JPS6254831A - Optical disc recording and reproducing device - Google Patents

Abstract

PURPOSE:To set an optimum recording condition by applying recording while the intensity of a laser beam is changed sequentially so as to obtain the laser beam intensity when the pulse width of a reproduced signal reaches a prescribed width. CONSTITUTION:A control circuit 5 gives a data to a D/A converter to change sequentially the laser drive current, a laser driver 3 drives the laser 21 of an optical pickup 2 in response to an analog signal and the recording with a prescribed frequency and sequentially different laser beam intensity is applied to a rotary optical recording disc 1. Thus, the recording pit (a) at a period t1 is the shortest and that at a period t5 is the longest. In order to apply the optimum recording where the duty ratio of the reproducing signal is 50%, it is decided that the laser beam strength is to be P3 and the information is recorded with the laser beam strength of P3.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention provides an optical disc recording and reproducing apparatus that forms bits corresponding to recorded information on a disc using a laser beam, and reproduces recorded information based on changes in detection signals of the bits. Regarding.

<Prior Art> In recent years, optical disc 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> Conventional optical disc devices suffer from variations in recording sensitivity that vary from disc to disc or depending on the recording position on the disc, fluctuations in the beam intensity of a laser element, and changes in recording sensitivity due to environmental temperature. The recording conditions change accordingly. As a result, the phase margin of the reproduced signal is lost due to variations in the recording bit length, and it is necessary to set the recording density in consideration of this, which has been an obstacle to increasing the density.

Means for Solving the Problems> The present invention provides a recording laser beam generating means for generating a laser beam of arbitrary intensity, and a recording laser beam generating means that sequentially generates laser beams of different intensities. A recording device that irradiates a disk with a beam to form recording bits, and a laser beam intensity detection device that detects the intensity of the laser beam when the pulse width of a reproduction signal for the recording bit reaches a predetermined length. , information is recorded on the disk based on the intensity of the laser beam.

<Embodiment> FIG. 1 shows the basic configuration of an optical disc recording/reproducing apparatus of this embodiment. 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. 5 optically picks up a laser beam with a constant frequency and sequentially varying intensities prior to actual information recording.
This is a control circuit that provides data to the D/A converter 4 to generate data. 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, in which 81 is a positive edge detector that detects the rising edge of the pulse from the comparator 7, and 82 is a positive edge detector 82 that detects the rising edge of the pulse from the comparator 7. The monostable multi-bi break 83 outputting the reference pulse is a flip-flop that samples the pulse from the comparator 7 at the rising edge of the reference pulse from the monostable multi-bi break 82. 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 output of the monostable multi-bi break 82. , e are the outputs of the 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 sequentially supplies data to the D/A converter 4 in order to convert the laser drive current in response to a signal of a constant frequency, and the D/A converter 4 converts this data into an analog signal and outputs the data to the laser driver 3. given to. The laser driver 3 drives the laser 21 of the optical pickup 2 in accordance with this analog signal, so that recording of constant frequencies with different laser beam intensities is performed on the rotating optical recording disk 1 sequentially. Now, period t1.
t2. ..., at t5, the laser beam intensities are Pi, P2 . . . . When recording is performed sequentially in P5, recording bits shown in FIG. 3a are formed on the optical recording disk 1. 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,
After being amplified by the amplifier 6 and converted into the signal shown in FIG. 3, it is level sliced by the comparator 7 to obtain the pulse signal shown in FIG. 3C. This pulse signal C has the shortest pulse length on the high level side during period t1,
Period t2゜t3. It becomes longer as it moves to... The rising edge of the pulse signal C is detected by the positive edge detector 81 in the pulse width discriminator 8, and the monostable multi-bi break 82 is activated by this rising edge.
As a result, from the monostable multi-by break 82, the duty ratio increases by 5 every time a rising edge of the pulse signal C occurs.
A reference pulse signal d of 0% is output.

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 is held at a low level. It remains as it is.

Next, in period t3, high-level pulses i, l! of pulse signal C! : When the low level pulse length of the reference pulse signal d becomes equal, the output e of the flip-flop 83 is inverted to high level. Thereafter, in periods t4-t5,
Since the high level pulse x of the pulse signal C is longer than the low level pulse length of the reference pulse signal d, the output e of the flip-flop 83 remains at a high level.

The duty ratio of the pulse signal C, that is, the reproduction signal, during the period t3 in which the output e of the flip-flop 83 is inverted is 5.
0%, 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%. Thereafter, actual information is recorded using this laser beam intensity P3.

In this embodiment, the pulse length and rising edge on the high level side of the pulse signal C are used for determination, but the pulse length and falling edge on the low level side 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 laser beam intensity can be set with higher precision.

Effect> 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. , even if the recording sensitivity differs depending on the disc or the laser beam intensity varies depending on the temperature,
It becomes possible to set optimal recording conditions based on the disc used and the environmental conditions, thereby improving the reliability of the reproduced signal and realizing high-density recording of information.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the basic configuration of the embodiment of the present invention, FIG. 2 is a block diagram showing the configuration of the pulse width discriminator of the embodiment of the present invention, and FIG. 3 shows the signal waveform of the embodiment of the present invention. FIG. 1... Optical recording disk 2... Optical pickup 3... Laser driver 4... D/A converter 5... Control circuit 6... Amplifier 7... Comparator 8... Pulse width discrimination Detector 81... Positive edge detector 82... Monostable multi-bi break 83... Flip-flop

Claims (3)

[Claims] (1) A recording laser beam generation means that generates a laser beam of arbitrary intensity, and this recording laser beam generation means sequentially generates laser beams of different intensities and irradiates the disk with the laser beams to form recording bits. and laser beam intensity detection means for detecting the intensity of the laser beam when the pulse width of the reproduced signal for the recording bit reaches a predetermined length, 1. An optical disc recording and reproducing device characterized in that information is recorded on an optical disc. (2) The optical disc recording and reproducing apparatus according to claim 1, wherein the signal recorded on the disc by the recording means has a constant frequency. (3) The laser beam intensity detection means includes a signal edge detection means for detecting a rising or falling edge of the reproduced signal, a timer means activated by the signal edge detection means, and a timer means activated when the timer means times out. The optical disc recording and reproducing apparatus according to claim 1, further comprising polarity determining means for determining the polarity of the reproduction signal.