JPS63848B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical information recording system capable of recording information stably and accurately.

Recently, large-capacity memory devices using optical disks as information recording media have been attracting attention. For example, an optical recording medium made by forming a thin metal film of Te, Bi, etc. as an optical recording material on an acrylic disc or glass disc is irradiated with a laser beam of about 1 μmφ that is pulse-modulated according to the recording signal, and the laser beam is Information is recorded by melting the metal thin film using Joule heat to form pits. In this case, bit data “0” of the recording signal
Or bit data “1” corresponding to “1”
Information can be recorded by forming pits only when the data is stored, or by modulating the above signal with MFM, 3PM, etc. in order to increase the recording capacity, and forming pits in accordance with the bit data of this modulated signal. It will be done.

Figure 1 a to g show an example of this. The recorded information data shown in a is subjected to MFM modulation as shown in figure b, and the laser light output is modulated as shown in figure c according to this modulation signal. and irradiate it onto the optical disc.
This modulated laser beam causes the first
As shown in FIG. d, pits are formed with a length corresponding to the bit data length, and information is recorded there.
However, since a part of the laser beam that forms the pits is transmitted through the substrate of the optical disk and preheats the area around the pit positions, the bit data length is long, and as a result, when the laser beam irradiation time is long, As shown, there is a problem in that the pit length becomes longer than when the irradiation energy is constant. For this reason, when the above-mentioned pit is irradiated with a reading laser beam to read out the information as shown in Figure 1e, and the signal is waveform-shaped and reproduced as shown in Figure 1f, the signal as shown in Figure 1g is obtained. This results in signal deviation. This shift in the rising and falling points of the signal causes errors in the read data, leading to an increase in the error rate.

The present invention was made in consideration of these circumstances, and its purpose is to always record information simply, stably, and accurately without the risk of data errors caused by changes in pit length. The object of the present invention is to provide an optical information recording system that can perform the following steps.

The outline of the present invention is to form a plurality of pits of a predetermined size at a predetermined interval during the pit formation period corresponding to bit data "0" or "1", and to represent the above data as a row of pits, so that the data is always stable and accurate. The above-mentioned purpose has been effectively achieved by making it possible to record information.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIGS. 2a to 2j are diagrams showing a signal recording format and its readout format according to one embodiment. Now, when trying to record optical information on a data string signal as shown in Figure 2a, the signal is first converted into a data string as shown in Figure 2b.
MFM modulated. This MFM modulated signal is sampled by the write clock signal shown in FIG. be done. By this modulation, the output of the laser beam is modulated as shown in FIG. 2d, and the optical disk is irradiated with the output. The optical disc receives the upper laser beam and forms pits of a predetermined size as shown in FIG. 2e. Here, an example is shown in which two pits are formed with the minimum bit length T of the data corresponding to bit data "1" of the modulated signal. Then, the signal width of bit data “1” of this MFM modulated signal is T, 3/
Since it consists of three types, 2T and 2T, 2 pieces, 3 pieces,
Four pit rows are formed corresponding to the bit data length.

Then, an optical disk formed with such pit rows is scanned using a reading laser beam,
When the reflected light information is extracted, the readout signal waveform becomes as shown in FIG. 2f. If this readout signal waveform is sampled by the readout clock signal shown in FIG. 2g and data is extracted in response to the gate signal shown in FIG. 2h, the reproduced information will be as shown in FIG. 2i. The phase of the read clock signal is delayed by 90 degrees compared to the write clock signal, so that information components with a stable waveform in the center of the bit data can be extracted. ing. By demodulating the signal reproduced in this manner, a data string as shown in FIG. 2j can be obtained, and data errors due to deviations of signal edges do not occur.

In other words, since information is recorded on an optical disk by forming a plurality of pits of a predetermined size at a predetermined interval corresponding to the bit data length of the recording signal, the width of the signal waveform ( length) is accurately determined. Therefore, no signal waveform edge shift occurs, and there is no risk of data errors caused by this edge shift.

Now, an optical information recording/reproducing apparatus realized by adopting this method is configured as shown in FIG. 3, for example. That is, the optical information recording and reproducing device uses optical disk A.
A head B is arranged to face the recording surface of the optical disk A and is relatively movable, an information recording section C that supplies a recording control signal to the head B, and an information recording section C that supplies information read from the optical disk A via the head B. It is composed of an information reproducing section D that reproduces information.

