JP2011227157A - Laser scanning optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser scanning optical device that can minimize the tilt of an image surface in the sub-scanning direction, which is caused by adjustment of scanning speed.SOLUTION: A laser scanning optical device comprises: a light source 1 which emits multiple beams; a lens 2 which shapes the beams emitted from the light source 1 into parallel light; a lens 3 which converges the beams in the sub-scanning direction; a polygon mirror 4 which deflects the beams in the main-scanning direction Y; fθ optical elements 11 and 12 which converge the beams deflected by the polygon mirror 4 onto a photoreceptor 40; and an optical element 13 for correcting plane tilt, all of which are held in a housing 20. The device also has an angle adjustment member 35 which adjusts a relative angle of the housing 20 to the photoreceptor 40 in the main-scanning direction Y, and when the relative angle of the housing 20 is adjusted by the angle adjustment member 35, the change amount of a relative angle of the optical element 13 for correcting plane tilt to the photoreceptor 40 in the main-scanning direction Y is smaller than the change amount of the relative angle of the housing 20.

Description

  The present invention relates to a laser scanning optical device, and more particularly to a laser scanning optical device mounted as an image writing unit in an image forming apparatus such as an electrophotographic copying machine or printer.

  In recent years, various types of laser scanning optical devices that simultaneously scan a photosensitive member with a plurality of beams using a multi-beam light source having a plurality of light emitting points have been developed along with high definition of image formation. It tends to increase. In this type of laser scanning optical apparatus, it is necessary to control the relative positions (the pitches between the beams) of a plurality of beams scanned simultaneously. And when adjusting optical performance other than a beam relative position, the structure which suppresses the change of a beam relative position as much as possible is needed.

  Therefore, in Patent Document 1, in order to adjust the scanning speed of the first half and the second half in the main scanning direction of the beam scanned on the photosensitive member (correction of one magnification deviation), the apparatus housing is rotated to perform main scanning on the photosensitive member. A configuration that changes the relative angle of the direction is proposed.

  However, in the configuration described in Patent Document 1, when the scanning speed is adjusted by rotating the housing, the relative angle between the surface tilt correction optical element having strong power in the sub-scanning direction and the photosensitive member in the main scanning direction changes, and the sub-scanning direction is changed. Deterioration of the beam wobble due to the tilt in the scanning direction and beam pitch deviation in the sub-scanning direction occur.

JP 2001-100136 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide a laser scanning optical apparatus that can suppress the inclination of the image plane in the sub-scanning direction, which is caused by adjusting the scanning speed, as much as possible.

A laser scanning optical device according to an aspect of the present invention is
A light source that emits a beam;
A light source optical system for shaping the beam emitted from the light source into parallel light and condensing it in the sub-scanning direction;
A deflector for deflecting the beam from the light source optical system in the main scanning direction;
A scanning optical system for condensing the beam deflected by the deflector onto the photosensitive member;
A housing for holding each member;
An angle adjusting member for adjusting a relative angle of the housing in the main scanning direction with respect to the photosensitive member;
With
The scanning optical system is composed of an fθ optical element mainly having power in the main scanning direction and a surface tilt correction optical element mainly having power in the sub-scanning direction,
When the relative angle of the housing is adjusted by the angle adjusting member, at least one of the surface tilt correction optical elements has a change amount of the relative angle in the main scanning direction with respect to the photosensitive member of the relative angle of the housing. Less than the amount of change,
It is characterized by.

  In the laser scanning optical device, the relative angle in the main scanning direction of the housing with respect to the photosensitive member is adjusted by the angle adjusting member. When the relative angle of the housing is adjusted in this way, at least one of the surface tilt correction optical elements has a smaller amount of change in the relative angle in the main scanning direction with respect to the photoreceptor than the amount of change in the relative angle of the housing. The tilt of the image plane in the sub scanning direction is suppressed as much as possible. It is preferable that the amount of change in the relative angle of the surface tilt correction optical element is zero or as close to zero as possible. As a result, the deterioration of the beam wobble due to the tilt in the sub-scanning direction and the beam pitch shift in the sub-scanning direction are reduced.

  According to the present invention, the tilt of the image plane in the sub-scanning direction, which is caused by adjusting the scanning speed, can be suppressed as much as possible. As a result, the deterioration of the beam wobble due to the tilt in the sub-scanning direction and the beam pitch shift in the sub-scanning direction are reduced.

It is a top view which shows schematic structure of the laser scanning optical apparatus which is one Example of this invention. It is a top view which shows the state after adjustment of the said laser scanning optical apparatus. It is sectional drawing which shows the adjustment mechanism (1st example) in the said laser scanning optical apparatus. It is sectional drawing which shows the 2nd example of an adjustment mechanism. It is sectional drawing which shows the 3rd example of an adjustment mechanism.

  Embodiments of a laser scanning optical apparatus according to the present invention will be described below with reference to the accompanying drawings. In each figure, common parts and portions are denoted by the same reference numerals, and redundant description is omitted.

