KR100200864B1 - Optical disc reproducing apparatus - Google Patents

Abstract

The present invention relates to an optical disc reproducing apparatus, comprising: a reproduction amplifier for amplifying a signal reproduced from a disc; A plurality of comparators for comparing the analog signals output from the reproduction amplifiers with a plurality of reference values and converting the analog signals into digital signals; An edge detector detecting an edge of each signal output from the comparator; A multiplexer for selectively outputting a plurality of edge signals output from the edge detector by a predetermined selection signal; A first latch for latching an output signal of the multiplexer by the regeneration clock; A second latch for latching an output signal of the comparator; A decoder which decodes the output signal of the second latch and outputs the selected signal of the multiplexer; And a regeneration clock reconstruction unit for reconstructing the regeneration clock from the output signal of the comparator.

Therefore, it is possible to omit the conventional complicated and poor performance moving device when constructing the playback signal processing unit, minimize the peak shift phenomenon, significantly reduce the position detection error, and simplify the error rate characteristics of the magneto-optical disc playback device. The configuration can be improved.

Description

Optical disc player

1 is a signal processing example of a conventional magneto-optical disc reproducing apparatus.

2 is a block diagram of a conventional comparator and edge detector.

3 is a conventional signal detection waveform diagram.

4 is a signal detection waveform diagram of the present invention.

5 is a detailed waveform diagram of signal detection according to the present invention.

6 is a block diagram of the present invention.

7 is a detailed block diagram of the present invention.

8 is a configuration and operation principle of the edge detector.

9 is a multiplexer operation table.

10 is a decoder operation table.

11 is a detailed waveform diagram of signal detection according to an embodiment of the present invention.

The present invention relates to a reproducing apparatus of a system for recording and reproducing digital information by using an optical disc including a compact disc and a magneto-optical disc. In particular, a CAV (Constant Angular Velocity) method for reproducing a signal by rotating an optical disc at a constant speed The present invention relates to an optical disc reproducing apparatus for reducing a recovery error rate of digital data generated by interference between signals due to optical system and disc characteristics.

Systems for recording and reproducing digital data using a magneto-optical disc include MODD (Mognetic-Optical Disc Driver), D-VDR (Digital Video Disc Recorder), and the like. A general magneto-optical disc reproducing apparatus is constructed as shown in FIG. The disk 1 is irradiated with a certain amount of light output from the laser diode LD, 7, and the reflected light is received by the photodiode PD, 2, converted into an electrical signal, and then amplified by the reproduction amplifier 3 as appropriate. . This reproduction signal causes interference between signals as shown in (c) of FIG. When the reproduction signal is detected by the single threshold comparator 21 of FIG. 2 and the signal is generated by the edge detector 22, the position of the edge is not detected exactly as shown in (d) of FIG. 3, which causes an error. This phenomenon is called peak shift. In the related art, the equalizer 4 of FIG. 1 is used to correct the reproduction signal. However, the equalizer 4 should be as shown in FIGS. 3E and 3F, but the actual equalizer is difficult to implement and has a complicated configuration.

Therefore, an object of the present invention is to adjust the reference voltage division of the comparator to correspond to the change in the characteristics of the disc by the radius to recover the digital data recorded from the reproduction signal without the equalizer 4 in order to solve the above-mentioned problems. The present invention provides an optical disc reproducing apparatus that compares a reproduction signal by dividing it into five levels, extracts an interference amount between signals from the comparison result, and detects the signal at a specified position.

