JP2749850B2 - Optical deflection device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical deflecting device used in a scanning optical device that optically scans a scanned portion, such as a laser beam printer, a laser aligner, and a bar code reader.

(Prior Art) In a scanning optical device used for a laser beam printer or the like, a rotary polygon mirror has been frequently used as an optical deflector to deflect and scan a light beam. Since the rotary polygon mirror mechanically processes the mirror surface, an error in the perpendicularity of each mirror surface with respect to a reference surface (a motor flange on which the rotary polygon mirror is mounted) (hereinafter, referred to as a surface tilt amount) becomes a problem. This is shown in FIG. 5 (A) is a view of an optical deflector having a rotary polygon mirror as an optical deflector as viewed from a direction perpendicular to the rotation axis, and FIG. 5 (B) is a view as viewed from the axial direction of the rotation axis. . In (A), 21 denotes a motor flange, 22 denotes a rotating polygon mirror which is an optical deflector,
Numeral 23 denotes a rotation axis of the motor, and a and b denote the reflecting surfaces of the rotating polygon mirror, respectively. In this case, the rotating polygon mirror has two reflecting surfaces. The surface C indicates the point where the mounting reference surface of the polygon mirror is in contact with the mounting surface of the polygon mirror of the motor flange. It is assumed that the face C is set perpendicular to the 23 rotation axes. In the polygon mirror 22, it is assumed that the surface A has a surface inclination amount of 0 and that the surface B has an angle of inclination.
The light beam entering the reflecting surface from the direction of the arrow in the figure is reflected only at the same angle in the direction of the rotation axis of the motor when the tilt amount is 0, while the tilt angle is 0. The reflected light beam is reflected in a direction shifted by two in the opposite direction. When this reflected light beam is imaged on a photosensitive member which is a scanning surface by a spherical fθ lens or the like, when the focal length of the fθ lens is f, the error of the imaging position due to surface tilt is 2f. Become. This causes variations (pitch unevenness) in the spacing between the scanning lines in the sub-scanning direction, which is the direction perpendicular to the deflection scanning direction of the light beam, in the output image, and adversely affects the output image.

The same effect is exerted even when the mounting surface of the rotary polygon mirror above the flange of the motor is inclined from the direction perpendicular to the rotation axis. An example is shown in FIG. In FIG. 6, (A) is a view as seen from the direction of the rotation axis of the motor, (B) and (C) are views as seen from the direction perpendicular to the rotation axis of the motor, and (B) is a view of the rotary polygon mirror. The light beam is reflected on the reflecting surface A, and FIG. 3C shows the state where the motor is rotated by 180 ° and reflected on the reflecting surface B. (A) As shown in the figure
Is assumed to be composed of two surfaces, and as shown in FIG. 2B, assuming that the mounting surface c of the polygonal mirror of the flange 21 is inclined only from a surface perpendicular to the motor rotation axis, as shown in FIG. Since the mounting reference surface of the polygon mirror of 22 is also inclined by the same angle as that of C, even if the amount of tilt of the polygon mirror of 22 is 0, the reflection surface A is only inclined and the reflected light beam is at an angle of -2. Is reflected. When the motor rotates 180 ° from this state, the position shown in FIG. When rotated by 180 °, the tilt of the mounting reference surface of the polygon mirror is only tilted in the opposite direction, so that the reflected light beam has an angle of +2. Therefore, if the mounting surface of the polygonal mirror of the flange is shifted only from the plane perpendicular to the motor rotation axis, the reflected light beam will shake at a width of 4 and will form an image with a spherical system fθ lens having a focal length of f. The position error occurs by 4f and adversely affects the output image due to uneven pitch.

In order to reduce such unevenness of the polygon mirror and pitch unevenness caused by the inclination of the mounting surface of the polygon mirror of the motor flange,
As disclosed in Japanese Patent Publication No. 62-36210, a scanning lens system using a toric lens or a cylindrical lens is used to make the reflecting surface of the rotating mirror and the photosensitive member conjugate with respect to the sub-scanning direction. It has been proposed to dispose a cylindrical lens near a photoconductor as disclosed.

However, in the above example, it is necessary to use a toric lens or a cylindrical lens as an imaging optical system in order to reduce the pitch unevenness of the scanning line, and there is a disadvantage that the cost is increased as compared with a rotationally symmetric spherical lens. That is, there is a disadvantage that the cost of the entire scanning optical device is increased.

(Object of the Invention) The present invention solves the above problems, and has the advantages of a rotating polygon mirror, and is not affected by the inclination of the mounting surface of the rotating polygon mirror on the flange of the motor or the tilting of the rotating polygon mirror. An object of the present invention is to provide a light deflecting device.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical deflector having an optical deflecting surface that rotates around an axis to change light, and to move the entire optical deflector in a direction other than the direction of the rotation axis of the optical deflector. This is achieved by the light deflecting device of the present invention having moving means for enabling movement.

