JPS63244318A - Optical disk reproducing device - Google Patents

Abstract

PURPOSE:To stably obtain an envelope binarized signal by providing two pairs of low pass filters and comparators, comparing envelope voltages, discriminating an address signal and a data signal by using one, and discriminating a data recorded section and a data not yet recorded section by using the other. CONSTITUTION:The envelope components of a regenerative signal, from which a direct current component is removed by a high pass filter 13, are extracted by a low pass filter (1) 14 and the low pass filter (2) 16, and sent too the comparator (1) 15 and the comparator (2) 17 respectively. The combination of the low pass filter 14 and the comparator (1) 15 is used for an address/data switching, and the cut-off frequency of it is set high so that the envelope voltage comes sufficiently small at a gap between an address signal section and a data signal section. On the contrary, the combination of the low pass filter 16 and the comparator (2) 17 is used for a data recorded/not yet recorded discrimination, and the cut-off frequency is set low so that the fluctuation of the envelope voltage, due to the frequency component of the data signal, is prevented. Thus, the discrimination of the respective signals, and the discrimination of the data recorded section and the data not yet recorded section, can be stably performed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical disk reproducing apparatus that reproduces signals using a light beam such as a semiconductor laser.

BACKGROUND OF THE INVENTION In recent years, signals have been reproduced from optical discs by focusing laser light to about 1 μm.

In such an apparatus, an optical disk is irradiated with a laser beam, and bits that are preformatted by reconfiguration on the optical disk and bits that have shading based on the difference in reflectance are read.

FIG. 2 shows an example of a conventional optical disc reproducing apparatus.

A laser beam from a semiconductor laser 1 is converted into a parallel beam by a condensing lens 2, and is incident on an aperture lens 5 by a total reflection mirror 4. The aperture lens 6 converts this incident light into an optical disk 8.
Narrow down to a spot as small as φ1 μm and 1 μm on the top. The reflected light from the optical disk 8 is again guided to the beam splitter 3 via the lens 6 and the total reflection mirror 4, and is received by the photodetector 6 and converted into an electrical signal. 7 rotates a disk 8 with a disk motor. A preamplifier 10 amplifies the photodetector signal. A reproduced signal output from the preamplifier is sent to an address signal processing circuit 11 and a data signal processing circuit 12. While the address signal is a reproduction signal of bits preformatted with a groove structure on the optical disk, the data signal is a reproduction signal of pits with shading due to the difference in reflectance. Different frequency bands and frequency characteristics. Therefore, separate circuits are provided for each process. The output of the image processing circuit becomes a binary signal. -Blade The reproduced signal from which the direct current component has been removed by the high-pass filter 13 is passed through the low-pass filter 14 to extract the envelope component. This envelope voltage is compared with a detection level, which is a constant DC voltage, by a comparator 15 and becomes a valued signal.

For example, if the envelope voltage is higher than the detection level,
1#.

If it is smaller, mark it as “o”. FIG. 3 shows the relationship between the reproduced signal and the envelope binarized signal. A is a reproduction signal of the preamplifier output. B is an envelope binary signal output from the comparator, which is "1" in the address and data recording sections and "0" in the data unrecorded sections.

The envelope binary signal is guided to a recorded/unrecorded discriminator 18 and an address/data switch 19.

First, the recorded/unrecorded discriminator 18 outputs a signal only when a data signal exists, that is, in a data recording section, and outputs nothing when a data signal does not exist, that is, in a data unrecorded section. This is to prevent the data signal processing circuit 12 from sending meaningless binary signals to the demodulator 20 since the data signal processing circuit 12 binarizes and outputs even weak signals such as noise.

The outputs of the recorded/unrecorded discriminator 18 and the address signal processing circuit 11 are input to the address/data switch 19 and become one signal line again. The address/data switch 19 converts the envelope of the address signal f out of the envelope binary signal and the edge (b in FIG. 3) indicating the end of the address.
The falling edge of b' is used to distinguish the address signal section and the data signal section and send them to the switching demodulator 2o.

