JPS61934A - Optical record reproducing device - Google Patents

Abstract

PURPOSE:To enable data file record reproduction of a high precision picture, digital picture and high transfer rate by an optical disk by condensing light from more than two laser light sources on the same light recording medium. CONSTITUTION:Out of light came out from two semiconductor lasers 11, 12, light from the semiconductor laser 12 becomes S polarized wave on the reflecting face of a polarizing prism 15 and totally reflected, and light from the semiconductor laser 11 becomes P polarized wave and totally transmitted. These light passes through a lambda/4 plate 16 for making it to circular polarized light and condensed on a light recording medium 18 at positions apart by a distance l. Reflected light from the laser 11 from the light recording medium 18 is reflected by a polarizing prism 15, branched by a mirror 22 into two, and arrives at light detectors 23, 24. A focus error signal is detected by a photodetector 24. Photodetectors 23, 25 detect tracking error signals, and one detects tracking servo, and another detects an error signal that corrects deviation from the track.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an apparatus for optically recording and reproducing information on a disk-shaped recording medium, and more specifically, for high-definition images that require a wide band.
The present invention relates to an optical recording and reproducing apparatus for digital image recording and reproducing apparatuses, high transfer rate data files, rewritable recording and reproducing apparatuses, and information files that can monitor the recording state while recording.

The structure of the conventional example and its problems In the conventional optical recording/reproducing device, for example, the light of a semiconductor laser is modulated, the light is focused onto the recording medium by a lens, and the recording medium is deformed by heat, or the reflectance is changed. Information is recorded by changing the direction of magnetization. The maximum frequency that can be recorded is limited by the relationship between the power of the semiconductor laser and the size of the focused spot. For example, when the disk rotation speed is 180 rpm and the radius is 55III+, the cutoff frequency for recording and reproduction is around 10 MIIz.

For example, in order to perform Y-C separation, which separates and records brightness No. 46, color and audio signals as a modulation method for high-quality video signals used for broadcasting, etc., a cutoff frequency for recording and playback of approximately 18 MHz is required. , and in the case of digital images, 30 MIIx or more is required. Furthermore, as a data file for a large computer, a higher transfer speed is required. However, there is a limit to increasing the rotational speed of the disk due to insufficient power of the semiconductor laser, safety issues, and other reasons. As a countermeasure to this problem, multi-beam recording may be considered. Simultaneous recording and reproduction of multiple beams allows the transfer rate to be increased without increasing the rotational speed of the disk. The multi-beam optical head can be used for the following three purposes, including multiplex recording. For simplicity, a two-beam optical head will be explained. FIGS. 1(a), 1(b) and 1(c) respectively show the spot positions on the recording track of the two-beam optical head. Figure 1(a) shows an example in which two beams are focused on the same track, one being the recording spot 1, and the other being used for playback, focusing, and ranking servo error signals. Examples of uses include monitoring the recording state immediately after recording with the playback spot, or detecting unrecorded trunks, sectors, etc. with the raw spot and then recording with the recording spot. In FIG. 1(b), T e
An example is shown in which recording/reproduction on a rewritable recording film such as a recording film in which Ge and Sn are added to Ox and erasing spots are arranged side by side. The elongated spot is the erasing spot, and the short round spots 1 to 1 are the recording/reproducing spots. Figure 1 (
In c), each spot is narrowed down to a different track, recording is performed simultaneously on both spots, and reproduction is also performed simultaneously. .

In the case of three or more spots, Figure 1 (a) (b) (
There is also a known example of the combination of c), such as simultaneous recording on 8 tracks with 8 beams. .

As a pickup optical system for obtaining these multiple beam spots, there is a known example as shown in FIG. The two semiconductor lasers (1) and (2) have wavelengths λ1 and λ2, which are different from each other. (3) is a lens, (4) is a polarizing prism 11, (5) is a λ/4 plate, and (6) is a dichroic mirror, which reflects the light of λ2 and transmits the light of λ1. λ1
The light is reflected from the recording medium (8), passes through the lens (7), passes through the polarizing prism (4), and is transmitted to the photodetector (10) for focus and tracking signal detection and reproduction signal detection.
reach. On the other hand, the wavelength λ2 emitted from the semiconductor laser (2)
The light is reflected downward by the polarizing prism (4), passes through the λ/4 plate (5), is reflected by the dichroic mirror (6), passes through the polarizing prism (4), and is recorded on the recording medium (8). The light is focused. The reflected light from the recording medium (8) is reflected by the polarizing prism (4) and reaches the vicinity of the semiconductor laser (1).

