JPH0581677A - Reproduced signal detecting circuit of optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To improve the reliability of information reproduction on an optical disk by generating a slice level according to the difference between the maximum value of the signal of a data start part and the maximum value of the signal of the following area and slicing the signal according to the level. CONSTITUTION:The reproduced signal from a gap part is separated by an amplifier 21 into a positive-polarity signal and a negative-polarity signal, and holders 22 and 23 detects their peak value and bottom value; and a difference circuit 24 calculates their difference and the difference signal is sampled and held. The difference signal generated by subtracting the sampled and held signal from the signal amplitude between the peak value and bottom value of the reproduced signal from a data part is multiplied by 1/2 through a multiplier 27 to become the slice level. A comparator 28 compares the signal from the amplifier 21 with the slice level and outputs a high level 1 when the signal is larger than the slice level, thereby converting the reproduced signal into a binary signal. Consequently, the accurate slice level is detected from the reproduced signal to stably read the signal out of the optical disk.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reproduction signal detecting circuit of an optical information recording / reproducing apparatus, and more particularly to a reproduction signal detecting circuit of an optical information recording / reproducing apparatus of a mark length recording system in which an edge of a recording domain has a meaning. .. 2. Description of the Related Art Conventionally, optical disc devices are expanding their fields of use in the hierarchy of external storage devices, which are indispensable for various information processing devices, due to their large capacity, exchangeability, and data reliability. The optical disk device includes a read-only one (for example, a CD-ROM),
There are a type that can be written only once and a type that can be freely read / written (for example, an ISO standard version 5 inch optical disc device), but the most convenient external storage device is that it can be freely read / written. It is a possible optical disk device. The readable / writable optical disk device is characterized in that it is possible to make a large number of copies cheaply based on the master disk, as compared with an external storage device such as a conventional magnetic disk device.

In the future, such an optical disk device will be further miniaturized, and a 3.5-inch version and a 2-inch version will be commercialized. As a result, there is a demand for an optical disk device that is smaller, has a large recording capacity, and has high reliability in detecting a reproduction signal.

[0003]

2. Description of the Related Art Currently, there are magnetic disks, magnetic tapes, optical disks and the like as an apparatus for recording digital information as an external storage device of an information processing apparatus. In these external storage devices, in order to achieve high density information recording and high reliability of recording / reproduction, a recording system in which some kind of encoding is applied to actual recording data is adopted. The coding method that is currently widely used is RLLC-2 / 7 (Run length Limit).
ed Code-2 / 7) and RLLC-1 / 7. These encoding methods limit the number of consecutive "1" s or "0" s in encoded data, do not include low frequency components, require a narrow band, and extract clocks from reproduced signals. Easy to do, etc. On the other hand, there are the following two types of methods for actually recording the encoded data on the medium.

(1) Mark position recording method A recording method in which recording pits as shown in FIG. 3 (b) are provided in a one-to-one correspondence with "1" of the encoded data shown in FIG. 7 (a). (2) Mark length recording method A recording method in which a recording pit as shown in FIG. 3 (c) is provided so that the recording pit starts or ends at “1” of the encoded data shown in FIG. 7 (a).

As is apparent from FIG. 7, in the mark length recording method, the edge of the recording pit corresponds to "1" of the coded data, so that one recording pit in the mark position recording method corresponds to the mark length recording method. Can represent two pieces of encoded data “1”. Therefore, the mark length recording method is more suitable for high density (= high speed transfer) than the mark position recording method.

However, the mark length recording method has a problem of how accurately the mark edge can be detected.
In the mark recording method, the edge portion of the reproduction signal corresponds to the edge portion. As the edge detection method of the reproduction signal, there are a slice level detection method in which signals are binarized by comparing the signals with an appropriate value, and a differentiation method in which peak points are detected after passing through a differentiation circuit. Each edge detection method will be described with reference to FIG.

FIGS. 8 (a) and 8 (b) show a slice level detection method for detecting an edge by a slice level.
In this slice level detection method, the output is set to "1" when the reproduction signal shown in FIG. 8 (a) exceeds a predetermined slice level, and the output is set to "0" when the reproduction signal is equal to or lower than the slice level. The binarized signal shown in () is created. Figure 8 (c),
(d) shows a differentiation method in which an edge is detected at the peak of the differential waveform of the reproduction signal. In this differentiating method, the reproduced signal shown in FIG. 8 (c) is differentiated to produce the differentiated signal shown in FIG. 8 (d), and the edge of the reproduced signal is detected by detecting the peak point of this differentiated signal. ..

