JPS60263351A - Erasable optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To reduce the effect of the erasing energy to record/reproduction and to erase and record signals at a time, by forming an erasing spot having the major axis of oblong shape to the relative shift direction and providing a maximum light intensity part at the head of the shift direction. CONSTITUTION:A diffraction element 118 gives a diffraction effect to an incident light beam (m) toward a guide groove 51 on a disk to change the intensity distribution of an erasing light spot M on the groove 51. When a point X on an optical recording medium enters the spot M, the temperature is suddenly increased at a high intensity area of the head part of the spot M. Then the temperature reaches a level near a fusing point and then drops less than the fusing point at a point where the light power starts its reduction. Thus the temperature is gradually lowered and a thin film is cooled down gradually for a period of time needed for crystallization for erasion of recorded signals. Then the recording light L of a semiconductor laser 101 is irradiated to the point X for record of new signals.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical recording/reproducing device. More specifically, a laser beam and a lens etc. are used to create a diameter of 1 μm.
Optical recording 3 ＼-・ Erasing that allows repeated recording and reproduction of signals by narrowing the light beam to a very small beam and irradiating it onto a recording medium to record and reproduce signals at high density, and once recorded signals are erased by laser irradiation. The present invention relates to a possible optical recording/reproducing device.

Conventional Structure and Problems Conventionally, as an example of an optical recording/reproducing apparatus, a method has been proposed in which a rotating optical recording disk is irradiated with a laser beam having the minute beam diameter. In this device, the signal is recorded by modulating the intensity of the laser beam irradiated onto the optical recording disk with the signal to be recorded, thereby recording a predetermined signal on the optical recording disk-L at high density using laser energy. to be recorded. - To reproduce the recorded signal, a laser beam of a certain intensity is irradiated to the signal recording area of the optical recording disk, and the recorded signal is reproduced by detecting the change in reflected light or transmitted light on the optical recording disk. , %t7'
.

This optical recording and reproducing device has high recording density, low memory cost per bit, high-speed access, and stable recording and reproducing without contact between the optical head and optical recording disk. It is attracting attention as a new memory medium for the future information society.

As the above-mentioned optical recording/reproducing method, a write-once type and an erasing type have been proposed.The write-once type recording/reproducing method uses the thermal energy of the irradiated laser to locally damage the optical recording thin film. A method of recording and reproducing signals by evaporating it to form small holes, and a method of recording and reproducing signals by locally changing the optical density of the recording thin film using the thermal energy of irradiated light have been proposed. .

On the other hand, erasure-type optical recording and reproducing devices use magneto-optical recording materials that record and reproduce signals through the cooperation of the thermal effect of a laser and an external magnetic field. As a recording method for changing the optical density in the write-once recording, a method has been proposed in which the optical density is reversibly changed using only thermal energy such as a laser.

One way to obtain reversible concentration changes in the recording film is to transition between the amorphous and crystalline states of the recording film, or between one amorphous state and another stable amorphous state. There is a method that repeatedly utilizes transitions between crystal particles or changes in the size of crystal grains in an amorphous matrix.

The present invention relates to an optical recording/reproducing device that utilizes the above-mentioned reversible density change of the optical recording thin film.Prior to explaining the present invention, the principle thereof will be briefly explained below.

For the sake of simplicity, the explanation will be based on the assumption that an optical density change is obtained using a transition between an amorphous state and a crystalline state.

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 optical 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 changed reversibly, the temperature of the recording thin film in the amorphous state AvC shown in FIG. 1 is raised locally to near or above the melting point.
When that part is slowly cooled, it becomes crystalline state C. On the other hand, if the temperature of the recording thin film in the crystalline state is locally raised to near or above the melting point and then rapidly cooled, the recording thin film becomes amorphous.
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 microspora 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 light spot 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 support member for the thin film, creating conditions for rapid heating and cooling.

