JPS618739A - Erasable optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To equalize recording conditions to record always signals of the same quality by increasing the power of a recording light spot in comparison with that for simultaneous easing and recording when signals are recorded only with the recording light spot and raising the temperature of a medium to the same value. CONSTITUTION:For the purpose of equalizing the maximum temperatures of the medium for simultaneous erasing and recording and for recording only by the recording light spot, a recording laser power PW2 for recording only by the recording light spot is made higher than a recording laser power PW1 for simultaneous erasing and recording. A voltage VSW1 and a voltage VSW2 are set in accordance with powers PW1 and PW2 respectively and a voltage VSW0 is set in accordance with a reproducing power to constitute a reference voltage generating circuit 29. The laser power and the variance of temperature given to the recording medium in case of recording only by the recording light spot are shown by dotted lines in figures, and maximum temperatures of the recording medium for simultaneous erasing and recording and for recording only by the recording light spot are equalized to a value Ta; and thus, signals of the same quality are always recorded because of the same recording conditions.

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.
Erasable optical recording and reproducing technology 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. It is related to the 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 that repeatedly utilizes 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 4.

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 (q), and the recording thin film in the crystal state has a high reflectance and a low transmittance.

This is a recording thin film whose optical density can be changed reversibly with the amorphous state shown in Fig. 1.If the temperature of the recording thin film, which is in the amorphous state C shown in Fig. 1, is raised locally to near the melting point and then slowly cooled, the recording thin film changes into the crystalline state (
It becomes q. On the other hand, if the temperature of a recording thin film in a crystalline state is locally raised to near the melting point and then the area is rapidly cooled, it becomes an amorphous state.

FIG. 2 shows one specific method for realizing rapid heating and cooling conditions and slow heating and slow cooling conditions on the recording thin film.

The 21st Qj a indicates a substantially circular minute spot L formed by a laser or the like on a track 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. This optical spot L enables recording of signals, for example.

On the other hand, as shown in Fig. 2, if an elongated light spot M is formed on the track in the direction in which the recording medium advances (arrow) using a laser or the like, and the intensity of the light spot M is increased continuously or intermittently. In this case, the heated portion of the recording thin film is 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 applying a minute circular beam to a relatively advancing recording thin film, temporally modulating its intensity, and irradiating it with pulsed light, heating and cooling conditions (for example, recording) can be obtained. Temperature raising and gradual cooling conditions (for example, erasing) can be obtained by continuously or intermittently irradiating the advancing recording thin film with a light beam elongated in the direction of its travel.

If we try to realize so-called simultaneous erasure, in which a track is erased and new information is immediately written to the track using both of the light spots, the light spots will move at a speed of V in the direction of the arrow, as shown in FIG. 2C. .

The light spots L-M (hereinafter referred to as erasing light spots) which are arranged close to each other in a straight line on a recording track that advances in a straight line are arranged so as to precede a substantially circular light spot (hereinafter referred to as recording light spots). Ru. If the track is to be used effectively and not wasted, it is desirable that the distance X between the two light spots be as short as possible. However, if the distance between the two light spots becomes short, for example, when recording a signal with the subsequent recording light spot L, the recording light spot will be affected by the heat of the preceding erasing light spot M. Figures 3a and 3b show temperature changes on the track and will discuss the effects mentioned above. The solid line in FIG.
(hereinafter referred to as simultaneous erasure), that is, Fig. 2C
Point X on the medium is spot;/toM.

The laser power given to point X and the temperature change at point X when passing through L are shown. Ta indicates the maximum temperature at that time.

On the other hand, the solid line in Section 3(3)b shows the laser power applied to point X and the temperature of point Show change. In this case, a temperature change of only the recording light spot L by rapid heating and cooling can be obtained. Tb indicates the maximum temperature. T
Comparing a and Tb, when erasing simultaneously, the erasing light spot M
In the conventional method in which the recording power Pw1 is equal during simultaneous erasing and during recording using only the recording light spot, Ta>Tb is inevitable, since the temperature is increased and rapidly cooled by the recording light spot (L) during the temperature increase and gradual cooling by the recording light spot.

