Laser control device

An apparatus which controls a power of a semiconductor laser in an optical recording/reproducing apparatus for performing recording/reproduction into/from an optical disk by a semiconductor laser, comprising:

• a photodiode for detecting a light of the semiconductor laser;
• a current/voltage conversion means for converting a current of the photodiode to a voltage and outputting the voltage;
• a reference voltage source for deciding a reproduction power of the semiconductor laser;
• an error detection means for detecting an error between the voltage outputted by the current/voltage conversion means and the reference voltage;
• a current source for passing a current through the semiconductor laser;
• a reproduction power control system for connecting an output of the error detection means to the current source, and controlling the reproduction power of the semiconductor laser;
• a bias current setting means for deciding a bias current to be passed through the semiconductor laser;
• a switch means for selectively switching between an output of the error detection means and an output of the bias current setting means, and at the reproduction, connecting an output of the error detection means to the current source to form the reproduction power control system and, at the recording, connecting an output of the bias current setting means, instead of the output of the error detection means, to the current source;
• a sample-hold means for sample-holding the output voltage of the current/voltage conversion means at the recording;
• an erase current setting means for deciding an erase current to be passed through the semiconductor laser;
• a peak current setting means for deciding a peak current to be passed through the semiconductor laser;
• and
• an operation means for operating set values of the erase current setting means and the peak current setting means on the basis of an output value of the sample-hold means.

An apparatus which controls a power of a semiconductor laser in an optical recording/reproducing apparatus for performing recording/reproduction into/from an optical recording medium by a semiconductor laser, comprising:

• a semiconductor laser power monitor means for monitoring an output of the semiconductor laser;
• an output error detection means for detecting an error between an output power reference value which is to be outputted by the semiconductor laser at reproduction just before recording and an actual output power value at the reproduction, which value is detected by the semiconductor laser power monitor means;
• a semiconductor laser power control means for setting a output power target value to a semiconductor laser driving means on the basis of a detected result of the output error detection means;
• and
• an output power target value correction means for correcting the output power target value on the basis of a monitor value of an output of the semiconductor laser driving means after the output power target value is set.

An apparatus which controls a power of a semiconductor laser in an optical recording/reproducing apparatus for performing recording/reproduction into/from an optical disk by a semiconductor laser, comprising:

• a photodiode for detecting a light of the semiconductor laser;
• a current/voltage conversion circuit for converting a current of the photodiode to a voltage, and outputting the voltage;
• a reference voltage source for deciding a reproduction power of the semiconductor laser;
• an error amplifier for amplifying a difference between the voltage outputted by the current/voltage conversion circuit and the reference voltage;
• a current source for passing a current through the semiconductor laser;
• a reproduction power control system for connecting an output of the error amplifier to the current source, to control the reproduction power;
• a D/A conversion circuit for deciding a current to be passed through the semiconductor laser;
• a switch means for selectively switching between an output of the error amplifier and an output of the D/A conversion circuit, to make a control signal of the current source;
• and
• an A/D conversion circuit for selecting one of an output voltage of the error amplifier and an output voltage of the D/A conversion circuit, and subjecting the voltages to digital conversion;
• wherein
• a digital value of the D/A conversion circuit is decided on the basis of a digital value of the A/D conversion circuit, and
• at the recording, the output of the error amplifier is switched over to the output of the D/A conversion circuit and the current of the current source is controlled.

An apparatus which controls a power of a semiconductor laser in an optical recording/reproducing apparatus for performing recording/reproduction into/from an optical disk by a semiconductor laser, comprising:

• a photodiode for detecting a light of the semiconductor laser;
• a current/voltage conversion circuit for converting a current of the photodiode to a voltage, and outputting the voltage;
• a reference voltage source for deciding a reproduction power of the semiconductor laser;
• an error amplifier for amplifying a difference between the output voltage of the current/voltage conversion circuit and the reference voltage;
• a current source for passing a current through the semiconductor laser;
• a D/A conversion circuit for deciding a current to be passed through the semiconductor laser;
• a switch means for selectively switching a control signal of the current source to switch between an output of the error amplifier and an output of the D/A conversion circuit;
• an A/D conversion circuit for subjecting an analog signal outputted from the current/voltage conversion circuit to digital conversion, and outputting the converted signal;
• and
• an operation circuit for, in a period during which recording is not performed, outputting a digital signal to the D/A conversion circuit, reading changes in the output signal of the A/D conversion circuit, obtaining a change amount in power in response to a change amount in the current of the semiconductor laser, and at the recording, outputting the digital signal value obtained above to the D/A conversion circuit.

