JPH0341623A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To acquire a satisfactory optical spot by inclining a semiconductor laser into a face including the optical axis of a beam splitter and the normal of a reflection face. CONSTITUTION:A semiconductor laser 1 can be inclined in an in-phase direction including the optical axis of a beam splitter 2 and the normal of a reflection face 3 in the beam splitter 2. The semiconductor laser 1 is inclined at -theta in the face including the optical axis and normal of the beam splitter 2 and an inclining angle phi13 of the semiconductor laser 1 is adjusted. Then, the eccentric distribution of optical intensity to the optical axis is corrected and the distribution of the optical intensity is made close almost symmetric to the optical axis. Thus, since the inclining angle theta is adjusted and the distribution of the optical intensity to the optical axis is made close to be symmetric, the satisfactory optical spot can be acquired.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical information recording/reproducing device, and more specifically, an optical system that focuses a laser beam on an information recording medium to form a light spot. The present invention relates to an optical information recording/reproducing device having the following.

[Conventional technology]

FIG. 3 shows a conventional optical information recording/reproducing device of this type. In the figure, a polarizing beam splitter (2) with a reflective surface (3) is located in the direction of emission of laser light from a laser light source (1).
), a collimator lens (4), a quarter-wave plate (5), and an objective lens (6) are arranged in sequence, and the laser beam is focused on the guide groove (8) of the information recording medium (7). Ru. In addition, the signal detection means (lO) is for reproducing signals recorded on the information recording medium (7) and detecting signals such as defocus and track deviation, and generally consists of an optical element for signal detection (11). It consists of a photodetector (12).

With this configuration, due to the characteristics of the polarizing beam splitter (2), only the light beam in the -opening direction and P polarization is transmitted from the diverging light beam emitted from the laser light source (1).This light beam is converted into parallel light by the collimator lens (4). The information recording medium (7) is irradiated with the light through the quarter-wave plate (5) and the objective lens (6) to form a light spot (9). The light spot (9) is reflected by the information recording medium (7>) and passes through the objective lens (6) and the 1/4 wavelength plate (5>) again, but the light spot (9) is polarized by going back and forth through the 1/4 wavelength plate (5). Since the direction is rotated by 90° to become S fti light, it is reflected by the polarizing beam splitter (2).Then, the light beam is passed through a signal detection means consisting of a signal detection optical element (11) and a photodetector (12). At step (10), the signal recorded on the information recording medium (7) is reproduced and signals such as defocus and track deviation are detected.

[Problem to be solved by the invention]

Since the conventional optical information recording/reproducing apparatus is configured as described above, it has the following problems.

This will be explained using FIGS. 4 to 7. As shown in FIG. 3, the light flux incident on the polarizing beam splitter (2) becomes a diverging light flux because the light flux emitted from the semiconductor lens (1) is directly incident thereon. Therefore, for any divergence angle θ of light, the incident angle δ on the reflective surface (3) of the polarizing beam splitter (2) is different. The situation is shown in Figure 4. Divergence angle θ1. θ2. The angle of incidence on the polarizing film δ, δ2.
δ corresponds. The angle of incidence thus depends on the angle of divergence. Figure 5 shows an example of the optical characteristics of a general polarizing beam splitter (2). The graph is for P-polarized light, the horizontal axis indicates the divergence angle θ, and the sign indicates the inclination of the divergent light from the optical axis with respect to the beam splitter. The vertical axis indicating the direction is the transmittance T. It can be seen from this graph that the transmittance T changes irregularly with respect to the divergence angle θ, and the transmitted light intensity becomes non-uniform. Therefore, FIG. 6 shows an example of the characteristics of a polarizing beam splitter whose dependence on the divergence angle is reduced by using a film needle. This graph is for P(I light, and the horizontal and vertical axes are the same as in Figure 5. From this point on, the change in transmittance with respect to the divergence angle near 0° will become smaller, and the divergence angle θ will continue to increase. It can be seen that the transmittance decreases rapidly with respect to the direction.The light spot of the light beam transmitted through the beam splitter (2) exhibiting such characteristics is a light spot with a divergence angle of +θ, as shown in Figure 7. The intensity is strong and the light intensity distribution is asymmetrical with respect to the optical axis, making it impossible to obtain a good light spot.

