JPS6113453A - Optical information recording device - Google Patents

Abstract

PURPOSE:To reduce optical power variation of a diffracted beam and perform stable recording, reproduction, and erasure by adding frequency composition in erasure on a time division basis. CONSTITUTION:Light emitted by a laser light source 1 is converted through a condenser lens 2 and then passed through the acoustooptic modulating element 3 (A/O element), prism 4, quarter-wavelength plate 5, and a mirror 6, and stopped down by a stop-down lens 7 into a fine spot of about 1mum on the surface of a disk 8. When the disk 8 is variable phase type reversible optical disk which performs information recording, reproduction, and erasure by utilizing the crystal-amorphous phase transition of a recording film, one frequency for obtaining a single circular spot required for recording and reproduction and plural frequencies for obtaining an elliptic spot necessary for erasure are applied to the A/O element 3. When information is erased, an elliptic spot composed of plural spot groups ES for erasing the information is present at some distance from one circular spot WS for reproduction which reads address information, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an erasable optical information recording device that records, reproduces, and erases information by a crystal-amorphous phase transition of a recording film. The present invention relates to an optical information recording device that can stably record, reproduce, and erase information using two lasers and an acousto-optic modulator.

[Background of the invention]

In recent years, there has been active development of rewritable and erasable optical disks in place of optical disks in which information is recorded and reproduced by drilling holes in a recording film.

There are mainly two types of them: magneto-optical type and phase change type. Among these, the phase change type records/erases information by utilizing phase transition between crystal and amorphous of a chalcogenide recording film. To realize phase transition, Japanese Patent Application Laid-Open No. 59-6884
As described in Section 4, by using two lasers with different wavelengths, the laser beam with the first wavelength is narrowed down to a circular spot for recording and reproduction, and the recording film is rapidly heated and rapidly cooled by irradiation with short pulse light. The amorphous laser beam having the second wavelength is focused as an oblong spot for erasing, and the recording film is crystallized by removing heat and slowly cooling it.

However, this method using two lasers requires two lasers, and it is difficult to align the two circular and oval spots, and their positional relationship may shift due to temperature or vibration, resulting in normal recording/ There is a problem that it cannot be reproduced/erased.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical information recording device which solves the above-mentioned problems and allows easy adjustment and stable recording/reproducing/erasing of information without positional deviation between the two spots.

[Summary of the invention]

In order to achieve such an object, the present invention uses one laser light source and one acousto-optic modulation element to generate the circular spot and oval spot necessary for recording/reproducing/erasing on a phase-change reversible optical disk, and uses a single laser light source and one acousto-optic modulation element during recording. A single diffracted beam is generated by applying one frequency, and during erasing, multiple diffracted beams are generated by applying multiple frequencies. Further, in the present invention, the optical power fluctuation of the diffracted beam is reduced by adding the frequency synthesis during erasure in a time-divisional manner. This allows for stable recording/
Play/delete becomes possible.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. In the figure, light emitted from a laser light source 1 (a semiconductor laser or a gas laser such as an Ar laser) is condensed by a condenser lens 2, and then transferred to an acousto-optic modulator 3 (hereinafter abbreviated as A10 element) and a prism 4°. 1/4 wavelength plate5. The light passes through the mirror 6 and is narrowed down to a minute spot of about 1 μm on the surface of the disk 8 by the focusing lens 7. A10i child 3 is T
It has the function of propagating ultrasonic waves of a wavelength corresponding to a drive signal in an acousto-optic material such as eO□ or PbMoO4, and modulating and deflecting an incident beam by the action of this ultrasonic wave.

As described in Japanese Patent Application No. 58-154855, the diffraction angle is proportional to the frequency of the applied drive signal, so if the drive signal includes a plurality of frequencies at the same time, a plurality of diffracted beams can be obtained. Therefore, if the disk 8 is a phase change type reversible optical disk that records/reproduces/erases information by utilizing phase transition between crystalline and amorphous recording film, recording/reproducing/erasing information is possible.
One frequency is applied to the A10 element 3 to obtain the single circular spot required during reproduction, and a plurality of frequencies are applied to the A10 element 3 to obtain the oblong spot required during erasing.

This special spot shape was obtained by patent application No. 58-15485.
A typical spot shape is shown in FIG. 2. First, during recording, information is recorded on the recording film by high-output pulse modulation of the laser light source 1 using only one circular spot WS. During reproduction, the laser light source 1 is continuously oscillated at low output using only one circular spot WS, as in the case of recording, to read information including addresses and data recorded on the recording film. When erasing, there is one circular spot WS for reproduction that reads address information, etc., and an oval spot consisting of a plurality of spot groups ES for erasing information after a certain distance. At the oval spot ES, the focal length of the aperture lens 7 is F, and the numerical aperture is N.
,A,, A10If the sound speed of element 3 is V, the interval between applied frequencies is Δf, and the ratio of spot interval d to spot diameter is K, then F-N,A.

For example, F = 511 Ifi, N,
A,=0,5.

v=3630m/see (for PbMoO4),
When Δf=1/2, Δf=0.8 MHz, so an arbitrary spot length can be designed based on these values.

