JP2797858B2 - Laser power adjustment circuit of optical disk device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser power adjusting circuit of an optical disk apparatus used for external storage of a computer, recording and reproduction of music and video signals, and other information.

[0002]

2. Description of the Related Art In recent years, with the development of electronic computers and the development of means for high-speed and large-scale transmission of information, a non-volatile memory device having low cost, high density, large capacity, and high-speed transfer capability has been demanded.
In many cases, a magnetic disk is used, but there are problems such as a low recording density, a high price per information unit, and a difficulty in medium exchange especially in a fixed magnetic disk device. An optical disk device is currently in the spotlight as a technology for solving those problems, and is expected in many fields.

In a conventional optical disk device, recording is performed by using laser irradiation intensity synchronized with a recording signal.
Further, since the size of the pit is influenced by the laser power at the time of recording, fine adjustment of the power is performed by reproducing the recorded portion.

Hereinafter, a laser power adjusting circuit of a conventional optical disk device as described above will be described with reference to the drawings.

FIG. 6 is a circuit diagram of a conventional laser power control circuit for adjusting the laser power.

In FIG. 6, a reverse bias of several volts is applied to the photodiode at a photodiode 71 for monitoring laser power and a bias voltage application terminal 72 thereof. The photodiode receives light emitted from the laser diode and outputs a current to the current-voltage converter 73. The current-voltage converter 73 converts the output current of the photodiode into a voltage so that the output of the laser diode is represented by a voltage.

The voltage generated by the current-voltage converter 73 is
The difference is compared with a recording power adjustment voltage 75 that is a target value by the differential amplifier 74, and is output to the current drive circuit 76. The current drive circuit drives the laser diode 78 with a current by the recording signal 77 and the signal of the differential amplifier 74.

[0008]

The above-described conventional laser power adjusting circuit of the optical disk apparatus has the following problems.

That is, there is a problem that the optimum recording power changes depending on the recording sensitivity of the disk medium and the environmental temperature during recording.

Further, since the recording power must be adjusted by repeating recording and reproduction several times, the adjustment procedure is complicated, and the adjustment process requires time.

An object of the present invention is to automatically adjust the laser power at the time of recording without any external adjustment,
The above drawbacks are eliminated, the adjustment process can be reduced at the time of assembling the device, the productivity can be improved, the assembly cost can be reduced, and the change in the environmental temperature and the difference in the recording sensitivity of the disk medium can be easily handled. An object of the present invention is to provide a laser power adjustment circuit of an optical disk device for improving data reliability.

[0012]

SUMMARY OF THE INVENTION A laser power adjusting circuit of an optical disk apparatus according to a first aspect of the present invention includes a photodetector for applying a laser beam to a disk and converting reflected light from the disk into an electric signal, and an output current of the photodetector. A current / voltage converter for converting to a voltage, an integrator for integrating the output of the current / voltage converter to extract a DC component, and an A / D converter for converting the output from the integrator into analog / digital (A / D). Signal determination circuit provided with a device, a control circuit for determining whether or not the output of the reproduction signal determination circuit is in an optimum recording state and changing output data, and a digital / analog (D / A) output of the control circuit A D / A converter for conversion;
In a laser power adjusting circuit of an optical disk apparatus having a laser power setting circuit for adding or subtracting the output of an A / A converter to or from a current driving circuit for laser light, a reproduction signal determination circuit irradiates the optical disk with laser light for recording / reproducing. Means for detecting and judging the state of a reproduced waveform at the time of reproducing data to be reproduced, and setting a laser power at the time of data recording to a predetermined value based on the result of the detection and judgment.

The laser power adjusting circuit of the optical disk device according to the second invention is the laser power adjusting circuit of the optical disk device according to the first invention, wherein the reproduction signal from the current / voltage converter is binarized. In a digital signal, a high (H) level time and a low (L) level time become equal in a predetermined time, and the signal is integrated to obtain an intermediate value. A means is provided for comparing the components with the ground potential, passing the binary digital signal through an integrator, and determining which of the signals is biased with respect to the intermediate potential of the intermediate value.

