JPS61928A - Optical reversible recording and reproducing device - Google Patents

Abstract

PURPOSE:To shorten the length of erasing spot light and improve stability by irradiating recording spot light at power equal to or higher than reproducing power and lower than recording power at the time of erasing, and prolonging further slow cooling time of erasing spot light. CONSTITUTION:Reference voltage VSW2 is selected to output erasing auxiliary recording power equal to or higher than reproducing power at the time of reproduction and lower than recording power at the time of recording as light output power of a semiconductor laser 101 for recording/reproducing at the time of erasing. That is, reference voltage VSW2 of VSW1 (whern reproducing)<=VSW2< VSW3 (when recording) is applied to a driving circuit 126 at the time of erasing, and light power of laser 103 for erasing is supplement by light power of a laser 101 for recording/reproducing. This, slow cooling time if made longer, and stable erasing condition can be obtained even by a short erasing laser spot light.

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 11t in diameter using a lens etc.
Erasable optical recording that can repeatedly record and reproduce signals by narrowing the light beam to a microscopic light beam of about m and irradiating it onto an optical recording medium, recording and reproducing signals at high density, and erasing the once recorded signals 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 crystalline state is indicated by C, and the recording thin film in the crystalline state has a high 1 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 FIG. 1 is locally raised to near the melting point, and when that portion is slowly cooled, it becomes the crystalline state C. On the other hand, if the temperature of the recording thin film in the crystalline state is locally burnt to near the melting point and then the area is rapidly cooled, it becomes an amorphous state A.

Figure 2 shows the temperature and rapid 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 with a diameter lx 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. This light spot L is hereinafter referred to as a recording spot light.

On the other hand, as shown in Fig. 2, an optical spora M with a long diameter m elongated in the direction in which the recording medium advances (arrow) is placed on the recording medium.
If the intensity of optical spora) M is increased continuously or intermittently by using a laser, etc., the heated part of the recording thin film will be cooled much more slowly than in the case of a, and temperature increasing and slow cooling conditions will be obtained. be able to. This optical spora) M makes it possible, for example, to erase a signal. Hereinafter, this optical spora) M will be referred to as erasure spot light.

FIG. 3 is a diagram showing temporal thermal changes in the area irradiated by both spotlights, with the horizontal axis representing time and the vertical axis representing temperature.

In Figure 3a, the temperature rise time due to the erasing spot light is 'E1
'The slow cooling time is tE2-b, the heating time by the recording spot light is twl, and the rapid cooling time is tW2. In the same figure, the erasing condition is greatly influenced by the slow cooling time tE2; the recording condition is greatly influenced by the rapid cooling time tW2, and the difference between the two conditions is tE2
The larger the difference between tW2 and tW2, the clearer the difference, which makes it easier to design the recording thin film and enables stable erasing and recording. In order to increase the difference between 'E2 and tW2, the larger the long axis m of the erasing spot light is compared to the diameter l of the recording spot light, the larger the difference becomes. However, the long axis mx of the erased spot light
The longer it is, the more difficult it becomes to line up the recording spot light and the erasing spot light M in a straight line on the same track. Therefore, from the viewpoint of stability of the arrangement of both spot lights, the shorter the extinction spot light M is, the better.Conversely, from the viewpoint of the design of the recording thin film, the erasure spot light M The longer the better.

Generally, when the recording medium is a disk, the circumferential speed becomes faster toward the outer circumference of the disk compared to the inner circumference. However, since the length mx of the erasing spot light is constant, the annealing time tE2 becomes relatively shorter toward the outer periphery, and the erasing conditions differ greatly between the outer and inner peripheries of the disk. For example, the diameter Di (10 crn) of the innermost circumference of the disk and the diameter D 0 (30 crn) of the outer circumference
crn) is 3 times, the length mx of the erasing spot light is relatively 3 Am at the outer circumference compared to the inner circumference! Therefore, the slow cooling time becomes considerably shorter. In this way, it becomes difficult to design a recording thin film that has stable erasing conditions with sufficient margin under conditions where the annealing time differs greatly between the outer and inner peripheries.