The problem that the invention seeks to solve.

In such devices, noise and signal leakage from adjacent tracks (crosstalk) occur even in areas where no data is recorded.
Therefore, the amplitude of the address signal due to the uneven groove structure bits is smaller than the amplitude of the data signal due to the dark and dark pits. . If you focus on the unrecorded section and set the detection level high so that the envelope binarized signal does not detect noise or crosstalk, the binarization of the envelope in the address signal section will become unstable, and the signal at the end of the address will become unstable. It becomes difficult to accurately detect edges that indicate

The amplitude margin of the envelope in the address signal section becomes smaller with respect to the tab detection level, resulting in variations in the address signal amplitude between disks, changes in the amplitude due to aging of the disk, dirt on the disk or lens, and fluctuations in the power of the semiconductor laser. If there is, accurate detection becomes difficult.

On the other hand, if we focus on the address amplitude and set the detection level to be low, noise and crosstalk may be detected, and there is a possibility that data will be determined to have been recorded even though it is an unrecorded section.

Furthermore, the frequency components included in the data signal section and the frequency components included in the address signal section usually do not match. Normally, the data signal section has a wider frequency band and contains lower frequency components.

In order to detect an etch indicating the end of an address signal, the envelope voltage needs to be sufficiently small in the gap between the address signal section and the data signal section. Therefore, the cutoff frequency of the low-pass filter is increased to prevent the signal from being smoothed between the gaps. However, since the data signal section includes low frequency components, if the cutoff frequency of the low-pass filter is high, the low frequency components will appear as fluctuations in the envelope voltage. As a result, as mentioned above, if the detection level is set high to avoid false detection due to noise and crosstalk in the data unrecorded section, the envelope fluctuation due to the low frequency component will intersect with the detection level, and the envelope fluctuations in the data recording section will overlap. Misvalued.

FIG. 4 shows the relationship between envelope voltage and detection level.

Even though A is a reproduced signal and b is an unrecorded section of data,
The signal is being reproduced due to noise or crosstalk. A
The envelope voltage of is B. C is the reference voltage of the envelope, f is the envelope voltage generated by noise and crosstalk of a, and C is the envelope voltage lowered due to amplitude fluctuations and low frequency components of the data signal. The detection level d must be set so that an envelope voltage of 1 is not detected, but an envelope voltage of C is detectable.

In this way, in the conventional configuration with one low-pass filter and one comparator, the detection level setting is very delicate, and it is difficult to set the detection level due to variations in the reproduced signal amplitude depending on the disc, aging, dirt on the disc or lens, and semiconductors. Taking into account laser power fluctuations, envelope 2 can be stably maintained over a long period of time.
(It was difficult to obtain a value signal, the address signal and data signal were switched incorrectly), a random signal was sent to the demodulator in an area where no data was recorded, or the data signal was sent to the demodulator in an area where data was recorded. There was a problem with not sending a signal.

In view of the above-mentioned problems, the present invention provides an optical disc reproducing device that can stably obtain an envelope binary signal over a long period of time, and can distinguish between an address signal and a data signal, and between a data recording section and a data-unrecorded section. is intended to do.

Means for Solving the Problems In order to solve the above problems, the present invention includes two sets of low-pass filters and comparators, and compares the envelope voltages of the low-pass filters at different detection levels. One is used to distinguish between an address signal and a data signal, and the other is used to distinguish between a data recording section and a data unrecorded section.

Effects According to the above means, there are variations in the reproduced signal amplitude between disks, changes over time, dirt on the disk or lens, fluctuations in the power of the semiconductor laser, etc.9, and the effects of noise and crosstalk. Even if there is 2
Equipped with a pair of low-pass filters and comparators to compare the envelope voltages at different detection levels, it provides a large detection margin, making it easy to distinguish between address signals and data signals, and between data recorded and unrecorded sections. A distinction can be made in the judgment.

