the fθ lens 130. Image. Also,
In the sub-scanning direction, by the cylindrical lens 115 is once converged in the vicinity of the polygon mirror 120, is incident on the fθ lens 130 as diffused light, as shown in FIG. 3, thus photosensitive drum 150 to the converging power of the fθ lens 130 Image on top. As described above, the laser light is once focused near the polygon mirror 120 and the fθ
Due to the conjugate effect of the lens, it is possible to prevent the scanning position from shifting in the sub-scanning direction due to the inclination (surface tilt) of the reflection surface of the polygon mirror 120. Conformal angle of this polygon mirror 120
The laser beam, which is deflected and scanned with the rotation at the speed, passes through the fθ lens 130 and is scanned on the photosensitive drum 150 at a constant speed.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0024

[Correction method] Change

[Correction contents]

FIG. 4 is a perspective view of the upper surfaces of the housing 10 and the lens frame 20 as viewed obliquely from the front . FIG. 5 shows the lens frame 2
0 is an enlarged side view, and FIG. 6 is a cross-sectional perspective view of the back surface of the lens frame 20 viewed obliquely from above along the line AA shown in FIG.
FIG. 7 is an enlarged longitudinal sectional view of the lens frame 20 along the line AA. 8 is a sectional view of the lens frame 20 taken along the line BB shown in FIG. 7, and FIGS. 9 and 10 are sectional views of the lens frame 20 taken along the line BB shown in FIG. It is a partially enlarged view.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] Fig. 4

[Correction method] Change

[Correction contents]

[4] on the housing and the lens frame in accordance with an embodiment of the present embodiment
Perspective view of the surface viewed diagonally from the front

Claims (4)

[Claims] A converging laser beam emitted from a light source and deflected and scanned by a deflector has a pair of flat edges substantially parallel to a main scanning direction of the deflector. In a scanning optical device incorporating a scanning optical system including a plastic lens having a power for converging a laser beam in a sub-scanning direction orthogonal to a scanning direction, a housing and a housing are screwed into the housing. A plurality of adjustment screws supporting one edge surface of the plastic lens at the tip, and each of the adjustment lenses is disposed at a position facing each of the adjustment screws with the plastic lens interposed therebetween, and the plastic lens is directed toward each of the adjustment screws. A scanning optical device comprising: a plurality of spring means for pressing. 2. A housing according to claim 1, wherein said housing has an abutting surface on which one edge of said plastic lens in the main scanning direction is abutted, and a position facing said abutting surface across said plastic lens. 2. The scanning optical device according to claim 1, further comprising: a spring means for pressing down the plastic lens from one side in the sub-scanning direction toward the contact surface and fixing the plastic lens in the housing. 3. The plastic lens according to claim 1, wherein the plurality of adjusting screws are disposed in the housing so as to support one edge of the edge of the plastic lens in the main scanning direction at equal intervals. Or the scanning optical device according to 2. 4. The apparatus according to claim 1, wherein said spring means is a leaf spring, and a pressing surface of said leaf spring presses said plastic lens from a side facing said adjusting screw in a sub-scanning direction. The scanning optical device according to any one of the above.