JPS6370826A - Optical device for semiconductor laser beam printer - Google Patents

Abstract

PURPOSE:To correct the ellipticity of a light emission pattern of an inexpensive and simple semiconductor laser, by selecting suitably a light emission radiation characteris tic of a semiconductor laser and an angular aperture of a pickup lens. CONSTITUTION:In an optical device of a semiconductor laser 17 of a laser beam printer which uses the semiconductor laser 17, with respect to a half-power full angle of a laser bean 18 of a component for expanding in the horizontal direction on a P-N joint surface of the semiconductor laser, and a half-power full angle of the laser beam 18 of a component for expanding in the vertical direction in the same way, the semicon ductor laser 17 having a light emission radiation characteristic by which the respective maximum values of the half-power full angles are <=16 deg. and 36 deg. when an optical output of the semiconductor laser 17 is 3mW is used as a light source, and by using a pickup lens 19 whose angular aperture NA=<=0.20, light of the semiconductor laser is picked up. In such a case, in the laser beam 18 emitted from the semiconductor laser 17, a laser cutting part 33 of a part caught by a fitting frame 35 of a laser beam 31 is cut by the fitting frame 35 for limiting an aperture of the pickup lens 19, and with respect to a laser light 34 passing through the aperture, the ellipticity is corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical system of a semiconductor laser beam printer, which has recently attracted attention as a non-impact printer.

[Conventional technology]

In the optical system of a conventional semiconductor laser beam printer, the ellipticity of a laser beam emitted in an elliptical shape unique to a semiconductor laser is corrected using a cylindrical lens, an anamorphic prism pair, or the like. FIG. 4 shows an optical path diagram of a conventional optical system of a semiconductor laser beam printer in which ellipticity correction is performed using a cylindrical lens 5.7.

1 is a semiconductor laser, 6 is a big amplifier lens, 5.7 is a cylindrical lens, 9 is a converging lens, 11 is a Y direction beam, and 16 is an X direction beam. 16 is the optical axis, and 15 is the minimum beam spot.

[Problem that the invention seeks to solve]

However, correcting the ellipticity using a cylindrical lens or a pair of anamorphic prisms poses problems such as complicated configuration and design of the optical system and increased cost.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical device for a printer that solves the above-mentioned problems and performs an inexpensive and simple ellipticity correction of a semiconductor laser beam.

[Means for solving problems]

In order to solve the above problem, in the present invention, the intensity of the laser beam emitted from the semiconductor laser is reduced to 1/1 of the maximum intensity.
The full width at half maximum of the component of the laser beam that spreads in the horizontal direction to the PN junction surface of the semiconductor laser is the same as the full width at half maximum in which the direction in which the direction becomes 2 is expressed as the divergence angle centered on the light emitting point of the semiconductor laser. The maximum value of each half-maximum full-width is 16° when the optical output is 3 mW, and the light source is a semiconductor laser having an emission characteristic of 36° or less, and the aperture angle NA= 0.
The light from the semiconductor laser was picked up using a pickup lens of 20 or less.

〔Example〕

FIG. 1 shows one embodiment of the optical system according to the present invention.

The laser beam 18 emitted from the semiconductor laser 17 is N
It is picked up by the pickup lens 19 of A 0.20 or less, is converged by the convergent lens 21, and the convergent lens 2
A minimum beam spot 29 is created near the focal position Po of 1.

Note that 26 is a Y-direction beam, 25 is an X-direction beam, 27 is an optical axis, and 65 is a mounting frame to be described later.

FIG. 2 (shows) how the pickup lens 19 is viewed from the position of the semiconductor laser 17 on the optical axis 27. In FIG. The laser cut portion 36 of the portion of the laser beam 31 that overlaps the mounting frame 35K is cut by the mounting frame 65 that limits the laser beam 31, and the ellipticity of the laser beam 64 passing through the opening is corrected.

FIG. 3 shows another embodiment of the invention. In Figure 3, N
Pickup lens 41 with a larger numerical aperture than Ao, 20
When using the aperture 4 between the converging lenses 45
The ellipticity correction can also be performed by inserting 3. In addition, 67 is a semiconductor laser, 69 is a laser beam,
47 is a Y direction beam, 49 is an X direction beam, 51 is an optical axis, and 53 is a minimum beam spot.

As the semiconductor laser 17, the radiation characteristic of the laser beam is the width at 1/2 of the peak intensity when the optical output is 3 mW (full width at half maximum)
Then, the maximum full width at half maximum of the laser beam component that spreads horizontally on the PN junction surface of the semiconductor laser = 16 deg, PN
A laser beam with a maximum full width at half maximum of a component that spreads in the direction perpendicular to the bonding surface was used. The pickup lens 19 has an NA of about 0.17 and a focal length of about 10 mm, and the diameter of the laser beam after passing through the pickup lens 19 is about 3.2 nm+m.

The converging lens 21 has an effective diameter of 10 mmφ and a focal length of approximately 300 mm.
It is mrn. Focal position 2 of the converging lens 21 at this time
FIG. 5 shows the laser beam spot profile in the X direction and Y direction at the 0 point. FIG. 5 (Al indicates the beam diameter in the X direction at the focal point Po, FIG. 5 (Bl indicates the beam diameter in the Y direction).

In FIG. 5, the horizontal axis represents 20 (μm/d iv), and the vertical axis represents relative light intensity. As can be seen from FIG. 5, in the case of this embodiment, the beam spot profile hardly changes in the Y direction and the X direction of the laser beam diameter at the focal position of the converging lens 21, and the ellipticity of the laser beam 18 is corrected. I understand that.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, by appropriately selecting the emission characteristics of the semiconductor laser and the aperture angle of the pickup lens, it is possible to correct the ellipticity of the emission pattern of the semiconductor laser easily and at low cost.

[Brief explanation of the drawing]

FIG. 1 is an optical path diagram of an optical system showing an embodiment of the present invention, and FIG. 2 is a schematic diagram showing correction of the beam shape of a laser beam by the pickup lens and mounting frame in FIG. 1.
FIG. 3 is an optical path diagram of an optical system showing another embodiment of the present invention, and FIG. 4 is a beam spot profile at a conventional focal plane corrected for ellipticity using a conventional cylindrical lens. 17.67... Semiconductor laser, 19.41...
...Pickup lens, 21.45...
Converging lens, 26.47...Y direction beam, 25.49...
...X direction beam, 29.53 ... Minimum beam spot, 27.51 ... Optical axis, 18.31.69 ... Laser beam, 66 ...
...Laser cutting part, 34...Laser light passing through the aperture, 35...
...Mounting frame, 46...Aperture. Figure 1 Figure 2 x7ff angle beam field (μm)

Claims (2)

[Claims] (1) In a semiconductor laser optical device of a laser beam printer using a semiconductor laser, the full width at half maximum of the laser beam of the component that spreads horizontally on the PN junction surface of the semiconductor laser and the full width of the laser beam of the component that also spreads in the vertical direction. When the optical output of the semiconductor laser is 3 mW, the maximum value of the full width at half maximum of the laser beam is 16°, and the light source is a semiconductor laser having emission characteristics of 36° or less, and the aperture angle NA = 0.20. An optical device for a semiconductor laser beam printer, characterized in that the light from the semiconductor laser is picked up using the following pickup lens. (2) The semiconductor according to claim 1, characterized in that the pickup lens has an aperture angle of NA=0.20 or less by a pickup lens with an aperture angle of NA=0.20 or more and an aperture. Optical device of laser beam printer.