(See one embodiment, FIGS. 1-3)
As shown in FIG. 1, a laser scanning optical apparatus according to an embodiment of the present invention is roughly composed of a light source 1, a collimator lens 2, a cylindrical lens 3, a polygon mirror 4, a scanning optical system 10, and the like. These members are mounted on the housing 20. A mirror (not shown) for bending the optical path is also appropriately arranged. The basic configuration of these optical systems for forming an image (electrostatic latent image) on the photoreceptor 40 is well known.

  The light source 1 is a multi-beam light source (laser diode array) having a plurality of light emission points, and the beam interval in the sub-scanning direction Z can be corrected by rotating the central axis of the plurality of light emission points. The beam emitted from the light source 1 is divergent light, shaped into parallel light by the collimator lens 2, condensed in the sub-scanning direction Z by the cylindrical lens 3, and enters the polygon mirror 4. The beam is deflected at a constant angular velocity in the main scanning direction Y by the polygon mirror 4, passes through the scanning optical system 10, and then scans / exposures while being imaged on the photoreceptor 40.

  The scanning optical system 10 includes fθ optical elements 11 and 12 having a power mainly in the main scanning direction Y, and a surface tilt correction optical element 13 having a power mainly in the sub-scanning direction Z.

  The laser scanning optical device includes a beam detection sensor (photoelectric conversion element) 15 for controlling the image writing position. The beam detection sensor 15 detects a beam that is transmitted through the fθ optical elements 11 and 12 and the condenser lens 16 on the start end side in the main scanning direction Y. A detection signal from the beam detection sensor 15 is input to a control circuit (not shown), and a synchronization signal (also referred to as an SOS signal) is generated.

  The surface tilt correction optical element 13 is elongated in the main scanning direction Y and is held by a holder 30. The holder 30 is held at the bottom plate portion of the housing 20 by leaf springs 31 and 32 at both end portions in the main scanning direction Y, and is supported by a support shaft 34 provided in the vicinity of one end portion of the surface tilt correction optical element 13 as a fulcrum. It is arranged so as to be rotatable on the Y plane. More details will be described below.

  A reference member 22 is disposed between one surface 41 a of the positioning member 41 that positions and holds the photoreceptor 40 and the wall portion 21 of the housing 20. An angle adjusting member 35 is screwed to the wall portion 21 of the housing 20. That is, the relative angle θ (see FIG. 2) of the housing 20 with respect to the photoreceptor 40 in the main scanning direction Y is on the XY plane by rotating the angle adjusting member 35 so that the housing 20 has the end of the reference member 22 as a fulcrum. It is adjusted by rotating at. FIG. 2 exaggerates the state in which the relative angle θ is adjusted in this way.

  As shown in FIG. 3, the angle adjusting member 35 constituting the first example of the adjusting mechanism has a male screw 36 formed on the outer periphery, and one end abuts against one surface 41 a of the positioning member 41 and the other end. Is in contact with one surface of the holder 30 that holds the surface tilt correction optical element 13. The holder 30 is elastically biased in the direction of the optical axis X by a leaf spring 32 (see FIG. 1), one end is elastically pressed against the support shaft 34, and the other end is positioned via an angle adjusting member 35. It is in pressure contact with the member 41.

  FIG. 1 shows a case where the relative angle θ is 0, which is a design value. In this state, the angle adjusting member 35 is rotated to adjust the relative angle θ in the main scanning direction Y with respect to the photoreceptor 40 of the housing 20. Thus, the scanning speeds of the first half and the second half of the plurality of beams scanned at the same time in the main scanning direction Y are adjusted (single magnification deviation correction).

  On the other hand, even when the angle adjustment member 35 rotates, the surface tilt correction optical element 13 does not change in a state where one end is restricted by the support shaft 34 and the other end is restricted by the end of the angle adjustment member 35. The relative angle in the main scanning direction Y with respect to is as close as possible to zero. Therefore, there is almost no inclination of the image plane in the sub-scanning direction Z, and deterioration of beam wobble and beam pitch deviation in the sub-scanning direction Z are suppressed.

  In this embodiment, the scanning optical system 10 may be provided with other surface tilt correction optical elements in addition to the surface tilt correction optical element 13, and at least one of the surface tilt correction optical elements adjusts the scanning speed. It is only necessary to suppress the inclination of the image plane in the sub-scanning direction Z. Further, one end of the angle adjusting member 35 may be in direct contact with the outer periphery of the end of the photoreceptor 40 instead of the positioning member 41. Furthermore, the end of the angle adjustment member 35 may be in direct contact with the surface tilt correction optical element 13 instead of the holder 30.

(Refer to the second example of the adjusting mechanism, FIG. 4)
A second example of the adjustment mechanism is shown in FIG. In this adjustment mechanism, a first male screw 36 a and a second male screw 36 b having a smaller pitch than the first male screw 36 a are formed on the outer periphery of the angle adjusting member 35. The first male screw 36 a is screwed to the wall portion 21 of the housing 20, and the second male screw 36 b is screwed to the holder 30 that holds the surface tilt correction optical element 13. The holder 30 is elastically biased toward the photoconductor 40 by the leaf spring 32 (see FIG. 1), and one end of the angle adjusting member 35 elastically contacts the one surface 41a of the positioning member 41 of the photoconductor 40. ing.