In this way, the recording conditions during simultaneous erasing in which the erasing and recording light spots are placed close to each other and the recording conditions using only the recording light spot are thermally different, making it difficult to design the recorder film and This results in a difference in the quality of the recorded signal (eg, reflectance, recording focus length, etc.).

Purpose of the Invention The present invention enables signal recording of the same quality at all times, even when erasing simultaneously with a preceding erasing light spot and recording a signal with a recording light spot, or when recording a signal with only a recording light spot. The purpose is to

Structure of the Invention The present invention is configured to increase the power of the recording light spot when recording a signal using only the recording light spot than during simultaneous erasing to raise the temperature of the medium to the same temperature, and to adjust the recording conditions. This allows a signal of the same quality to be recorded at all times.

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
,) Grooves 2 with a rack 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 d so as to function as an optically detectable guide track for the laser irradiation light 6.
1 width W is designed. This groove allows the irradiation light 6 to record or reproduce a signal along a specific groove.

FIG. 6 shows an embodiment of the present invention.

In the figure, 6 indicates a semiconductor laser that generates light of wavelength λ1, and its output light beam is indicated by l. Reference numeral 7 denotes a condensing lens, which condenses the output light of the semiconductor laser 6 having a magnification of 9 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 l 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 L to create a substantially circular recording light beam L on the guide track 2. 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. Further, in order to perform the known trunking control on the guide track which is originally eccentric, the aperture lens 11 is driven in a direction perpendicular to the incident optical axis and the guide track.

In FIG. 5, 13 is a semiconductor laser that generates a light beam m of wavelength λ2, and 14 is a condenser lens.

The light beam m is reflected by the beam combiner 6, passes through almost the same optical path as the light beam l, and enters the aperture lens 11, and is formed in an elliptical or oblong shape on the same guide track 2 as the recording light spot (L). An erasing light spot M whose major axis direction coincides with the longitudinal direction of the guide track 2 is formed.

FIG. 6 shows two light spots 7) L, M and the guide track 2 formed on the guide trunk 2 with different wavelengths as described above.
It shows an expanded view of the interrelationships between the two.

The light spots) L and M are located close to each other on the same guide trunk, and are arranged so that the erasing light spot) M is in front of the guide track 2 which is moving at a speed v0.

The light reflected by the optical disk passes through the aperture lens 11° mirror 10, enters the beam splitter 9, is reflected by the beam splitter 9, and enters the filter plate 15. Here, a filter plate is shown that transmits only the light of wavelength λ1 and does not transmit the light of wavelength λ2. 16 is a single lens which converts the reflected light beam l into apertured light. Reference numeral 17 denotes a reflecting mirror, which serves to block about half of the light focused by the single lens 16, reflect it, and guide the light toward the photodetector 18.

Reference numeral 19 denotes 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 11. 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 12 from the mirror 17.

Further, a reproduced signal of the signal recorded on the guide track 2 on the optical 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.

Recording light spot) L is a nearly circular minute spot, which is used for recording (amorphization) or reproducing signals along the guide track 2, and for detecting control signals such as focus control and tracking control. Also used for On the other hand, the erasing light spot (M) having a long axis in the tangential direction of the guide track is used for erasing (crystallization) by applying heating and slow cooling conditions to the optical disk.

23 is a recording light spot power control circuit for controlling the power of the recording light spot L; 24 is the erasing light spot)
This is an erase light spot power control circuit that controls the power of M.

FIG. 7a shows an example of the configuration of a recording light spot power control circuit used in the present invention, and FIG. 7b shows an example of the configuration of an erasing light spot power control circuit. Since both circuits basically have almost the same configuration, they will be explained at the same time. 6 is a semiconductor laser for recording/reproduction, 13 is a semiconductor laser for erasing, and 25 and 26 are visidiodes built into each semiconductor laser, which monitor the semiconductor laser power emitted from the rear of each semiconductor laser and calculate the power. It generates currents IP'W and PE which are proportional to .

27.28 is a current-voltage converter, IPw.

