JPS6195314A - Optical scanner - Google Patents

Abstract

PURPOSE:To eliminate the uneven correction and interference of a polarizer and to make possible the scanning with high accuracy by inclining a cylindrical lens in such a manner that the inside surface reflected light and scanning light trace the optical paths in different directions in a sub-scanning direction. CONSTITUTION:The cylindrical lens 7 is so inclined that the inside surface reflected light 2B reflected from the inside surface of an incident end face 7a and exit end face 7b and emitted from the lens 7 out of the light beam 2 made incident on said lens and the scanning light 2A passing through the lens 7 trace the optical paths in the different directions in the sub-scanning direction. A light shielding plate 9 extending in the main scanning direction is provided on the optical path of the light 2B to shut off the light 2B. The optical paths of the light 2A and the light 2B are thus superposed by which the generation of the uneven interference of the scanning plane as a resulted of an increase or decrease of the intensity of the light 2A by the light 2B according to the scanning angle is eliminated.

Description

[Detailed description of the invention] ゛::=2:26 gates Qa'rts, T*. ,0. gate,
This invention relates to an optical scanning device that can be used as an optical scanning device, and in particular, it performs highly accurate scanning without unevenness in the pitch of scanning lines or unevenness in the interference of light beams, so it is suitable for optical scanning devices.

(Technical background of the invention and prior art) In recent years, light beams have been used to read and/or read images.

Alternatively, various recording systems have been developed. In such a system, a light beam emitted from a light source is reflected and deflected by seven deflectors such as a rotor and a mirror, and is sent at a constant speed in a direction perpendicular to the direction of deflection (
(sub-scanning) i-scanning is performed on the scanning surface.

However, in conventional scanning devices, the deflector that reflects and deflects the light beam to perform main scanning is driven at high speed, which tends to cause wobbling due to vibration.
For this reason, there is a possibility that the scanning line that is deflected and scanned on the scanning surface may be distorted in the sub-scanning direction. Also,
In particular, a rotating polygon mirror was used as a deflector! In this case, it is technically difficult to make each surface of the rotating polygon mirror on which the light beam enters completely parallel to the rotation axis. There is a problem that unevenness occurs.

In order to compensate for this surface tilt, various scanning devices have been proposed in which an optical system such as a cylindrical lens is provided between the deflector and the scanning surface. This will be explained with reference to FIG.

A light beam 102 emitted from a beam light source 101 passes through a cylindrical lens 104 made to an appropriate thickness by a beam expander 103, and is directed to a rotating polygon mirror 105, which is a deflector, perpendicular to the □ rotation axis of the rotating polygon mirror. It is incident as an m image, and the i-transformed polygon l! 105 is reflected and polarized as it rotates in the direction of the arrow layer. FIG. 4 shows the optical path of the reflected and deflected light beam 102, and FIG. It is. First, the main scanning of the deflected light beam 102 as shown in FIG. 4 will be explained.
The optical vinyl 102 is a scanning lens 1 provided on the optical path.
The light beam 102 that is incident on the scanning lens 106 as a parallel beam is incident on the scanning lens 106 at a focal length f
1 scanning lens by 106 'tQ□if apart from 106
The focused light beam is focused on the scanned surface 10a, and main scanning is repeatedly performed in the direction of the arrow in the range from al to 82. In addition, the scanning lens 106 and the scanning vA
A cylindrical lens 101 extending in the main scanning direction is provided between the cylindrical lens 108 and the main scanning direction. In FIG. 4, only the light beam 102 is transmitted. Incidentally, as mentioned above, the rotating polygon mirror 105 often suffers from surface tilt, and a system for correcting this will be explained with reference to FIG.

Rotating multi-sided! The light beam 102 reflected by 1105 enters the scanning lens 10G, passes through the scanning lens, and spreads slightly 5! The light beam becomes the same as the scanning thi10
8 in the sub-scanning direction (direction perpendicular to the page in Figure 4)
The light enters the cylindrical lens 107 which focuses the light only on the light. At this time, there was no surface tilt etc. on the rotating polygon @ 1'05,
If the rotational polygon mirror 11x is oriented, the light beam 102 will pass through the optical path shown by the solid line in the figure, but if the rotating polygon mirror has a tilted surface or the like, the reflecting mirror 105a of the rotating polygon mirror 105 will shift to the position 105j+'./ At C11, the i optical path moves to the position shown by the dashed line in the figure.