On the other hand, as shown in Fig. 2, an elongated optical spora (K) M is formed on the recording medium 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 temperature is increased, the heated portion of the recording thin film will be cooled much more slowly than in the case of a, and a gradual heating and cooling condition can be obtained.

A minute circular beam is applied to the relatively advancing recording thin film,
By temporally modulating the intensity and irradiating it with pulsed light, conditions for heating and rapidly cooling can be obtained, and the relatively advancing recording thin film is continuously or intermittently irradiated with an elongated light beam in the direction of its progress. By doing so, it is possible to obtain heating and slow cooling conditions.

Based on the above principle, as an example of an erasable optical recording/reproducing device, for example, as shown in FIG. A method has been proposed in which two main beams are arranged in a guide groove (Japanese Patent Application No. 59-52607).
issue). In FIG. 3, reference numeral 51 indicates a known guide groove coated with an optical recording material provided on the optical recording disk, and the arrow indicates the position of the optical recording medium relative to the irradiated light spora) M and L. It indicates the direction of movement, and X indicates one point on the optical recording medium. The signal recorded on point X is erased when it passes under the oblong spot (M), and the signal can be recorded and reproduced subsequently on the circular spot. FIG. 4 shows the irradiated light spot M shown in FIG. 3.

An example of the profile of the intensity distribution of L is shown. rm indicates the optical axis of the optical spora) M, and the intensity has a substantially Gaussian distribution centered on the optical axis rm, forming a long original spot along the guide groove 61. Similarly, the original spot L also has a substantially Gaussian distribution centered on the optical axis rl,
A circular light beam is formed on the guide groove 61. therefore,
The signal recorded and given at point Recording and erasing are performed in this manner. The feature of this method is that it is possible to erase records in real time with a very simple configuration, but during erasing it is necessary to expand the laser beam for a long time to maintain the temperature required for crystallization. A major problem is that a laser with a very high output is required to ensure sufficient optical power density.

Also, as is clear from Fig. 4, the point X approaches the melting point only when it approaches 1 m from the optical axis of the erasing light M. Therefore, in order to slowly cool the heated part, it is necessary to (Photospora)
It is necessary to further increase the length of M in the groove direction. This requires a laser with even greater power. Therefore, this method has the disadvantage that the power intensity of the erase spot M and the length of the erase spoiler M cannot necessarily be freely and independently selected.

In order to record a signal immediately after erasing with the optical device shown in FIGS. 3 and 4, an appropriate distance N is required between the optical spoilers M and L. That is, at the point when the point X on the recording thin film passes under the erasing light M and comes under the recording light, the thermal influence of the erasing light M is considerably attenuated, and the temperature drops to a state close to a steady state. It is preferable to have This is because, if point X comes below the original spot L while in a thermally rapid transient state,
The thermal influence of the optical spora) L on the thin film changes significantly depending on the distance between the two optical spots N, and when actually used in the device, depending on the setting variation of the distance N,
Erasing performance, recording sensitivity, and recording performance will change.
Overall, it is necessary to increase the distance from the optical spora M to the optical spot L as shown in FIG. When creating the light spots M and L using the same aperture lens, the shorter the light spot length in FIG. 3, the better, considering the arrangement adjustment of the light spots and lens aberrations.

OBJECTS OF THE INVENTION In view of the drawbacks of the prior art, it is an object of the present invention to provide an erasable optical recording/reproducing device that can lengthen the substantial annealing period without affecting others.

Another object of the present invention is to provide an erasable optical recording and reproducing device that can reduce the influence of erasing energy on recording and reproducing energy and simultaneously erase and record signals in a mutually more thermally stable state. With the goal.

Structure of the Invention The present invention is an erasable optical recording/reproducing device that changes the shape of the light intensity distribution in the direction of relative movement of a source spot that applies heating and slow cooling conditions to a recording thin film. The temperature of the recording thin film is immediately raised to near or above the melting point, and then the recording thin film is slowly cooled in the subsequent part.

