JPS62188025A - Recording and reproducing device for optical disk - Google Patents

Abstract

PURPOSE:To eliminate the need for a high-output laser by recording modulated information while lowering laser power toward outer divided areas of an optical disk, making reproduction length shorter by the detection window width of a modulation system, and demodulating the information while correcting the period of a playback signal by the reciprocal of the direction window width during reproduction. CONSTITUTION:The positions of storage areas A and B of the disk are detected 17, a bias value 18 is mixed with a modulating signal to control the laser power, and information is recorded in the area B to length which is one clock shorter than the original length as shown by bits 55. When the information in the area B is reproduced, a corrected output signal 60 from an OR 25 through clock regeneration 23 and delay 24 is selected and when information in the area A is reproduced, the output signal 57 (uncorrected) of a waveform equalizing circuit 21 is selected to perform correct reproduction. Lastly, the modulated signal is demodulated by using the output of a switch circuit 26. In this constitution, even when the disk diameter increases to increase the linear speed at the outer periphery, the laser output is reduced and a high-output laser is not necessary.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical disc recording and reproducing apparatus for recording and reading information on a disc.

2. Description of the Related Art In recent years, applications of document file disks, still image disk files, and the like have been considered as recordable and reproducible large-capacity memories using optical disk media.

A thin film of a material (for example, a Te-based metal oxide) whose reflectance changes depending on the strength of the power of the semiconductor laser is deposited on the optical disk.
Information is recorded as a signal with different gradations of reflectance depending on the recording signal.

FIG. 6 shows a schematic diagram of a conventional optical disc recording and reproducing apparatus. Reference numeral 1 denotes an optical disk, on which tracks for recording information are formed and a recording film is deposited. 2 is optical disc 1
The optical disc 1 is mounted on the turntable using a motor that rotates the motor and a turntable. 3 is a condensing lens,
An optical head consisting of a beam splitter, collimator lens, etc. 4 is a semiconductor laser attached to the optical head 3, and 6 is a light receiving element for detecting the amount of light reflected from the optical disk 1. 6 is a semiconductor laser drive circuit that changes the strength of the power of the semiconductor laser 4 in accordance with the write data. 7 modulates the write data with a modulation circuit (for example, MFM).

3PM, (2,7) RLL, etc.), and 8 is a circuit that demodulates reproduced data. Note 1 shows the optical path along which the light beam from the optical disc 3 is incident on the optical disk.

The operation of the conventional optical disc recording and reproducing apparatus configured as described above will be explained below.

The optical disc 1 is mounted on a turntable 2 on a motor, and is rotated at a constant speed of, for example, 1800 revolutions per minute. A light beam from a semiconductor laser 4 fixed to the optical head 3 is focused onto the optical disk 1 as shown at 81 by optical components such as a collimator lens and a condensing lens within the optical head 3. Similarly, the reflected light from the optical disc 1 is irradiated onto the light receiving element 6 by optical components. Generally, the disk 1 rotates with surface wobbling and track eccentricity, so in order to record or reproduce information on a predetermined track, the optical beam must follow the surface wobbling of the optical disk 1. Focus control and tracking control to follow the track are required. With focus control and tracking control being performed in this way, the data to be written is processed by a modulation circuit using, for example, MF, which is a known modulation method.
M method (Modified Frequency Mo
duration). The semiconductor laser 4 emits light by the laser drive circuit 6 in response to the output signal of the modulation circuit γ, and data is recorded by focusing the light onto the optical disc 1 while being modulated to a high power. For example, as described above, if a Te 2 -based metal oxide film is deposited on the optical disc 1, a signal corresponding to the cycle of data to be written is recorded as a dark and dark signal with different reflectance. Next, a constant low-power laser beam is focused on the recorded information track, the reflected light is detected by the light receiving element 6, and the signal is demodulated by the demodulation circuit 8 to read out the written data.

In the above configuration, as shown in Fig. 6, since recording is performed with a light beam modulated with the power intensity values of the semiconductor laser, PK and Py, being constant, the recording film on the information track is If the sensitivity to the semiconductor laser is different or if the semiconductor laser is insufficient in power, the time for the reflectance to become dark and dark will change, and the bit period for the darkness will differ from the period of the recording signal, resulting in a so-called jitter component during demodulation. , which had the disadvantage of being misread. In addition, as a means to solve this drawback, Japanese Patent Application Laid-Open No. 60-8323
The method disclosed in Publication No. 4 records a signal of a certain frequency on a predetermined track different from the track to be recorded before recording, and reproduces the recorded signal to determine the density ratio of the waveform. Means is used to control the bias value of the laser power and the like during recording so that the number is 50.

