JPH05135499A - Automatically waveform equalization adjusting device - Google Patents

Abstract

PURPOSE:To automatically adjust a constant and to efficiently work for adjusting the constant by counting a binarized pulse signal respectively at every slice level and comparing the number of a puse at every slice level. CONSTITUTION:The binarization signals of respective comparators are outputted to a counter column 6 and the number of pulse are counted respectively by the pulse counter of the counter 6. The count values of respective counters are outputted to a pulse number comparing/deciding circuit 7 and whether respective count values are same or not is decided in the circuit 7. By the pulse number comparing/deciding circuit 7, a switch 8 is connected to (a) side and the signal instructing a gain adjustment is outputted to a waveform equalizing circuit 4 through a data converter 9 and the gain is adjusted. At this time, when respective numbers of pulses coincide, the gain arrives at the optimum value, and when the optimum condition is satisfied, the switch is changed to (b) side by the pulse number comparing/deciding circuit 7. Thus, the gain of the waveform equalizing circuit 4 is adjusted automatically to the optimum value and the signal without the interference of an intercode is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveform for automatically adjusting a constant such as a gain in a waveform equalizer for equalizing a reproduced signal from an information recording medium and optimally adjusting the waveform equalization processing performance. The present invention relates to an automatic equalization adjusting device.

[0002]

2. Description of the Related Art Conventionally, as an optical information recording medium used in an optical disk device, a read-only type, a write-once type using a metal thin film or a dye recording material, a magneto-optical recording method or a phase transition recording method. There is a rewritable type. Various forms of these recording media are known, such as disc-shaped, card-shaped, and the like.
In addition, as a method of recording information on such a recording medium, pit position recording (recording between marks) that makes the center position of the pit significant, and pit edge recording (meaning pit edge recording that makes the edge position of the pit significant) There is a mark length record). The pit position recording has an advantage that information can be accurately recorded, but the pit edge recording has a feature that a recording capacity can be made larger than that of the pit position recording.

Recently, in order to increase the recording density, the recording frequency is increased so that the shortest pit length is 1.0 μm or less, and the pit edge recording is adopted, which tends to increase the recording capacity. However, when the shortest pit length is shortened in this way, the read signal is easily affected by the adjacent pits because the laser reading spot has a finite area. That is, since intersymbol interference occurs, it may be difficult to slice the level of the reproduced signal. Therefore, conventionally, various waveform equalization processes for narrowing the waveform have been performed.

For example, a waveform equalization circuit using a transversal filter as shown in FIG. 3 is known. This transversal filter is known as a waveform equalization circuit which is particularly effective in reducing intersymbol interference. The transversal filter shown in FIG. 3 has 5 taps.
4 delay lines 20-23, 4 amplifiers 24-
27 and a subtractor 28. The reproduction signal read from the optical disk is sequentially delayed by each delay line,
Each delayed output is output to the subtractor 28 after having a predetermined gain by an amplifier. In this case, the delay line 21
The output of 1 is not given a gain, and the subtractor 28 subtracts another output from this output to generate a waveform equalized output signal.

[0005]

However, in the above-mentioned conventional waveform equalizing circuit, in order to obtain sufficient waveform equalizing performance, highly accurate gain adjustment of the amplifier is required, and the gain adjusting work takes a long time. Was needed. Further, the reproduction signal may change as compared with the initial adjustment due to changes in environmental conditions during recording or reproduction and various other factors. In such a case, since the gain is initially fixed, the waveform equalization performance deteriorates according to changes in the reproduced signal,
In some cases, sufficient performance could not be obtained.

The present invention has been made to solve such a problem, and its purpose is to make constant adjustment work significantly efficient by automatically adjusting constants such as gains of waveform equalization. Another object of the present invention is to provide an automatic waveform equalization adjusting device.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a means for equalizing the waveform of a reproduced signal read from an information recording medium, and a predetermined constant of the waveform equalizing means for varying the waveform. The means for changing the equalization processing performance and the output signal of the waveform equalization means are respectively divided into a plurality of different slice levels.
The means for digitizing, the means for counting the binarized pulse signal for each slice level by the binarizing means, and the number of pulses for each slice level counted by the counting means are compared, When the number of pulses for each slice level does not match, the constant variable means has means for instructing adjustment of the constant, which is achieved by the automatic waveform equalization adjustment device.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the automatic waveform equalization adjusting apparatus of the present invention. In FIG. 1, 1
Is a magneto-optical disk used as an information recording medium. The magneto-optical disk 1 is rotated by driving the spindle motor 10. Reference numeral 2 denotes an optical head arranged near the surface of the magneto-optical disk 1, which irradiates the magneto-optical disk 1 with a light beam for recording information or irradiates a light beam for reproduction with
The reflected light is detected and a reproduction signal is generated. Reference numeral 3 is an amplifier for amplifying the reproduction signal obtained by the optical head 2, and 4 is a waveform equalization circuit for performing waveform equalization processing on the amplified reproduction signal. As the waveform equalizing circuit 4, for example, a circuit using a transversal filter as described above is used. Further, a digital potentiometer 11 for adjusting the gain of the amplifier is provided in the waveform equalization circuit 4. The waveform equalization circuit 4 is not limited to the transversal filter and may be another circuit.