However, in the slice level detection system shown in FIGS. 8A and 8B, when the reproduced waveform is cut in the low frequency range, the reference potential of the reproduced waveform varies unless the duty ratio of the reproduced waveform is 50%. A baseline fluctuation occurs, which makes accurate edge detection impossible. Therefore, it is necessary to take some measures to follow the baseline fluctuation. Further, this slice level detection method has a problem that it cannot follow abrupt changes. On the other hand, the differentiating method shown in FIGS. 8C and 8D is not affected by the fluctuation of the baseline, but has a drawback that the high frequency noise is emphasized by the differentiating operation.

By the way, in the writable / erasable magneto-optical disk, when the mark length recording having a high recording density is adopted in order to increase the recording capacity, it is necessary to select one of the above-mentioned two types of edge detection methods. is there. Generally, in the data area of a magneto-optical disk that records and reproduces information magneto-optically, the signal quality becomes a problem because the rotation angle of the polarization plane due to the magnetic Kerr effect, which is the principle of signal reproduction, is very small, 1 degree or less. ing. So, for the magneto-optical disk equivalent,
The differential detection that increases noise in the high frequency range is not suitable, and the slice detection method is used.

As described above, in order to binarize the low-frequency cut signal at the slice level, it is necessary to correct the variation of the baseline. Therefore, a method that is often used is a method of detecting the peak value and the bottom value of the reproduction signal and setting the intermediate value between them as the slice level. The peak and bottom detection circuit and its operating principle will be described. FIG. 9 shows a configuration example of a conventional peak detection circuit. The peak detection circuit is composed of a circuit that detects a positive-side peak of the input signal and a circuit that detects a negative-side peak (bottom) of the input signal. Each circuit includes an amplifier Ap, which buffers the signal. Ab and a diode Dp connected in series to it,
There are capacitors Cp, Cb and resistors Rp, Rb connected in parallel as a load of Db and its diodes Dp, Db. The buffer amplifiers Ap and Ab function as so-called impedance converters that receive an input signal with high impedance and output it with low impedance. Here, the operation of the circuit on the positive polarity side will be described.
If it is larger than the charge stored in p (= voltage ∴Q = Cp V), the diode Dp turns on and charges the capacitor Cp, so the voltage value follows the input voltage. When the voltage of the capacitor Cp is higher than the voltage of the input signal, the diode Dp is turned off and the voltage is held. This makes it possible to capture the peak value of the input signal. The resistor Rp connected in parallel with the capacitor Cp functions to determine the held time. That is, the electric charge stored in the capacitor Cp is discharged with the time constant Rp * Cp of the resistor Rp and the capacitor Cp. FIG. 10 shows how the peak hold value changes at this time. The operation of detecting the bottom of the circuit on the negative polarity side is the same as the operation of the circuit on the positive polarity side described above, and therefore its description is omitted.

The intermediate voltage (center value) between the peak value and the bottom value thus captured is obtained from the connection point where the peak value output and the bottom value output are connected by resistors R1 and R2.
Then, conventionally, the above-mentioned problem of the baseline shift has been solved by binarizing the reproduction signal using the center value as a slice level.

[0012]

However, when the above-described peak / bottom detection is performed using the circuit of FIG. 9, the time when the input signal is above the peak reference point (GND) and the time when the input signal is below the peak reference point (GND). When the input signal is different for a certain time, there arises a problem that the intermediate voltage cannot capture the exact peak-bottom intermediate. This will be explained below.

FIG. 11 shows a peak value () with respect to a change in the input signal (solid line) that causes a typical baseline shift.
, Peak value output (dashed line), bottom value (●), bottom value output (dashed line), and center value output (dashed line). Considering the sections and in Fig. 11, the bottom output value accurately follows the bottom value of the input signal in the section, but one peak output value is a constant determined by the time constant of the circuit. It just causes a voltage drop. Therefore, the central value cannot be said to be a correct value. On the other hand, in the case of a section, the peak value output is the correct one, and the bottom value output is the incorrect one,
Similarly to the section, the center value of the section does not become an accurate intermediate voltage. The reason for this is that the time to catch the peak and the time to catch the bottom come alternately and at different times.

