JPS6350809A - Optical writer - Google Patents

Abstract

PURPOSE:To easily adjust the titled writer by arranging an optical element for subscanning-directional pitch adjustment between an optical system for beam shaping and one beam composing element. CONSTITUTION:Both beams change into circular polarized light beams by passing through a 1/4 wavelength plate 9 and are made flat in the subscanning direction by a cylindrical lens 10 and made incident on a polygonal mirror 11. Their reflected light beams scan on the surface of a photosensitive drums 16 linearly at the same time through an anamorphic ftheta lens 12 so that their spot diameters are specific and a shift by specific pitch is generated in the main scanning direction and subscanning direction. For synchronous detection, luminous flux before the start of scanning is guided to cylindrical lenses (2) and 13 and made incident on a synchronous detector 14. The subscanning- directional pitch of a beam projected by a laser LD1 and a beam projected by a LD2 is corrected by moving a prism 17 as shown by an arrow B. Namely, accurate adjustments are easily made by an adjusting screw 21.

Description

Detailed Description of the Invention Technical Field The present invention relates to an optical writing device such as a laser printer, and particularly to a writing device for a laser printer that uses two semiconductor lasers to simultaneously scan two beams on two lines. The present invention relates to an optical writing device that facilitates pitch adjustment of two beams in the sub-scanning direction.

BACKGROUND ART As mentioned above, in a writing device for a laser printer that uses two semiconductor lasers to simultaneously scan two beams for two lines, conventionally, when adjusting the pitch of the two beams, Part (LD unit) 20 including two half-four body lasers and some optical systems such as collimating lenses
, by using the adjusting screw 21 as shown in FIG. ! 1I
911 was on.

However, in order to adjust the pitch of the two beams, the amount of pitch deviation on the image plane is ±10 μm. The focal length of the cylinder lens is 10011IIlf.If the lateral magnification of the θ lens is 5 times, the adjustment angle Δ0 is: Δ0 = tan- 1 ((1015)/100) = 0.0
0002 phantom 4.1 seconds, Δ2 in FIG. 3 becomes Δfl==LXtanΔθ=50×O,00002=0.001 mm, which requires adjustment in μm units.

It is clear that this is extremely difficult to implement.

Purpose The present invention has been made in view of the above circumstances, and its purpose is to solve the above-mentioned problems in conventional optical writing devices and to provide an optical writing device that is easy to adjust.

Structure The above object of the present invention is to have two sets of semiconductor lasers and a beam shaping optical system, to combine the two beams by a beam combining element, and to form two lines on the surface of a photoconductor by a deflector and an imaging optical system. This is achieved by an optical writing device that performs simultaneous scanning, characterized in that an optical element for pitch adjustment in the sub-scanning direction is disposed between the beam shaping optical system and at least one beam combining element. Ru.

Hereinafter, the configuration of the present invention will be explained in more detail based on examples.

FIG. 1 is a block diagram of an optical writing device showing an embodiment of the present invention. In the figure, 1 and 2 are semiconductor lasers (hereinafter referred to as
rLDl, LD2J), 3 and 4 are collimating lenses, 5 and 6 are apertures, 7 is a 1/2 wavelength plate, 8 is a polarizing beam splitter, 9 is a 1/4 wavelength plate, 10 is a cylinder lens (1), 11 12 is a polygon mirror as a deflector, 12 is an anamorphic fθ lens, 13 is a cylinder lens (2), 14 is a synchronization detector, 15 is a mirror, and 16 is a photosensitive drum, respectively. Further, 11A is a drive motor for the polygon mirror 11, and 17 is a prism for pitch adjustment in the sub-scanning direction, which is a feature of this apparatus.

In both the semiconductor lasers LDI and LDZ, the active layer is arranged perpendicular to the main scanning direction, and the far field pattern is an ellipse with the main scanning direction long.

The beam emitted from the LDI is turned into parallel light by a collimating lens 4, and shaped into a predetermined beam diameter by an aperture 6. Next, by passing through the 1/2 wavelength plate 7, the polarization directions of the beam emitted from the LD 2 become perpendicular to each other, and the light beam passes through the polarizing beam splitter 8 as P-polarized light.