Reference numeral 5 is a comparator array for binarizing the output of the waveform equalizing circuit 4 at a plurality of different slice levels. The comparator row 5 has three comparators 1.
2 to 14, and the slice levels of the comparators are different, such as V0, V1, and V2. Reference numeral 6 is a counter train that counts the number of pulses binarized by each comparator. The counter train 6 is composed of pulse counters 15 to 17 corresponding to the respective counters. Reference numeral 7 denotes a pulse number comparison / judgment circuit that fetches and compares the count values of the pulse counters 15 to 17, and switches the switch 8 according to the comparison result. When the count values of the respective pulse counters are different, the switch 8 is switched to the side a, and the signal for instructing the gain adjustment from the pulse number comparison / determination circuit 7 is transmitted via the data converter 9 to the waveform equalization circuit 4. Is output to. The switch 8 is switched to the b side when the count values of the pulse counters become equal. The data converter 9 is a conversion circuit for converting the signal of the pulse number comparison / determination circuit 7 into a current value or a voltage value.

Next, the operation of this embodiment will be described with reference to FIG. FIG. 2 is a waveform diagram showing an output signal of the waveform equalization circuit 4, and FIG. 2A is a signal waveform when intersymbol interference is large. First, it is assumed that the signal with large intersymbol interference is output from the waveform equalization circuit 4 to the comparator array 5. In this case, the comparator 12 of the comparator row 5 has the slice level V0, the comparator 13 has the slice level V1,
The comparator 14 binarizes each at the slice level V2. FIG. 2A shows the output signal of the waveform equalization circuit 4 and the slice level. The number of pulses when binarized at each slice level by each comparator is 2 at the slice level V0, 4 at V1, and V2. Then it becomes 4. The binary signal of each comparator is output to the counter row 6,
The pulse numbers described above are counted by the pulse counters of the counter train 6. The count value of each pulse counter is output to the pulse number comparison / determination circuit 7, and it is determined here whether or not the count values are the same. In this case, since the count value of the number of pulses at each slice level is different, the pulse number comparison / judgment circuit 7 connects the switch 8 to the side a, and a signal for instructing gain adjustment is sent via the data converter 9 to the waveform equalizer circuit. Output to 4. In the waveform equalization circuit 4,
The digital potentiometer 11 operates and adjusts the gain of the waveform equalization circuit 4. In this embodiment, since the transversal filter is used as the waveform equalizing circuit, the gain of the amplifier shown in FIG. 3 is adjusted. In this case, the gain reaches the optimum value when the respective pulse numbers match, and the pulse number comparison / determination circuit 7 switches the switch 8 to the b side when the optimum condition is satisfied. As a result, the gain of the waveform equalization circuit 4 is automatically adjusted to the optimum value, and a signal without intersymbol interference can be obtained.

FIG. 2B shows an example of a signal waveform with insufficient waveform equalization. The comparator array 5 is binarized at different slice levels as described above, and the number of pulses at this time is 5 at slice level V0, 5 at V1 and 4 at V2, as shown in FIG. Therefore, the pulse number comparison / determination circuit 7
Since the number of pulses is different, outputs a signal instructing gain adjustment to the waveform equalization circuit 4 as in the above. As a result, the gain is adjusted by the digital potentiometer 11, and a signal with sufficient waveform equalization is output. Also, FIG.
(C) is an example of a signal with sufficient waveform equalization. At this time, the number of pulses of the comparator train 5 is 5, as shown in the figure, for all of the slice levels V0, V1, and V2. in this case,
Since the pulse numbers at each slice level match, the pulse number comparison / determination circuit 7 connects the switch 8 to the b side.
Therefore, when all the numbers of pulses match, it is determined that the waveform equalization is sufficient, and the current gain is maintained without adjusting the gain.

In the above embodiment, an example in which binarization is performed at a positive slice level has been shown. However, by providing a negative slice level, it is possible to perform gain adjustment with higher precision.

[0013]

As described above, according to the present invention, after waveform equalization, binarization is performed at different slice levels, and a predetermined constant of the waveform equalizer circuit is adjusted until the number of pulses at each slice level matches. By doing so, the waveform equalization performance can be automatically adjusted to satisfy the specifications. Therefore, there is an effect that initial adjustment at the time of manufacturing the device or constant adjustment at the time of exchanging the optical head can be easily performed and workability can be significantly improved. Further, even when the reproduction signal changes due to changes in the operating environment of the apparatus and various other factors, optimum constant adjustment can be automatically performed and sufficient waveform equalization can be performed.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a waveform equalization automatic adjustment device of the present invention.

FIG. 2 is a signal waveform diagram for explaining the operation of the embodiment of FIG.

FIG. 3 is a block diagram showing a waveform equalization circuit using a conventional transversal filter.

[Explanation of symbols]

 1 Magneto-optical disk 2 Optical head 4 Waveform equalization circuit 5 Comparator row 6 Counter row 7 Pulse number comparison judgment circuit 8 Switch 9 Data converter 11 Digital potentiometer 12-14 Comparator 15-17 Pulse counter

Claims (1)

[Claims] 1. A means for performing waveform equalization of a reproduction signal read from an information recording medium, a means for varying a predetermined constant of the waveform equalization means to change the waveform equalization processing performance, the waveform, etc. Means for binarizing the output signal of the digitizing means at a plurality of different slice levels, means for counting the binarized pulse signals for each slice level by the binarizing means, and counting by the counting means The number of pulses for each slice level is compared, and if the number of pulses for each slice level is not matched, the constant variable means has a means for instructing adjustment of a constant, etc. Automatic adjustment device.