JPS60256924A - Optical reversible recording and reproducing device - Google Patents

Abstract

PURPOSE:To improve the weather resistance of an optical disc and to make the quality of recording identical by irradiating an erasure spot light onto a disc at both simultaneous erasure and recording of a non-recording track so as to use the identical thermal recording condition. CONSTITUTION:An output light of wavelength lambda1 of a semiconductor laser 6 is made to a parallel optical beam by a condenser lens 7, made incident on an aperture lens 11 through an optical element of an optical beam combiner 8 or the like so as to form a circular optical spot L on a guide track 1. On the other hand, an output light of wavelength lambda2 of a semiconductor laser 13 is formed by bringing an elliptic optical spot M whose major diameter is coincident with the lengthwise direction of the track 1 close to the spot L. The spot L is used for recording and reproducing the signal and the spot M gives a temperature rise gradual cooling condition to the optical disc, so as to attain crystal state.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical recording/reproducing device. More specifically, the laser beam is heated to a diameter of 1 μm using a microwave or the like.
Erasable optical recording that can repeatedly record and reproduce signals by narrowing the beam to a very small beam of light, irradiating it onto an optical recording medium, recording and reproducing signals at high density, and erasing the once recorded signal by laser irradiation. The present invention relates to a playback device.

As an optical recording and reproducing device that can eliminate the conventional structure and its problems, a method has been proposed in which the optical density is reversibly changed using only thermal energy such as a laser. One of the methods described above is a method of repeatedly utilizing the transition between the amorphous state and the crystalline state of the recording thin film.

FIG. 1 briefly shows a model of the transition between the amorphous state and the crystalline state.

In FIG. 1, the amorphous state of the recording thin film is shown as A.

The recording thin film in an amorphous state has a low light reflectance and a high light transmittance. Further, the crystal state is indicated by C, and the recording thin film in the crystal state has a high reflectance and a low transmittance.

With this recording thin film whose optical density can be reversibly changed, the temperature of the recording thin film in the amorphous state A in Figure 1 is raised locally in a trench near the melting point, and when that part is slowly cooled, it changes to the crystalline state C. . On the other hand, if the temperature of the recording thin film in the crystalline state is locally raised to near the melting point and the area is rapidly cooled, it becomes amorphous state A.
become.

Figure 2 shows the heating and cooling conditions on the recording thin film.

One specific method for realizing the temperature raising and slow cooling conditions will be shown.

FIG. 2a shows a substantially circular minute spot L formed by a laser or the like on a recording medium that moves relatively in the direction of the arrow. When the light intensity of this optical spora) L is increased for a short period of time to raise the temperature of a local part of the thin film, the temperature rise in this local area is quickly diffused into the recording thin film and the supporting member of the thin film, creating conditions for rapid heating and cooling. This optical spora) L makes it possible, for example, to record a signal.

On the other hand, as shown in Figure 2, an elongated optical spot (M) is formed on the recording medium using a laser or the like in the direction in which the recording medium advances (arrow), and the intensity of the optical spot (M) is adjusted continuously or intermittently. If the heating temperature is made stronger, the heated portion of the recording thin film will be cooled much more slowly than in case a, and a gradual heating and cooling condition can be obtained.

This light spot) M makes it possible, for example, to erase a signal.

By directing a minute circular beam onto a relatively advancing recording thin film, temporally modulating its intensity, and irradiating it as a pulsed light, heating and cooling conditions (for example, recording) can be obtained. By continuously or intermittently irradiating the advancing recording thin film with an elongated light beam in the direction of its advance, heating and slow cooling conditions' (for example, erasing) can be obtained.

If we try to realize so-called simultaneous erasure, in which new information is immediately written to the recording track while erasing the recording track already written on the disc using both of the spot lights, the above-mentioned information will be erased as shown in FIG. Both spot lights have a velocity V in the direction of the arrow. Arranged so that light spots (light spots) M (hereinafter referred to as erasing spot light) which are elongated and arranged close to each other in a straight line on a recording track that advances in a straight line precede a substantially circular light spot (light spot) Q (hereinafter referred to as recording spot light). be done. In order to use the recording track effectively without wasting it, it is desirable that the interpolation X of the two spot lights be as short as possible. However, if the fusion between the two spot lights is short, for example, when a signal is recorded using the subsequent recording spot light, it will be affected by the heat of the preceding erasing spot light. FIGS. 3a and 3b show the heat distribution on the recording track, and the above effects will be described. FIG. 3a shows the heat distribution when simultaneous erasing is attempted on a recording track on which signals have already been recorded. In the case of simultaneous erasing, since both spot lights are irradiated at the same time, if the two spot lights are brought close to each other, the recording spot light will begin to rapidly raise and cool the temperature while the erase spot light is gradually increasing the temperature. Figure 3 shows the heat distribution when trying to record a signal on an unrecorded track. In this case, a heat distribution of rapid heating and cooling of only the recording spot light is obtained. When the two spot beams are placed close to each other in this way, the recording conditions for simultaneous erasure and the recording conditions for unrecorded tracks are thermally different, making it difficult to design a recording thin film. Differences occur in the quality of the recorded signals (eg, reflectance, length of recording pits, etc.). In particular, in the case shown in FIG. 3, a larger recording power is required than in case a because there is no residual heat effect due to the erasing spot light.