Therefore, the present invention is a typical magneto-optical disk apparatus in which a mark length method is used, in which a reproduction signal causes a baseline shift by utilizing a data format recorded on an optical disk. However, the accurate slice level can be detected from the reproduced signal,
As a result, it is an object of the present invention to provide a reproduction signal detecting circuit of an optical information recording / reproducing apparatus capable of stably reading a signal on an optical disc.

[0015]

FIG. 1 shows a principle configuration of a reproduction signal detecting circuit of an optical information recording / reproducing apparatus of the present invention which achieves the above object. As shown in FIG. 1, the present invention can optically record information on a recording medium 1 by a recording method in which an edge of a recording domain has a meaning, and record information can be optically reproduced. Further, a reproduction signal detecting circuit of an optical information recording / reproducing apparatus in which a single recording cycle signal having a duty ratio of 50% is recorded at a data start portion of a data recording area on the recording medium 1, the reproduction from the recording medium 1 is performed. Maximum value detecting means 2 for detecting the maximum value of the signal, sample holding means 3 for sample-holding the detected maximum value when the reproduced signal is the maximum value from the data start portion, and the maximum value sampled and held. And a slice level creating means 4 for creating a slice level by taking the difference between the maximum value of the same polarity detected from the reproduction signal from the data part after the data start part, and the created slice level. It said slicing the reproduced signal, is characterized in that it comprises a binarizing means 5 for binarizing the reproduced signal change point of the output as an edge position of the recording domain by Sureberu.

The above-mentioned maximum value may be only the peak value or the bottom value of the reproduction signal. When both the peak value and the bottom value are used, the reproduction from the recording medium 1 is performed before the maximum value detecting means 2. A complementary signal generating means for generating a set of complementary reproduction signals from the signals is provided, and the maximum value detecting means 2 is a peak detection circuit for capturing the peak value of the positive polarity signal and a bottom detection circuit for capturing the bottom value of the negative polarity signal. And a difference detecting means for detecting the difference between the detected peak value and the bottom value, and the slice level creating means 4 creates a slice level from this difference. You can

[0017]

According to the reproduction signal detecting circuit of the optical information recording / reproducing apparatus of the present invention, the maximum value of the single recording period signal having the duty ratio of 50% recorded at the data start portion of the data recording area on the recording medium 1 is obtained. Is detected and this is sampled and held.After that, the maximum value of the same polarity of the data recorded in the area following the data start part is detected and the difference between the two is taken, and the slice level is created based on this difference. To be done.
Since the slice level created in this way includes the baseline fluctuation, the reproduced signal is sliced based on this slice level, and the reproduced signal is binarized with the change point of the output as the edge position of the recording domain. It As a result, an accurate binarized signal can be obtained regardless of the baseline fluctuation of the reproduction signal, and the reliability of information reproduction on the recording medium is improved.

[0018]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 2 is a block circuit diagram showing the configuration of an embodiment of the reproduction signal detecting circuit of the optical information recording / reproducing apparatus of the present invention. Although the recording medium in this embodiment is an optical disc, the optical disc is not shown in this figure.

In the embodiment shown in FIG. 2, the reproduced signal from the optical disk is amplified by the complementary amplifier 21 to generate two signals of positive polarity and negative polarity in phase. this is,
This is to solve the above-mentioned problem that occurs when the peak and bottom are directly detected from the positive and negative polarities of the reproduction signal as in the conventional case, and the same time is taken to capture the peak and bottom values. This is to align the length of discharge time and the timing. Therefore, in the present invention, positive and negative reproduction signals obtained complementarily by the complementary amplifier 21 are used to capture one peak value and the other bottom value, respectively.

However, as it is, the intermediate values of the peak output and the bottom output do not naturally reflect the amount of the base line shift, and the sum of the shifts having different signs becomes zero, that is, the ground level. But,
The difference signal between the peak value and the bottom value includes a baseline shift amount, and if the signal amplitude amount can be subtracted from this difference signal, the baseline amount can be extracted. In order to subtract the signal amplitude from the difference between the peak value and the bottom value, a signal that does not include the baseline shift is necessary. Therefore, the present inventors have set a duty ratio that does not include a baseline shift before the data recording area of the optical disc.
Paying attention to the fact that the signal of 50% single recording period is recorded, the peak value of the signal of this single recording period is used to obtain the signal amplitude not including the baseline shift, and the reproduction of this signal and data is performed. The baseline shift is detected by detecting the difference from the signal.