A similar problem also occurs when a light beam that has been improved by an information recording medium is reflected by a beam splitter, which adversely affects signal reproduction and signal detection characteristics such as defocus and track deviation.

The present invention was made to solve the above problems, and an object of the present invention is to obtain an optical information recording/reproducing device that can generate a good light spot.

[Means to solve problems]

The optical information recording/reproducing device according to the present invention is capable of tilting a semiconductor laser in an in-plane direction including the optical axis of a beam splitter and the normal line of a reflecting surface.

[For production]

In this invention, by tilting the semiconductor laser in an in-plane direction including the optical axis of the beam splitter and the normal to the half mirror surface, the bias in the intensity distribution of the light spot is corrected and the light intensity distribution is symmetrical about the optical axis. do.

〔Example〕

FIG. 1 shows an embodiment of the present invention, and in the figure, reference numeral 〈
1> to (12) are the same parts as in Fig. 3,
The basic operation is the same.

The semiconductor laser (1) can be tilted in an in-plane direction including the optical axis of the beam splitter (2) and the normal to the reflective surface (3) of the beam splitter <2. (13) has an angle φ
shows.

Next, the operation will be explained with reference to FIG. FIG. 2 shows the light intensity distribution on two sides of each configuration. FIG. 5A shows a light intensity distribution in the case of a conventional device in which diverging light from the semiconductor laser (1) is incident on the polarizing beam splitter (2). Figure (b) shows the intensity distribution when the semiconductor laser (1) is tilted by −θ in a plane that includes the optical axis and normal line of the beam splitter (2).
), it is possible to correct the clarity of the light intensity distribution with respect to the optical axis, and to make the light intensity distribution nearly symmetrical with respect to the optical axis, as shown in FIG.

〔Effect of the invention〕

As described above, according to the present invention, the semiconductor laser can be tilted within a plane that includes the optical axis of the beam splitter and the normal to the beam splitter reflecting surface, so that the tilt angle can be adjusted to It is possible to make the intensity distribution symmetrical and obtain a good light spot.

[Brief explanation of drawings]

FIG. 1 is a schematic front view of an embodiment of the present invention, FIG. 2 is an explanatory diagram of the correction of light intensity distribution in the embodiment, and FIG. 3 is a schematic perspective view of a conventional optical information recording/reproducing device. Figure 4 is a schematic diagram showing the relationship between the divergent luminous flux and the beam splitter of the one in Figure 3, Figure 5 is an optical characteristic diagram of the beam splitter in Figure 3, and Figure 6 shows the incident angle dependence of the one in Figure 3. FIG. 7 is an optical characteristic diagram of a smaller beam splitter, and FIG. 7 is a light intensity distribution characteristic diagram with respect to the divergence angle of the beam splitter of FIG. 3. (1)...Semiconductor laser, (2)...Beam splitter, (3)...Reflecting surface, (7)...Information recording medium, (8)
...Guide groove, (13)...The inclination of the semiconductor laser is an angle. In each figure, the same reference numerals indicate the same or corresponding parts. Figure 2, figure 3, figure 5, figure 6

Claims (1)

[Scope of Claims] An optical information recording and reproducing device that optically records and reproduces information by irradiating an information recording medium with a light beam from a semiconductor laser, wherein a diverging light beam emitted from the semiconductor laser is reflected light and transmitted. a beam splitter that splits the semiconductor laser into the beam splitter, and a signal detection means that reproduces the signal recorded on the information recording medium and detects signals such as defocus and track misalignment, and An optical information recording/reproducing device that can be tilted in a plane that includes the optical axis and the normal to the reflective surface.