JPH0421251B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is an optical disk recording/reproducing method in which bits are formed on a disk according to recorded information using a laser beam, and recorded information is reproduced based on changes in detection signals of the bits. Regarding equipment.

<Prior Art> In recent years, optical disk devices using laser light have been put into practical use. This optical disk can have a recording track density two orders of magnitude higher than that of a magnetic disk, and can constitute a large-capacity memory.
Another major feature of this optical disk is that the recording medium can be moved because a laser beam is focused on the disk surface and the head can be positioned without contact using pre-groups cut on the disk in advance.

<Problems to be Solved by the Invention> In conventional optical disk devices, there are variations in recording sensitivity depending on the disk or recording position on the disk, fluctuations in the beam intensity of the laser element, and recording sensitivity due to environmental temperature. Recording conditions fluctuate due to changes in etc. As a result,
Variations in the recording bit length result in a loss of the phase margin of the reproduced signal, and it is necessary to set the recording density in consideration of this, which has been an obstacle to increasing the recording density.

<Means for Solving the Problems> The present invention includes a recording laser beam generating means that generates a laser beam of arbitrary intensity, and a laser beam whose intensity is sequentially varied by the laser beam generating means prior to information recording. a recording means for generating recording bits at a frequency and irradiating this laser beam onto a disk to form recording bits, and when the pulse width of a reproduction signal for each recording bit recorded by this laser beam reaches a predetermined length; a laser beam intensity detection stage for detecting the intensity of the laser beam; comprising a reference pulse generating means that is activated every time an edge is detected and outputs a reference pulse of a constant pulse width, and a polarity determining means that determines the polarity of the reproduced signal at the rise or fall of the reference pulse, It is characterized in that information is recorded on the disk based on the laser beam intensity detected by the laser beam intensity detection means.

<Example> FIG. 1 shows the basic configuration of an optical disc recording/reproducing apparatus of this example. 1 is an optical recording disk, and 2 is an optical pickup for recording and reproducing information on this optical recording disk. The optical pickup 2 includes a laser 21 that generates a laser beam of arbitrary intensity.
and a reproduced signal detector 22. 3 is a laser driver that drives the laser 21, and 4 is a D/A converter that provides a drive signal to the laser driver 3. Reference numeral 5 denotes a control circuit which supplies data to the D/A converter 4 in order to cause the optical pickup 2 to generate a laser beam having a constant frequency and sequentially varying intensities prior to actual information recording. 6 is an amplifier for amplifying the output of the reproduced signal detector 22; 7 is a comparator for level slicing the output of the amplifier 6 and outputting a pulse signal; 8 is for measuring the magnitude relationship between the pulse width of the pulse from the comparator 7 and a predetermined value. It is a pulse width discriminator that discriminates.

FIG. 2 shows the configuration of the pulse width discriminator 8, 81
82 is a positive edge detection circuit that detects the rising edge of the pulse from the comparator 7; 82 is a monostable multivibrator that outputs a reference pulse with a constant pulse width for each rising edge detected by the positive edge detection circuit 81; 83 is a monostable multivibrator; vibrator 82
A flip-flop samples the pulse from comparator 7 on the rising edge of the reference pulse from . The output of this flip-flop 83 is inverted depending on whether the pulse length on the high level side of the pulse from the comparator 7 is larger or smaller than the pulse length on the low level side of the reference pulse.

FIG. 3 shows signal waveforms in the main parts of this optical disk recording/reproducing device, where a is the recording bit of the optical recording disk, b is the output of the amplifier 6, c is the output of the comparator 7, and d is the monostable multivibrator 82.
and e is the output of flip-flop 83.

The operation of this optical disk recording and reproducing apparatus will be described below with reference to the case where the laser beam intensity is determined so that the duty ratio of the reproduced signal becomes 50%.

The control circuit 5 supplies data to the D/A converter 4 in order to sequentially change the laser drive current in response to a signal of a constant frequency.
This data is converted into an analog signal and given to the laser driver 3. The laser driver 3 drives the laser 21 of the optical pickup 2 in response to this analog signal, and recording is performed on the rotating optical recording disk 1 at a constant frequency with successive laser beam intensities. Now, if recording is performed sequentially at laser beam intensities P1, P2, ..., P5 during periods t1, t2, ..., t5, the recording bits shown in Figure 3a will be recorded on the optical recording disk 1. is formed. The laser beam intensity P1 during this period t1 is smaller than the laser beam intensity P2 during the period t2, and similarly, P2 is smaller than P3, P3 is smaller than P4, and P4 is smaller than P5. Therefore, the recording bit a is the shortest in the period t1 and the longest in the period t5.