Problems to be Solved by the Invention However, with the above-mentioned means, variations in the pit period due to variations in the optical disc can be dealt with on a case-by-case basis, but even within a single optical disc, the linear velocity changes due to differences in the radius of rotation. When a laser power shortage occurs, it is necessary to always perform correction, and the recording area decreases. For example, if the writable innermost diameter of an optical disc with a radius of 20Q11 is 9.5CIIt and the outermost diameter is 19CI11, the control is performed at a constant rotation (CAT control: Con5t&nt A
ngular velocity), the linear velocity is twice as high on the outer circumference as on the inner circumference. By the way, 18
When rotating at 0 rpm, the innermost track has approximately 9
m1B outermost track is approximately 18m/! The linear velocity of I and the laser power per unit area of the former are % compared to the latter. Therefore, when writing data near the outermost periphery with the same power, depending on the sensitivity of the recording film, as shown in Figure 7, the b pit is shorter and narrower than the normal gray bit length a. It is formed. The difference in bit length causes jitter in the time axis direction, but a decrease in pit width leads to deterioration of O/N, resulting in deterioration of the quality of the reproduced signal. Generally, in order to compensate for the deterioration, measures are taken to increase the power by changing the drive bias value of the semiconductor laser, as in the above-mentioned publication. FIG. 7 shows an example of the power output characteristics of the semiconductor laser when the bias current value is changed. In Fig. 8, when the amplitude value io of the drive current is kept constant and the bias value is changed from 11 to 1□, the maximum power changes from (P1+po) to (P2+po) and (p
, -p, ).

However, when the power is increased, there is temperature diffusion due to the laser not only in the linear direction of the track but also in the width direction, and as shown in C in Figure 7, when the bit width is large, crosstalk between tracks increases. do.

Furthermore, if the difference in linear velocity is large between the inner and outer peripheries (in other words, the diameter of the disk is large), the power control range becomes large, and a semiconductor laser with higher output power is required. The maximum rated power of semiconductor lasers currently in practical use is 8
Although the development of even higher output lasers, which have a wavelength of 30 nu and a power of about 2 mmW, is underway, it will take some time before they can be put into practical use. 830 n1ll, short wavelength 78
01m.

At wavelengths on the order of e s o nu, it is thought that practical use will be in the near future.

In view of this, an object of the present invention is to provide an optical disc recording/reproducing apparatus that reduces the output of a semiconductor laser and does not require a semiconductor laser with a higher output than the conventional one even when the disc diameter is large.

Means for Solving the Problems The present invention divides the data recording area of an optical disk into concentric circles in the radial direction, and provides means for controlling the power of a semiconductor laser and driving the semiconductor laser within the divided areas. means for recording data, means for reproducing the recorded signal, means for correcting the period of the reproduced output signal of the reproducing means, and means for selecting a signal based on a recording area determination signal. This is an optical disc recording/playback device.

Effect of the Invention With the above-described configuration, the present invention reduces the power of the semiconductor laser in the divided areas of the optical disk so that the output is shortened by the detection window width of the modulation method as it goes to the outer area. The power is controlled and recorded. During reproduction, the period of the reproduced signal is corrected by the reproduced clock (reciprocal of the detection window width) to enable demodulation.

Embodiment FIG. 1 shows the configuration of an optical disc recording and reproducing apparatus in an embodiment of the present invention. Reference numeral 11 is an optical disk on which tracks for recording information are formed, and a recording film is deposited thereon. 12 is a motor for rotating the optical disc 11 and a turntable, and the optical disc 11 is mounted on the turntable. 13 is an optical head composed of a condenser lens, a beam splitter, a collimator lens, etc.

14 is a semiconductor laser attached to the optical head 13;
15 is a light receiving element that detects the amount of light reflected from the optical disc. 16 is a modulation circuit, and write data is, for example, 4 disclosed in Japanese Patent Application Laid-Open No. 58-203609.
/8 modulation modulation. 4/8 modulation is an algorithm that divides the original data into every 4 pits and sequentially converts them into 8-bit code data. According to the above 4/8 modulation modulation, the number of consecutive bits (pitch) - 10'' between bit tt1'' and bit f1'' of the code after conversion (
(called run length) is a minimum of 2. The maximum is 7. 1
Reference numeral 7 denotes a circuit that detects the track position based on address information recorded in advance on the optical disc 11. Reference numeral 18 denotes a bias value generation circuit which generates a bias voltage or current for changing the power of the semiconductor laser according to the linear velocity within the divided regions of the optical disk 11.