  In the adjustment mechanism configured as described above, when the angle adjustment member 35 is rotated to adjust the relative angle θ in the main scanning direction Y with respect to the photoconductor 40 of the housing 20, the second adjustment occurs as the angle adjustment member 35 rotates. The holder 30 to which the male screw 36 b is screwed also rotates around the support shaft 34 as a fulcrum in synchronization with the rotation of the housing 20. Since the pitch of the second male screw 36b is smaller than that of the first male screw 36a, the amount of change in the relative angle of the surface tilt correction optical element 13 in the main scanning direction Y with respect to the photoreceptor 40 is small. Therefore, the inclination of the image plane in the sub-scanning direction Z is small, and deterioration of beam wobble and beam pitch shift in the sub-scanning direction Z are suppressed.

(Refer to the third example of the adjusting mechanism, FIG. 5)
A third example of the adjustment mechanism is shown in FIG. This adjustment mechanism is provided with a hemispherical projection 37 eccentric from the axial center at the other end of the angle adjusting member 35, an inclined cam surface 13a is provided on the cylindrical lens 13, and the projection 37 is brought into contact with the cam surface 13a. Is.

  In the adjustment mechanism having the above-described configuration, when the angle adjustment member 35 is rotated to adjust the relative angle θ in the main scanning direction Y with respect to the photoreceptor 40 of the housing 20, the cam surface is accompanied with the rotation of the angle adjustment member 35. The surface tilt correction optical element 13 in which 13 a comes into contact with the protrusion 37 also rotates in synchronization with the rotation of the housing 20. The rotation amount (the change amount of the relative angle) of the surface tilt correction optical element 13 by the cam surface 13a and the projection 37 is smaller than the rotation amount (the change amount of the relative angle θ) of the housing 20 due to the rotation of the angle adjustment member 35. Therefore, the inclination of the image plane in the sub-scanning direction Z is small, and deterioration of beam wobble and beam pitch shift in the sub-scanning direction Z are suppressed.

  In the third example, the cam surface 13 a against which the protrusion 37 abuts may be provided on the holder 30.

(Other examples)
The laser scanning optical apparatus according to the present invention is not limited to the above-described embodiments, and can be variously modified within the scope of the gist thereof.

  In particular, the configuration and arrangement of the light source optical system and the scanning optical system are arbitrary. Also, the number of beams scanned simultaneously is arbitrary.

  As described above, the present invention is useful for laser scanning optical devices, and is particularly excellent in that the inclination of the image plane in the sub-scanning direction can be suppressed as much as possible by adjusting the scanning speed.

DESCRIPTION OF SYMBOLS 1 ... Light source 2 ... Collimator lens 3 ... Cylindrical lens 4 ... Polygon mirror 10 ... Scanning optical system 11, 12 ... f (theta) optical element 13 ... Surface tilt correction optical element 13a ... Cam surface 20 ... Housing 30 ... Holder 34 ... Spindle 35 ... Angle adjusting member 36, 36a, 36b ... male screw 37 ... projection 40 ... photoconductor 41 ... positioning member Y ... main scanning direction θ ... relative angle

Claims (5)

A light source that emits a beam;
A light source optical system for shaping the beam emitted from the light source into parallel light and condensing it in the sub-scanning direction;
A deflector for deflecting the beam from the light source optical system in the main scanning direction;
A scanning optical system for condensing the beam deflected by the deflector onto the photosensitive member;
A housing for holding each member;
An angle adjusting member for adjusting a relative angle of the housing in the main scanning direction with respect to the photosensitive member;
With
The scanning optical system is composed of an fθ optical element mainly having power in the main scanning direction and a surface tilt correction optical element mainly having power in the sub-scanning direction,
When the relative angle of the housing is adjusted by the angle adjusting member, at least one of the surface tilt correction optical elements has a change amount of the relative angle in the main scanning direction with respect to the photosensitive member of the relative angle of the housing. Less than the amount of change,
A laser scanning optical device.   2. The laser scanning optical apparatus according to claim 1, wherein the relative angle of the housing is adjusted with a support shaft provided in the vicinity of one end of the surface tilt correction optical element in the main scanning direction. The angle adjusting member has a male screw formed on the outer periphery thereof screwed to the housing,
One end of the angle adjustment unit is in contact with the photosensitive member or a positioning member of the photosensitive member, and the other end is in contact with the surface tilt correction optical element or a holder that holds the surface tilt correction optical element.
The laser scanning optical apparatus according to claim 1 or 2, wherein   4. The laser scanning optical device according to claim 3, wherein the other end of the angle adjusting member is in contact with a cam surface provided on a holder for holding the surface tilt correction optical element. The angle adjusting member has a first male screw formed on the outer periphery, and a second male screw having a smaller pitch than the first male screw,
A first male screw is screwed to the housing, and a second male screw is screwed to a holder holding the surface tilt correction optical element;
One end of the angle adjusting member is in contact with the photosensitive member or a positioning member of the photosensitive member;
The laser scanning optical apparatus according to claim 1 or 2, wherein

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