Purpose of the Invention The present invention has been made in view of the above-mentioned problems.The present invention is an invention that has been made in view of the above-mentioned problems. Another object of the present invention is to provide a stable optical reversible recording/reproducing device by increasing the length of the erasing spot light and shortening the length of the erasing spot light. The purpose of the present invention is to provide a new optical reversible recording and reproducing device which allows the cooling time to be almost constant regardless of the outer or inner circumference by changing the irradiation power f of the recording spot light, and which facilitates the design of the recording thin film. And so.

Structure of the Invention The present invention provides for the erasing spot light to temporally precede the recording spot light on the same track, and for the recording spot light to be at a distance such that the recording spot light has a thermal effect on the area irradiated by the erasing spot light. Both spot lights are arranged, and when erasing, the recording spot light is irradiated with a power that is equal to or higher than the reproduction power and lower than the recording power,
It is configured so that the annealing time of the erase spot light is longer.

In addition, by controlling the irradiation power of the recording spot light so that it becomes thicker toward the outer periphery of the disk where the circumferential speed becomes faster, the actual slow cooling time is approximately I try to make it the same.

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, a transparent material is used as the base material 6o, and grooves 51 having a width W, a depth d, and a rack pitch p are formed thereon in a spiral or concentric shape. A recording thin film 62 having a thickness t is formed thereon by vapor deposition or other methods, and a protective layer 63 is provided thereon. The groove 61 is designed to have a depth d9 and a width W so that it functions as an optically detectable guide track for the laser irradiation light 54. This groove allows the irradiation light 64 to record or reproduce a signal along a specific groove.

FIG. 5 shows an embodiment of the present invention.

In the figure, reference numeral 101 indicates a 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 magnification of 9 into a substantially parallel light beam.

Reference numeral 106 indicates a light beam combiner that transmits light of wavelength λ1 and reflects light of wavelength λ2, which will be described later. Reference numeral 106 indicates a beam splitter, and reference numeral 107 indicates a reflecting mirror. The light beam l of the semiconductor laser 101 passes through these optical elements and enters the aperture lens 108.
incident on . The aperture lens 108 focuses the incident light beam l
is narrowed down to create a substantially circular recording spot light on the guide track 51. 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. Further, in order to perform a known tracking control on a guide track that is inherently eccentric, the aperture lens 108 is driven in a direction perpendicular to the incident optical axis and the guide track.

In FIG. 5, 103 is a semiconductor laser that generates a light beam m of wavelength λ2, and 104 is a condenser lens. The light beam m is reflected by the beam combiner 105, passes through almost the same optical path as the light beam l, and enters the aperture lens 108. 6 shows two light spots L having different wavelengths formed on the groove 61, and the mutual relationship between M and the groove 61, as described above. Shown enlarged.

Optical spora) L and M are located close to each other on the same guide groove, and are arranged so that the erasing spot light M precedes the groove 61 which advances at a speed V, and is spaced apart within a range where the recording spot light has a thermal effect on the erasing spot light. be done.

The light reflected by the optical disk passes through the aperture lens 1o8° mirror 107, enters the beam splitter 106, is reflected by the beam splitter 106, and passes through the filter plate 111.
incident on . Here, a filter plate is shown that allows only the light of wavelength λ1 to pass through, but not the light of wavelength λ2. 112 is a single lens which converts the reflected light beam l into aperture light. 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 the light toward the photodetector 116. Reference numeral 114 indicates a two-split photodiode for detecting a focus error signal, which is placed at the focus point of the single lens 112 and captures the split light 11.
A conventionally known focus error signal is detected in response to the movement. Reference numeral 116 designates a two-split photodiode for detecting a tracking error signal, which detects a conventionally known tracking error signal by using the reflected light 12 from the mirror 113. Also, it reproduces the signal recorded in the groove 61 on the optical disk. The signal is obtained from a photodetector 114 or 115.