An apparatus which controls a power of a semiconductor laser in an optical recording/reproducing apparatus for performing recording/reproduction into/from an optical disk by a semiconductor laser, comprising:

• a photodiode for detecting a light of the semiconductor laser;
• a current/voltage conversion circuit for converting a current of the photodiode into a voltage, and outputting the voltage;
• a reference voltage source for deciding a reproduction power of the semiconductor laser;
• an error amplifier for amplifying a difference between the output voltage of the current/voltage conversion circuit and the reference voltage;
• a current source for passing a current through the semiconductor laser;
• a reproduction power control system for connecting an output of the error amplifier to the current source, and controlling the reproduction power;
• a D/A conversion circuit for deciding a current to be passed through the semiconductor laser;
• a switch means for selectively switching between the output of the error amplifier and an output of the D/A conversion circuit, to make a control signal of the current source;
• an A/D conversion circuit for subjecting the output of the error amplifier to digital conversion;
• and
• an operation circuit for, in a period during which recording is not performed, outputting a digital signal to the D/A conversion circuit, reading changes in an output signal of the A/D conversion circuit, obtaining a change amount in power in response to a change amount in the current of the semiconductor laser, and at the recording, outputting a digital signal value obtained in the period during which the recording is not performed, to the D/A conversion circuit.

An apparatus which controls a power of a semiconductor laser in an optical recording/reproducing apparatus for performing recording/reproduction into/from an optical recording medium by a semiconductor laser, comprising:

• a semiconductor laser power monitor means for monitoring an output of the semiconductor laser;
• an output error detection means for detecting an error between an output power reference value to be outputted by the semiconductor laser at reproduction just before recording and an actual output power value at the reproduction, which value is detected by the semiconductor laser power monitor means;
• a semiconductor laser power control means for setting an output power target value to a semiconductor laser driving means on the basis of the detected result of the output error detection means;
• a switch means for making a state between the semiconductor laser power monitor means and the output error detection means OFF at the recording, and making the state ON at the reproduction;
• and
• an output error setting means for setting the output of the output error detection means so as to be equal to the output power reference value at the recording.

An apparatus which controls a power of a semiconductor laser in an optical recording/reproducing apparatus for performing recording/reproduction into/from an optical disk by a semiconductor laser, comprising:

• a photodiode for detecting a light of the semiconductor laser;
• a current/voltage conversion circuit for converting a current of the photodiode to a voltage, and outputting the voltage;
• a reference voltage source for deciding a reproduction power of the semiconductor laser;
• an error amplifier for amplifying a difference between the output voltage of the current/voltage conversion circuit and the reference voltage;
• a current source for passing a current through the semiconductor laser;
• a reproduction power control system for connecting an output of the error amplifier to the current source, and controlling the reproduction power;
• a D/A conversion circuit for deciding a current to be passed through the semiconductor laser;
• a switch means for selectively switching a control signal of the current source to switch between the output of the error amplifier and an output of the D/A conversion circuit;
• and
• a switch means for cutting off an input from the current/voltage conversion circuit into the error amplifier, wherein
• at the recording, switching from the output of the error amplifier to the output of the D/A conversion circuit is performed to control the current of the current source, as well as the input from the current/voltage conversion circuit into the error amplifier is cut off,
• at the reproduction, switching from the output of the D/A conversion circuit to the output of the error amplifier is performed to control the current of the current source, as well as the output of the current/voltage conversion circuit is connected to the input to the error amplifier, and
• the voltages of the reference voltage source, which decide the reproduction power, have different values at the recording and at the reproduction and, when switching from recording to reproduction is performed, the voltage of the reference voltage source is changed passing through at least one intermediate value.