Information data to be recorded is guided to the information recording section C and temporarily stored in the buffer memory 1 thereof. The data stored in the buffer memory 1 is read out in synchronization with the write clock signal output by the recording clock generator 2, and is sent to the modulation circuit 3 for example.
MFM modulated. This modulation circuit 3 not only performs MFM modulation of the recording data, but also generates an address information signal, a synchronization signal, a cue code signal, etc. in accordance with a predetermined recording format, and inserts them into the modulation data. However, the drive circuit 4
In synchronization with the write clock from the recording clock generating section 2, a pulse signal is generated corresponding to the bit data "0" and "1" of the MFM modulated data string, for example, when the bit data is "1". This is given to head B. When the minimum period of bit data “1” is T, this pulse signal is T/2
It emits two pulses at a time interval of 3/2T, and the period of bit data “1” is 3/2T,
In the case of 2T, three and four pulses are generated at intervals of T/2, respectively. Therefore, in the information recording section C configured in this way,
A plurality of pulse signals are generated at predetermined intervals (T/2) corresponding to the length of bit data "1" to be recorded optical information, and these pulse signals are supplied to head B to control the light of head B. It is designed to drive a spot-generating light source.

The head B is equipped with a semiconductor laser element 5 as a light source, and the laser beam generated and output from the laser element 5 is passed through a lens 6, a polarizing beam splitter 7, and a quarter-wave plate 8, and then passed through an objective lens. 9, the beam is converged to a spot diameter of approximately 1 μmφ and irradiated onto the optical disk A. Further, the reflected light from the optical disk A of this irradiated laser is guided from the objective lens 9 to the polarizing beam splitter 7 via the 1/4 wavelength plate 8, where the light is split laterally and taken out. It's becoming like that. The light extracted in the lateral direction is received by the light receiver 10,
After being photoelectrically converted, the signal is provided to the focus control section 12 via the buffer amplifier 11. This focus control section 1
Reference numeral 2 drives the voice coil 13 that supports the objective lens 9 in accordance with the input signal, that is, the light reception signal from the light receiver 10, and moves the support position of the objective lens 9 up and down. That is, the facing distance between the optical disk A and the head B varies due to the warpage of the optical disk A, and as a result, the diameter of the irradiation spot of the laser beam may change due to a focal position shift. In order to prevent this, the reflected light of the irradiated laser beam is detected by the receiver 10, and depending on the state, the focus control unit 12 drives the voice coil 13 so that the distance is always approximately 1 μm.
Automatic focus control is used to obtain the same beam diameter. Under this automatic focus control, the semiconductor laser element 5 is driven in response to a pulse signal from the information recording section C, and its output is intensity-modulated. As a result, a modulated spot light as shown in FIG. 2d is irradiated from the head B onto the disk A, forming a row of pits on the optical disk A to record information. The modulation of this irradiation light has an intensity sufficient to form a pit on the optical disk A, for example.
This is done by selectively switching between two levels: Pw and an intensity P _R sufficient to obtain a low level of reflected light that does not contribute to pit formation. Therefore, even during non-signal recording in which pits are not formed, low-level spot light is irradiated onto the optical disk A, and the above-mentioned automatic focus control is performed from the reflected light. Information recording, which is indicated by a row of pits of predetermined size, thus takes place here. Then, the time width change of the MFM modulated signal is recorded as a change in the number of pits of the same size and a predetermined interval that are continuously formed.

By the way, the information recorded on the optical disc A in this manner is read out in the following manner. When reading this information, the semiconductor laser element 5 emits a spot light having an intensity P _R of a sufficiently low level necessary for reading the information, and the head B detects the reflected light. This reflected light detection signal is amplified to a predetermined level via the buffer amplifier 11, and then guided to the information reproducing section D. Needless to say, the above-mentioned automatic focus adjustment is also performed during this information reading. Further, the diameter of the light spot at this time is also set to approximately 1 μmφ.