The optical system shown in FIG. 2 has a major problem. 1st
When used in applications such as those shown in Figures (b) and (C), high power lasers are required for both of the two beams. It is difficult to separate λ1 and λ2 using a dichroic mirror unless the wavelengths are separated by 50 nm or more, but if λ = 830 nm, then λ2≦780 nm. However, a semiconductor laser with a wavelength of 800 nm or less has a
It is difficult to obtain a large output compared to laser beams below 1 nm, and therefore it is not suitable for use as a recording or erasing laser beam. In addition, it is difficult for dichroic mirrors to completely separate light of two wavelengths, and the leaked light becomes a cross 1-1, leading to a decrease in the quality of the reproduced signal.1. Another known example is the use of a laser array of semiconductor lasers to obtain multiple beam spots on the disk. However, at present, the laser array of J) is not available on a commercial basis.

Purpose of the Invention The present invention solves the above-mentioned conventional problems, and makes it possible to perform multiple recording and reproduction without using a laser array, and also to record and reproduce high-definition images and data at a high transfer rate. With the goal.゛Structure of the Invention In order to achieve the above object, the optical recording/reproducing device of the present invention includes at least two laser light sources, and laser light from these laser light sources are incident from different directions and are polarized in substantially the same direction. A polarization separation means for emitting laser beams with a difference of 90 degrees, a quarter-wave plate for making these lights circularly polarized, a condensing means for condensing these lights onto an optical recording medium, and an optical recording medium. The apparatus is equipped with a light detection means for detecting a focus and tracking error signal and an information reproduction signal from at least one of these reflected lights, and a control means for performing focus and tracking servo based on these error signals.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings.

First, the first embodiment will be explained based on FIG. 3 showing the first embodiment.

The light emitted from the two semiconductor lasers (11,) (12) is once condensed by the first condensing lens (13) (14), then diverges and enters the polarizing prism (15). A semiconductor laser (12
) becomes S-polarized and is totally reflected, and the light from the semiconductor laser (11
) becomes P-polarized light and is completely transmitted. These lights pass through a λ/4 plate (16) to form circularly polarized light, and are focused onto an optical recording medium (18) by an objective lens (17). These two beams are at a distance Q from each other on the optical recording medium (18).

The light is focused at a location far away. The reflected light from the laser (12) from the optical recording medium (18) is reflected by the polarizing prism (1
5), reflected by the mirror (20), and detected by the photodetector (25).
). The reflected light from the laser (11) is reflected by the polarizing prism (15) and reflected by the mirror (19).
After that, the light is focused by the lens (21), and the light is focused by the mirror (22).
and reaches the photodetectors (23) and (24).

These photodetectors (23) (24) are connected to the optical recording medium (1).
In addition to detecting the signal of the information recorded on 8Ll-, the photodetector (24) detects a focus error signal, and the photodetector (23)
) (25) detects the tracking error signal. The photodetectors (23) and (25) detect the 1-racking error signal of each light, and the tracking servo is activated from one of these, and the tracking servo is detected from the other due to displacement due to minute thermal drift in the relative position of the two spots. Detects an error signal that corrects the deviation from the track. The distance Q1 between the incident light and the reflected light near the mirror (19) is Q, = f□/f2・Q, where f□ is the focal length on the laser side of the objective lens (17) and f2 is the focal length on the disk side. becomes. In this example, f, /f2 = i5, and the distance between spots on the disk Q = 0.04 mm, and fi□ = 0.6 mm.
It becomes. Therefore, separation using mirrors (19) and (20) is easy.

-1- In the embodiment described above, two spots can be focused on different tracks on the optical recording medium (18) to perform simultaneous recording and reproduction, and recording and reproduction can be monitored by focusing the light on the same track.

Next, a description will be given based on FIG. 4 showing a second embodiment.