1. The present invention provides an erasable optical recording/reproducing device in which a portion of a recording medium scanned by a light spot with a changed shape of intensity distribution is subsequently scanned by a substantially circular writing or reproducing light spot. This allows erasing and recording at the same time.

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

FIG. 6 shows an embodiment of an optical recording/reproducing apparatus in which the present invention is implemented. In the figure, reference numeral 101 indicates a recording/reproducing semiconductor laser that generates light of wavelength λ1, and its output light beam is indicated by l. Reference numeral 102 denotes a condensing lens which condenses the output light of the semiconductor laser having a spread into a substantially parallel original beam.

105r/'i of wavelength λ is transmitted, and the wavelength λ2 described below is transmitted.
f 69′-″ combiner that shoots 4′. 6 is 1-”1
The splitter 107 indicates a reflecting mirror. The light beam l of the semiconductor laser 01 passes through these optical elements and enters the aperture lens 108. The aperture lens 108 narrows down the incident light beam l to guide the guide track 51 on the optical recording disk.
A substantially circular light spot L is created above. Reference numeral 109 denotes an actuator for driving the aperture lens 108, which drives the aperture lens in the optical axis direction in response to surface wobbling of the disk to perform known focus control. The actuator also drives the aperture lens 108 in the radial direction of the disk to perform known tracking control.

In FIG. 6, 103 is a semiconductor laser that generates an original beam m of wavelength λ2, and 104 is a condenser lens thereof. The condenser lens 104 converts the output light beam m of the semiconductor laser 103 into substantially parallel light having an elliptical cross section. This original beam m is reflected by the beam combiner 105, passes through almost the same optical path as the original beam l, and enters the aperture lens 108, and is placed on the same groove 51 as the optical spora L as shown in FIGS. 3 and 4. like,
An original spot M is formed which is elliptical and whose major axis direction coincides with the longitudinal direction of the groove 51 .

In Figure 5, the light reflected by the optical recording disk is the aperture lens 1.
08, Beam splitter 13' through the mirror 107: Enters the resota 106, changes the optical path, and passes through the filter plate 1
11. Here, a filter plate is shown that allows only light l with a wavelength λ1 to pass through, but not light m with a wavelength λ2. 1
12 is a single lens which converts the reflected light beam l into an aperture beam. Reference numeral 113 denotes a reflecting mirror, which functions to block and reflect about half of the light focused by the single lens 112 and guide it toward the photodetector 116.

Reference numeral 114 denotes a two-split photodiode for detecting a focus error signal, which is placed at the focus point of the single lens 112 and detects a conventionally known focus error signal in response to movement of the split light 11. Reference numeral 116 designates a two-split photodiode for detecting a tracking error signal, and detects a conventionally known tracking error signal using reflected light 12 from the mirror 113.

The signal recorded in the guide groove 51 on the optical recording disk is reproduced by a photodetector 114 or 116.

116 is a laser drive circuit that drives the semiconductor laser 103, and the intensity of the oval optical beam (14) M formed on the groove 61 is controlled by a signal applied to the terminal O. 117 is a laser drive circuit that drives the semiconductor laser 101. In the laser drive circuit, the intensity of the approximately circular light spot (L) formed on the groove 61 is controlled by a signal applied to the terminal P. In FIG. 5, 118 changes the distribution of light intensity used in the present invention. An example of inserting a diffraction element is shown below. The diffraction element 118 mainly acts on the guide groove 6 on the disk with respect to the incident light beam m.
It is a diffraction element that gives a diffraction effect in one direction (mainly only in one-dimensional direction), and is used for the purpose of changing the intensity distribution of the erasing light spot on the guide groove 51. A specific example of the function and configuration of this diffraction element will be described below.

FIG. 6a shows the relationship between the diffraction element 118, the aperture lens 108, and the guide groove 51 on the optical recording disk in FIG. 5. Arrow A indicates the direction in which the groove 51 moves.

