JPH03116442A - Optical disk device and optical disk - Google Patents

Abstract

PURPOSE:To obtain an inexpensive optical disk device capable of recording and reproducing musical information by deciding the kind of the optical disk and setting internal conditions of the optical disk device automatically, and performing power control at the time of recording or rewriting. CONSTITUTION:A reflection factor monitor 4 measures the reflection factor of the optical disk 2, a control circuit 5 decides a playback only type, rewritable type, or DRAW type, and the speed of revolution of a spindle motor 1, a tracking gain, and a focus gain are adjusted according to the kind of the disk. When a signal is regenerated, the amplification factor of a preamplifier 6 is adjusted according to the decision result to make the width of an input signal to a binarization circuit nearly constant. Further, a binarization circuit 7 is switched by a switch 9 so as to process a playback signal as a pulse-width modulated(PWM) signal when the optical disk 2 is the playback only type or as a pulse- position modulated(PPM) signal when the disk is the DRAW type or rewritable type. Consequently, the inexpensive optical disk device capable of recording and reproducing the musical information is obtained.

Description

[Detailed description of the invention] Industrial application field The present invention i! This relates to optical disk devices and optical disks that reproduce or write optical information at high speed and high density using laser beams, etc.A. Conventional technology The technology for reproducing or recording high-density information using laser beams is well known. Although they are mainly put into practical use as optical discs, optical discs can be broadly classified into playback-only, postscript, and rewritable types.
A CD is an optical disc on which music information that has been subjected to 8-14 conversion (EFM) is recorded in advance using a pulse width modulation (PWM) method. The PWM recording method changes the length and interval of the recording marks to provide information at the edge positions of the recording marks. The write-once type and the erasable type have a recording film on the substrate, such as metal thin film Te plywood, organic thin film, or ferromagnetic thin film, and record signals by causing some kind of change in the recording film by irradiation with a laser beam. These methods are called heat modes, which utilize heating of the recording medium by irradiation with laser light or the like.

One of the problems with heat mode recording is that the shape of the recorded mark is not front-to-back symmetrical, and is distorted into a teardrop shape by being thin near the tip and thick near the end. This causes an increase in jitter in the reproduced waveform. This phenomenon is especially large at low linear velocities, and in order to reduce the distortion of 41 recording marks when recording CD-format EFM signals on write-once or rewritable optical discs at CD-like linear velocities, Japanese Patent Application Laid-Open No. 63
Although proposals such as Japanese Patent Application Laid-Open No. 63-266633 have been made, these methods compose a recording waveform for forming one recording mark with multiple pulses and change the pulse width to create an optical disc. Optical disc devices are also used as data recorders for computers, and in this case, the optical disc is stored in a cartridge. The type and conditions necessary for recording and playback are generally recorded on the control track on the optical disc. The control track records, for example, the modulation, the number of revolutions of the optical disc, the magnitude of the recording/reproducing power, etc., and by reproducing this information, it is possible to set the internal conditions of the optical disc device. One of the desirable conditions for an optical disk device such as a CD is that it should be simple in structure and inexpensive, and this is true even if a recording or rewriting function is added. From this point of view, JP-A No. 63-160017 and JP-A No. 63-266
The method shown in Publication No. 633 has the drawback that the recording device becomes complicated because the recording waveform is formed in a complicated manner.Also, since the recording mark length changes with the fluctuation of the recording power in PWM recording itself, the recording power margin is narrow. However, there is also a problem in applying the method of identifying optical discs and the method of setting various conditions for recording and playback used in conventional optical disc devices for data recorders to optical disc devices such as CDs. This is because optical discs such as CDs do not have cartridges and therefore do not have sensor holes, and there is a method of recording recording and playback conditions on a control track, playing them back, and setting the internal conditions of the optical disc device based on that information. Although complicating the structure of an optical disk device increases the cost of the device, the presence of a control track on the optical disk shortens the recording time. Set the internal conditions of the optical disk device.
In addition, the optical head has a simple configuration and has a wide power margin during recording or rewriting.There is no inexpensive optical disc device that can record and reproduce music information. means for determining whether an optical disc installed in the spindle motor is a read-only type, a write-once type, or a rewritable type; a means for adjusting focus gain, tracking gain, and signal amplitude to the signal processing circuit according to the determination result; If the optical disc is a read-only type, the reproduced signal is binarized as a pulse width modulated signal; if the optical disc is a write-once type or a rewritable type, the reproduced signal is binarized as a pulse position modulated signal; and when further signals are to be recorded. In this paper, we propose an optical disc device having means for recording by pulse position modulation.

Furthermore, it is possible to provide areas with repeated patterns having different reflectances or transmittances along the inner circumference or outer circumference of the optical disk.According to the optical disk device and optical disk according to the present invention, the internal conditions of the optical disk device can be determined by determining the type of the optical disk. It is possible to provide an inexpensive optical disc device that can record and play back music information, which automatically sets the power and has a wide power margin during recording or rewriting, making power control easy. The present invention will be described in detail. Optical disks are currently used for a variety of purposes, one of which is CDs.4 Although CDs are read-only, attempts are being made to add additional functions such as recording and rewriting.