The amplifier 118 amplifies the difference signal between each element of the divided photodiode 115, and generates a tracking error signal at the terminal TR. The amplifier 129 is a circuit that amplifies the sum signal of each output of the divided photodiodes 116, and is connected to the terminal P.
A playback signal is output to B. The amplifier 119 is a circuit that amplifies the difference signal between each element of the divided photodiode 114, and outputs a focus error signal to the terminal FD.

The recording spot light is a small, approximately circular spot, and is used for recording (amorphizing) or reproducing a signal along one guide track 61. It is also used to detect control signals such as focus control and tracking control. On the other hand, the erasing spot light M having a long axis in the tangential direction of the guide track is used for erasing (making it amorphous) by applying heating and slow cooling conditions to the optical disc.

117 is a recording spot light power control circuit for controlling the power of the recording spot light, and 116 is an erasing spot light power control circuit for controlling the power of the erasing spot light.

FIG. 7a shows a configuration example of a recording spot light power control circuit used in the present invention, and FIG. 7b shows a configuration example of an extinction spot light power control circuit. Since both circuits basically have almost the same configuration, they will be explained at the same time. 1.01 is a semiconductor laser for recording/reproduction, 103 is a semiconductor laser for extinction, 120, 121
is a pin diode built into each semiconductor laser, and monitors the semiconductor laser power emitted from the rear of each semiconductor laser. 122 and 123Fi reference voltage generation circuits output vsw and vsE. The reference voltage vsw.

vsE is varied depending on, for example, the position in the radial direction of the disk that is irradiated with both spot lights. 124° and 126 are differential width amplifiers, and output voltages vPw and vPE from both bin diodes 120 and 121 and the reference voltage generation circuit SW,
Output each difference with vsE. 126° and 127 are both laser drive circuits, always vPw-VSW, vPE"vSE
A switching circuit 0128 controls the power by supplying a current to each laser so that the power is controlled at high speed according to the signal to be recorded applied to the terminal Q, and modulates the recording laser power. FIG. 8 shows the optical output power Pw1 of the bidirectional conductor laser during reproduction, erasing, and recording. Pw2゜PW3・PE1・PE2 and・Reference voltage vSW1・VSW
2.78w3. ■sE1. The relationship between vsE2 is shown.

In the figure, during erasing, the optical output power of the semiconductor laser for recording/reproducing is outputted as erasure auxiliary recording power Pw2, which is equal to or higher than the reproduction power Pw1 during reproduction, and lower than the recording power Pw3 during recording. The reference voltage ■sw2 is selected. In other words, when erasing, vsw
Add the reference voltage ■sw2, which is l x 78w2 x 78w3,
The optical power of the recording/reproducing laser is configured to supplement the optical power of the erasing laser.

In addition, in Fig. 8, the time difference between the rise and fall of both laser beams is t = t = since both spot lights are placed a distance X (Fig. 6) apart, and the speed of the disk is V.
This time difference is provided because it is necessary to irradiate the erasing spot light M earlier by X/V.

Figure 9 is a diagram to explain how the recording/reproducing laser thermally assists the quenching laser.
When the optical output Pw2 of the reproducing semiconductor laser 1o1 is 2w2-0. When b, 1l-t, Pw1-PW'2 (
= reproduction power), c indicates the difference in slow cooling time (tE1 to (E3)) when Pwl<2w2 x 2w3 is selected. The horizontal axis is time, and the vertical axis is temperature. As can be seen from the figure, if the erasing auxiliary recording power is the same as or higher than the reproduction power and lower than the recording power during erasing, and the 1o1 outputs it, the annealing time will be longer and the annealing time will be shorter. Even with the erasing laser spot light M, stable erasing conditions can be obtained.

On the other hand, as can be seen from FIG. 9, the slow cooling time can be varied depending on the strength of the erasing auxiliary recording power. Therefore, if only the erasing spot light is used, the annealing time becomes shorter toward the outer periphery of the disk, so by increasing the erasure auxiliary recording power of the recording spot light, the shortened annealing time can be corrected.
It is possible to obtain a substantially constant slow cooling time regardless of the inner or outer circumference of the disk.