In this figure, the parallel light m incident on the diffraction element 118 has an intensity of 15'' which is close to a Gaussian distribution, as shown in Figure 6 (1).
.

It has a degree distribution. The light incident on point x1 on the diffraction element 118 is not diffracted and travels straight, for example, at point x on the aperture lens.
Proceed to 1. Also, the light at the center of the optical axis of the incident light m is transmitted through the diffraction element 1
The zero-order light enters the x2 point of No. 18, undergoes diffraction at the x2 point, and travels straight to reach the x2 point on the aperture lens. For example, one dimension X2 is an angle θ in the direction of point x1 on the aperture lens.
1 is subject to diffraction. One of the primary beams x3 of the light incident on the x3 point of the diffraction element 118 is also diffracted at an angle θ2 in the direction of the x1 point on the aperture lens. If the diffraction element is constructed so that θ2>θ1, a light intensity distribution shown in enlarged form in FIG. 6b (2) will be obtained at the focal position of the diaphragm lens. This light intensity distribution has a shape different from the intensity distribution (Gaussian distribution) of light incident on the diffraction element. In the above manner, a new recording area on the disk can obtain erasing light that has a strong intensity part in the part where it enters this light spot (here, we will call it the leading part of the light spot). .

In order to obtain a light spot having such an intensity distribution, as an example of the diffraction element 118, the diffraction angle is changed from point x1 to x3.
A one-dimensional diffraction element that changes linearly toward the radial angle or a one-dimensional diffraction element whose amount of diffraction is controlled is used.

Next, according to FIG. 7, the above light intensity distribution is changed,
Erasing light M [FIG. 7b] created along the guide groove 51,
The difference in effect from the conventional erasing light (FIG. 7C) will be explained.

FIG. 7a shows the shape and arrangement of two light spots (L, M) formed on the guide groove 61 with the device of FIG. 6. Arrow A indicates the traveling direction of the recording medium with respect to the irradiation light spot, and point X indicates one point on the recording medium.

FIG. 7 is a diagram showing an example of the intensity distribution of the light spot along the groove direction according to the present invention, and FIG. 7C is a diagram showing an example of the intensity distribution of the conventional light spot. b by
The effect in the case of a figure will be explained while comparing with the case of a zero figure.

In figures b and c, ml is the point at which the temperature of the recording thin film rises to near the melting point, and m2 is the point at which the temperature of the recording thin film decreases by 17' below the melting point.

In figure b, when a point X on the optical recording medium enters the erasing light M, the temperature rises rapidly at the high-intensity part at the beginning of the optical spora) M, reaching near the melting point at point m1. At m2 point, where the optical power begins to decrease, it becomes below the melting point, and in the interval indicated by dl, it is slowly cooled to gradually cool the time recording thin film required for crystallization, erasing the prerecorded signal. Subsequently, point X is irradiated with recording light in interval W1 and a new signal is recorded. 1, point p and ml in figure 0
There is a considerable amount of optical power in between, and this optical power contributes to the slow temperature rise of the recording thin film, but it does not contribute much to melting, and compared to Figure b, the more effective optical power is wasted. There will be.

In the case of figure 0 in figure 2, the slow cooling section is the d2 interval from point m2 to point q, and if the light intensity of the optical spora) M in figure b is equal to the light intensity of the optical spora) M in figure 0, then figure 0 The amount of light in the d2 section of FIG. Therefore, if you want to further lengthen the slow cooling section d2 for crystallization in Figure 0, you will need to lengthen the length of the light spot M along the groove, and it will be necessary to irradiate even more optical power. The semiconductor laser used as the light source also needs to have a high output power.

Therefore, by creating two light spots with the light intensity distribution shown in FIG. 7 according to the present invention, it is possible to create a device having the following features.

(1) The thin film can be heated to near the melting point at the beginning of the erasing light (the point where any point on the recording medium begins to be irradiated with the erasing light). There is little power loss due to heating, and the corresponding optical power is used for slow cooling. be able to.