Similarly, the beam emitted from the LD 2 is turned into parallel light by the collimating lens 3, and shaped into a predetermined beam diameter by the aperture 5. After that, the prism 17
The light beam is slightly tilted in the sub-scanning direction, and is reflected as S-polarized light to the polarizing beam splitter 8. In addition,
The beam emitted from this LD2 is arranged to be shifted from the beam emitted from the LDI by a predetermined pitch in the main scanning direction.

Next, both of the beams are changed into circularly polarized light by passing through the quarter-wave plate 9. This is flattened in the sub-scanning direction by a cylinder lens 10 and made incident on the polygon mirror 1. This reflected light is transmitted through the anamorphic fθ lens 12
The imaging optical system scans two lines simultaneously on the surface of the photosensitive drum 16 with a predetermined spot diameter and a predetermined pitch shift in the main scanning direction and the sub-scanning direction (see arrow A).

Synchronous detection uses a cylinder lens (2) to collect the luminous flux before the start of scanning.
13 and input it to the synchronization detector 14. Control of the start of optical writing using two beams after detection is performed using, for example, an LDI
, LD2 may be detected separately, and a conventional phase synchronization circuit may be used.

The pitch between the beam emitted from ILDI and the beam emitted from LD2 in the sub-scanning direction can be corrected by moving the prism A17 as shown by arrow B. This will be explained in detail below.

FIG. 2 is an enlarged view of the prism 17, in which 17A is the prism body, 17B is a prism holding plate, 17C is the center of rotation of the prism holding plate 17B, and 21 is an adjusting screw.

In this example.

When the angle α between the entrance surface and the exit surface of the prism 17 is 5 degrees, in order to realize the adjustment angle Δ0=4.1 seconds, the prism needs to be tilted by the adjustment angle Δβ=35. From this, the adjustment amount Δ by the adjustment screw 21
h is Δh=LXtanΔβ=50X0.01=0,5mm, compared to the case of the conventional method shown earlier.

It's about 500 times easier.

According to the above embodiment, the pitch in the sub-scanning direction between the beam emitted from the LDI and the beam emitted from the LD2 is
The adjustment screw 21 allows easy and precise adjustment.

In the above embodiment, the adjustment can be made easier by making the angle α between the entrance surface and the exit surface of the prism 17 smaller. Further, in the above embodiment, the prism is arranged only on the LD2 side, but this
It goes without saying that they may be placed on both sides of D2.

Effects As described above, according to the present invention, there are two sets of semiconductor lasers and a beam shaping optical system, the two beams are combined by a beam combining element, and a photosensitive beam is formed by a deflector and an imaging optical system. In the optical writing unit that simultaneously scans two lines on the body surface, an optical element for adjusting the pitch in the sub-scanning direction is disposed between the beam shaping optical system and at least one of the beam combining elements, so that adjustment is easy. This has the remarkable effect of realizing an optical writing device.

[Brief explanation of drawings]

FIG. 1 is an elliptical diagram of an optical writing device showing an embodiment of the present invention, FIG. 2 is an enlarged view showing the main parts thereof, and FIG. 3 is a configuration diagram showing a conventional adjustment device. 1.2: Semiconductor laser (LDI, LD2), 3° 4: Collimating lens, 5.6: Aperture. 7: 1/2 wavelength plate, 8: Polarizing beam splitter, 9
: 1/4 wavelength plate, 10 Nijilinda lens (1), 1
1: polygon mirror, 12: anamorphic fθ lens, 13 Nijilinda lens (2), 14: synchronous detector. 15: mirror, 16: photosensitive drum, 17: prism. Figure 2 Figure 3 Written amendment to figure procedure (voluntary) November 1988 58 1988 Patent Application No. 196146 2 Title of invention Optical writing device 3 Relationship with the person making the amendment case Patent FF If person 4 , Agent 5.r Number of inventions increased by amendment No. 1) Figures 1 and 2 of the drawings are supplemented with the attached ones.

Claims (1)

[Claims] (1) It has two sets of semiconductor lasers and a beam shaping optical system, and combines the two beams with a beam combining element,
In an optical writing unit that simultaneously scans two lines on a photoreceptor surface using a deflector and an imaging optical system, an optical element for pitch adjustment in the sub-scanning direction is provided between the beam shaping optical system and at least one beam combining element. An optical writing device characterized by arranging.