JPS60127535A - Optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To obtain a high-quality recording/reproducing signal of an uniform duty ratio even in case of a semiconductor laser having a relatively low output by changing the length in the time base direction of a recording signal in accordance with the inside or outside circumference of a disc by a time base varying circuit and inputting this signal to a semiconductor laser driving circuit. CONSTITUTION:The recording signal is inputted from a terminal A to a time constant varying circuit 17. Meanwhile, the reflected light of a laser light projected onto a disc 9 is detected by a photoelectric transducer 8, and an address signal recorded on the disc 9 is extracted and formed by an address signal forming circuit 15 and is read by an address signal reading circuit 16, and a block division (inside circumference, middle circumference, or outside circumference) signals J1-J3 in the diametral direction of the disc 9 is sent to the circuit 17, and the signal obtained by changing the length in the time base direction of the recording signal in accordance with this signal is sent from the circuit 17 to a semiconductor laser driving circuit 1. Thus, the recording/reproducing signal of a uniform duty ratio is obtained without controlling the power even in case of a semiconductor laser having a relatively low output.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a disc-shaped record carrier (hereinafter referred to as a disc) coated with a light-sensitive recording material, as seen in the example of a video disc, in which a light source such as a semiconductor laser is used. The present invention relates to a device that performs high-density recording and reproduction of signals such as video signals and digital signals as irregularities or changes in shading by focusing a beam to a minute light of about 1 μm.

Conventional Structures and Problems In recent years, optical video discs have become generally well known among the above-mentioned technologies as devices that only reproduce signals recorded in advance at high density.

Furthermore, the above-mentioned recording technology is used in an apparatus for making master discs of video discs.

Recently, optical recording and reproducing apparatuses have been attracting attention for recording and reproducing video signals, audio signals, digital signals, etc. by coating a disc with the above-mentioned photosensitive recording material.

In an optical recording/reproducing device, a signal is recorded by irradiating the recording thin film of the disk with a laser beam or the like to melt and evaporate the light irradiated portion of the recording thin film, or by changing the reflectance or transmittance. Recording cannot be performed. That is, it is common practice to thermally utilize the energy of laser light to change the optical properties of a recording material.

The optical recording/reproducing apparatus as described above will be explained below using the drawings.

The first country shows a conventional example of an optical recording/reproducing device. In FIG. 1, a recording signal such as a video signal or a digital signal is input to terminal A. Reference numeral 1 denotes a semiconductor laser drive circuit that drives a semiconductor laser 2 that generates a light beam to be recorded on a disc. C surrounded by a dotted line indicates the optical nozzle and the semiconductor laser 2. Lens 3. Beam splitter for splitting the light beam4. Tracking mirror for towing and tracking control 5. It is composed of a lens 6 incorporated in a voice coil etc. for performing focus control etc., a lens 7 for converging reproduction light, etc.

Reference numeral 8 denotes a photoelectric converter for receiving reflected light from the disk 9 and converting it into an electric signal in order to obtain a reproduction signal. The same circular and spiral guide tracks 10 are formed on the disk 9, and each guide track 10 is provided with a unique address signal in advance. Also, the disk 9 is connected to the motor 1
1 rotates at a constant speed, such as 1800 rpm. 13
is a transfer motor, which moves the disk 9 in the radial direction of the track by means of a transfer shaft 12. Reference numeral 14 denotes a preamplifier, which outputs the reproduced signal converted into electrical arrays by the photoelectric converter 8 from amplification l to output terminal B.

When recording with the above optical recording/reproducing device,
In the semiconductor laser drive circuit 1, the light beam outputted from the semiconductor laser 2 is modulated by the intensity of the light using the recording signal inputted from the terminal A, and outputted, and the light beam is narrowed down to a minute beam of about 1 μm by the optical head section C. known focus control,
Tracking control is performed to irradiate the disc 9 and perform recording.

When performing reproduction, a weak light beam is output from the semiconductor laser 2 by the semiconductor laser drive circuit 1, and is irradiated onto the disk 9 with focus control and tracking control as in the case of recording, and the reflected light is split by the beam splitter 4 and transmitted through the lens. The light is received by a photoelectric converter 8 via a photoelectric converter 7, amplified by a preamplifier 14, and outputted from an output terminal B as a reproduced signal.

