Optical disk reproduction apparatus and optical disk reproduction method
View Patent ↗Deterioration of error rate at reproduction time is prevented even if a photodetector with a poor characteristic is included. An optical pickup unit ( 3 ) is provided with 4 photodetectors. A controller ( 13 ) obtains an error correction result of a reproduced signal, which is reproduced based on an RF signal generated while changing combination of the 4 photodetectors at startup time, and determines a combination at reproduction time in accordance with the obtained error correction result, to be given to an RF amplifier unit ( 10 ). The controller ( 13 ) is provided with a counter that counts for a fixed time period the error correction result per combination of the photodetectors, a comparator that compares a count result of the counter with a threshold set in advance, and an output controller that judges whether or not to use a combination of the photodetectors based on a comparison result of the comparator and performs change control of the combination of the photodetectors, of which there is a plurality. At reproduction time, control is performed to obtain the reproduced signal from output outside of the photodetector with the poor characteristic.
1. An optical disk reproduction apparatus comprising:
a plurality of photodetectors;
an RF amplifier unit that selects a combination of output signals of said plurality of photodetectors to generate an RF signal; and
a controller that obtains an error correction result of a reproduced signal, which is reproduced based on said RF signal generated while changing said combination at startup time, and that determines said combination at reproduction time in accordance with said obtained error correction result, to be given to said RF amplifier unit.
2. The optical disk reproduction apparatus according to claim 1 , wherein said controller comprises:
a counter that counts for a fixed time period said error correction result, per combination of said photodetectors;
a comparator that compares a count result of said counter with a threshold set in advance; and
an output controller that judges whether or not to use a combination of said photodetectors based on a comparison result of said comparator, and that performs change control of the combination of said photodetectors.
3. The optical disk reproduction apparatus according to claim 1 , wherein
said plurality of photodetectors comprises 4 photodetectors, with 2 photodetectors being arranged on each of an inner circumferential side and an outer circumferential side of a track;
said combination at reproduction time is formed by selecting whichever of either a sum of output signals of 2 photodetectors among said 4 photodetectors, or a sum of output signals of 2 other photodetectors thereof has fewer error corrections; and
said RF amplifier unit, for a case in which all of said 4 photodetectors are selected, doubles degree of amplification of a photodetector output signal.
4. The optical disk reproduction apparatus according to claim 2 , wherein
said plurality of photodetectors comprises 4 photodetectors, with 2 photodetectors being arranged on each of an inner circumferential side and an outer circumferential side of a track;
said combination at reproduction time is formed by selecting whichever of either a sum of output signals of 2 photodetectors among said 4 photodetectors, or a sum of output signals of 2 other photodetectors thereof has fewer error corrections; and
said RF amplifier unit, for a case in which all of said 4 photodetectors are selected, doubles degree of amplification of a photodetector output signal.
5. The optical disk reproduction apparatus according to claim 1 , wherein
said plurality of photodetectors is formed of 4 photodetectors, with 2 photodetectors being arranged on each of an inner circumferential side and an outer circumferential side of a track;
said combination at reproduction time is formed by selecting 3 photodetectors that have fewer reproduced signal error corrections; and
said RF amplifier unit, for a case in which all of said 4 photodetectors are selected, increases degree of amplification of a photodetector output signal by a factor of 4/3.
6. The optical disk reproduction apparatus according to claim 2 , wherein
said plurality of photodetectors is formed of 4 photodetectors, with 2 photodetectors being arranged on each of an inner circumferential side and an outer circumferential side of a track;
said combination at reproduction time is formed by selecting 3 photodetectors that have fewer reproduced signal error corrections; and
said RF amplifier unit, for a case in which all of said 4 photodetectors are selected, increases degree of amplification of a photodetector output signal by a factor of 4/3.
7. The optical disk reproduction apparatus according to claim 1 , wherein, by counting a SUBQ synchronization signal as input; reproduction time of one disk rotation is measured to obtain a fixed time period; and said counter counts number of errors of a C1C2 error signal in said fixed time period as an error correction result.
8. The optical disk reproduction apparatus according to claim 2 , wherein, by counting a SUBQ synchronization signal as input; reproduction time of one disk rotation is measured to obtain a fixed time period; and said counter counts number of errors of a C1C2 error signal in said fixed time period as an error correction result.
9. An optical disk reproduction method for an optical disk reproduction apparatus comprising: selecting a combination of output signals of a plurality of photodetectors to generate an RF signal, and outputting a reproduced signal, which is reproduced based on said RF signal;
said method further comprising:
obtaining an error correction result of said reproduced signal, which is reproduced based on said RF signal while changing a combination of output signals of said plurality of photodetectors at startup time;
determining said combination at reproduction time in accordance with said obtained error correction result; and
outputting said reproduced signal obtained based on said determined combination.