In order to achieve the above object, an optical disc reproducing apparatus according to the present invention comprises: a reproducing amplifier for amplifying a signal reproduced from a disc;

A plurality of comparators for converting the analog signals output from the reproduction amplifiers into digital signals by comparing them with a plurality of reference values;

Five edge detectors for detecting an edge of each signal output from the plurality of comparators;

A multiplexer for selectively outputting a plurality of edge signals output from the edge detector according to a predetermined selection signal;

A first latch for latching an output signal of the multiplexer by a regeneration clock;

A second latch for latching an output signal of the comparator by a signal inverting a reproduction clock;

A decoder for decoding the output signal of the second latch and outputting the selected signal of the multiplexer; And

And a regeneration clock recovery unit for reconstructing the regeneration clock from the output signal of the comparator.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 6, the configuration of the present invention includes a reproduction amplifier 601 for amplifying a signal reproduced from a disc, and a plurality of D / As for converting a plurality of reference level signals from a system controller into analog signals. (Digital to Analog) converter 610, a plurality of comparators 602 for converting the analog signal output from the reproduction amplifier 60 to a digital signal by comparing with the D / A converter output value, and the plurality of comparators ( Five edge detectors 603 for detecting the edge of each signal output from the 602, and a multiplexer 604 for selectively outputting a plurality of edge signals output from the edge detector 603 according to a predetermined selection signal ), A first latch 605 for latching the output signal of the multiplexer 604 by the regeneration clock, a second latch 606 for latching the output signal of the comparator 602 with the signal inverted the regeneration clock. , A decoder 607 for decoding the output signal of the second latch 606 and outputting it as a selection signal of the multiplexer, and a playback clock recovery unit 609 for restoring the playback clock from the output signal of the comparator 602. Is done.

The operation of the present invention will be described with reference to FIGS. 4 to 11 as follows.

Referring to FIG. 6, after the output of the reproduction amplifier 601 and the reference signal value of the system controller converted into an analog signal by the D / A converter 610 are passed through the comparator 602 and converted into a digital signal, The edge detector 603 detects the data of each edge, selects the appropriate signal by the multiplexer 604, and latches its output in the latch 605 with a regeneration clock to obtain recovered data. The regeneration clock recovery unit 609 obtains the regeneration clock from the output of the comparator 602. The output of the comparator 602 is latched by the clock signal passed through the inverter 608 and used as a selection signal of the multiplexer 604 through the decoder 607.

A more detailed description with reference to FIG. 7 is as follows.

The output of the reproduction amplifier 701 is supplied to the five comparators 702, and the reference level of the comparator 702 is made into five stages (V1 to V5). Each reference level is then connected to the output of the D / A converter 711 and the input of the D / A converter 711 is received from the system controller. Each comparator 702 output is coupled to an edge detector 703 to extract edge information, and the five outputs of the edge detector 703 are supplied to the multiplexer 704 to select one according to the selection signal.

The output selected by the multiplexer 704 is re-locked to the regeneration clock through the latch 1 705 to become recovered data. The output of each comparator 702 is latched to inverted clock through latch 2 706 and supplied to decoder 709. At this time, the inverted clock is made through the inverter 708 the restored clock. The output of latch 2 706 is again latched to latch inverted via latch 3 707 and supplied to decoder 709. The decoder 709 generates the selection signals C3 to C1 and supplies them to the multiplexer 704 according to the table of FIG.

The regeneration clock recovery unit 710 restores the regeneration clock by inputting the edge signal of the comparator 702 of the V3 reference potential. The above process is explained with the waveform diagram of FIG. 4 as follows.

In Fig. 4, when the recording data a is NRZI-converted and recorded, it becomes like the recording signal b. To restore the original recording data, the edge of the recording signal b must be extracted accurately. Since the waveform of the reproducing amplifier output c is distorted due to the interference between the signals, when the signals are detected by the reference voltages of V1 to V5, signals indicating different positions are generated. Edge detection of the V3 comparator output d, which is the intermediate reference potential, results in (e). The configuration and principle of the edge detector 703 is shown in FIG. The (e) signal is used to restore the playback clock.

In a typical digital system, data is extracted from the rising edge of the regeneration clock, so that the regeneration clock is inverted to find the amount of interference between signals before the half clock. In the rising of the inverted clock g, it can be seen that the output state of the comparator 702 depends on the amount of interference between signals.