FIGS. 2 and 3 show configuration diagrams of the disk 9. As shown in FIG.

FIG. 2(A) shows a top view of the disk 9. FIG. Guide tracks 1o are preliminarily provided on the disk 9 in a concentric or circular shape (see FIG. 2 (~ shows concentric guide tracks as an example)). An address signal board is pre-formed.In general, the address signal board on the outer periphery is numbered 1, 2, 3, etc. from the inner periphery.
They are arranged in order like...-. Recording was carried out at 5% on the guide track, Tuk 1○, and an enlarged view of the recording pit is shown in FIG. 2(B). In Figure 2 (B), 1O
is a guide track, and the black dot d therein indicates an example of the recording pitch.

FIG. 3 shows a radial cross-sectional view of the disk 9.
1. The photosensitive recording material described above is coated thereon to form a recording portion q. 108.10b.

1Oo ・・・・・・1○ indicates the guide tiger, 7ri, and e indicates the groove. Each guide track 1o has a width W
(e.g. W=o, s μm) Pitch P (e.g. P-2,
6 μm) and a depth δ (for example δ-0.7p). An example of pits recorded on the guide track is shown in d.

FIG. 4 1 shows a semiconductor laser drive circuit 1 with a semiconductor laser 2.
An example of the output characteristics when driven is shown below. The characteristic curve is the forward current (I) flowing through the semiconductor laser and the emission output power (
P) shows the relationship. Forward current ('I) is equal to threshold current (I
th), it enters the laser emission region and a light emission output power approximately proportional to the current value is obtained.

Figure 4 (The gradient indicates the recording signal input from terminal A in Figure 1, and the recording signal modulates the forward current (I) with (IAC) centered on (ID). Figure 4 (Fl) , when the above modulation current (IAC) is input, the semiconductor laser 2
An example of the output light is shown below. The output power (PD) is the forward current (ID), and the output power (PAc) is the modulation current (IAc). As shown in FIG. 4 (F'), a light beam modulated in the range of (PAc) centered on (PD) is output from the semiconductor laser by a signal inputted to terminal A in FIG. 1. Figure 4 (at the output power of Pi (P
p, )(d indicates peak power, and (PB) indicates bias power.

In the device shown in Figure 1, when recording a signal on disk 9, d
1. The output light of the semiconductor laser 2 is modulated as shown in FIG. 4(F), and the optical head section C narrows this down to a very small amount of light and irradiates it onto the disk. Regarding the relationship between this irradiation light and the recorded pits on the disk, a recorded pit is formed at a portion tl, and an unrecorded portion is formed at a portion t2.

When reproducing a signal recorded on a disk, the forward current is set to (IL) and a weak output power (PL) is emitted.

FIG. 5 shows the relationship between the modulated/output light output from the semiconductor laser, the pits formed on the disk, and the reproduction signal reproduced from the disk.

Figure 5 (-) shows the semiconductor laser 2 shown in Figure 4 (F').
shows the output light of (PP) is the peak power, and recording pits are formed at this portion. PD is DC power for modulation, and PB is bias power, which enhances the residual heat effect of the recording material. Recording is performed in the section 11.13.16 of FIG. 5(a) to form recording pits as shown in FIG. 6(b)(a). Also t2. In the section t4, (
An unrecorded section shown in b) is formed. To play,
Recording pattern 1 as shown in Fig. 6 Φ). The difference in the amount of reflected light between (a) and the unrecorded section (b) is received by a photoelectric conversion device (8 in FIG. 1) to obtain a reproduced signal as shown in FIG. 5(c).