The laser power adjusting circuit of the optical disk device according to the third invention is the laser power adjusting circuit of the optical disk device according to the second invention, wherein the reproduction signal determining circuit controls a signal output from the integrator. An A / D converter compares the signal with an intermediate potential so that it can be recognized by a circuit, and determines whether the signal is a binarized signal, or whether the potential is slightly higher than the intermediate potential or lower than the intermediate potential. It has means for converting by a detectable window comparator and sending it to the control circuit.

The laser power adjusting circuit of the optical disk device of the fourth invention is the laser power adjusting circuit of the optical disk device of the third invention, wherein the control circuit is an A / D converter.
Based on the converted or binarized signal, it is determined whether or not the laser power at the time of recording is an optimum value, and analog data obtained by D / A converting data from the control CPU to a laser power setting circuit is transmitted. It has a means for adjusting power.

The laser power adjusting circuit of the optical disk device of the fifth invention is the laser power adjusting circuit of the optical disk device of the fourth invention, wherein the laser power setting circuit detects the amount of light output from the laser diode. A photodiode for monitoring, a current-to-voltage converter for converting the output current of the photodiode to a current-to-voltage,
It comprises a differential amplifier for adding or subtracting an output from the current-voltage converter and a signal obtained by D / A-converting the data output from the control circuit.

The laser power adjusting circuit of the optical disk device of the sixth invention is the laser power adjusting circuit of the optical disk device of the fifth invention, wherein the control circuit is an A / D converter.
It is determined whether the signal A / D-converted by the converter or the binarized signal is at an intermediate potential, and data recorded for a certain period is reproduced to determine whether the recording power is an optimum value. Then, when the recording power is changed and the recording and reproduction are repeated to obtain the optimum value, or when the recorded data is reproduced while changing the recording power in one recording,
There is a means for judging which part is the optimum value and setting the recording power at that time to the optimum value.

[0018]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a laser power adjusting circuit according to one embodiment of the present invention, FIG. 2 is a diagram showing the effect of a reproduction signal on recording power, and FIG. 4 is a graph illustrating a relationship between detection voltages of an adjustment circuit.

As shown in FIG. 2, the method utilizes the fact that changing the recording power changes the size of the pits formed on the disk medium and changes the pulse width of the reproduced signal. The recording signals 21 and 22 indicate laser power, and both have the same recording width. However, when the recording signal 22 is larger by ΔP, 24 becomes larger in the pits 23 and 24 formed on the disk medium.
Therefore, when these pits are reproduced, the recording signal 22
The reproduction waveform 26 when recording is made wider. The voltage comparison outputs 27 and 28 are waveforms when the reproduction signal is compared with the intermediate potential of the reproduction signal and binarized.

E used in compact discs and the like
The FM signal has the same time when the signal level is H and when the signal level is L, and has no DC component. Utilizing such a property of the signal, an excess or deficiency of the laser power at the time of recording is detected by the reproduction signal determination circuit 19 shown in FIG.

Next, a method for detecting the optimum recording power of the laser power adjusting circuit of this embodiment will be described with reference to the drawings.

In FIG. 1, a reproduction signal receives light reflected from a disk from a photodetector 1, converts the amount of light into a current, converts the current into a voltage by a current / voltage converter 3, and extracts a signal. The reproduction signal may be extracted by a change in the amount of reflected light as in a compact disk or a dye-based medium, or may be extracted by the polarization angle of light as in a magneto-optical disk. The same signal can be obtained by adding or subtracting the current from the photodetector 1 by the converter 3.

The DC component of the reproduced signal is cut by a differentiating circuit 4, and a signal grounded by a resistor 6 is compared with a ground potential by a voltage comparator 7 to be binarized. When the binarized signal is smoothed by the integrator 8, the output voltage changes according to the recording power as shown in FIG. In the case of an EFM signal, since there is no DC component, when the recording power reaches an optimum value,
It shows the intermediate value when binarized, and when the recording power decreases like recording power 1 in the figure, the voltage also drops below the intermediate potential,
Conversely, when the recording power increases, the voltage increases from the intermediate potential.