This second embodiment uses an optical system capable of recording and erasing.
vinegar. In Fig. 4(a), the cylindrical lens (2 [
Same as the first embodiment except that i) is included;'ptQ. The focal position of the condensed spot is shifted only in the track direction by the cylindrical lens (26), and the optical recording medium (1
8) The upper part can be irradiated with an elongated spot and a round spot as shown in FIG. 4(b). These are the erase spot 1- and the recording spot of the rewritable recording material. Information can be recorded and erased repeatedly using a moon charge whose reflectance changes reversibly as a result of phase changes between crystal and amorphous and changes in crystal grain size, but information is recorded using a small light spot. The material is rapidly heated and cooled to reduce the crystal diameter or become amorphous, and when erasing, the recording material is slowly cooled by removing heat using a long and narrow spot to increase the crystal diameter. The higher the laser power, the better for both recording and erasing. Therefore, it is better to use two laser beams with the most advantageous wavelengths in terms of power for recording and erasing, as in this embodiment, rather than using a two-wavelength one or a laser array, which has disadvantages in terms of power. It is reasonable.

Next, a description will be given based on FIG. 5 showing a third embodiment.

In this example, semiconductor lasers (27) (28)
is a gain guide type, and the beam waist is at the output end in the direction perpendicular to the laser junction surface, but the beam waist in the direction parallel to the junction surface is inside the output end.

Therefore, the emitted light has astigmatism, and each astigmatism is corrected by the cylindrical lenses (29) and (30).

Since the bonding surface of each laser is perpendicular to the plane of the paper, the polarization direction of the laser beam, that is, the vibration direction of the electric field, are both perpendicular to the plane of the paper, but the polarizing prism ( The light from the laser (27) that is incident on the laser (27) becomes P-polarized. These lights are focused on two points on the optical recording medium (]8), and the reflected lights are each divided into four parts by a photodetector (32) (
33). These photodetectors (32) (33
), it is possible to detect the focus error signal of the astigmatism method and the tracking error signal of the far field method.

In addition to the above-described embodiments, it is also possible to implement a multi-beam recording/reproducing optical system with three or more beams by combining the present invention with the use of a laser array or lasers of different wavelengths. Furthermore, it goes without saying that the present invention can be used to focus the light beams of the multibeams 11 onto a record carrier using the same objective lens even if a laser other than a semiconductor laser is used. Also, 1st. In the second embodiment as well, a parallel objective lens can be used.

Effects of the Invention As described above, according to the present invention, there is no need to use light sources of different wavelengths or a laser array.

Light from two or more high-output laser light sources can be focused onto an optical recording medium by the same focusing means, making it possible to perform multiplex recording and reproduction. Furthermore, by using a laser with the same power and a recording medium with the same sensitivity, it becomes possible to record and reproduce data at a transfer rate that is more than twice as high, making it possible to record and reproduce high-definition images, digital images, and data files at high transfer rates using optical discs. 11 functions, and the industrial effects are extremely large.

[Brief explanation of the drawings] Figures 1 (a) to (C) are explanatory diagrams of spot shapes on the disk track of a general two-beam system, and Figure 2 is a diagram of a conventional two-beam spot shape using lasers of different wavelengths. 3 to 5 are explanatory diagrams of the optical system in the first to third embodiments of the present invention, respectively. (11) (12)... Semiconductor laser, (13) (1
4)... Condensing lens, (15)... Polarizing prism,
(16)...λ/4 plate, (17)...Objective lens,
(18)...Optical recording medium, (19) (20)...
Mirror, (21)...Lens, (22)...Mirror, (23) (24) (25)...Photodetector, (2
6)... Cylindrical lens, (27) (28)
... Semiconductor laser, (29) (30) ... Cylindrical lens, (31) ... λ/2 plate, (32)
(33)...Photodetector agent Yoshi Morimoto
Hiroshi Figure 1 ttLs tiz) (a) Figure 2 Figure 3 1, ?

Claims (1)

[Claims] 1. At least two laser light sources, a polarization separation means for making the laser lights from these laser light sources enter from different directions and emitting them as laser lights with polarization directions different from each other by 90 degrees in substantially the same direction, and A quarter wavelength plate for polarizing the light, a focusing means for focusing the light onto an optical recording medium, and focusing and tracking error signals and information from at least one of these reflected lights from the optical recording medium. An optical recording/reproducing device comprising a light detection means for detecting reproduction signals and a control means for performing focus and tracking servo based on these error signals.