As described above, when recording signals on a disk that rotates at a constant rotational speed, the circumferential speed varies depending on whether the recording location is on the inner or outer circumference of the disk, for example. t, that is, on the outer circumference, the circumferential speed is faster than on the inner circumference due to the larger radius during rotation. This means that, as described above, when recording signals using the thermal effect of laser light, more irradiation laser power (recording energy) is required on the outer circumference than on the inner circumference. For example, if recording is performed on the inner circumference with the recording power required for the outer circumference, high-quality recording and reproduction cannot be achieved because the recording pins and the recording material itself are deformed. Furthermore, when recording is performed on the outer circumference with the optimum recording power on the inner circumference, good recording pits cannot be formed due to insufficient power.

Therefore, in general, the laser power irradiated to the disk is
The recording power is controlled so that the recording power is greater at the outer circumference than at the inner circumference, depending on the location of recording, that is, the disk diameter. FIG. 6 shows an example of a recording nozzle control method for a typical disk diameter. In Figure 6, the horizontal axis represents the inner circumference of the disk.

The middle circumference and outer circumference are shown, and the vertical axis shows power (P). Modulated recording power (Pi, (PD), (PAC)
With a modulation width of , control is performed so that the pitch is higher on the outer circumference than on the inner circumference in proportion to the disk diameter. Such control of the recording power is carried out by the semiconductor laser drive circuit 1 shown in FIG.
Let's do it. Further, detection of the recording location and detection of the tape diameter can be easily realized by reading the address signal etc. formed in advance on the disk described above.

When the recording power is controlled as described above, the required life and power as the output of the semiconductor laser is determined by the optimum recording power for one rotation. The optimum recording power depends on the sensitivity of the recording material of the disc, for example, about 7 to 10 mW, and the output of an actual semiconductor laser is approximately 7 to 10 mW.
Including the amount of attenuation in the Rad section, a semiconductor laser with a high output of about 15 to 20 mW is required. Few such high-output semiconductor lasers have been put into practical use. Therefore,
It's expensive.

As mentioned above, another problem when recording signals using the thermal effect of laser light is the tute ratio of the recording signal and the signal deterioration caused by the recording pits formed on the disk-IL. The point is that the utility ratios do not match. For example, even if the laser beam irradiated onto the disk is modulated as pulsed light with a tute ratio of 50% by the 1゛ recording signal, the pits formed on the disk and the difference between the pit and the next pit. The length of the unrecorded part that exists between them is not necessarily equal to 1. Since thermal effects are used in recording, there are losses due to heat conduction in the recording material and the base material forming the disk (Figure 3 (f)), and changes in the applied recording power and the recording threshold of the recording material. It's for influence. As mentioned above, the fact that the recording duty ratio does not match the recorded signal means that when recording and reproducing, for example, video signals or digital signals, in the optical recording and reproducing apparatus described above, the signal is faithfully transmitted. If it cannot be done, it becomes a serious cause of failure.

Purpose of the Invention The present invention is an optical recording and reproducing apparatus that records and reproduces signals such as video signals and digital signals on a disk coated with a photosensitive recording material by concentrating the output light of a semiconductor laser or the like into a very small amount of light. The present invention provides an optical recording and reproducing device that enables recording and reproducing using a semiconductor laser with relatively low output power, and also allows the duty ratio of recording bits formed on a disk to be equal to 60%.

Structure of the Invention The present invention has a position detection means for detecting a recording position on the disk when recording a recording signal such as a video signal or a digital signal on the disk, and the position detection means detects the recording signal. The length of the recording signal in the time axis direction is set so that the outer circumference is longer than the inner circumference, and the recording signal is inputted to the half drive circuit and recorded. It is configured to do so.

Description of examples The present invention will be described in detail below with reference to the drawings.

FIG. 7 shows the relationship between the recording power threshold of the recording material (recording power at which recording starts) and the recording pits formed on the disc when recording is performed on a disc coated with a photosensitive recording material.

An example of output light with a uniform duty ratio of 60% is shown below. (PP) is the peak power, (PB) is the bias power, and (FD) is the center power for modulating the output light (F') with a width of (PAc).