However, to date, no optical disc device that can record and rewrite music information, has a simple configuration, and is inexpensive has been proposed.The inventors therefore conducted a detailed study on how to realize this.9 In other words, the following 1. ), 2), 3
) The optical head must be the same regardless of whether the optical disc is a read-only type, a write-once type, or a rewritable type, and the light source used must be a single semiconductor laser, and in the case of a CD, the signal reproduction method must be the same. Presence of record mark 11 (
(The number of songs performed by detecting changes in the amount of reflected light corresponding to the number of songs. P.S.) Rewriting type also needs to perform playback by detecting changes in the amount of reflected light in the same way.

2) Determining the type of installed optical disc using a simple configuration In this case, the conventional method of providing a sensor hole is inappropriate because it requires a cartridge, and the method of providing a control track complicates the device configuration. In addition, the presence of a control track shortens the recording time, and current CDs do not have control tracks and cannot be applied, making it unsuitable. 3) Power margin when recording or rewriting signals. In order to widen the power control and make power control easier (in the case of write-once type or rewritable type, pulse position modulation (P) is used.
PM) recording method is used. As an optical disk device that satisfies the above l), 2), and 3), we propose, for example, an optical disk device as shown in the block diagram of Fig. 1. Spindle motor 1
Optical disc 2 installed in C1 playback only Additional supervision
It is one of the rewrite type, and the write-once type is amorphous.
A phase change type is used to cause a state change between crystals, or a mold is used to make holes in the recording film by laser irradiation. The type of optical disc is determined based on the reflectance. That is, at the wavelength of 780 nm of the semiconductor laser incorporated in the optical head 3,
The recording film thickness and structure of the optical disk are designed so that the reflectance of a read-only optical disk, that is, a CD, is 70% or more, and is 10 to 25% for a write-once type and 25 to 40% for a rewritable type.

For example, a write-once type optical disc has a TePd0 recording film or a TeS recording film on a polycarbonate substrate.
It can be manufactured by providing a bGe recording film, etc., and as a rewritable type, it can be manufactured by providing a TeGe5nAu recording film or a Te5eGeSb recording film, etc. sandwiched between top and bottom protective films ZnS on a polycarbonate substrate, and then crystallizing the recording film. These optical discs can satisfy the above reflectance range. Here, the reflectance of the optical disc 2 is measured by the reflectance monitor 4, and the reflectance is determined to be 50% by the control circuit 5.
If it is above, if the playback-only wind is 25% or more and 50% or less, then if the rewriting supervision is 25% or less, it is judged as a write-once type. The rotational speed of the spindle motor l, tracking gain, and focus gain are adjusted as necessary depending on the type of disc. When reproducing a signal, the amplification factor of the preamplifier 6 is adjusted based on the determination result of ζ, and the width of the human input signal to the binarization circuit 7 is kept approximately constant. The binarization circuit can also be switched by switch 9 to process the playback signal as a PWM signal if the optical disc is a read-only type, or as a PPM signal if it is a write-once type or a rewritable type. +iPWM signal as is, PPM
The signal is converted into a PWM signal via a flip-flop 8, and then sent to an EFM demodulation circuit 10, where it is successively converted into a music signal. When recording a signal on a write-once optical disc, a semiconductor laser is directly driven by a PPM signal waveform from the EFM modulation circuit 11.

When recording a new signal while erasing an old signal on a rewritable optical disc, overwriting is performed by modulating a semiconductor laser between erasing power and stronger recording power. In phase-change optical disks, signals are recorded as amorphous marks on tracks in a crystalline state.A weak erasing power is used to crystallize the amorphous recording marks, and a strong recording power is used to melt the recording film, which is then cooled. It is possible to form an amorphous recording mark. In other words, by modulating the semiconductor laser at two levels, recording power and erasing power, using the PPM signal waveform from the EFM modulation circuit 10, the laser spot can erase old signals and generate new signals just by passing over the track once. Recording becomes possible. In this case too, the signal is recorded in PPM
Do it according to the method. That is, both the write-once and rewritable types have a wider recording power margin than the PPM and PWM systems, making it extremely easy to set the power of the optical disc device. This device uses a force that utilizes the difference in reflectance as a method of determining the type of optical disk (if the optical disk according to the present invention is used as shown below), the optical sensor installed at the inner or outer circumference of the optical disk before focusing It is also possible to determine the type of optical disc based on output changes and set the internal conditions of the optical disc device.
An example of an optical disc according to the present invention is shown in FIG. A repeating pattern 15 having different reflectances is provided along one circumference of the inner circumferential portion of the optical disc 13 than the signal recording area 14 . As a method for forming repeating patterns with different reflectances, for example, if the recording film is a phase change material that changes state between amorphous and crystalline, laser light is irradiated along the inner circumference of the optical disc to separate the crystalline region and amorphous region. However, with this method, it is possible to know in advance the magnitude of the reflectance of the crystalline region and the amorphous region. It is convenient for setting the internal conditions of the optical disc device such as the settings of ~ This can be easily achieved by masking the optical disc substrate when forming a recording film by vacuum evaporation or sputtering.Furthermore, in the case of an optical disc that has a reflective film in addition to the recording film, By making the area where the reflective film is formed and the area where the reflective film is formed different,
It is also possible to form a repeating pattern.For example, when forming a recording film using a vacuum evaporation method or a sputtering method, the recording film is partially removed along one circumference by masking the optical disc substrate, and then the entire surface is By forming a reflective film, a pattern can be formed by repeating the recording film and the reflective film. As a method of using an optical disc having such a repeating pattern, for example, an optical disc device having an optical sensor 16 installed on the inner circumference as shown in FIG. 15, and thereby set the internal conditions of the optical disc device.a The repeating pattern records at least information that can determine the type of optical disc (for example, whether it is a write-once type, a rewritable type, or a read-only type). When using a current CD as a read-only optical disc (as there is no repeating pattern, if no change in reflectance is detected, it is determined to be a read-only type). Although it is possible to determine the type using a simple method and set the internal conditions of the optical disk device, from the perspective of recording and playing back music signals, the recording time may need to be 60 minutes, which is the same length as a CD. Current CDs have a maximum length of about 75 minutes.
This is because recording is performed using the PWM method, and when recording using the PPM method, the length is about half, about 38 minutes. However, in PWM recording, it is necessary to accurately detect the edge position of the recording mark, so the crosstalk is approximately 135 dB or more (in PPM, only the presence or absence of the recording mark is detected, so the crosstalk is only about 126 dB). (Xo also changed the track pitch to the current CDI.