029 and 30 converting PE into voltages vPw and vPE generate appropriate reference voltages SW and vSE in accordance with information inputted to the reference voltage generation circuit. Specifically, the 'reference voltage generation circuit 29 outputs vswl when inputs B and E are H'', outputs 78w2 when input B is 'L'' and E is II HII, and input E is 'L'. ”, it outputs vswo. On the other hand, the reference voltage generating circuit 3Q outputs the input F when the input F is “HI”.
It outputs vsEl when it is I, and does not output when it is n L II. v8wo, ■8w1. v8w2°vsEl can be set arbitrarily. 31. 32 is a differential amplifier, in which the voltages vPw and vPE from the pin diodes and the reference voltage vsw,
Output each difference with vsE. 33 and 34 are both laser drive circuits, so that the output of each differential amplifier 31 and 32 is 0, that is, always 1■PW-vSWpvPE=
Power control is performed by applying current to each laser so that vSE is achieved. Therefore, recording/recording according to the reference voltages vsw and vsE
Reproducing laser power and erasing laser power are output. 3
5 is a switching circuit which switches at high speed according to the signal applied to Q and modulates the recording laser power. 3
6 is a delay circuit. A record command signal is input to A, and a simultaneous erasure command signal is input to B.

With the above configuration, FIG. 8 shows the relationship among the input signal, reference voltage, and laser power during reproduction, simultaneous erasure, and recording to one unallocated track. Here, when simultaneously erasing
In order to equalize the maximum temperature reached by the medium when recording with only the recording light spot, the recording laser power Pw2 during recording with only the recording light spot should be made larger than the recording laser power PW1 during simultaneous erasing. Therefore, set vswl corresponding to PWl and vSW corresponding to 2w2.
2 and set vSWo corresponding to the reproduction power to configure the reference voltage generation circuit 29.

With the above configuration, the laser beam and temperature change applied to the recording medium during recording with only the recording light spot will be as shown by the dotted line in Figure 3, and the difference between simultaneous erasure and recording with only the recording light spot will be as shown by the dotted line in Figure 3. Since the maximum temperature (Ta) reached by the recording medium is the same during recording and the recording conditions are the same,
Signal recording of the same quality is always possible.

In FIG. 8, the time difference t between the rise and fall of both the recording and erasing laser beams is t=x/vo because both laser beam spots are placed apart by a distance X (FIG. 6).
This time difference is provided because it is necessary to irradiate the erasing light spot as quickly as possible.

Effects of the Invention As described above, according to the present invention, recording conditions can be made equal between simultaneous erasing where there is a thermal influence of the preceding erasing light spot and recording with only the recording light spot which is not affected. Therefore, it is possible to always record signals with the same quality, and the design of the recording medium thin film is also facilitated.

[Brief explanation of the drawing]

FIG. 1 is a diagram modeling the transition between an amorphous state and a crystalline state, and FIG. 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 medium. Fig. 3 is a diagram showing changes in laser power applied to the medium and temperature changes of the medium during simultaneous erasing and recording with only the recording light spot, and Fig. 4 shows the optical guide track used in the present invention. 5th radial cross-sectional view of an optical disc having
Figure 6 is a block diagram showing one embodiment of the present invention, Figure 6 is a diagram showing the arrangement of the recording and erasing light spots on the guide trunk, and Figure 7 is a diagram showing an embodiment of the laser scanner control circuit used in the present invention. The block diagram shown in FIG. 8 is a diagram showing changes in both laser powers in each state. 2... Guide track, 6... Mark/recording/reproduction laser, 13... Erasing laser, L...
Recording light spot, M... Erasing light spot, Pw
l, 2w2... Recording laser power during simultaneous erasing and recording using only the recording light spot, vswl, 78w
2...Recording laser reference voltage during simultaneous erasing and recording using only the recording light spot. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure [Fir 1 Figure 3! 1 ((1) (b) Figure 4 Figure 5 Figure 7
10A(b) (a)

Claims (1)

[Claims] Information is thermally recorded by a first minute light spot focused on the recording medium, and an aperture is placed on the same track as the first minute light spot and ahead of the first minute light spot. The power of the first minute light spot in the case of recording with the first minute light spot while erasing with the second minute light spot is Also, an erasable optical recording/reproducing device characterized in that the erasable optical recording/reproducing device is configured to increase the power of the first minute light spot when recording only with the first minute light spot.