(Pth) indicates the recording threshold power of the recording material, and when a laser power stronger than this level is irradiated, the disk forms a recording focus. In addition, the bias power (p
B) gives a residual heat effect for the recording material to form recording pits, and the closer the bias power (PB) is to the recording threshold power (Pth), the shorter the time it takes for recording pits to form. It gets faster. Therefore, in the recording material in which recording pits are formed by thermal effects as described above, as shown in Fig. 7 (
As shown in the figure, the energy <'am part) exerted on the recording material by the recording power (Ptb''P) and irradiation time (tl) with respect to the recording threshold power (Pth) is the residual heat power (Pth + PB). When the irradiation time (t2) increases the energy given to the recording material (shaded area), as shown in the recorded pit (A), the recorded bit (A) is larger than the unrecorded area (B). Recording pits are formed with different duty ratios.

In addition, as shown in FIG. 7(n), in the opposite case to (I), the recording bit (
(a) is formed smaller than the unrecorded portion (b), and has the characteristic that recording bits are formed with different duty ratios, similar to FIG. 7(r). Therefore, when recording with uniform recording signals or output light (F) with a duty ratio of 60%, the recording power (
The energy given to the recording material by P, h + Pp) and the irradiation time (tl) is made equal to the energy given to the recording material by the residual heat power (Pth + Pp) and the irradiation time (t2), that is, the energy given to the recording material by the residual heat power (Pth + Pp) and the irradiation time (t2) is equalized. By aligning the center (PD) of the modulation width (PAC) of the laser output light (Fl) with the recording threshold power (Pth), the duty ratio can be adjusted as shown in (a) of the recording peer in Fig. 7 θ11). Recording bits with a uniform ratio of 60% are formed.

Next, FIGS. 8 and 9 show the characteristics of the recording material when recording was performed with different duty ratios of the output light (G).

Figure 8 shows the modulation width (PA) of the output r(F) of the semiconductor laser.
Recorded bits (A) and playback when C) is recorded symmetrically with respect to the recording threshold power ("th") and the length of the output light (F) in the time axis direction is changed and the duty ratio is varied. An example of signal (c) is shown.

Figure 8 (I) shows the recording power (Pth0PP (shaded area)
) in the time axis direction is the residual heat power (Pth+PB(
When the length of the shaded part)) in the time axis direction is shortened, the result in Figure 8 (
II) shows when the length of the recording power (Pth0pP) in the time axis direction is made wider than the residual heat power (Pth0PB), and a diagram of each recording pit is shown in (a). The recording section is shown in (←), and an example of the waveform of the reproduced signal is shown in (c).

As mentioned above, recording power CPth0Pp) and irradiation time (t
If the energy given to the recording material differs depending on the residual heat power (P, h PB) and the irradiation time (t2), then the energy given to the recording material as shown in Figure 7 (
Similar to r) and (n), signals with different duty ratios are recorded and reproduced.

Figure 9 (r), (II) Similar to Phantom 1 and Figure 8, the length in the time axis direction is changed, and the center of the modulation width (PAc) (PD
) with respect to the recording threshold power (Pth) to perform recording/recording.
The energy given to the recording material by the power (Pth0PP) and the irradiation time (tl) and the residual heat power (Pth0P)
B) shows recording pits and waveform diagrams when the energy applied to the recording material is made equal depending on the irradiation time (t2). FIG. 8(f) shows an example of recording when the length of recording power (p, h0PP) is shortened, and FIG. 8(II) shows an example of recording when it is lengthened, and (a) shows an example of recording pit formation. , the unrecorded portion is shown in (b), and the waveform diagram of the reproduced signal is shown in (c). As mentioned above, the energy given to the recording material by the recording power (Pth0PP) and the irradiation time (tl) and the residual heat power (Pt
If the energy applied to the recording material is equalized by the irradiation time (t2) and the irradiation time (t2), the duty ratio of the recording peaks formed on the disk is 6, as shown in Figure 7 (011).
0% aligned recording pits ((a) are formed.