Embodiment FIG. 1 shows an embodiment of the optical disc reproducing apparatus of the present invention. In FIG. 1, the same numbers as in FIG. 2 indicate the same parts.

The reproduced signal from which the DC component has been removed by the high-pass filter 13 is passed through the low-pass filter (1) 14 and the low-pass filter (2) 1.
6, the envelope components are extracted, and each comparator (1
)15 and comparator? ) sent to 17. If the combination of low-pass filter 14 and comparator (1) 15 is for address/data switching, the cutoff frequency is set high so that the envelope voltage is sufficiently small in the gap between the address signal section and the data signal section. The detection level is set to a low voltage so as not to be affected by signal amplitude fluctuations. On the other hand, the low-pass filter 16 and the comparator? ) 17 is for data recording/non-recording discrimination, and the cutoff frequency is set low to prevent fluctuations in the envelope voltage due to low frequency components of the data signal, and the detection is not affected by noise or crosstalk. Set the level to a high frequency.

FIG. 6 shows the relationship between envelope voltage and detection level in one embodiment of the present invention. A is the input of the comparator 20, and since the cutoff frequency of the low-pass filter 2 is low, the envelope voltage is sufficiently smoothed.

The detection level a is set to a high level so as not to detect noise or crosstalk. B is an envelope binary signal of the output of the comparator 2. C is the input of the comparator 1, and since the cut-off frequency of the low-pass filter is high, the voltage at the gap d between the address signal and the data signal is sufficiently low. C is a detection level and is set low so as to have a margin with respect to the envelope voltage of the address signal.

In FIG. 1, based on the envelope binary signal output from the comparator (2) 17, the recorded/unrecorded discriminator 18 outputs the signal from the data signal processing circuit 12 only in the data recording period. This signal and the signal from the address signal processing circuit 11 are transferred to the address/data switch 1 by the output of the comparator (1) 15.
9, the signal from the address signal processing circuit 11 is sent to the demodulator 20 in the address signal section, and the signal from the data signal processing circuit 12 in the data signal section.

Effects of the Invention As described above, according to the present invention, it is possible to distinguish between an address signal section and a data signal section and record data by detecting the envelopes of the address signal and data signal in an optical disc playback device using a light source such as a semiconductor laser. The difference between discs and unrecorded discs is due to variations in the reproduction signal amplitude between discs, changes over time,
Even if there are fluctuations in the reproduced signal amplitude due to dirt on the disc or lens, fluctuations in the power of the semiconductor laser, noise, or crosstalk, it can be performed stably over a long period of time, and is extremely useful in practical terms. It is.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an optical disc playback device according to an embodiment of the present invention, FIG. 2 is a block diagram of a conventional optical disc playback device, and FIG. 3 is a waveform diagram showing the relationship between a playback signal and an envelope binary signal. FIG. 4 is a waveform diagram showing the relationship between the reproduction signal and the envelope binary signal of a conventional original disk reproduction device, and FIG. 6 is a waveform diagram showing the envelope binary signal in an embodiment of the present invention. 1... Semiconductor laser, 8... Optical disk, 14, 16... Low pass filter, 15...
17... Comparator, 18... Recorded/unrecorded discriminator, 19... Address/data switch.

Claims (1)

[Claims] An apparatus for reproducing signals from an optical disk in which address signals and data signals are provided in different areas, the apparatus comprising: means for removing a DC component of a reproduced signal to obtain an AC signal; and a first low-pass filter to obtain an AC signal. means for obtaining a first envelope signal; and means for comparing the first envelope signal at a first detection level to distinguish between an address signal and a data signal;
means for obtaining a second envelope signal of the alternating current signal using a second low-pass filter; and means for comparing the second envelope signal at a second detection level to distinguish between a data recording section and a data non-recording section. An optical disc playback device having: