JPS58168029A - Multibeam recording device - Google Patents

Abstract

PURPOSE:To obtain a small-sized, high-performance multibeam recording device, by shaping beams circularly through prisms and also putting them together simultaneously. CONSTITUTION:Semiconductor laser light sources 1a and 1b, collimator lenses 2a and 2b, and the prisms 3a and 3b each having a 45-56 deg. vertical angle and a 10-25 deg. angle of beam projection are provided; the prism 3b is fitted with a dichroic mirror as an interference filter. Further, a reflecting mirror 5, galvano- mirror 6, ftheta lens 7, and photosensitive medium 8 are also provided. Two light beams from semiconductor laser light sources 1a and 1b having, for example, 840mum wavelength and 780mum wavelength are collimated separately by the collimator lenses 2a and 2b into parallel beams, which are shaped into round beams by the prisms 3a and 3b. Those beams are put together by the dichroic mirror 4 and scanned by one galvano-mirror 6 to form an image on the photosensitive medium 8 through the ftheta lens 7, thus performing recording.

Description

[Detailed description of the invention] The present invention relates to a multi-beam recording device.

Optical disk devices, optical printer devices, and the like that use semiconductor lasers have been developed, but these devices require high speed and high resolution.

To this end, multi-beam recording devices that record with a plurality of light beams and recording devices that use laser array elements have been proposed.

However, since the light spot formed by condensing the light beam from this semiconductor laser with a lens or the like has an elliptical shape, it is difficult to increase the recording density in optical disk devices and optical printer devices compared to the case of a circular light spot. There is a drawback that it cannot be done.

Therefore, in the past, a circular slit or the like was provided in the optical device to change the light beam into a circular shape, but the light beam was vignetted by the slit, resulting in a significant decrease in power efficiency.

The present invention aims to solve the above-mentioned drawbacks, and is characterized in that it transforms the beam shape using a prism to create a circular light beam, and at the same time combines multiple light beams to enable multi-beam recording. shall be.

An embodiment of the present invention will be described below.

First, the semiconductor laser will be explained. As shown in FIG. 1, the original beam emitted from the semiconductor laser light source 1 has an elliptical emission pattern with different sizes in the X-axis and Y-axis directions. A: Due to its structure, a conductor laser does not have a circular beam shape, and the light beam radiation angle is expressed in full width at half maximum, and the ratio of the direction parallel to the junction to the direction perpendicular to it (hereinafter referred to as ellipticity U) is 1 to 5. It will also happen.

However, with recent advances in technology, it has become possible to obtain radiation angles that are close to circular by adjusting the stripe width and the refractive index difference between the stripes and both ends of the semiconductor laser. If the circular ratio is around 1:2 to 1:3 and the circular beam is larger than that, the optical output will decrease.
In addition to being difficult to process in terms of phosphorography, the most easily available semiconductor laser has an ellipticity of about 1:2 to 1:3.

FIG. 2 is a diagram showing the principle of the present invention. 1 is a semiconductor laser light source, 2 is a collimator lens, and 3 is a prism. The light beam emitted from the semiconductor laser light source 1 is turned into a parallel light beam by the collimator lens 2. The semiconductor laser light source 1 is arranged as shown in FIG.

When this parallel light beam passes through the prism 3, it is emitted at an angle according to the law of refraction, so that the shape of the light beam in the refracted direction changes.

Therefore, if the incident angle of the light beam entering the prism 3 is changed, the exit angle will change according to the law of refraction, so the beam shape of the light beam can be changed arbitrarily.

This is a prism with an apex angle α made of optical glass with a refractive index n, and an incident angle θ (as it is reversible, the exit angle may also be used)
When a light beam is incident at , the shape of the light beam in the refracted direction of the output light beam is determined by the following magnification m.

m-cos[: arcstn(n5in(α-a r
c sin (sin θ/.))):]/40 Figure 3 is a graph showing the deformation of a light beam incident on a prism made of optical glass BK7 material with a refractive index of 1.5, expressed as a magnification m. The shaded area indicates the range of the original φ.

FIG. 4 is an explanatory diagram showing one embodiment of the present invention, 1a,
1b is a semiconductor laser light source, 2a and 2b are collimator lenses, 3a and 3b are prisms, and 3b is a dichroic mirror 4 as an interference filter. 5 is a reflection mirror, 6 is a galvanometer mirror, 17 is an fθ lens, 8
is a photosensitive medium. .

Therefore, for example, a semiconductor laser light source 1 with a wavelength of 840 nm is used.
The two light beams from the semiconductor laser light source 1b having a wavelength of 780 nm and a collimator lens 2a,
The light beam is transformed into a parallel light beam by the light beam 2b, and the shape of the light beam is transformed into a circular shape by the prisms 3a and 3b in the manner shown in FIG.

The respective circularly deformed light beams are combined by a dichroic mirror 4, scanned by one galvanometer mirror 6, and imaged onto a photosensitive medium 8 by an f0 lens I for recording.

With the above configuration, the power of a semiconductor laser light source tends to decrease toward the visible region, but since the photosensitive medium 8 has good sensitivity in the visible region, it is possible to use two light beams with wavelengths of 840 nm and 780 nm, for example. Even if a multi-beam recording device is configured, the device can sufficiently satisfy its performance.

Note that the dichroic mirror 4 as an interference filter cannot efficiently separate the incident light beams by wavelength unless the angle of incidence is within a limited range. This is because, from the characteristics of the dichroic mirror 4, the larger the incident angle is, the more the characteristics of S-polarized light and P-polarized light are separated, and the overall wavelength transmittance characteristics have a gentler characteristic. This means that the smaller the wavelength difference between the semiconductor laser light sources 1a and ib, the more difficult it becomes to combine the two light beams unless the incident angle is made smaller.

Generally, in such applications, dichroic mirrors cannot efficiently separate wavelengths unless they are used at an incident angle of 25° or less. This also applies when a normal interference filter is used.

Furthermore, due to the device configuration or the arrangement of optical components, if the angle of incidence on the dichroic mirror is less than lθ°, restrictions on the arrangement of components etc. become large, making it difficult.

Therefore, the best results can be obtained by designing the incident angle within a range of 25° from l O'.

According to the multi-beam recording device as described above, the magnification m of the prism is set in the range of 1/2 to 1/3 according to the ellipticity of the light beam, as shown by the shaded area in FIG. By setting the dichroic mirror to the range of the radiation angle of the dichroic mirror, it is possible to arrange the dichroic mirror without making a special angle with respect to the prism, and it is possible to obtain a circular light beam.

Furthermore, since a dichroic mirror surface is formed on the prism surface when a plurality of light beams are combined, a multi-beam recording device that is compact overall and has good performance can be achieved.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the light beam of a semiconductor laser, Figure 2 is a diagram of the principle of the present invention, Figure 3 is a graph showing the amount of deformation of the light beam, and Figure 4 is an example of an embodiment of the present invention. FIG. 1... Semiconductor laser light source 2... Collimator lens 3... Prism 4... Guicroic mirror 5
... Reflection mirror 6 ... Galvano mirror 7 ... Lens 8 ... Photosensitive medium Patent applicant Oki Electric Industry Co., Ltd. Representative patent attorney Takashi Kanakura Nikaku 2 Prison Dragon 30 Output angle θ @4'giA

Claims (1)

[Scope of Claims] 1. A plurality of semiconductor laser light sources that emit light beams with different wavelengths, a collimator lens that converts each of the light beams into a parallel light beam and is disposed opposite to each of the semiconductor laser light sources, and A prism installed opposite each collimator lens to input the light beam emitted from the collimator lens to form a circular light beam, and one of the above prisms to combine the light beams emitted from the prism to form a multi-beam. A multi-beam recording device characterized by comprising an interference filter provided on the side surface of two prisms. 2. The apex angle of the prism is in the range of 4r to 56°, and the output angle of the light beam from this prism is in the range of 1□' to 25°.
2. The multi-beam recording apparatus according to claim 1, wherein the beam is in the range of .degree.