JP2557555B2 - Laser output setting method for optical disk recording - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a laser output setting method at the time of recording an optical disc, and particularly, a laser output most suitable for each optical disc and an optical disc recording apparatus is set in a laser output calibration area of the optical disc. Regarding how to ask using.

[Prior Art] At present, a write-once (WO) optical disc recording / reproducing apparatus capable of writing to an optical disc only once using a laser beam is known.

In this optical disc recording / reproducing apparatus, a laser beam is modulated by an EFM signal and irradiated onto the optical disc to write a pit train, and the laser light reflected by the pit train is converted into an electric current to reproduce the recording.

The HL logic duty ratio of the EFM signal is 0.5, but the length of the front and rear edges of the pit changes depending on the size of the laser power, causing asymmetry.

Further, since the edge shape of the waveform changes depending on the performance of the optical pickup when reading the signal, the duty ratio of the read signal may not be 0.5.

Therefore, a laser output calibration area is provided in an unrecorded optical disc, a recommended laser output for a predetermined wavelength is recorded therein, and the recommended laser output is read and the laser output is set before recording on the optical disc.

[Problems to be Solved by the Invention] The shape of pits recorded on an optical disc varies depending on each optical disc and the optical disc recording / reproducing apparatus.
Since the waveform shape of the read signal also changes depending on the optical pickup, there is a problem that the most suitable laser output for each optical disk or optical disk recording / reproducing apparatus cannot be obtained by the above conventional method.

The present invention has been made to solve the above problems, and an EFM signal is recorded on an optical disc by an optical disc recording / reproducing apparatus, and the optimum EMF signal is read from the signal read by the same optical disc recording / reproducing apparatus to obtain an optimum laser output. It aims to provide a way to set up.

[Means for Solving the Problems] A laser output setting method for recording an optical disc according to the present invention is to read a recommended laser output recorded on a blank disc, and perform laser scanning in several steps above and below the read output for several frames. Recording is performed by changing the output, and the TTL level EFM signal obtained by reproducing the recording location is converted to DC through the low pass wave filter, and the recording laser output of the frame whose DC voltage is closest to 2.5V is recorded in the recording area. The laser output is used.

Further, in the laser output setting method at the time of recording on the optical disc, an identification code is recorded in a subcode frame for recording it at each stage of the recording laser output, and the optimum laser output is confirmed by the identification code.

[Operation] Since the TTL level signal obtained by reproducing the pit train of the EFM signal recorded on the optical disk changes to H and L at the edge of the signal read by the optical pickup, its TT
When the DC voltage of the L-level signal is 2.5V, the duty ratio becomes 0.5, and by setting the recording laser output that gives the DC voltage closest to 2.5V, the laser output was used for recording, and then it was read. Good symmetry of the signal is obtained.

If the laser output is recorded as an identification code during recording, it becomes easy to confirm the laser output during reproduction.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

 FIG. 1 is a block diagram showing an embodiment of the present invention.

When recording on the optical disc, the laser light emitted from the laser diode of the optical pickup 1 is rotated while the optical disc 20 is rotated by the spindle motor 21.
Focus on.

At that time, the current supplied to the laser diode of the optical pickup 1 is modulated by the laser current modulator 2 by the EFM signal created by the CD encoder 3, and the intensity of the current is a digital signal set by the microcomputer 5. Is converted into an analog signal by the DA converter 4 and controlled by the analog signal.

Further, when reproducing the optical disc 20 recorded in this way, the laser current modulator 2 supplies a constant low current to the laser diode, and the light emitted from the laser diode is recorded on the optical disc 20 as described above. Is reflected by the pit row of the optical pickup 1, and the reflected light is received by the photodiode of the optical pickup 1. The current obtained from the photodiode of the optical pickup 1 is converted into a voltage by the IV converter 6, amplified by the RF amplifier 7, and further, a capacitor. The DC component is removed by 8 and input to the comparator 9.

When setting the laser output, the analog switch 17 is connected to the laser output calibration (PCA) side by the microcomputer 5 as shown in the figure, and the voltage (Vc) which is half the power supply voltage (Vc
c / 2) is applied as a comparison voltage to the comparator 9 via the buffer 18 and the differential amplifier 19.