19 is a mixing circuit that adds a bias value to the modulation signal.

2o is a semiconductor laser drive circuit that changes the strength of the power of the semiconductor laser 14 in accordance with the write data. 21
is a waveform equalization circuit, which includes a circuit for amplifying the output signal of the light-receiving element 16, an equalization circuit for compensating for a drop in amplitude at high frequencies, and a zero-cross detection circuit. Reference numeral 22 denotes a control signal detection circuit which detects, for example, a pre-recorded signal for each recording area and outputs a control signal. 23 is a clock reproducing circuit which generates a clock synchronized with the rise and fall of the output signal from the waveform equalization circuit 21 using a PLL circuit or the like. A delay circuit 24 delays the input signal in synchronization with the clock of the clock recovery circuit 23. 25 is an OR circuit which takes the logical sum (OR) of two inputs and outputs the result. A switch circuit 26 selects an input signal according to the output signal of the control signal detection circuit 22. A demodulation circuit 27 demodulates the reproduced data. For example, it is composed of a demodulation circuit using a 478 modulation method.

FIG. 2 shows the operation of the optical disc recording and reproducing apparatus of this embodiment configured as described above.

This will be explained using FIGS. 3 and 4.

The optical disc 11 is mounted on a turntable 12 on a motor, and is rotated at a constant speed of, for example, 1800 revolutions per minute.

A light beam from a semiconductor laser 14 fixed to the optical head 13 is focused onto the optical disk 11 as shown at 82 by optical components such as a collimator lens and a condensing lens within the optical head.

Similarly, the reflected light from the optical disc 11 is irradiated onto the light receiving element 16 by optical components. As in the conventional example, data to be written while performing focus control and tracking control is converted by the modulation circuit 16 into a data string using the known 4/8 modulation method.

Waveform 51 in FIG. 2 is an example. Furthermore, it is converted by NRZ and becomes a recording signal of waveform 62.

The output signal of the modulation circuit 16 is input to a mixing circuit 19, and the signal is mixed with a bias value from a bias value generation circuit 18, which will be described later. The semiconductor laser 14 attached to the optical head 13 emits light only in the °H'' section of the modulation signal by the laser drive circuit, and as a result, pits with different reflectances as shown at 63 in FIG. 2 are formed on the optical disk 11. .If the diameter of the optical disc 11 is 20CI11, the innermost diameter of the recording area is 9.5 scratches, and the outermost diameter is 19cm, the linear velocity is twice as different between the former and latter tracks.The laser output at the innermost circumference is optimized. However, when recording the outermost track, the pit length of 53 is originally recorded as short as 64. This is because the linear velocity is twice as high as described above, and the laser power per unit area is This is because the value is insufficient to change the reflectance of the recording film in the irradiation section.

Therefore, in the present invention, in order to solve the conventional problems, the third
As shown in the figure, the recording area is divided into two areas B, and the same power control as before is performed in area M, and a different power is controlled in area B, and the pit length is changed to 66 pits in Fig. 2. is recorded one clock shorter than the original pit length. FIG. 4 shows a conceptual diagram of the power control. Conventionally, the power is increased almost uniformly according to the diameter from the innermost circumference to the outermost circumference, but in the present invention, the power is relatively decreased in region B. In addition to this, 65 in Figure 2
It is possible to record the pit length as short as a predetermined length. Conventional power control requires a semiconductor laser capable of outputting the maximum power output indicated by p wax in FIG. 4, but in the present invention, a power lower than Pmax (Pmax in the figure) is sufficient.

The above power control is made possible by adding the bias value from the bias value generation circuit 18 to the mixing circuit 19 in the embodiment shown in FIG. The state of power control within the area is the same as in the case of FIG. 8, which was also used in the conventional example. Area M and area B are detected by the position detection circuit 17, and a signal for controlling the bias value within the area is sent to the bias value generation circuit 18 based on the track position information within the area.