Although it is possible to make the track pitch narrower than 6 μm, Figure 4 shows the relationship between crosstalk and track pitch determined through experiments. From Figure 4, even if the track pitch can be narrowed to about 1°25 μm, the crosstalk will still be 128 dB or more. The resulting recording time is 38 x 1.6/1.25 = 48 minutes. In order to further increase the recording density, it would be a good idea to shorten the wavelength of the semiconductor laser.
Recording density is inversely proportional to the square of the recording wavelength.The wavelength of semiconductor lasers used in current CDs is 780 nm.In order to achieve a recording time of 60 minutes for LPPMPP, a semiconductor laser with a wavelength of about 700 nm or less must be used. If you use it ~ Effects of the invention As stated above, according to the optical disc device and optical disc according to the present invention, whether the optical disc is a read-only type or not.
It automatically determines whether it is a write-once type or a rewritable type and automatically sets the internal conditions of the optical disk device, and it is possible to reproduce, record, or rewrite signals with a simple optical head configuration, and when recording or rewriting. Since the power margin is wide, power control is easy.
It is possible to provide an inexpensive optical disc device that can record and reproduce music information.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of an optical disk device according to the present invention. FIG. 2 is a block diagram showing an example of an optical disk according to the present invention. FIG. FIG. 4 is a diagram showing the relationship between crosstalk and track pitch. l...Spindle motor 2.13...Optical disk drive 3...Optical spatula K 4...Reflectance monitor 5...Control circuit 〇...Brience 7.
...Binary appositive 8...Flip-flop, 9
...Switch, lO...EFM demodulation rotation 1l.
... EFM modulation times ii & 12 ... laser drive times i 14 ... signal recording area 15 ... repeating pattern, 16 ... optical sensor.

Claims (9)

[Claims] (1) A means for determining whether the optical disc installed in the spindle motor is a read-only type, a write-once type, or a rewritable type, and a means for adjusting the focus gain, tracking gain, and signal amplitude to the signal processing circuit based on the determination result. and means for binarizing the playback signal as a pulse width modulation signal if the optical disc is a read-only type, and binarizing the playback signal as a pulse position modulation signal if the optical disc is a write-once type or a rewritable type; 1. An optical disc device comprising: means for recording signals by pulse position modulation. (2) The optical disc device according to claim 1, wherein the type of optical disc is determined based on a difference in reflectance from the optical disc. (3) If the reflectance from the optical disc is larger than a preset value, the optical disc is determined to be a read-only type, and if it is smaller, the optical disc is determined to be a write-once type or a rewritable type. Optical disk device. (4) The optical disc device according to claim 1, wherein the type of the optical disc is determined based on a change in the output of an optical sensor installed at an inner or outer periphery of the optical disc before the optical disc is rotated and focused. (5) The optical disc device according to claim 1, wherein the light source is a semiconductor laser having a wavelength of 700 nm or less. (6) An optical disc characterized in that a repeating pattern area with different reflectance or transmittance is provided along one circumference of the inner circumference or the outer circumference. (7) The recording film is a phase change material that undergoes a state change between amorphous and crystal, and the areas of low reflectance or high transmittance of the repeating pattern are in the amorphous state, and the areas of high reflectance or high transmittance are in the amorphous state. 7. The optical disc according to claim 6, wherein the small region is in a crystalline state. (8) Claim 6, wherein the repeating pattern is provided by partially cutting out the recording film along one circumference.
The optical disc described. (9) In the optical disc having a recording film and at least a reflective film, the repeating pattern is provided in different areas in which the recording film is formed and the reflective film is formed. optical disk.