In Figure 10, the strength of the erasing auxiliary recording power of the recording spot light (indicated on the vertical axis) is expressed as the inner and outer periphery of the disk (indicated on the horizontal axis).
This shows how it changes depending on the situation.

In order to vary the erasure auxiliary recording power, information on the radial position of the disk irradiated by both spot lights is applied to the terminal P in FIG. 7, and the reference voltage sE is varied.

As described in detail, according to the configuration of the present invention, even if the length mx of the erasing spot light is shorter than that of the conventional art, a long annealing time can be obtained, and the two spot lights can be aligned in a straight line. A double spot light arrangement that is easy to line up and is stable against environmental changes such as temperature can be obtained. Even if the length mx of the erasing spot light is still constant, by varying the optical power of the easily variable recording spot light, it is possible to eliminate the difference in annealing time caused by the difference in peripheral speed between the outer and inner circumferences of the disk. , an erasing condition that is clearly different from the recording condition and always constant can be obtained, and the design of the recording thin film is also facilitated.

[Brief explanation of the drawing]

Figure 1 is a diagram showing a model of the transition between an amorphous state and a crystalline state, and Figure 2 is a diagram showing an example of a light spot that realizes rapid heating and cooling conditions and slow heating and cooling conditions on a recording thin film. , 3rd
The figure shows temporal thermal changes during gradual heating and cooling and rapid heating and cooling, Figure 4 is a radial cross-sectional view of an optical disc having an optical guide track used in the present invention, and Figure 5 is a diagram showing one example of the present invention. FIG. 6 is a block diagram showing the embodiment; FIG. 6 is a diagram showing the arrangement of both spot lights on the groove track; FIG. 7 is a circuit diagram showing an embodiment of the power control circuit for both lasers used in the present invention; FIG. Figure 9 shows the power change in each state of both laser powers.
The figure shows how the slow cooling time changes according to the present invention, and FIG. 10 shows how the intensity of the recording spot light changes in the radial direction of the disk. 61...Groove track, 52...Recording medium, 101...Recording/reproducing laser, 103...
...Erasing laser, 116... Erasing laser drive circuit, 117... Recording/reproducing laser, L... Recording spot light (first minute Spot light), M...Erasing spot light (second minute spot light), Pwl, 2w2, 2w3...Intensity of recording spot light during playback, erasing, and recording, tEl”
Wl...""Temperature rising time, tE2-tE4...
- Slow cooling time, tW2...Quick cooling time. Figure 1 Figure 2 [ Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 (of (1))

Claims (3)

[Claims] (1) A first minute spot light focused on a recording medium causes a heating and rapid cooling effect on the recording medium to record a signal, and is arranged substantially in a straight line on the same track as the first minute spot light, and At least one or more second minute spot lights placed temporally ahead of the irradiation area of the first minute spot light are placed at a distance from a range that exerts a thermal influence on the irradiation area of the first minute spot light, causing a temperature raising and slow cooling effect on the recording medium. The apparatus performs erasing by giving a , wherein the first minute spot light simultaneously irradiates the area to be irradiated and erased by the second minute spot light,
An optical reversible recording and reproducing apparatus characterized in that the intensity of the first minute spot light at that time is lower than the intensity of the first minute spot light at the time of recording. (2) The first minute spot light simultaneously irradiates the area on the recording medium to be irradiated and erased by the second minute spot light, and the intensity of the first minute spot light at that time is the signal reproduction higher than the intensity of the first minute spot light at
2. The optical reversible recording and reproducing apparatus according to claim 1, wherein the intensity is lower than the intensity during signal recording. (3) The area on the recording medium to be irradiated and erased by the second minute spot light is simultaneously irradiated with the first minute spot light, and at that time, the intensity of the first minute spot light is equal to the area on the recording medium that is to be erased. 3. An optical reversible recording/reproducing apparatus according to claim 1 or 2, wherein the optical reversible recording/reproducing apparatus changes according to the traveling speed of the optical disc.