However, since both the light beam in the optical path shown by the solid line and the light beam in the optical path shown by the dashed-dotted line are emitted from the same point on the copper mirror 105a, the cylindrical lens 10F also Since the light beams indicated by the dashed-dotted line can both be focused on the same position Ha3 on the scanning line 108, it is possible to
Even if the optical path of the light beam 102 deviates, it is possible to correct the deviation.

In this way, the □ light with correction of the surface, rR spring - i
102 performs main scanning in the direction of arrow A on the scanning surface 108 which is sub-scanned in the direction of arrow C. ′
□However, in a scanning device that uses an optical system such as the one described above to correct surface tilting of the deflector, etc., 1. Since a cylindrical lens extending in the main scanning direction is used for correction, this cylindrical lens A part of the light beam incident on the lens 101 is reflected by the inner surfaces of the entrance end surface 107a and the exit end surface 107b of the cylindrical lens, and the light reflected from the inside overlaps with the light beam that has passed through the cylindrical lens and is deflected by the cylindrical endothelium. Strengthens or weakens the light beam passing through the lens. Therefore, if the light beam 102 is deflected by the rotating polygonal mirror '105 within a range of ±θ゛ from the central position of deflection, as shown in FIG. There is a problem in that interference irregularities extending in the sub-scanning direction occur, resulting in interference artifacts in the resulting image. To remove this interference unevenness, there is a method of coating the cylindrical lens with an anti-reflection film, but a long cylindrical lens extending in the main scanning direction is coated with a uniform anti-reflection film that does not cause interference unevenness. It is very difficult to
Furthermore, the cost of a cylindrical lens coated with a uniform antireflection film generally increases significantly.

(Object of the Invention) The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to correct wobbling and surface tilt of a deflector, and also to correct uneven interference of a light beam without increasing costs. It is an object of the present invention to provide an optical scanning device that can perform accurate scanning. It is a thing.

(Makinari of the Invention) The optical scanning device of the present invention has a cylindrical lens provided between a deflector and a scanning surface, in which a light beam passing through the interior and a light beam emitted after being reflected on the inner surface of the cylindrical lens are provided. The cylindrical lens is tilted so as to take optical paths in different directions in the sub-scanning direction, and is characterized in that a light shielding plate is provided on the optical path of the light beam that is emitted from the cylindrical lens after being reflected on the inner surface of the cylindrical lens. be.

The light beam emitted from the light source is incident on the deflector as a line image perpendicular to the drive axis of the deflector, and is reflected and deflected.
A scanning lens and a cylindrical lens provided on the optical path focus the light onto the scanning plane as a point image, and correct pitch irregularities in the scanning line. In addition, the light beam that passes through the cylindrical lens and scans the scanning surface is prevented from interfering with the reflected light reflected from the inner surface of the cylindrical lens because its optical path overlaps with the light beam, so that the light beam scans the scanning surface with a constant intensity. .

(Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view showing an outline of an optical scanning device according to one embodiment of the present invention.

After passing through a beam expander 3 and a cylindrical lens 4, a light beam 2 emitted from a beam source 1 enters a rotating polygon mirror 5 rotating in the direction of arrow m as a line image perpendicular to the rotation axis of this rotating polygon mirror 5. Reflected and deflected. The reflected light beam 2, which is parallel to the main scanning direction, enters an fθ lens 6, which is a scanning lens, and then enters a cylindrical lens 7, which is provided on the optical path of the light beam 2 and extends in the main scanning direction. It will be done. A portion of the light beam incident on this cylindrical lens is reflected by the inner surfaces of the entrance end surface 1a and the exit end surface 1b of the cylindrical lens, becomes internally reflected light 2B (not shown in FIG. 1), and exits from the exit end surface. The cylindrical lens 7 receives this internally reflected light 2.
A light beam that performs main scanning except for B (hereinafter referred to as scanning light)
) 2A is focused on the scanning surface 8 only in the sub-scanning direction. Further, the distance from the scanning lens 6 to the scanning surface 8 is equal to the focal length of the scanning lens 6, which is 6. Therefore, regardless of the presence or absence of wobbling or surface tilt of the rotating polygon mirror 5, the scanning light 2A is focused on a predetermined position on the scanning surface 8, and performs main scanning in the direction of the arrow on the scanning surface 8, which is sub-scanned in the direction of the arrow C.

By the way, the cylindrical lens 7, as shown in FIG. 2, out of the incident light beam 2, reflects the inner surface reflected light 2B on the inner surfaces of the entrance end surface 1a and the exit end surface 1b of the cylindrical lens and exits from the cylindrical lens 7.
and the scanning light 2A passing through the cylindrical lens 7 are tilted so that their optical paths take different directions in the sub-scanning direction.