(Embodiment) FIG. 1 shows a first embodiment of a scanning optical apparatus using the light deflecting device of the present invention. FIG. 1A is a schematic view of the optical scanning device when viewed from the axial direction of the motor of the light deflecting device, and FIG. 1B is a view as viewed from a direction perpendicular to the motor axis. In FIG. 1A, reference numeral 1 denotes a light beam emitted from a semiconductor laser 1 as a light source, which is made almost parallel by a collimator lens 2, a beam diameter of a parallel light is adjusted by a stop 3, and a light deflection 4 Incident on a rotating polygon mirror. The polygon mirror of No. 4 is mounted and fixed on a flange of a motor for rotating the polygon mirror of No. 8,
It rotates at high speed with the rotation of the flange. The light beam incident on 4 is deflected and scanned at high speed, and is incident on an fθ lens composed of 5, 6 spherical systems. The light beams that have passed through the fθ lenses 5 and 6 have their scanning linearity (fθ characteristics) corrected and undergo a convergence action to form an image on the photosensitive drum which is the scanning surface 7. The light beam on the photosensitive drum is shown in FIG.
Is scanned linearly in the direction of the arrow. In FIG. 1 (B), reference numeral 9 denotes a rotation axis of the motor. A polygon mirror composed of two reflection surfaces 4 rotates around the rotation axis. Reference numeral 10 denotes a spring for pressing the polygon mirror 4 against the mounting surface of the flange 8, and reference numeral 11 denotes an E-ring for fixing the spring 10 to the rotating shaft 9. 12 represents a screw which is a means of moving the polygon mirror,
By turning the 12 screws by turning the screws inside the polygon mirror, the entire polygon mirror is moved in a direction other than the direction of the rotation axis of the motor, and the polygon mirror and the mounting surface of the polygon polygon mirror are mounted. The angle can be adjusted. Here, even if the polygonal mirror mounting surface of the flange 8 has only the inclination of the angle with respect to the rotation axis 9, the surface in contact with the flange of the polygonal mirror 4 is rotated by rotating the screw 12. By making the mirror more floating, the mounting reference plane of the polygon mirror can be made perpendicular to the rotation axis. Therefore, the influence of the inclination of the mounting surface of the flange can be eliminated. In FIG. 1 (B), when the surface tilt of the polygon mirror is zero, the pitch unevenness is zero. In addition, even if the polygon mirror has a surface tilt amount, if the polygon mirror has a two-plane configuration as shown in FIG. By adjusting, it is possible to make the pitch unevenness of the scanning line zero. FIG. 2 (A) shows a state in which only the relative reflection surface of the two-sided mirror is tilted. , 2 faces each to the motor rotation axis / 2
, The difference in tilt between the two surfaces becomes zero, and the pitch unevenness of the scanning lines can be made zero. This is shown in FIG. 2 (B).

Here, it is the direction of movement of the polygon mirror to adjust the angle and the mounting surface of the polygon mirror and the polygon polygon mirror, but on the perpendicular bisector of the reflection surface of the polygon mirror in the plane perpendicular to the rotation axis of the motor. If there is an axis of rotation of the motor, the polygon moves along a straight line or curve that is non-parallel to the axis of rotation of the motor in a plane perpendicular to the reflective surface of the polygon.

In the above-described embodiment, a screw for adjusting the angle of the reflecting surface is provided on the polygon mirror side, but an adjusting mechanism may be provided on the flange side of the motor as shown in FIG.
In addition, as shown in FIG. 4, it is possible to receive a portion in contact with the mounting reference surface of the polygon mirror with a line or a surface.
Various adjustment mechanisms are conceivable for the polygon mirror and the flange of the motor, but it is obvious that they are within the scope of the present invention.

In the embodiment described above, a polygon mirror having a two-surface reflecting surface opposed to the rotation axis has been described as an example, but the same effect can be obtained by using an optical deflector having only one reflecting surface.

In the above-described embodiment, a rotary polygon mirror that rotates about a rotation axis has been described as an example. However, similar effects can be obtained by applying the present invention to a galvano mirror or the like that rotates around an axis and performs sine vibration. The moving direction for adjusting the galvanomirror is the same as in the case of the rotary polygon mirror described above.

(Effect of the Invention) As described above, by providing a mechanism capable of adjusting the relative angle between the rotating polygon mirror and the mounting surface of the polygon mirror of the motor flange, the beam deflection direction caused by the inclination of the reflection surface. And the amount of beam deflection in the vertical direction can be reduced to zero or reduced. In addition, if the optical deflecting device of the present invention is used for a scanning optical device, there is no need to use expensive rotationally asymmetric optical elements such as a toric lens or a cylindrical lens as a conventional pitch unevenness correction optical system. It can be composed of a system. Therefore, the cost of the entire scanning optical device can be reduced, the reliability can be improved with a simple configuration, and the size can be reduced.

[Brief description of the drawings]

1 (A) and 1 (B) show an embodiment of a scanning optical device using the optical deflecting device of the present invention, and FIGS. 2 (A), (B) to 4 show the optical deflecting device of the present invention. A diagram showing another embodiment of the device,
5 (A), (B) and FIGS. 6 (A), (B),
(C) is a diagram showing a conventional light deflecting device. 4 ... rotating polygon mirror 8 ... motor flange 9 ... motor rotating shaft 12 ... screw

Claims (2)

(57) [Claims] An optical deflector having an optical deflecting surface that deflects light by rotating about an axis, and enabling the entire optical deflector to move in a direction other than the direction of the rotation axis of the optical deflector. A light deflecting device, comprising: moving means. 2. An optical deflecting device according to claim 1, wherein said deflector has two light deflecting surfaces.