Furthermore, recording thin films are generally more stable in an amorphous state than in a crystalline state with respect to temperature resistance and humidity. Therefore, it is desirable for the initial state of the optical disc to be amorphous. However, if the unrecorded track is initially amorphous, the recording spot light cannot record the signal (make it amorphous), and the initial state of the optical disc is It has no choice but to be in a crystalline state. Therefore, with the conventional configuration, the weather resistance of the optical disc is also unstable.

Purpose of the Invention The present invention was made in view of the above-mentioned problems, and it is possible to simultaneously erase data while erasing an already written recording track, and to record a signal on an unrecorded track at the same time. The purpose is to provide a recording thin film with a heat distribution of .

Structure of the Invention In order to achieve the above object, the present invention provides that the erasing spot light is turned off only when reproducing a signal from an optical disc, and that the erasing spot light is turned off only when a signal is reproduced from an optical disc, and when recording, simultaneously erasing, or recording a signal on an unrecorded track. The disk is also configured to perform recording by irradiating the erase spot light onto the disk so that the heat distribution conditions during recording are always constant.

Description of examples The present invention will be explained in detail below based on examples.

FIG. 4 shows a radial cross-sectional view of an optical disk having optical guide tracks used in the present invention. Here, as an example of an optical guide track, an example of a grooved optical disk having grooves over the entire signal recording area on the optical disk is shown. In the figure, the base material 1 is made of a transparent material, and the width W and depth d are
, the grooves 2 with a track pitch p are formed in a spiral shape or a concentric circle shape. A recording thin film 3 having a thickness t is formed thereon by vapor deposition or other methods, and a protective layer 4 is provided thereon. The groove 2 has a depth d9 so as to function as an optically detectable guide trunk for the laser irradiation light 5.
The width W is designed. This groove allows the irradiation light 6 to record or reproduce a signal along a specific groove.

FIG. 5 shows an embodiment of the present invention.

In the figure, numeral 6 indicates a semiconductor laser which generates light of wavelength λ1, and its output light beam is indicated by t. Reference numeral 7 denotes a condensing lens which condenses the output light of the semiconductor laser 6 having a spread into a substantially parallel light beam.

Reference numeral 8 indicates a light beam combiner that transmits light with a wavelength λ1 and reflects light with a wavelength λ2, which will be described later.9 indicates a beam splitter, and 10 indicates a reflecting mirror. The light beam t of the semiconductor laser 6 passes through these optical elements and enters the aperture lens 11. The aperture lens 11 narrows down the incident light beam t to form a substantially circular light spot L on the guide track 1. Reference numeral 12 denotes an actuator that drives the aperture lens 11, and performs known focus control by driving the aperture lens in the optical axis direction in response to surface wobbling of the disk. Furthermore, in order to perform a known tracking control on a guide track that is inherently eccentric, the aperture lens 11 is driven in a direction perpendicular to the incident optical axis and the guide track.

In FIG. 6, 13 is a semiconductor laser that generates a light beam m of wavelength λ2, and 14 is a condenser lens. light beam m
is reflected by the beam combiner 8 and enters the aperture lens 11 on almost the same optical path as the light beam t, and forms an elliptical or oblong shape on the light spora L and the decoy groove 1, and its major axis. A light spot M whose direction coincides with the longitudinal direction of the groove 1 is formed.

FIG. 5 shows an enlarged view of the mutual relationship between the two light spots L and M formed on the groove 1 having different wavelengths and the groove 1 as described above.

The optical spora) L and M are arranged close to each other on the same guide groove and separated by a desired distance.

The light reflected by the optical recording disk passes through an aperture lens 1 and a mirror 10, enters a beam splitter 9, is reflected by a beam splitter 9, and enters a filter plate 16. Here, a filter plate is shown that transmits only the light of wavelength λ1 and does not transmit the light of wavelength λ2. A single lens 16 converts the reflected light beam t into apertured light. Reference numeral 17 denotes a reflecting mirror, which functions to block and reflect about half of the light focused by the single lens 16 and guide the light toward the photodetector 18 . 19 shows a two-split photodiode for detecting a focus error signal, which is placed at the focus point of the single lens 16 and detects a conventionally known focus error signal in response to movement of the split light t1. . The photodetector 18 is a two-split photodiode for detecting a tracking error signal, and detects a conventionally known tracking error signal using reflected light t2 from the mirror 17.

Further, a reproduced signal of the signal recorded in the groove 1 on the optical recording disk is obtained from the photodetector 18 or 19.

The amplifier 2o amplifies the difference signal between each element of the divided photodiode 18, and generates a tracking error signal at the terminal TH. The amplifier 21 is a circuit that amplifies the sum signal of the respective outputs of the divided photodiodes 18, and outputs a reproduced signal to the terminal PB.