Therefore, in the embodiment of FIG. 2, the reproduction signal from the optical disk is first input to the complementary amplifier 21. The complementary amplifier 21 amplifies the reproduced signal to generate a positive signal and a negative complementary signal having the same phase as the negative signal but the polarity reversed.
The positive polarity signal output from the complementary amplifier 21 is input to the peak holder 22, the peak value is detected, and the peak value is output to the difference circuit 24. Also, a complementary amplifier
The negative polarity signal output from 21 is input to the bottom holder 23, and the bottom value is detected and output to the difference circuit 24.

The difference circuit 24 calculates the difference between the peak value and the bottom value, and the difference signal is input to the sample hold circuit 25 or another difference circuit 26. Sample and hold circuit 25
Is to sample and hold the difference signal from the difference circuit 24 by a gap region signal described later. On the other hand, the difference circuit 26 calculates the difference between the difference signal from the difference circuit 24 and the sample and hold signal from the sample and hold circuit 25,
It is output as a positive polarity signal, and the output difference signal is multiplied by K in the multiplier 27 and input to the comparator 28. Since the signal output from the difference circuit 26 includes a double baseline shift amount, the multiplication factor K in the multiplier 27 is actually 1/2.

The positive-polarity signal input from the multiplier 27 to the comparator 28 is the slice level of the positive-polarity signal from the complementary amplifier 21, and the comparator 28 slices the signal from the multiplier 27. The positive signal from the complementary amplifier is sliced based on the level, and when the positive signal from the complementary amplifier is higher than the slice level, for example, a high level "1" signal is output and the playback signal is output. Binarize.

FIG. 3 shows a data format to be recorded on the optical disk, and the data recording state in n tracks is shown in this figure. There are, for example, k sectors in the n track, and each sector has a gap portion G and a sync byte portion S as shown by enlarging the sector i.
There is a B and a data part D. The gap portion G is an area for pulling in a PLL required when extracting a clock from the data, and a signal of a single recording cycle with a maximum recording density and a duty ratio of 50% is recorded. Also, the sync byte SB
Is a window for finding a data bit, and a signal for matching the phase of the data bit is recorded. Data is recorded in the data section D.

In the reproduction signal detecting circuit of FIG. 2, when reproducing each sector, the reproduction signal from the gap portion G is first input to the complementary amplifier 21 and is of the same polarity as the positive polarity signal but the polarity is inverted. And a complementary signal of negative polarity. And the peak holder 22 and the bottom holder
The peak value and the bottom value are detected by 23, the difference is taken by the difference circuit 24, and this difference signal is sampled and held by the sample hold circuit 25. This sample hold is performed by the gap area signal input to the sample hold circuit 25. The sample-and-hold signal from the sample-and-hold circuit 25 has a signal amplitude that does not include the baseline shift, and is as shown by the alternate long and short dash line in FIG.

On the other hand, the output of the peak value and the bottom value of the signal reproduced from the data section D is as shown by the chain double-dashed line in FIG. Therefore, the difference signal obtained by subtracting the sample hold signal from the signal amplitude between the peak value and the bottom value of the signal reproduced from the data section D includes a double baseline shift amount, which is 1 in the multiplier 27. When multiplied by 2, the slice level includes the baseline shift amount. Therefore,
Thereafter, the comparator 28 slices the positive polarity signal from the complementary amplifier based on this slice level, and when the positive polarity signal from the complementary amplifier is higher than the slice level, outputs a high level "1" signal, for example. In this way, the reproduced signal is binarized. As described above, according to the present invention, the accurate slice level can be detected from the reproduction signal of the optical disc on which the mark length is recorded, and as a result, the signal on the recording medium can be stably read.

FIG. 5 shows the construction of another embodiment of the reproduction signal detecting circuit of the optical information recording / reproducing apparatus of the present invention. In this embodiment, no complementary amplifier is used, only the positive polarity signal of the input signal from the optical disc is detected by the peak holder 52 by the diode 51, and the peak value output is input to the sample hold circuit 53 and the difference circuit 54. It Then, the output of the difference circuit 54 becomes a slice level and is input to the comparator 55.