(2) In FIG. 7a, if the length of the light spot is constant, method b allows for a much longer slow cooling period than method C, so that reliable crystallization can be achieved.

(3) In figure b, the point that rises to the melting point due to the erasing light, 19.
・] Since the distance between the m19m2 section and the recording/reproducing light can be made larger than in Figure 0, the next signal can be stably recorded after the thermal state of the erasing light M is stabilized.

As a specific example of the diffraction element 118 shown in FIG. , it is conceivable to cause the diffraction to occur in a direction perpendicular to the stripe. Alternatively, a similar function can be obtained by providing a groove on transparent glass, providing a diffraction element whose width and pinch are linearly changed, and causing diffraction to occur in a direction perpendicular to the groove.

Furthermore, these diffraction elements are easy to design when inserted in a place where the light beams are parallel, as shown in FIG. 5, and are easy to assemble and adjust in practice. Therefore, the diffraction element f 2 is preferably inserted into the parallel beam path.

In addition, in Fig. 5, the erasing light source was explained as one semiconductor laser, but it is also possible to erase semiconductor lasers that have multiple light emitting surfaces arranged in an array on one chip and in the direction of the guide groove. When used as a light source, the above-mentioned diffraction element exhibits the same effect, and can obtain an erasing light spot that is oval in the direction of the guide groove and has most of the light intensity at the leading portion.

Since the present invention is configured as described in the detailed description of the invention, the substantial slow cooling period can be lengthened without affecting others.

Furthermore, the influence of erasing energy on recording/reproducing energy can be reduced, and signals can be simultaneously erased and recorded in a thermally more stable state.

[Brief explanation of drawings]

Figures 1 and 2 are diagrams showing the principle of the erasable optical recording material used in the present invention, Figure 3 is a diagram showing the arrangement of the light spot on the optical recording thin film and the direction in which the optical recording thin film moves, FIG. 4 is a diagram showing an example of the intensity distribution of a light spot on an optical recording thin film, and FIG. 6
The figure is an explanatory diagram of the diffraction element in the same embodiment, and FIG. 7 is a characteristic diagram showing the intensity distribution of the light spot on the optical recording thin film according to the conventional method and the present invention. 101...Semiconductor laser for recording and reproduction, 103...
... Semiconductor laser, 118 ... Diffraction element. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figures (Figure 3, Figure 4, Figure 5)

Claims (3)

[Claims] (1) A light spot forming means for forming a source spot for erasing at least one recorded signal on a recording medium or for changing an amorphous state in a recording thin film of the recording medium to a crystalline state; The light spot has a substantially elliptical shape having a major axis with respect to the direction of relative movement between the recording medium and the original beam on the recording medium, and the portion of the light spot where the light intensity is maximum is relative to the ellipse. An erasable optical recording/reproducing device characterized in that it is located at the leading portion in the direction of movement. (2) The light spot forming means includes one laser light source, a diffraction means for diffracting the output light of the laser light source in the direction of relative movement between the recording medium and the original spot, and means for focusing the diffracted light into a minute light beam. An erasable optical recording and reproducing device according to claim 1, having the following. 2”-7′ (3) The light spot forming means includes a laser array having a plurality of light emitting sources, means for arranging the laser array so as to form an image on the recording medium along the scanning direction of the light spot, and Erasure according to claim 1, comprising a diffraction means for diffracting output light in a direction in which a light spot scans on a recording medium, and means for focusing the light passing through the diffraction means into a minute light beam. Possible optical recording/reproducing device 0(4) means for forming a light spot having an oval shape in the direction of relative scanning of a recording medium and having a portion with high light intensity at the leading portion thereof, and the light spot 1. An erasable optical recording and reproducing apparatus, characterized in that the erasable optical recording and reproducing apparatus comprises means for subsequently scanning a portion of a recording medium scanned by a substantially circular writing or reproducing light spot.