Next, during reproduction, a constant low-power laser beam is focused on the recorded information track, the reflected light is detected by the light receiving element 16, and a reproduction signal is input to the waveform equalization circuit 21. In the waveform equalization circuit 21, the reproduced signal is amplified to a predetermined level, frequency compensated, and converted into digital data. The output signal of the waveform equalization circuit 21 is output to a control signal detection circuit 22, a clock recovery circuit 23, a delay circuit 24, and the like. The clock regeneration circuit 23 receives an input signal (second
A clock synchronized with the rising and falling edges of the waveform 67 in the figure is generated by a PLL circuit or the like. The clock of the 478 modulation method has a frequency that is the reciprocal of the detection window width), and if the transmission rate is 1/T (T: data clock period), then 2/T
becomes. Therefore, the output signal waveform of the clock regeneration circuit 23 is similar to 58 in FIG. 2, and is input to the delay circuit 24.

The delay circuit 24 delays the input signal 67 by one clock using the clock 58 and outputs the signal to the OR circuit 26 . The OR circuit 25 receives the one clock delay signal 59 and the input signal 57 of the delay circuit 24.
The output signal 60 is logically summed with the switch circuit 26.
Output to. An input signal 67 is separately input to the switch circuit 26, which performs selection based on the control signal from the control signal detection circuit 22, and outputs the selected signal to the demodulation circuit 27. The control signal detection circuit outputs a control signal depending on the distinction between areas A and H, as shown in FIG.

That is, in the case of the present invention, bits are recorded in area B one clock shorter than the original data period, and
The correction thereof is carried out by the circuit group indicated by 26. Therefore, when reproducing data in area B, the corrected output signal 6o from the OR circuit 26 is used, and when reproducing area large, the output signal 57 (uncorrected signal) from the waveform equalization circuit 21 is used. By selecting, it is possible to reproduce the correct data. In this embodiment, it is assumed that a signal for distinguishing areas M and B is recorded in advance. However, since various means can be considered for detecting the control signal, the present invention is not limited to this embodiment. For example, read the address signal during playback. If it is registered in advance whether the address corresponds to a track in area M or B at the time of recording, it can be detected at the time of playback and this operation can be performed. In addition, since the error detection code is generally recorded at the same time as the data, the control signal can also be detected by inputting the data before and after correction, that is, the input signal 60°67 of the switch circuit 260, to the error detection circuit and detecting the presence or absence of an error. Detection is possible. In other words, if the data recorded in the large area is corrected, it will naturally be converted to incorrect data, and conversely, the data recorded in area B will be incorrect unless corrected, so an error will be detected. can. Although this case is different from the configuration of this embodiment, it is in keeping with the gist of the present invention.

Finally, the output signal of the switch circuit 26 is input to a demodulation circuit 27, where demodulation of 478 modulation is performed.

In the above description, the 4/8 modulation method was used as an example, but a similar configuration is possible with other modulation methods. There are no restrictions on the area division or on the location where the number of divisions is two.

As described in detail, according to the present invention, it is possible to reduce the output of a semiconductor laser, and in particular, even if the disk diameter increases and the linear velocity increases, the output of the semiconductor laser can be reduced. is unnecessary, conventional semiconductor lasers can be used, and its practical effects are great.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an optical disc recording/reproducing apparatus according to an embodiment of the present invention, FIG. 2 is a waveform diagram for explaining the operation of FIG. 1, and FIG. 3 is a recording area of an optical disc according to the same embodiment. 4 is an explanatory diagram showing an example of semiconductor laser output control in the same embodiment; FIG. 5 is a configuration diagram of a conventional optical disc recording/reproducing device; and FIG. 6 is a conventional laser drive waveform. 7 are explanatory diagrams of problems in the conventional example, and FIG. 8 is an explanatory diagram of laser drive. 11... Optical disk, 12... Motor and turntable, 13... Optical head,
14... Semiconductor laser, 16... Light receiving element, 16... Modulation circuit, 17... Position detection circuit, 18... Bias value generation circuit , 19・
... Mixing circuit, 20 ... Laser drive circuit, 21 ... Waveform equalization circuit, 22 ... Control signal detection circuit, 23 ...... clock regeneration circuit,
24...delay circuit, 26...OR circuit, 26...switch circuit, 27...demodulation circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 10 1710 l Ol 710+010101
110101 I 1llllllll
l lII II
1155 1σr 1 11m+
1
1 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8

Claims (1)

[Claims] A data recording area of an optical disk is divided concentrically in the radial direction, and within the divided area, a means for controlling laser output, a means for driving the laser to record data, and a means for recording the recorded signal. 1. An optical disc recording/reproducing apparatus comprising: means for reproducing, means for correcting the cycle of an output signal of the reproducing means, and means for selecting a signal based on a recording area determination signal.