Next, the recording bit a formed on the optical recording disk 1 is detected by the reproduction signal detector 22 of the optical pickup 2, amplified by the amplifier 6 and converted into the signal shown in FIG. Therefore, the pulse signal shown in FIG. 3c is obtained by level slicing. In this pulse signal c, the pulse length on the high level side is the shortest in period t1, and in period t2,
It gradually becomes longer as it moves to t3, .... The rising edge of this pulse signal c is detected by the positive edge detection circuit 81 in the pulse width discriminator 8.
This rising edge activates the monostable multivibrator 82, and as a result, the monostable multivibrator 82 outputs a reference pulse signal d with a duty ratio of 50% every time a rising edge of the pulse signal c occurs.

During periods t1 and t2, the duty of the pulse signal c is biased, and the high-level pulse length of the pulse signal c is shorter than the low-level pulse length of the reference pulse signal d, so the output e of the flip-flop 83 remains at a low level. There is even.

Next, in period t3, when the high level pulse length of the pulse signal c and the low level pulse length of the reference pulse signal d become equal, the output e of the flip-flop 83 is inverted to high level. After that, period t4,
At t5, the high-level pulse length of the pulse signal c is longer than the low-level pulse length of the reference pulse signal d, so the output e of the flip-flop 83 remains at a high level.

Period during which the output e of the flip-flop 83 is inverted
The duty ratio of the pulse signal c, that is, the reproduction signal at t3 is 50%, and the laser beam intensity during this period 3t is P3. Therefore, it is determined that the laser beam intensity should be set to P3 in order to perform optimal recording with a reproduction signal duty ratio of 50%. After this,
Actual information recording is performed using this laser beam intensity P3.

In this embodiment, the high-level side pulse length and rising edge of the pulse signal c are used for determination, but the low-level side pulse length and falling edge of the pulse signal c may also be used. Needless to say. Furthermore, if the determination is made using both the high-level side and low-level side pulse lengths of the pulse signal c, the intensity of the laser beam can be set with higher precision.

<Effects> As explained above, in the present invention, recording is performed while sequentially changing the laser beam intensity, and the laser beam intensity is obtained when the pulse width of the reproduced signal reaches a predetermined length. Therefore, even if the recording sensitivity differs depending on the disk or the laser beam intensity varies depending on the temperature, it is possible to set the optimal recording conditions based on the disk used and the environmental conditions, and the reliability of the reproduced signal is improved. In addition, it is possible to realize high-density information recording. Furthermore, recording bits are formed by generating a laser beam with a sequentially variable intensity at a constant frequency, and a reference pulse width of a constant pulse width is generated for each rising or falling edge of the reproduced signal on the recording bits. Since the laser beam intensity during recording is set by detecting that the pulse width matches the reference pulse width, there is an advantage that the optimum laser beam intensity can be quickly set with a simple circuit configuration.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the basic configuration of an embodiment of the present invention, FIG. 2 is a block diagram showing the configuration of a pulse width discriminator according to an embodiment of the present invention, and FIG. 3 shows a signal waveform of an embodiment of the present invention. FIG. DESCRIPTION OF SYMBOLS 1... Optical recording disk, 2... Optical pickup, 3... Laser driver, 4... D/A converter, 5... Control circuit, 6... Amplifier, 7...
Comparator, 8... Pulse width discriminator, 81...
Positive edge detector, 82... monostable multivibrator, 83... flip-flop.

Claims (1)

[Claims] 1. A recording laser beam generating means for generating a laser beam of arbitrary intensity; and prior to recording information, the laser beam generating means generates a laser beam whose intensity is sequentially variable at a constant frequency;
and a recording means for forming recording bits by irradiating the laser beam onto the disk, and a recording means for forming recording bits by irradiating the disk with the laser beam, and a recording means for irradiating the laser beam with the laser beam when the pulse width of the reproduction signal for each of the recording bits recorded by the laser beam reaches a predetermined length. a laser beam intensity detection means for detecting the intensity, and a signal edge detection means for detecting a rising or falling edge of the reproduced signal;
a reference pulse generating means that is activated every time an edge of the signal edge detecting means is detected and outputs a reference pulse of a constant pulse width; and a polarity determining means that determines the polarity of the reproduced signal at the rise or fall of the reference pulse. An optical disk recording and reproducing apparatus comprising: an optical disk recording and reproducing apparatus, characterized in that information is recorded on the disk based on a laser beam having an intensity detected by the laser beam intensity detecting means.