The operation of this part is shown in detail in FIG. 5 is a diagram showing the positions of .①, .②, .③ in FIG. That is, looking at the output of the comparator 702 at the position of .①, it can be seen that (V5 V4 V3 V2 V1) = (0 0 0 1 1). It can be seen that the comparator output e of V4 is the correct edge position of the recording signal. Based on this principle, a signal of a relatively accurate position according to the five comparator output states is obtained among the five comparator outputs. The example on the right of FIG. 5 shows that the V3 comparator output corresponds to the correct position when the comparator output is the same as the previous state.

Therefore, by extracting the exact characteristics of the optical system and the disc of the recording / reproducing system from the reproduction signal, it is possible to know the rules of the comparator output selection for the interference between the respective signals. In this way, two latches and a decoder can be used to generate the selection signals C3, C2, and C1 of the multiplexer 704 of FIG. 7 from the output information of the comparator. As a result, the edge information is extracted at the correct position as shown in (h) of FIG. 3, and the restored data of (i) is generated.

9 shows the relationship between the multiplexer 704 selection signals C3 to C1 and the multiplexer 704 output. In the above description, the configuration of the decoder and the selection signal of the multiplexer 704 should be made in accordance with the characteristics of the system.

One more thing to consider is that in the case of CAV (Constant Angular Velocity) method, the relative speed becomes faster as the radius of the disc goes out, so there is less interference between signals. That is, since the amount of interference between signals varies according to the radius, the distance between the reference levels of the comparator should be changed accordingly. Therefore, the statistical characteristics of the signal-to-signal interference of the disk are obtained in advance, and the reference level value of the optimum comparator is stored in the system controller accordingly, and the reference level of the comparator is changed to the D / A converter 711 according to the change of the disk radius in the system controller. By supplying a value, the detection operation is optimized.

For example, if the signal reproduced at the radius of 30 cm of the disc is the same as the example of the left fern of the fifth degree, the same signal is recorded and reproduced at the position of 40 cm of the radius, which is the reproduction signal as shown in FIG. That is, since the amount of interference between signals varies by radius, the total radius of the disc is divided into appropriate areas, and the reference signal level of the comparator is supplied as an appropriate value by investigating the interference property between signals for each area. As in the previous example, if the area of radius 30-40 cm is area I and the area of radius 40-50 cm is area II, in area I, as shown in FIG. 11, V1, V2, V3, V4, V5 of the playback signal S1 The reference level is made by supplying appropriate data to the D / A converter of FIG. 7 so as to be the reference level. The comparator output at this time is the same as (d)-(h) in FIG. In the region II, since the reproduction signal is a signal whose characteristics are changed as in S2, in order to obtain the same comparator output as in the case of region I, the level of V1-V5 should be the comparator reference level of V1'-V5 '. Therefore, the statistical characteristics of the characteristic change of the reproduction signal according to the radius of the disc are obtained and divided into several regions to make the air level by supplying the appropriate data to the D / A converter so as to be a comparator reference level suitable for each region.

As described above, the optical disk reproducing apparatus according to the present invention can omit the conventional complicated and inferior equalizer in the configuration of the reproduction signal processing unit, and can significantly reduce the position detection error by minimizing the peak shift phenomenon. .

In addition, the correction can always be made optimal in response to the change of the characteristic according to the radius of the disk. Therefore, the error rate characteristic of the magneto-optical disc reproducing apparatus can be improved by constructing a simple digital circuit.

Claims (2)

A reproduction amplifier for amplifying a signal reproduced from the disc; A plurality of comparators for converting the analog signals output from the reproduction amplifiers into digital signals in comparison with a plurality of reference values; Five edge detectors for detecting an edge of each signal output from the plurality of comparators; A multiplexer for selectively outputting a plurality of edge signals output from the edge detector according to a predetermined selection signal; A first latch for latching an output signal of the multiplexer by a regeneration clock; A second latch for latching an output signal of the comparator by a signal inverting a reproduction clock; A decoder for decoding the output signal of the second latch and outputting the selected signal of the multiplexer; And a regeneration clock recovery unit for reconstructing a regeneration clock from the output signal of the comparator. The apparatus of claim 1, wherein the plurality of comparators include a digital to analog (D / A) converter which receives a plurality of reference level values from a system controller and converts the plurality of reference level values into an analog signal. And an output value.