In the apparatus of this embodiment, the waveform of the sample hold value of the input signal reproduced from the gap G is shown in FIG.
The waveform of the input signal passing through the diode 51 is as shown by the solid line in FIG. 6, and the peak value output waveform of the input signal reproduced from the data section D is as shown by the chain line. become. In this embodiment, since the difference between the peak value output and the sample hold signal becomes the baseline shift amount as it is, the output of the difference circuit 55 of FIG. 5 becomes the slice level as it is and is directly input to the comparator 55. Then, the comparator 55 compares the slice level with the reproduction signal and outputs it as binary data. That is, FIG.
Although not shown in FIG. 3, the change point of the output of the comparator 55 is detected as a recorded domain edge, and the signal on the optical disc is reproduced with high reliability.

[0029]

As described above, according to the present invention,
In the magneto-optical disk device recorded by the mark length method, by using the data format recorded on the optical disk, even if the reproduction signal is a typical one that causes a baseline shift, an accurate slice is reproduced from the reproduction signal. The level can be detected, and as a result, the signal on the optical disk can be read stably.

[Brief description of drawings]

FIG. 1 is a principle configurational diagram showing a configuration of a reproduction signal detecting circuit of an optical information recording / reproducing apparatus of the present invention.

FIG. 2 is a block circuit diagram showing a configuration of an embodiment of a reproduction signal detecting circuit of the optical information recording / reproducing apparatus of the present invention.

FIG. 3 is a diagram showing a data format recorded on an optical disc.

FIG. 4 is a waveform diagram showing the operation of the apparatus of FIG.

FIG. 5 is a block circuit diagram showing the configuration of another embodiment of the reproduction signal detecting circuit of the optical information recording / reproducing apparatus of the present invention.

6 is a waveform chart showing the operation of the apparatus of FIG.

FIG. 7 is an explanatory diagram of a coded data recording method in a conventional optical disc, where (a) is an example of coded data, (b) is a mark position recording pit, and (c) is a mark length recording method. It is a figure which shows a recording pit.

FIG. 8 is a diagram illustrating a conventional edge detection method,
(a) and (c) are reproduction signals, (b) is a binarized signal by a slice method, and (d) is a differential signal by a differential method.

FIG. 9 is a circuit diagram showing a configuration of a conventional peak detection circuit.

10 is a diagram illustrating a relationship between an input signal, a peak value, and a peak hold value in the circuit of FIG. 9.

11 is a waveform diagram showing an operation when an input signal including a baseline shift is input to the peak bottom detection circuit of FIG. 9.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Recording medium 2 ... Maximum value detection means 3 ... Sample hold means 4 ... Slice level creation means 5 ... Binarization means 21 ... Complementary amplifier 22, 52 ... Peak holder 23 ... Bottom holder 24, 26 ... Difference circuit 25, 53 … Sample and hold circuit 27… Multiplier 28, 55… Comparator

Claims (3)

[Claims] 1. Information can be optically recorded on a recording medium (1) by a recording method in which an edge of a recording domain has a meaning, and the recorded information can be optically reproduced, and a recording medium. (1) A reproduction signal detection circuit of an optical information recording / reproducing apparatus in which a single recording cycle signal with a duty ratio of 50% is recorded at the data start portion of the upper data recording area, A maximum value detecting means (2) for detecting the maximum value of the reproduction signal, and a sample holding means (3) for sample-holding the detected maximum value when the reproduction signal is the maximum value from the data start portion, and the sample Slice level creating means (4) for creating a slice level by taking the difference between the held maximum value and the maximum value of the same polarity detected from the reproduction signal from the data part after the data start part, and Sliced level And a binarizing means (5) for slicing the reproduction signal with a video signal, and binarizing the reproduction signal with the change point of the output as the edge position of the recording domain. Playback signal detection circuit. 2. The reproduction signal detecting circuit of the optical information recording / reproducing apparatus according to claim 1, wherein the maximum value is only a peak value or a bottom value of the reproduction signal. 3. Complementary signal generating means for generating a set of complementary reproduction signals from reproduction signals from the recording medium (1) is provided in front of the maximum value detecting means (2), and the maximum value detecting means ( 2) comprises a peak detection circuit for capturing the peak value of the positive polarity signal obtained from the complementary signal creating means, and a bottom detection circuit for capturing the bottom value of the negative polarity signal, and the sample and hold means (3) A difference detecting means for detecting a difference between the detected peak value and the bottom value is provided before the slice level creating means.
The reproduction signal detecting circuit of the optical information recording / reproducing apparatus according to claim 1, wherein (4) creates a slice level from this difference.