Therefore, in order to set the recording power to the optimum value, the integral value of the reproduced signal should be close to the intermediate potential. For this reason, data obtained by A / D integration of the integrated value is transferred to the control circuit 10 and determined by the control circuit 10, or the fact that the recording power is the optimum value is detected and transferred to the control circuit 10. Determine the optimal value.

If the control circuit 10 determines that the value is not the optimum value, the corrected data is sent to the differential amplifier 16 of the laser power setting circuit 20 via the D / A converter 11 to correct the recording power. I do.

As a preliminary recording method for determining the recording power, as shown in FIG. 3, recording was performed while changing linearly from recording power 1 to recording power 2, and the portion was reproduced. There are two methods: a method of sometimes determining an optimum value by a temporal change, and a method of correcting the recording power by changing the recording power every time the recording power is changed. However, in any of the recording methods, if the recording power is too small or too large, the boundary between the pits disappears, and the output of the integrator becomes unstable. However, this range is realized by storing the range in the control circuit 10 in advance.

Next, the determination of the reproduction signal of the laser power adjusting circuit of this embodiment will be described with reference to the drawings.

FIGS. 4 and 5 are diagrams showing a specific example of a configuration for judging a reproduction signal of the laser power adjusting circuit of this embodiment.

In FIG. 4, the DC component of the reproduced signal input to the reproduced signal input terminal 37 is eliminated by the capacitor 38, and the central potential of the reproduced signal becomes equal to the ground potential of the resistor 39. The reproduced signal is obtained by the voltage comparator 40.
The reproduced signal is binarized by comparing with a potential equal to the potential grounded by the resistor 39.

The binarized signal is subjected to waveform shaping by inverter buffers 41 and 42 and resistors 43 and 4.
4 and the capacitors 45 and 46 integrate the binarized signal, and accurately determine the recording state based on the integrated voltage.

If the recording power is larger than the optimum value, the integrated value becomes higher than the central potential of the binarized signal, and if the recording power is smaller, the integrated value becomes lower than the central potential. The potential obtained by the integrator is converted into digital data by the A / D converter 47 and sent to the control circuit 10 to determine the recording state.

FIG. 5 is simplified by a window comparator so as to judge only whether the output voltage of the integrator is within a certain range. An H-level potential and an L-level potential are applied to voltage application terminals 63 and 64, respectively, and resistors 58, 59 and 60 are applied.
Creates a potential slightly higher and lower than the intermediate potential,
These potentials and the output of the integrator are compared with voltage comparators 61 and 62.
To compare. When the output 65 is at the H level, the recording power is high, and when the output 66 is at the H level, the recording power is low. When the outputs 65 and 66 are both at the L level, the recording power becomes the optimum value and can be easily determined.

[0034]

As described above, the laser power adjusting circuit of the optical disk apparatus of the present invention inputs a reproduction signal to the determination circuit and determines whether the laser power at the time of recording is an appropriate value based on the output of the determination circuit. Judgment is made by the control circuit, the D / A converted voltage value is sent from the control circuit to the laser power setting circuit to correct the power at the time of recording, and the laser power is automatically corrected inside the device, thereby assembling the device. It can reduce the number of adjustment steps, improve productivity and reduce assembly costs, and can easily respond to changes in environmental temperature and differences in the recording sensitivity of disk media, improving the reliability of recorded data. effective.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a laser power adjustment circuit according to one embodiment of the present invention.

FIG. 2 is a diagram showing an influence of a reproduction signal by a recording power.

FIG. 3 is a graph showing a relationship between a recording power and a detection voltage of the laser power adjusting circuit of the present embodiment.

FIG. 4 is a diagram illustrating a specific example of a configuration for determining a reproduction signal of a laser power adjustment circuit according to the present embodiment.

FIG. 5 is a diagram illustrating a specific example of a configuration for determining a reproduction signal of the laser power adjustment circuit according to the present embodiment.