Thus, the read signal waveform is superimposed with a pulsation component corresponding to the interval between pits, and its period is T/2. In the information reproducing section D, such read signals are inputted to the demodulation circuit 14 and the read clock reproducing section 15, respectively. The read clock reproducing unit 15 detects the data change point of the read signal, as will be described later, and reproduces a read clock with a period T/2 whose frequency and phase are controlled from the pulsating component contained in the read signal. This read clock signal is supplied to demodulation circuit 14 and buffer memory 16.
The demodulation circuit 14 shapes the waveform of the read signal according to the read clock signal and demodulates the data, and the demodulated reproduced data is temporarily stored in the buffer memory 16. By reading the data stored in this buffer memory 16, the optical disc recorded information is reproduced here. In this case, unlike the conventional demodulation of the data by detecting the rising and falling edges of the read signal, the demodulation of the data is performed by detecting the recording clock component superimposed as a pulsating component included in the read signal. Since the readout is performed according to the readout clock generated by this detection, it is extremely stable. Therefore, it is possible to significantly improve the data error rate.

Above, we have explained optical information recording using this method and its information reading, but the important points are as follows.
I will explain further.

Figures 4a, b and 5 show how the pulsation of the readout signal changes depending on the pit spacing and beam diameter, and Figure 4a shows how the pit diameter changes depending on the beam diameter. diameter, and the pit spacing Δd is 1/10 of the beam diameter, and Fig. 4b
This shows an example in which the pit diameter is smaller than the beam diameter and the interval Δd is larger.
Reasons for the pit diameter to become smaller include a decrease in the irradiation energy of the laser beam under the same writing conditions, or a decrease in the photosensitivity of the optical disk. The readout signal waveform in such a case becomes as shown in characteristics a and b in FIG. 5, respectively. For example, under the conditions shown in FIG. 4a above, the pulsating component of the readout signal is
It will be around 14%.

Therefore, it has now been found that in order to perform high-density recording as much as possible, the size of each pit and the interval between them should be made as small as possible. However, the size of the pit is limited by the diameter of the optical spot when recording and reading information. Particularly during reading, as the diameter of the pit becomes smaller with respect to the diameter of the optical spot, the degree of modulation of the readout signal at the pit portion decreases, and the S/N ratio deteriorates. Therefore, when the optical spot diameter is about 1 μm, it is desirable that the pit diameter is also about 1 μm. On the other hand, as is clear from the characteristics shown in Figure 5, the distance between the pits is 1/10 of the pit diameter.
It is possible to sufficiently detect the pulsation component even if the pulsation component is small. Conversely, as the pit interval becomes longer, the degree of modulation of the pulsation component increases, and as a result, it becomes difficult to distinguish between data "0" and data "1".
This adversely affects data demodulation processing, etc. Therefore, desirably, for the readout signal at the center of the pit,
The level change of the readout signal at the intermediate position of the pit is
In order to suppress the value to 1/2 or less of the value level, the pit interval may be set to 1/2 or less of the optical spot diameter.

Furthermore, as shown in FIGS. 4a and 4b and FIG. 5, the position of the peak point of the pulsating component of the read signal does not change on the time axis. In other words, the period of the pulsating component depends only on the interval between pit formation positions (distance between centers) and is not affected by pit dimensions. Furthermore, the period of this pulsating component is precisely defined as T/2 corresponding to the pit interval. Therefore, by detecting this pulsating component, it is possible to reproduce the read clock necessary for data demodulation (MFM demodulation) of the read signal with sufficient accuracy.

FIG. 6 is a block diagram showing an example of the read clock generating section 15 which reproduces the read clock from this pulsating component, and FIGS. 7 a to 7 d are operational waveform diagrams thereof.

That is, the readout signal read out from the optical disk A through the head B is input to the band pass filter 21 to obtain a pulsating signal component having a pit recording period (T/2) included in the readout signal. Further, this read signal is guided to a binarization circuit 22, where it is binarized and output as a phase comparison gate signal. On the other hand, the output signal of the voltage controlled oscillator 23, which oscillates at a frequency of approximately 2f (f=1/T), is passed through the bandpass filter 24.
The signal is guided to the phase comparator 25 via the phase comparator 25. This phase comparator 25 compares the phases of the signals applied through the filters 21 and 24 during the period when the gate signal is applied, and the phase difference signal is passed through the low-pass filter 26 to the voltage The control oscillator 23 is provided with the same signal. The voltage controlled oscillator 23 changes its oscillation frequency and signal phase in accordance with the phase difference component extracted through the filter 26, and synchronization with the pulsating component of the oscillation output is established. In other words, the read clock generator 15
It is realized by a PLL circuit, and the output of the voltage controlled oscillator 23 is taken out as a reproduction readout clock signal. The gate signal is used to perform phase comparison only during the period when a pulsating component is present in the readout signal, so that the loop control operation is performed only when a signal phase shift occurs.