The amplifier 22 is a circuit that amplifies the difference signal between each element of the divided photodiode 19, and outputs a focus error signal to the terminal FD.

In the above configuration, as shown in FIG. 6, two light droplets (L and M) are formed close to each other on the same guide track, and one light dropper L is approximately circular and the other light droplet is approximately circular. The spot M is oval along the guide track, and these lights contain a desired intensity or a desired signal and are irradiated onto the recording thin film of the optical recording disk while tracking the guide track 1 on the optical recording disk. Ru.

Optical spot) L is a substantially circular minute spot with wavelength λ1, which is used for recording (amorphizing) or reproducing signals along guide track 1, and for controlling control signals such as focus control and tracking control. Also used for detection. On the other hand, the optical spot (7) M having a long axis in the tangential direction of the guide track has a wavelength λ2 different from that of the optical spot (7) L, and applies heating and slow cooling conditions to the optical disc to bring it into a crystalline state.

In FIG. 6, reference numeral 23 denotes an erasing laser drive circuit that modulates the intensity of the erasing spot light M, and when the signal input to the terminal Q is "H", the erasing laser is irradiated onto the optical disk.

24 is a recording/reproducing laser drive circuit that modulates the intensity of the recording spot light, and the light intensity is switched between recording/reproducing and lowering according to a signal input to a terminal P.

Terminals R, S, and T contain digital signals of information to be recorded,
A recording command signal and an erasing command signal are respectively applied, and the timing of the signals at each terminal is shown in FIG. 7 RT.

Here, 26 is an AND circuit, 26 is an OR circuit, and 27 is a time t. This is a delay circuit.

In FIG. 7, to is the distance X between the two spots and the speed V of the optical disc. This is because the erasing spot light precedes the recording spot light by a distance X, so the erasing spot light is irradiated 10 hours in advance.

Each laser drive port @24.
23 is modulated, the optical output of each laser is as shown in Figure 8a,
It becomes as shown in b. In FIG. 8, a shows the optical output waveform of 6 which is a semiconductor laser for recording/reproduction, and b shows the optical output waveform of 13 which is a semiconductor laser for erasing. In FIG. 8, 28 is the recording power level, 29 is the reproduction power level, and 3o is the erasing power level. As described above, since erasing power is always applied to the recording thin film during signal recording, the heat distribution of the recording thin film during recording always becomes the heat distribution given in FIG. 3a. Furthermore, in the case of an erasable optical disc, the guide track is shipped in a crystalline state, but in the present invention, even when recording on an unrecorded track, initialization is performed by irradiating erasing light. It is possible to make the initial state of the part into an amorphous state which is highly weather resistant.

In the above embodiment, the erasing semiconductor laser is 1
Although the explanation has been given as one, erasing may be performed using a plurality of semiconductor lasers.

゛-As explained in detail, according to the configuration of the present invention, the thermal recording conditions at the time of so-called simultaneous erasure, in which new information is written while erasing previously written information, and unrecorded tracks are Since the thermal recording conditions when writing information can be made the same, it is easier to design the recording thin film, and the quality after recording (e.g. light reflectance, recording pit length, etc.) is also the same. It becomes possible to do so. In addition, since the residual heat effect of the erasing power is always obtained in advance during recording, the sensitivity of the recording thin film is substantially increased, and the recording power of the recording spot light can also be reduced. Since it is possible to improve the quality of the optical disc, it has the effect of improving the weather resistance of the optical disc.

[Brief explanation of the drawing]

Figure 1 is a diagram schematically showing the operating principle of an optical recording thin film that shows reversible changes, and Figure 2 shows the recording thin film under heating and rapid cooling conditions.
3 is a diagram illustrating the difference in thermal distribution of the recording thin film. 4 is a partial cross-sectional perspective view illustrating an example of the structure of an optical disc. A block configuration diagram illustrating an embodiment of the present invention, FIG. 6 is a diagram showing the arrangement of light spots and the traveling direction of the optical disk used in the present invention, and FIG. 7 is a diagram showing control signals for controlling both laser drive circuits. Waveform diagram FIG. 8 is a waveform diagram showing the optical output waveforms of both laser beams, respectively. 6... Laser for recording and reproduction, 13... Laser for erasing, 1... Guide track on optical disk, L... Recording spot light (first light spora)
), M, old... erased spot light (second light spot),
X: River: Interval between both spot lights, to: Relative time between both spot lights, which is obtained by dividing the interval between both spot lights by the speed v0 of the optical disc. Name of agent: Patent attorney Toshio Nakao (1st person)
Fig. 2 Fig. 3 Fig. 4 Fig. 6 Fig. 7

Claims (1)

[Claims] Information is thermally recorded by a first light spot narrowed down on the optical disk, and at least one light spot placed ahead of the first light spot and narrowed down on the guide track of the optical disk records information thermally. When the first light spot is in a recording state on the optical disc, the area irradiated by the first light spot is always An optical reversible recording/reproducing device characterized in that a second light spot is irradiated prior to the first light spot.