Furthermore, a light shielding plate 9' extending in the main scanning direction is provided on the optical path of the internally reflected light 2B to shield the internally reflected light 2B. Therefore, as in the conventional scanning device, the optical paths of the scanning light 2A and the internally reflected light 2B overlap, so that the internally reflected light 2B increases or weakens the intensity of the scanning light 2Δ depending on the scanning angle, and the internally reflected light 2B irradiates the scanning surface ( The inconvenience of interference unevenness is eliminated.The angle α at which the cylindrical lens 7 is tilted is □ For example, the focal length 1ift of the cylindrical lens 7 is 60 m, and the N of the cylindrical lens 7 is 6 m. When the distance 2 of In addition, the position and shape of the light shielding plate are not limited to those in the above embodiment, but as in another embodiment shown in FIG. 19a is provided, and the light shielding portion is the slit 1.
The light shielding plates 19 disposed above and below the light shielding plate 98 may be stacked in layers. Furthermore, if the cylindrical lens 7 is coated with an antireflection film, interference unevenness can be removed even more effectively. The antireflection film in this case is sufficiently effective even if it is not highly precise. □ In the above embodiment, the light beam that enters the rotating polygon mirror as a line image is deflected and enters the fθ lens as parallel light in the main scanning direction, but this deflected light beam is not necessarily The light does not need to be parallel to the main scanning direction, and if the light beam is not parallel to the main scanning direction, the θ lens is not provided at a distance of its own focal length from the scanning surface, but rather the light beam is not parallel to the main scanning direction. Suitable for focusing on the scanning plane /) m If ICitQ Gt '3 t'L
Z you 1. Wow, good. It goes without saying that a galvanometer mirror or the like other than the rotating polygon 1 can also be used as the deflector.
(Effects of the Invention) As explained in detail above, according to the Mitsunaga scanning device of the present invention, a k-th cylindrical lens for correcting scan/line pitch unevenness, etc. is used to absorb a portion of the light beam incident on the cylindrical lens. This is because the internally reflected light and the remaining scanning light are tilted to take optical paths in different directions in the sub-scanning direction, and the internally reflected light is completely blocked by the light shielding plate. , it is possible to compensate for wobbling and surface tilt of the deflector and to remove interference unevenness, making it possible to realize high-precision scanning without increasing the cost.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an outline of an optical scanning device according to two embodiments of the present invention, and FIG. 2 is a schematic diagram for explaining the arrangement and operation of a cylindrical lens and a light shielding plate according to the above embodiments. , FIG. 3 is a perspective view showing the shape and arrangement of the light shielding plate according to another embodiment of the present invention, and FIG. 4 is a perspective view showing the optical path of the light beam in a conventional scanning device parallel to the drive axis of the deflector. □Figure 5 is a schematic diagram of the optical path of the light beam in a conventional scanning device as seen from the direction of the drive of the deflector.
146, a schematic diagram viewed from a direction perpendicular to the axis, is a schematic diagram 1 showing an example of interference unevenness occurring on a scanning surface of a conventional scanning device. 1... Beam light source: 2... Light beam 2A
...-Scanning/Light 2B...Internally reflected light ゛5...
Rotating polygon mirror 6. ...fθ lens 7...
cylindrical lens

Claims (1)

[Claims] a beam light source that emits a light beam; a deflector provided on the optical path of the light beam emitted from the beam light source to reflect and deflect the light beam; and a deflector provided between the beam light source and the deflector on the optical path of the light beam. an entrance optical system that makes the light beam incident on the deflector as a line image perpendicular to the drive axis of the deflector; a scanning lens provided on the optical path of the light beam deflected by the deflector; A cylindrical lens is provided extending in the main scanning direction on the optical path of the light beam that has passed through the lens, and focuses the light beam that has passed through the lens on the scanning surface only in the sub-scanning direction, and the lens is provided as a line image on the deflector. The incident and deflected light beam is focused as a point image on the scanning surface, which is sent at a constant speed in the sub-scanning direction by the scanning lens and the cylindrical lens, and the light beam reflected and deflected by the deflector is focused in the main scanning direction. In the light beam scanning device, the cylindrical lens is tilted so that the light beam passing through the interior and the light beam emitted after being reflected on the inner surface take optical paths in different directions in the sub-scanning direction. An optical scanning device characterized in that a light shielding plate is provided on the optical path of a light beam emitted from a cylindrical lens after being reflected on an inner surface of the cylindrical lens.