FIG. 10 shows the object of the present invention, which enables recording and reproduction with a relatively low output semiconductor laser and has a duty ratio of 5.
FIG. 3 is a diagram showing a recording method that can obtain 0% uniform reproduction signals. (I) shows the inner circumference, (II) shows the middle circumference, and (110 shows the recording threshold power (Pth) of the outer circumference, the output light (F') of the semiconductor laser, the recording pit (A), and the reproduction signal r- As mentioned above, in a disk that rotates at a constant speed, the peripheral speed is different between the inner and outer peripheries, and more recording power (recording energy) is required for the outer periphery. The threshold power (Pth) is shown in Figure 10 (
This is because (Pth) of (r), (II), and Q+t) increases as shown in (Pth).

However, as mentioned in FIG.
h) Recording power (Pth + PP), irradiation time (tl), residual heat power (Pth + PB) and irradiation time (t
If the energy given to the recording material in 2) is made equal, recording pits with uniform duty are formed regardless of the duty of the output light (F'), so the modulation width (PAC)
Even if the inner, middle, and outer circumferences are constant, and the recording peak power (PP) and bias power (PB) are also constant,
As shown in the inner circumference of FIG. 10 (I), the recording threshold power (Pt
The lower the output light (Fl recording power (P, h+
The time (tl) for irradiating the recording material with PP) is shortened, and the time (t2) for irradiating the recording material with residual heat power (P,h0PB) is lengthened.

Next, in the middle of FIG.
, and the residual heat power (P th + P B) are also made equal.

Next, as shown on the outer periphery of FIG. 10 (III), as the recording threshold value ζwa (Pth) increases, the recording power (Pth+
The time (tl) for irradiating the recording material of PP) is made longer than the time (t2) for irradiating the residual heat burner (Pth+PB).

As described above, the recording power (Pt
If the energy given to the recording material by h0PP) and the irradiation time (t, ) is equal to the energy given to the recording material by the residual heat power (Pth''PB) and the irradiation time (t2), Figure 10, (1), ([1).

As shown in II), recording pits (A) with uniform duty ratios of 60 inches are formed on the inner, middle, and outer circumferences.

(b) indicates an unrecorded portion. Further, (c) shows an example of a reproduced signal.

Next, FIG. 11 shows an embodiment of an optical recording/reproducing apparatus for carrying out the recording method of the present invention as described above.

In FIG. 11, parts similar to those in FIG. 1 are given the same numbers and detailed explanations will be omitted.

In FIG. 11, terminal A is an input terminal into which recording signals such as video signals and digital signals are input. 1 is a semiconductor laser drive circuit, C surrounded by a dotted line is an optical head section, and semiconductor laser 2. Lens 3, beam splitter/lid 4.
It consists of a tracking mirror 5° lens 6, a lens 7, etc. 8 is a photoelectric converter, 9 is a disk, 10 is a guide truck,
11 is a motor, 12 is a transfer shaft, 13 is a transfer motor,
14 is a preamplifier, and terminal B is an output terminal for outputting a reproduction signal from the disc. 15 and 16 constitute a position detection circuit for detecting a recording position or a reproduction position. 15
1 is an address signal forming circuit, and 16 is an address signal reading circuit, which is generally composed of a microcomputer or the like. The address signal is pre-recorded on the disk 9 as shown in D in FIG. The number signal reading circuit 16 reads the address signal.

As a result of reading the address signal, the master address signal reading circuit 16 reads a signal 11 divided into several blocks (for example, inner circumference, middle circumference, and outer circumference) in the radial direction of the disk 9 as a signal indicating the recording position.
．． J2. T. Send out. Reference numeral 17 denotes a time axis variable circuit, which converts the -length of the recording signal input from terminal A in the time axis direction to the signal (1) indicating the recording position described above. ■2. ■It changes according to 3. The time axis variable circuit is generally composed of a monomulti or the like.

FIG. 12 shows an example of the configuration of the time axis variable circuit 17.
Figure 3 shows the waveform diagram.

In FIG. 12, terminal A is an input terminal for a recording signal, and the waveform diagram of the input signal is shown in FIG. 13 (01).

