JPH032712A - Beam scanner - Google Patents

Abstract

PURPOSE:To reduce the number of used scanning mirrors and ftheta lenses to miniaturize a device by scanning two or more light beams with a single scanning mirror and a single ftheta lens and separating the scanned light to two beams again by a beam splitter. CONSTITUTION:Linearly polarized light beams emitted from a semiconductor laser 1 and a semiconductor laser 2 attached in the direction orthogonal to the semiconductor laser 1 are converted to parallel rays by collimator lenses 3 and 4 respectively, and one is reflected by a mirror 5, and two beams are made incident on a beam splitter 6 from directions perpendicular to each other. Mixed light is scanned by a rotating polygonal mirror 7 and passes the ftheta lens and is made incident on a beam splitter 9 and is separated in two directions again by the polarized direction. Consequently, phases of plural scanning periods are completely equalized by one scanning means with respect to light beams which can be independently modulated. Thus, the device is miniaturized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical beam scanning device used in a recording section of a laser beam printer, a facsimile device, or an intelligent copier device.

[Conventional technology]

In laser printers, when scanning with a plurality of light beams, a method has been used in which a plurality of separate scanning sections, f-theta lenses, etc. are arranged and scanning is performed.

[Problem to be solved by the invention]

Therefore, when the number of scanning light beams increases, a large number of rotating polygon mirrors are required, resulting in an increase in the size of the device.

Furthermore, in order to synchronize the scanning of a plurality of beams, a complicated control system including phase control of driving parts such as a rotating polygon mirror and a galvano mirror is required.

[Means to solve the problem]

The present invention combines laser beams emitted from two light sources whose polarization planes are orthogonal to each other using a beam mixer, or combines two or more light beams that are close to each other and parallel to each other using a single scanning mirror or an fθ lens. By scanning with a beam splitter or splitting the scanned light into two beams using a beam splitter, the number of scanning mirrors, f-theta lenses, etc. used can be reduced, reducing the cost and downsizing of the device. It can be measured.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

Referring to FIG. 1, in a first embodiment of the present invention,
The straight-line-changing light emitted from the semiconductor laser 1 and another semiconductor laser 2 mounted in a direction perpendicular to the semiconductor laser 1 is made into parallel light by a collimator lens 3 and a collimator lens 4, respectively, and one is reflected by a mirror 5 and becomes a parallel light. The books enter the beam splitter 6 from directions perpendicular to each other.

The mixed light is scanned by a rotating polygon mirror 7, passes through an fθ lens, enters a beam splitter 9, and is again separated into two directions depending on the deflection direction.

The two separated scanned light beams are each passed through a mirror 10. It is reflected by the mirror 11 and scans different locations on the scenic object.

Next, the functions of each part will be explained.

The semiconductor laser has a T8° polarization plane parallel to the PN junction plane. If a collimator lens that oscillates in a mode is used and the numerical aperture of the collimator lens is appropriately selected, a deflection ratio of about 100 can be easily obtained. The beam mixer 6 is made of optical glass cut at an angle of 45° and coated with a multilayer dielectric film having low absorption. Two beams having polarization planes perpendicular to each other are incident on the multilayer film surface from different 45° directions. At this time, the light beam mainly composed of P waves emitted from the semiconductor laser 2 can pass through the laser 6 as is. Also, the light beam 4 from the semiconductor laser 1 is 6
Since the parallel light beam is reflected by the dielectric layer, the parallel light beam incident on the rotating polygon mirror can be a composite wave of P waves and S waves whose optical axes coincide with each other. The rotating polygon mirror 7 is a polygon mirror attached to a motor that rotates at a constant speed. At this time, the scanning angular velocity of the light beam reflected and scanned by these mirror surfaces is constant, so in order to make the scanning speed constant on the photoreceptor 12 surface, an fθ correction function and a parallel beam are applied to the photoreceptor 12 surface. There are functions that help you focus.

The beam splitter 9 has the same configuration as the beam mixer 6, but has a longer shape and separates the scanned light in the polarization direction. In the arrangement shown in Figure 1, the light emitted from semiconductor laser 1 is 9
・The light emitted from the semiconductor laser 2 is reflected at 9. Mirror 10 and mirror 11 are arranged so that the optical distance from the fθ lens to the scanning surface of photosensitive drum 12 is the same for the two beams. Since the photosensitive drum rotates at a constant speed, a latent image can be easily formed on the charged photosensitive drum surface by modulating the laser light source with an image signal. Moreover, since the scanning phases of the two beams are aligned, there is no deviation between the two latent images in both the main scanning direction and the sub-scanning direction.

A second embodiment of the present invention will be described with reference to FIG.