FIG. 7a shows an example of the readout signal waveform, and the bandpass filter 21 extracts only the pulsating component thereof, as shown in FIG. 7b. Also, Figure 7c
indicates a gate signal obtained by the binarization circuit 22. The PLL circuit (read clock generating section 15) receiving such a signal operates stably by obtaining the oscillation output shown in FIG. 7c from the voltage controlled oscillator 23, thereby regenerating the read clock. become.

As described above, by recording information as a row of pits, the information can be read out stably and accurately, and the data error rate can be improved. In addition, unlike the conventional technology, it is not subject to major restrictions on the usage environment or other factors, and has great effects such as excellent practicality.

Note that the present invention is not limited to the above embodiments. For example, in the embodiment, MFM modulated signal data is recorded, but the information data before modulation may be recorded as is, and 3PM modulation etc.
Other modulation methods may be employed to record modulated data. Further, the dimensions of the pits, their intervals, etc. may be determined depending on the diameter of the light spot. In short, the present invention can be modified in various ways without departing from its gist.

[Brief explanation of the drawing]

1A to 1G are diagrams showing an example of optical information recording using a conventional method; FIGS. 2A to 2J are diagrams showing optical information recording and reading thereof according to an embodiment of the present invention;
The figure is a schematic configuration diagram of an optical information recording/reproducing apparatus to which this method is applied. FIGS. 4a, b, and 5 are diagrams showing the information read operation in this method. FIG. 6 is an example of a read clock generation section. Configuration diagram, Figure 7 a-d
1 is a signal waveform diagram showing read clock reproduction; FIG. A...Optical disk, B...Head, C...Information recording section, D...Information reproducing section, 1...Buffer memory, 2...
Recording clock generator, 3... Modulation circuit, 4... Drive circuit, 5... Semiconductor laser element, 6... Lens, 7... Polarizing beam splitter, 8... 1/4 wavelength plate, 9... Objective lens, 10... Light receiver, 11... Buffer amplifier,
12... Focus control section, 13... Voice coil, 14...
Demodulation circuit, 15... Readout clock generator, 16...
Buffer memory, 21...Band pass filter, 22
... Binarization circuit, 23... Voltage controlled oscillator, 24... Band pass filter, 25... Phase comparator, 26... Low pass filter.

Claims (1)

[Scope of Claims] 1. When recording information by forming pits at the optical signal irradiation position of an optical recording medium, pits of a predetermined size are formed at predetermined intervals to adjust the bit data length of "0" or "1" of the recording signal. An optical information recording and reproducing system characterized in that a plurality of pits are formed according to the conditions, and information indicated by a row of pits is recorded. 2. When recording information by forming pits at the optical signal irradiation position of the optical recording medium, a plurality of pits of a predetermined size are formed at predetermined intervals according to the bit data length of "0" or "1" of the recording signal. When reproducing the recorded information, a readout clock is reproduced from the pulsating component of the reflected light that changes depending on the pits, and the above-mentioned reflected light is reproduced according to the reproduced readout clock. An optical information recording and reproducing method characterized by discriminating light levels and reproducing information. 3. The optical information recording and reproducing system according to claim 1 or 2, wherein the recording signal is a modulated digital signal obtained by modulating an information signal. 4. The optical system according to claim 1 or 2, wherein the pits of a predetermined size are formed on the optical recording medium by irradiating information light pulses with a repetition period that is an integral multiple of the recording signal bit data. Information recording and playback method. 5. The optical information recording and reproducing system according to claim 1 or 2, wherein the interval between the pits forming the pit row is set to 1/2 or less of the diameter of the information reading optical spot.