On the other hand, the TTL level EFM signal obtained by the comparator 9 passes through the buffers 13 and 14 on the one hand, and then passes through the low pass filter.
It is converted to direct current at 15, converted into a digital value at the AD converter 16 and input to the microcomputer 5, amplified at the EFM signal amplifier 10, demodulated to an 8-bit symbol by the EFM decoder, and recorded in the subcode frame. The identification code is identified by the subcode identifier 12 and input to the microcomputer 5.

With such a circuit configuration, the laser output setting method of the present invention is implemented.

First, the recommended laser output recorded in the calibration area of the unrecorded optical disk in the reproduction state is read, and the microcomputer 5 sets the laser output in several stages centering on the recommended laser output.

A predetermined frame in the optical disc calibration area is recorded with the laser output set in this way.

At this time, the laser output is coded and recorded in the subcode frame.

Next, the test area thus recorded is read, but at this time, the analog switch is connected to the PCA side.

The direct current component of the TTL level EFM signal is input to the microcomputer 5 as a digital value, and the recording laser output of the frame whose value is closest to 2.5 V is set as the laser output at the time of subsequent recording.

The laser output is easy to recognize because the code recorded in the sub-code frame is read by the microcomputer 5 at the same time.

FIG. 2 shows in detail the loop portion including the analog switch 17 shown in FIG.

This loop forms the autoasymmetry circuit of a normal CD player.

That is, when the analog switch 17 is connected to the RECPB side, the TTL level EFM signal obtained by the comparator 9 has its output impedance converted by the buffer in which two CMOS inverters 13 and 14 are connected in series, and the resistance is changed. Further, the DC component is taken out by the low-pass filter 15 formed by the smoothing circuit of the capacitor.

The direct current component is impedance-converted by the buffer 18 of the operational amplifier whose output terminal is connected to the inverting input terminal, and further differentially amplified by the differential amplifier 19 whose comparison voltage is 1/2 of the power supply voltage. Is input as the comparison voltage of.

In this way, the threshold voltage of the comparator 9 is controlled by the average voltage of its output, so that the asymmetry of the automatically read signal is adjusted.

According to the present invention, an analog switch 17 is provided in such a conventional autoasymmetry circuit to open the loop of the autoasymmetry circuit to add the DC component of the TTL level EFM signal.
It can be implemented by inputting the digital signal to the microcomputer by the converter 16.

[Effects of the Invention] As described above, according to the present invention, an analog switch, a Vcc / 2 reference voltage, and an AD converter that use the servo loop of an autoasymmetry circuit used in a CD player as an open loop are added. The optimum value of the laser output can be set with a simple circuit, and the error in reading the recorded data is reduced.

If the laser output is recorded as the identification code on the subcode data when recording with the laser output at each stage,
It is possible to recognize the laser output in a short time.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a circuit for carrying out the present invention, and FIG. 2 is a circuit diagram showing a part of the circuit shown in FIG. 1 ... Optical pickup, 2 ... Laser current modulator, 3 ...
… CD encoder, 4 DA converter, 5 Microcomputer, 6 IV converter, 7 RF amplifier, 8
Capacitor, 9 …… Comparator, 10 …… EFM amplifier, 1
1 ... EFM decoder, 12 ... subcode identifier, 13,14 ...
… Buffer, 15 …… Low-pass filter, 16 …… AD converter, 17 …… Analog switch, 18 …… Buffer, 19…
… Differential amplifier, 20 …… Optical disk, 21 …… Spindle motor.

Claims (2)

(57) [Claims] 1. A TTL obtained by reading a recommended laser output recorded on a blank disc, changing the laser output in several steps above and below the read output for several frames, and reproducing the recording location. A laser output setting method for optical disc recording in which the level EFM signal is converted to DC through a low pass wave filter, and the recording laser output of the frame whose DC voltage is closest to 2.5V is used as the recording laser output of the recording area. 2. The laser output setting method for optical disc recording according to claim 1, wherein an identification code is recorded in a sub-code frame for recording each stage of the recording laser output.