FIG. 6 is a laser power control circuit diagram for adjusting laser power according to a conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photodetector 2 photodiode bias terminal 3 current-voltage converter 4 differentiator 5 capacitor 6 resistor 7 voltage comparator 8 integrator 9 A / D converter (or binary converter) 10 control circuit 11 D / A Converter 12 Photodiode bias terminal 13 Laser power monitoring photodiode 14 Laser diode 15 Current-voltage converter 16 Differential amplifier 17 Current drive circuit 18 Recording signal input terminal 19 Reproduction signal determination circuit 20 Laser power setting circuit 21, 22 Recording signal 23, 24 Pit shape 25, 26 Reproduction signal 27, 28 Binarized signal 37 Reproduction signal input terminal 38 Capacitor 39 Resistor 40 Voltage comparator 41, 42 Inverter buffer 43, 44 Resistor 45, 46 Capacitor 47 A / D converter 48 playback signal Input terminal 49 Capacitor 50 Resistor 51 Voltage comparator 52, 53 Inverter buffer 54, 55 Resistor 56, 57 Capacitor 58, 59, 60 Resistor 61, 62 Voltage comparator 63 H level voltage application terminal 64 L level voltage application Terminals 65, 66 Output 71 Laser power monitoring photodiode 72 Bias voltage application terminal 73 Current voltage converter 74 Differential amplifier 75 Recording power adjustment voltage 76 Current drive circuit 77 Recording signal 78 Laser diode

Claims (2)

(57) [Claims] 1. A photodetector for applying a laser beam to a disc to convert reflected light from the disc into an electric signal; a current / voltage converter for converting an output current of the photodetector to a voltage; An integrator that integrates an output to extract a DC component and an A / D that performs an analog-to-digital (A / D) conversion of an output from the integrator
A reproduction signal determination circuit having a converter; a control circuit for determining whether or not the output of the reproduction signal determination circuit is in an optimum recording state and changing output data; and a digital / analog (D / A) / A) a laser power adjusting circuit of an optical disk device, comprising: a D / A converter for conversion; and a laser power setting circuit for adding or subtracting the output of the D / A converter to or from the current drive circuit for the laser light.
The reproduction signal determination circuit detects and determines the state of a reproduction waveform at the time of reproduction of data to be recorded and reproduced by irradiating the optical disk with a laser beam, and based on the detected and determined result, the laser power at the time of recording the data. Has a means to set a predetermined value, the reproduction signal from the current-voltage converter,
In the binarized digital signal, a high (H) level time and a low (L) level time become equal at a predetermined time, and the reproduction signal determination circuit is a modulation method that becomes an intermediate value when the signal is integrated. Compares the AC component of the reproduced signal with a ground potential, passes the binarized digital signal through the integrator, and determines which of the signals is biased with respect to the intermediate potential of the intermediate value Means for causing the A / D converter to perform A / D conversion so that the reproduction signal determination circuit can recognize the signal output from the integrator by the control circuit.
D conversion or comparison with the intermediate potential, binarized signal, or conversion by a window comparator capable of detecting whether the potential is slightly higher than the intermediate potential or lower than the intermediate potential, and converted by the window comparator. Means for sending to the circuit, the control circuit determines whether or not the laser power at the time of recording is an optimum value based on the A / D conversion or the binarized signal. A means for adjusting the laser power at the time of recording by sending analog data obtained by D / A conversion of the data from the control CPU, wherein the laser power setting circuit is used for monitoring the amount of light output from the laser diode; A photodiode, a current-to-voltage converter for converting the output current of the photodiode to current-to-voltage, and an output from the current-to-voltage converter. Laser power adjusting circuit of an optical disk apparatus, characterized in that it is composed of a differential amplifier for adding or subtracting a signal output data converted the D / A from the control circuit. 2. The control circuit according to claim 1 , wherein the A / D converter includes an A / D converter.
It is determined whether the / D-converted signal or the binarized signal is at the intermediate potential, and data recorded for a certain period is reproduced to determine whether the recording power is an optimum value. Which part has the optimum value by changing the recording power and repeating the recording and reproduction to obtain the optimum value, or when reproducing the data recorded while changing the recording power in one recording, which part is the optimum value? 2. The laser power adjusting circuit according to claim 1, further comprising means for judging the recording power and setting the recording power at that time to an optimum value.