FIG. 3 shows an A10 driver 9 that synthesizes a plurality of frequencies during erasing. A10 driver 9 has frequency f. −
An oscillation circuit 101.f, having n+1 oscillators. A mixer circuit 102 that controls the strength of these signals. Adding circuit 103 to further add RF to amplify the combined signal
It consists of an amplifier 104 and is applied to the transducer 105 attached to the A10 element 3 to generate n
One beam is obtained, and a pseudo-elliptical spot consisting of one circular spot for reproduction and n circular spots for erasure is formed. At this time, in the mixer circuit 102 that controls the signal strength, the recording and reproducing side uses a control signal that maximizes the diffraction efficiency when driving one frequency during recording and reproducing, and a control signal that drives multiple frequencies when erasing. sometimes fo
A control signal is applied from the control circuit 106 such that the diffraction efficiency for the beam is maximized. Further, the erasure frequency side is connected to a sequential switching circuit 107, which controls the signal strength and sequentially switches and adds n frequencies at a time with a period of dt. When driving the A10 element with multiple frequencies, the diffraction efficiency per element changes depending on the number of applied frequencies, so the number of frequencies applied to the A10 element must always be constant. Therefore, when selecting the time division period Δt, if the time required for the sound wave to propagate through the effective aperture of the A10 element, that is, the access time, is T, then At=-2 m'.
n It's going to happen. At this time, m represents the number of sets when n frequencies propagating in the crystal of the A10 element are set as one set. However, since it is multi-frequency drive, m≧1 in the above formula.
．． n≧2. N22. There is a condition that m=K·N (K: positive integer). - For example m=1. n=9. The case where time division addition is performed with N=3 will be explained using FIG.

The vertical axis corresponds to frequencies f, to f, and the horizontal axis is a time axis, which is divided into periods Δ. Between ta"""tt is the frequency f,
, f4. f, is frequency f 2 tf between t and t2,
, f, but between t2 and t8, f, , fG, f.

is applied, and after t, the above process is repeated, and the frequency is propagated in the crystal of the A10 element in the arrangement shown in FIG. In this example, if the access time of the A10 element is 1.2 μs, the time division period Jt is Jt=
It becomes 0.4 μs. In the example shown in Fig. 4, it is assumed that the frequencies included in lt increase sequentially from fl to f9, and the division is shown in every two pieces, but there is no restriction in principle, and any It may be a combination.

Next, automatic focusing (AF system) and tracking deviation correction (TR system) will be explained. The light reflected by the disk 8 passes through the aperture lens 7, the mirror 6°λ/4 plate 5,
The plane of polarization is rotated and reflected by the prism 4, and the optical path is separated. The separated light is transmitted through the harp prism 10 and divided into an AF system for performing automatic focus detection and a TR system for reflecting and detecting track deviation. AF system is patented in 1986-1.
Detection is performed using the image rotation method described in 83911.

This is a convex lens 11. Cylindrical lens 12° knife lens 13. It is composed of a photodetector 14, and performs automatic focusing by moving a diaphragm lens up and down. AF using erase spot group generated during erasing
The influence on the system is removed by shielding it with a knife 13. The TR system employs the diffraction light differential system described in Japanese Patent Application No. 56-152086. This is convex lens 1
5 and a photodetector 16, and track tracking is performed by driving the mirror 6 using diffracted light from a track guide groove formed on the disk t1.

As explained above, driving the A10 element in time division reduces the applied frequency at a spatial position within the crystal, which reduces the mutual interference force S between each frequency, and as a result, the A10
This means that fluctuations in the light intensity of the diffracted beam from the element can be reduced.

〔Effect of the invention〕

According to the present invention, it is possible to provide an optical information recording device that can easily perform the alignment force between a circular spot and an oblong spot necessary for recording/reproducing/erasing, and can perform stable recording/reproducing/erasing. be able to.

[Brief explanation of drawings]

Figure 1 shows the first embodiment, Figure 2 shows the shape of the numbered spot, Figure 3 shows the configuration of the IT A10 driver, and Figure 4 shows a specific example of the time division system. figure,
FIG. 5 is a diagram showing the state of propagation within the A/○ element. 3... A10 element, 101... Oscillator, 102...
- Mixer, 103... Adder, 104... RF amplifier. 105...Transducer, 106...Control circuit, Atsushi 1 Figure 2

Claims (1)

[Claims] 1. It has one laser light source and one acousto-optic modulation element, and when recording and reproducing information, a single frequency is applied to the acousto-optic modulation element to form one light beam, and the information is In an optical information recording device that records, reproduces, and erases information as multiple light beams by applying multiple frequencies during erasing,
1. An optical information recording device characterized by being provided with a frequency sequential switcher that adds a plurality of frequencies in a time-divisional manner during erasing. 2. In the optical information recording device according to claim 1, when the time division period is Δt, Δt=
An optical information recording device characterized by satisfying the relationship {N}/{m·n}·T. [However, n is the number of frequencies,
N is the number of frequencies occurring simultaneously during time division, T is the access time of the acousto-optic modulation element, m is the number of sets when n included in T is one set, m≧1, n≧ 2, N≧
1, n=K·N (K: positive integer). ]