JPH11120701A - Reproducing device of disk-like record medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the expansion of a reproducing margin in so-called 'read system' of the reproducing device including a demodulation system and an error correction system by absorbing the individual difference of reproduction quality of the disk. SOLUTION: After set constants of an amplifier circuit 3 are adjusted by judging the condition of the reproduced signal read out from the disk through the comparison with specific values, they are subjected to digital process and outputted. That is, a gain changing circuit 3a is connected to the amplifier circuit 3, and the gain setting is changed in accordance with the result of the comparison between the amplitude of the reproduced signal and the specific value. Also, an equalizer 3b is connected to the amplifier circuit 3, and the setting of frequency or the setting of Q value is changed in accordance with the result of the comparison between the amplitude ratio of the low frequency component/high frequency component and the specific value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an apparatus for reproducing a disk-shaped recording medium (hereinafter, a disk) such as a CD.

[0002]

BACKGROUND OF THE INVENTION For example, in the case of a CD, an individual difference may occur in the shape of a pit, so that an error also occurs in a reproduced signal composed of signal components of 3T to 11T, which causes variation in reproduction quality for each individual. This individual difference is amplified by a scratch or dust on the disc, and may cause a reproduction error in some cases.

[0003] Individual differences between discs are expected to be more remarkable in recordable discs. However, some reproducing devices up to now have a function of judging a variation in reproduction quality and absorbing the individual differences. not exist. Therefore, the present invention provides a reproducing apparatus having an individual difference absorbing function.

[0004]

That is, the present invention relates to a disk-shaped recording medium reproducing apparatus for amplifying an analog reproduced signal read from a disk-shaped recording medium by an amplifier circuit, and then performing digital processing on the signal and outputting it. It is characterized in that the state of the reproduced signal read from the recording medium is determined by comparison with a specified value, and the set constant of the amplifier circuit is adjusted.

In this reproducing apparatus, since the reproduced signal is amplified while adjusting the set constant of the amplifier circuit according to the state of the reproduced signal, individual differences in reproduction quality can be reduced. In addition, since the setting constant is changed by the amplifier circuit for the analog reproduction signal, the margin in digital processing in the so-called "read system" including the demodulation system and error correction system at the subsequent stage can be expanded in advance, and a reproduction error occurs. Can be reduced.

It is preferable that the reproducing apparatus has a gain changing circuit connected to the amplifying circuit, and the gain setting is changed in accordance with a result of comparing the amplitude of the reproduced signal with a specified value.

[0007] For example, it has been recognized that a reproduction error occurs due to a lack of amplitude of a reproduction signal. in this case,
In this reproducing apparatus, since the amplitude of the reproduced signal is amplified and adjusted by increasing the gain of the amplifier circuit, it is possible to reduce the occurrence of reproduction errors due to the amplitude state. This gain changing circuit is configured as, for example, an external constant of a negative feedback operational amplifier, or an LSI on the same chip as the negative feedback operational amplifier.
It may be constituted as. As an example, it can be constituted by a variable resistor connected to a feedback loop of an amplifier circuit constituted by a negative feedback operational amplifier. Note that the specified value is the amplitude of a model reproduction signal in which the number of error occurrences is smaller than a predetermined number, or a predetermined amplitude range including the amplitude.

In the above reproducing apparatus, an equalizer is connected to the amplifier circuit, and the frequency setting or the Q value setting is changed according to the result of comparing the amplitude ratio between the low frequency component and the high frequency component contained in the reproduced signal with a specified value. It is more preferable that it is performed.

In this reproducing apparatus, the amplitude ratio between the low frequency component and the high frequency component of the reproduced signal is compared with a specified value. If there is a difference between the specified value and the amplitude ratio, the amplitude of one of the frequency components is insufficient. It can be seen that the cause of the reproduction error has occurred. Then, according to this judgment, the frequency component having a problem in the amplitude state is equalized and the frequency setting is changed or the setting of the Q value of the equalizer is changed, so that the amplitude of the frequency component is adjusted and the amplitude state is changed. It is possible to reduce the occurrence of a reproduction error caused by this. This equalizer may be configured, for example, as an external constant of the negative feedback operational amplifier, or may be configured as an LSI on the same chip as the negative feedback operational amplifier. As an example, it can be realized by a filter composed of RC, LC or the like connected to the feedback loop of the negative feedback operational amplifier. The specified value is an amplitude ratio between a low-frequency component and a high-frequency component or a predetermined amplitude ratio range including the amplitude ratio of a model reproduction signal having a desired amplitude when reproduction is performed by the reproduction apparatus. That is.