2o is a monomulti, and the time constant of the monomulti 20 is
It is determined by capacitor C and resistors R1, R2, and R3. SL, S2.5311rJ: With switch,
The signal T1.indicating the recording position output from the address signal reading circuit 16 shown in FIG. J2. T. by 0N1
Perform 0FF. For example, if the signal indicating the recording position is ■, = inner circumference, ■2 = middle circumference, J3 - outer circumference, when ■1 is input, switch S1 is turned on, and the monomulti 200 time constant is the capacitor C and the resistance Determined by R1, mono multi 2
An example of an output signal of 0 is shown in (f) of FIG. Next, when (2) is input, only the switch S2 is turned on, the time constant is determined by the capacitor C and the resistor R2, and the output signal of the monomulti 2° has the waveform shown in FIG. Similarly, engineering. is input, the time constant of the monomulti 2o is determined by the capacitor C and the resistor R3, and the output signal is the first
The waveform will be as shown in Figure 3 (h). Further, the output signal of the monomulti 20 is sent from the terminal G to the half drive circuit 1.

As described above, the length of the recording signal in the time axis direction, that is, the duty ratio, is changed by the time axis variable circuit 17 as shown in FIG. In the laser drive circuit 1, the center (PD) of the modulation width (PAc) of the output light (G) at the middle frequency is equal to the recording threshold power (Pth
), the sixth
As shown in the figure, reproduced signals with uniform duty ratios can be obtained without the need for load control.

Effects of the Invention As in the present invention, the power is controlled by the semiconductor laser drive circuit by changing the length of the recording month in the time axis direction depending on the inner and outer circumferences of the disk using the time axis variable circuit and supplying it to the semiconductor laser drive circuit. Even with a relatively low-output semiconductor laser, it is possible to obtain high-quality recording and reproducing signals with a uniform duty ratio without performing this process, which is highly effective.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram showing an example of a conventional optical recording/reproducing device, Figure 2A is a two-sided view of a disk, Figures 2 and 4 are output characteristic diagrams of a semiconductor laser, and Figure 5 is Waveform diagram showing the relationship between the output light of the semiconductor laser, the recording pit, and the reproduction signal, No. 6
Figure 7 is an explanatory diagram showing an example of conventional power control, Figure 7 is a recording characteristic diagram of a disc using a photosensitive recording material, and Figure 8 is a diagram showing the tuning characteristic of the output light of the semiconductor laser in the disc shown in Figure 7. 9 (2) is a waveform diagram showing the relationship between recording pits and reproduction signals when recording is performed by changing the output light of the semiconductor laser. Similarly to FIG. Waveform diagram showing the relationship between
Figure 0 is a waveform diagram showing the recording method according to the present invention.
FIG. 1 is a block diagram showing an embodiment of the optical recording/reproducing apparatus of the present invention, FIG. 12 is a circuit diagram showing an example of the structure of the time axis variable circuit in the same embodiment, and FIG. FIG. 3 is a waveform diagram of the time axis variable circuit shown in FIG. 16... Address signal reading circuit, 17... Time constant variable circuit. Name of agent: Patent attorney Toshio Nakao Haga1 Neo
1 Figure (E) ノ(f/Igiri No. 5 Figure 7 No. 6 @ r,. Hawaii ゛口η゛S License Agency Director-General■ Indication of the case 1982 Patent Application No. 235769 2 Name of the invention Optical Relationship with 41 persons making corrections to recording and reproducing equipment 3 4th Permission Application Address 1006 Bold Kadoma, Kadoma City, Osaka Name (582) Matsushita Electric Industrial Co., Ltd. Representative Toshihiko Yamashita 4 Agent 571 Address 1006 Oaza Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. Date and details of the 5th amendment order Letter 22, lines 4-5, "Figure 2 A is +t + J
−′

Claims (2)

[Claims] (1) a position detecting means having a means for recording and reproducing a signal on a disk coated with a photosensitive recording material by concentrating the output light of a semiconductor laser or the like into a very small amount of light, and detecting a recording and reproducing position on the disk; An optical recording/reproducing device characterized by comprising: time axis variable means for changing the length of the recording signal in the time axis direction based on the output signal of the position detecting means. (2) The time axis variable means shortens the length of the recording signal in the time axis direction at the inner circumference and lengthens it at the outer circumference, according to the output signal of the position detection means. The optical recording/reproducing device described in 2.