The structure up to the beam mixer 6 is the same as that of the first embodiment, so a description thereof will be omitted. Cylindrical lens 7, rotating polygon mirror 8A,
Toroidal lens 9A, inner circular vertical beam splitter 10, and outer circular vertical mirror 11. fθ lens 12.
It is composed of an fθ lens 13 and a photosensitive drum 14.

The operations up to the beam mixer 6 are the same as in the first embodiment, and will therefore be omitted. The silitorical lens focuses parallel light only in the X direction on the reflecting surface of the rotating polygon mirror 8A, and is combined with the toroidal lens 9 to correct the tilt angle of the polygon mirror.

The synthesized wave that has been converted into parallel light by the toroidal lens 9 is incident on a deflection beam splitter 10A whose separation surface 10-1 has a circular shape. At what scanning angle is this incident light I?
Even if it enters the OA, the angle between the separation plane and the incident light is 45°.
Since the beam splitter has a circular separation surface as shown in FIG. This circular separation surface may be a part of a circular surface that includes the reflection point of the rotating polygon mirror, has a central axis in the X direction, and has an apex angle of 90°.

The component polarized in the X direction is reflected by the separation surface 10-1.

This beam travels in a direction parallel to the X axis at any scan angle. Since this surface is concave, the beam tends to be focused.

(The component polarized in the X direction transmits 10 as is.)
The circular surface mirror 11 is also circular with an apex angle of 90° and whose central axis coincides with the circular axis of the beam splitter and whose apex is separated by the distance between the beam splitter 10 and the mirror 11. It is part of the outer surface of the surface. The light reflected by this surface is returned to the original scanning angle,
Furthermore, since the outer circular vertical surface is a convex surface with the same curvature as the separation surface, it is possible to return the light to parallel light. The light reflected by 11 is f
The beam is corrected by the θ lens 13 to obtain a uniform scanning speed and is focused on the drum 14. The same applies to the fθ lens 12.

The same fθ lenses 12 and 13 can be used.

A third embodiment will be described with reference to FIG.

Semiconductor laser 1. Semiconductor laser 2. Collimator lens 3. Two parallel beams are obtained by the collimator lens 4. To make two parallel beams of light close to each other and parallel to each other. The prism 5A is arranged so that these two light rays are included in a plane that includes the rotation of the rotating mirror 7. 6A and 8A
are a cylindrical lens and a toroidal lens, respectively, but these can be omitted if the angle of inclination of the mirror 7 is small. If it is removed, just make the mirror thick enough.

The fθ lens 9B and the fθ lens IOB are arranged so that the two beams scanned by the mirror 7 pass through the central optical axis of the fθ lens. In the third embodiment, a part of the circle is cut so that the two fθ lenses 9 and 1'0 do not interfere with each other.

If the f.theta. lenses cannot actually be arranged so close to each other, a two-sided mirror may be arranged in front of the f.theta. lenses.

The embodiment in this case is as shown in FIG.

The two beams exiting the fθ lens have the same effect as in the second embodiment, so their explanation will be omitted.

A fourth embodiment will be described with reference to FIG. Cylindrical lens 2 By removing the toroidal lens from FIG. 3 and placing the separating biface mirror 8 behind the rotating polygon mirror, the two parallel beams are separated from each other and then transferred to the fθ lens 9B and the fθ lens 10. It can be made incident. In this case, there is no interference between the fθ lens 9B and the IOB, which is advantageous in practice.

〔Effect of the invention〕

As explained above, the present invention makes it possible to perfectly align the phases of multiple scanning cycles using only one scanning means for light that can be modulated independently, and when applied to multiple laser printers, color shift will not occur. It produces an effect such as "no".

lens, 5...mirror 5A...prism, 6...beam mixer 6A...
...Cyridical lens, 7...Rotating polygon mirror,
7A... Cylindrical lens, 8...
・fθ lens, 8A...Rotating polygon mirror, 8B...
...Toroidal lens, 8C...Double mirror,
9...Beam splitter-9A...Toroidal lens, 9B...fθ lens, 10.
...Mirror 10A ... Deflection beam splitter 10B ... fθ lens, 11 ...
...Mirror 12...Photosensitive drum, 12A...
...fθ lens, 12B...Mirror 13
・・・・・・fθ lens, 13A・・・mirror
13B...Photosensitive drum, 14...Photosensitive drum.

Agent Patent Attorney Susumu Uchihara

[Brief explanation of the drawing]

1 to 4 are diagrams showing first to fourth embodiments of the present invention.

Claims (2)

[Claims] (1) A beam scanning device characterized by having a beam mixer for mixing two linearly modified light beams whose polarization planes are orthogonal to each other, and means for scanning the mixed light beam emitted from the beam mixer. (2) It has two or more light beams whose optical axes are parallel to each other and has a means for independently changing the emission intensity, and a means for scanning these light beams, and the scanning line of the plurality of scanned light beams is A beam scanning device arranged to pass through the optical axis of each of a plurality of f^θ lenses.