It is preferable that the reproducing apparatus determines the type of error that has occurred in the reproduced signal before executing the adjustment of the set constant. This is effective when the reproduction errors are ranked. In other words, for example, if the set constant is changed when a minor error occurs, the occurrence of a severe error can be prevented. Further, if the set constant is changed when a serious error occurs, the occurrence of an unreproducible error can be reduced.

It is preferable that the above-mentioned reproducing apparatus adjusts the set constant according to the result of comparing the number of errors generated in the reproduced signal with a specified value. That is, since the setting constant of the amplifier circuit is adjusted so that the number of reproduction errors occurring in the reproduction signal is reduced, it is effective to prevent the occurrence of reproduction errors.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. FIG. 1 is a diagram showing a configuration example in which the present invention is applied to a CD reproducing apparatus 1. Since the analog reproduction signal read from the CD by the optical system 2 including the pickup has a low voltage level, it is amplified by the amplifier circuit 3 and then subjected to digital processing. The amplified analog reproduction signal is subjected to digital processing by a so-called "read system" including a DSP 4 for performing demodulation, error correction and the like and a CPU 5 as a control system thereof, and is output to the outside.

FIG. 2 is a flowchart showing a procedure for adjusting the set constant of the amplifier circuit 3 performed by the reproducing apparatus 1 of FIG. The basic idea of adjusting the set constant in this example is C
(2) An object of the present invention is to prevent the occurrence of a burst-like reproduction error requiring error correction. Therefore, in this example, first, the type of error in the reproduced signal, that is, the C1 error is determined, and the number of occurrences is counted, and a predetermined number (for example, 200
), The setting constant of the amplifier circuit 3 is adjusted so as to further suppress the occurrence of the C1 error and prevent the occurrence of the C2 error. Hereinafter, the procedure will be described with reference to FIG.

When reproduction of a CD is started by the optical system 2 (S1)
0), the CPU 5 detects the C in the reproduced signal detected by the DSP 4
A signal indicating the number of one error is received. The CPU 5 stores a specified value of the number of C1 errors, and compares the specified value with the number of C1 errors occurring in a predetermined time (S12). As a result C
If the number of one error is equal to or less than the specified value, there is no particular problem in the error occurrence state of the reproduced signal, so that the setting constant of the amplifier circuit 3 is not changed, and the DSP 4 performs the following processing such as C1 error correction (S14). .

On the other hand, if the number of C1 errors exceeds a specified value, the CPU 5 sets the stored specified value of the amplitude value to the DSP value.
The value is compared with the amplitude value detected in S4 (S16). If the amplitude value is less than the specified value, the CPU 5 controls the resistance value of the variable resistor 3c of the gain changing circuit 3a to control the amplification circuit 3c.
(S18) to amplify the amplitude of the reproduced signal. Thereafter, the number of C1 errors in the amplified reproduced signal is re-detected (S12). If the number of C1 errors is changed to a specified value or less, the next processing is performed while maintaining the resistance value of the variable resistor 3c (S14). If the number of C1 errors is still larger than the specified value (S12), the gain is further increased and adjusted (S18) or the equalizing is already performed according to the result of comparison between the amplitude value and the specified value (S16). It is determined whether it has been changed (S20).

On the other hand, if the amplitude value is larger than the specified value in step 16 (S16), the CPU 5 determines whether or not the equalizing has been changed (S20). In this example, since the equalizing has not been changed, the CPU
5 judges the comparison result between the amplitude ratio of 3T and 11T in the reproduced signal output from the amplitude comparator 6 and the specified value (S2).
2). If the amplitude ratio is larger than the specified value, the state of the reproduced signal cannot be improved even if the amplitude is adjusted. Therefore, the CPU 5 maintains the current setting of the amplifier circuit 3 and the DSP 4 executes the next processing such as C2 error correction. (S24).

On the other hand, when the amplitude ratio is smaller than the specified value, C
PU5 closes the switch SW to change the time constant of the equalizer 3b (S26). That is, the lowest frequency 3T
Is subjected to equalization to make the degree of amplification of 3T particularly larger than other signal components. As a result, if the number of C1 errors becomes equal to or less than the specified value (S12), the next processing is performed while maintaining the current setting of the amplifier circuit 3 (S14). Also,
If the value is still larger than the specified value (S12), the amplitude value of the reproduced signal is compared with the specified value in the same manner as described above (S1).
6) Perform gain increase adjustment (S18). If the amplitude value is smaller than the specified value (S16), since the equalizing has already been changed (S26), the CPU 5
Is maintained (S20, S24).

When the set constant of the amplifier circuit 3 is adjusted as described above, the number of C1 errors of the reproduced signal eventually becomes less than the specified value, and the reproducing operation for correcting the C1 error is performed. (S12) Or, it is determined that the burst error cannot be improved even if the set constant of the amplifier circuit 3 is adjusted, and a reproducing operation for correcting the C2 error is performed (S12).
24).

In the reproducing apparatus according to the present invention, it is also possible to change the above-described adjustment process of the set constant and to carry out the process. That is, in the above-described embodiment, the process of detecting the number of C1 errors and comparing the detected number with the specified value is shown (S12). Prior to executing the reproduction retry, the setting constant of the amplifier circuit may be changed as described above. It is also possible to change the set constant of the amplifier circuit 3 by judging only the comparison result between the amplitude of the reproduced signal and the specified value without considering the reproduction error.

To perform equalization on signal components other than 3T and 11T, ie, 4T to 10T, with the equalizer 3b, a switch SW and a capacitor 3d are provided in multiple stages in parallel. What is necessary is just to give the selection range a width. Also, the equalizer 3b
Instead of changing the frequency setting, a circuit for changing the setting of the Q value may be separately provided to change the amplitude for a specific frequency component.

In the above embodiment, the amplitude comparator 6 outputs 3
Although the T / 11T amplitude ratio is taken and compared with a specified value, an amplitude ratio detection circuit for an analog reproduction signal is provided instead of the amplitude comparator 6 and the detected amplitude ratio is given to the CPU 4. The CPU 4 may cause the comparison with a specified value to be performed.

In the above embodiment, the single-stage amplifier circuit 3
Although the gain adjustment and the equalizing adjustment are performed in the above, a gain changing circuit and an equalizer may be independently provided for the multi-stage amplifier circuit or the amplifier circuit, and these may be connected to the amplifier circuit.

[0023]

According to the present invention, the gain of the amplifier circuit can be set based on the state of the amplitude value and the number of errors of the analog reproduction signal.
Since the reproduced signal is amplified while adjusting the setting constants such as the frequency setting, it is possible to increase the margin when executing various digital processes for a so-called “read system” such as a demodulation system and an error correction system. Further, since the set constant is changed in accordance with the state of the reproduction signal, individual differences in reproduction quality can be eliminated, a uniform reproduction signal can be obtained, and the rate of occurrence of reproduction errors can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a playback device according to one embodiment.

FIG. 2 is a flowchart showing a procedure for adjusting a setting constant of the amplifier circuit according to the embodiment;

[Explanation of symbols]

 Reference Signs List 1 playback device 2 optical system 3 amplifier circuit 3a gain changing circuit 3b equalizer 3c variable resistor 3d capacitor 4 DSP 5 CPU

Claims (5)

[Claims] A reproducing apparatus for a disk-shaped recording medium, which amplifies an analog reproduced signal read from the disk-shaped recording medium by an amplifier circuit and then outputs the amplified signal after digitally processing the reproduced signal. A reproducing apparatus characterized in that a state is judged from comparison with a specified value and a set constant of an amplifier circuit is adjusted. 2. The reproducing apparatus according to claim 1, wherein a gain changing circuit is connected to the amplifier circuit, and the gain setting is changed according to a result of comparing the amplitude of the reproduced signal with a specified value. 3. An equalizer is connected to the amplifier circuit, and a frequency setting or a Q value setting is changed according to a result of comparing an amplitude ratio between a low frequency component and a high frequency component included in the reproduced signal with a specified value. Or the playback device according to claim 2. 4. The reproducing apparatus according to claim 1, wherein the type of error generated in the reproduced signal is determined to adjust the set constant. 5. The reproducing apparatus according to claim 1, wherein the setting constant is adjusted according to a result of comparing the number of errors generated in the reproduced signal with a specified value.