JPS63244317A - Optical disk reproducing device - Google Patents

Abstract

PURPOSE:To stably obtain an envelope binarized signal, extending over a long period of time by constituting an device so that two comparators are provided, and each of them compares at a different detection level respectively, and one is used for switching an address signal and a data signal, and the other is used for discriminating a data recorded section and a data not yet recorded section. CONSTITUTION:An envelope component is extracted from a regenerative signal, from which a direct current component is removed by a high pass filter 13, by an envelope detection circuit 13. The said envelope voltage is led to the comparator (1) 15 and the comparator (2) 16. The detection level of the comparator (1) 15 is set low so as to binarize the envelope voltage of the address signal and detect stably an edge showing the section of the address signal and its termination. The detection level of the comparator (2) 16 is set higher than that of the comparator (1) 15, so as to detect safely a discrimination between the data recorded section and the data not yet recorded section, even if a noise or a cross talk is present. Thus, the discrimination of the address and the data, and the discrimination of the data recorded/data not yet recorded sections can be stably performed, extending over a long period of time, without suffering from the influence of the noise or the cross talk.

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 to read pits that have been reformatted by a groove structure on the optical disk and pits that are dark and dark due to differences in reflectance.

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 condenser lens 2, and is incident on a total reflection mirror 4 and an aperture/diaphragm 6. Aperture lens 6 directs the incident light from the cigarette to 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 reflected by the photodetector 6 and converted into an electric signal.7 rotates the disk 8 with a disk motor. There is. 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. A disk in which the address signal is preformatted on the optical disk in a concave and convex groove structure.

The data signal is a reproduced signal of gray bits due to the difference in reflectance, whereas the data signal is a reproduced signal of bits of shading due to the difference in reflectance, so the two differ in signal amplitude, frequency band, and frequency characteristics. Therefore,
Separate processing circuits are provided for each. On the other hand, from the reproduced signal from which the DC component has been removed by the high-pass filter 13, the envelope detection circuit 14 extracts the envelope component.

This envelope voltage is compared with a constant DC voltage by a comparator 15 and becomes a binary signal. For example, if the envelope voltage is larger than the detection level, it will be “1”, if it is smaller, it will be “0”.
''. Figure 3 shows the relationship between the reproduced signal and the envelope binary signal. A is the reproduced signal of the preamplifier output.

B is an envelope binary signal of the output of the comparator, which is "1" in the address and data recording section and "0" in the data unrecorded section.

The envelope binary signal is guided to a recorded/unrecorded discriminator 17 and an address/data switch 18.

The recorded/unrecorded discriminator 17 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 because the data signal processing circuit converts even weak signals such as noise into binarized signals, which causes the demodulator 19 to generate meaningless 2-value signals.
This is to prevent a value signal from being sent.

The outputs of the recorded/unrecorded discriminator 17 and the address signal processing circuit 11 are inputted to the address/data switch 18, and are switched to 1 again.
It becomes the signal line of the book. The address/data switch 18 uses the envelope of the address signal of the envelope binary signal and the edge indicating the end of the address shown at 1> and b/ in FIG. 3 to distinguish between the address signal section and the data signal section. The signals are differentiated, switched, and sent to the demodulator 19.

Problems that the invention aims to solve In such devices, noise and signal leakage from adjacent tracks (crosstalk) occur even in areas where no data is recorded.
Therefore, there is a possibility that an envelope binary signal is detected as if data were recorded therein. The amplitude of the address signal due to the uneven groove structure bit is smaller than the amplitude of the data signal due to the gray bit. If you focus on the unrecorded section and set the detection level high so that the envelope binarized signal does not detect noise and crosstalk, the binarization of the envelope in the address signal section will become unstable and the edge indicating the end of the address will It becomes difficult to detect accurately.

The amplitude margin of the address signal envelope is small relative to the detection level, or the disk changes over time.

Dirt on the disk or lens If there are amplitude fluctuations due to power fluctuations in the semiconductor laser or variations in address amplitude between disks, the envelope binarization of the address part will become unstable, making it difficult to accurately identify the edge that indicates the end of the shear address. It becomes difficult to detect. On the other hand, if the detection level is set low by focusing on the address amplitude, there is a possibility that the envelope will be detected even though the data is not recorded, and it will be determined that the data has been recorded.

Figure 4 shows the relationship between envelope voltage and detection level.
is a reproduced signal, and although b is an unrecorded section, the signal is reproduced due to noise and crosstalk. The envelope voltage of A is B. e is an envelope reference voltage, and C1 is an envelope voltage generated by noise and crosstalk of a. d is a detection level and must be set so that the envelope voltage of C is not detected.

In this way, in the conventional configuration, the setting of the detection level is very delicate, and it is difficult to obtain an envelope binary signal stably over a long period of time. However, there was a problem in that a random signal was sent to the demodulator in an area where no data was recorded.

Means for Solving the Problems In order to solve the above problems, the present invention provides an envelope 2
Equipped with two comparators that obtain converted signals, each of which is compared at a different detection level. One is used to switch between the address signal and the data signal, and the other is used to distinguish between the data recording section and the data non-recording section. Configure it as follows.

According to the above means, by using two comparators with different detection levels even if there are fluctuations in the address amplitude or the effects of noise or crosstalk, it is possible to prevent noise and crosstalk from fluctuations in the amplitude. Since there is a large detection margin even when the
It is possible to stably distinguish between unrecorded and unrecorded data.

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 envelope detection circuit 14 extracts the envelope component of the reproduced signal from which the DC component has been removed by the high-pass filter 13. This envelope voltage is led to comparator (1) 16 and comparator (to) 16. The comparator (1) 15 binarizes the envelope voltage of the address signal and sets the detection level low so that the section of the address signal and the edge indicating the end thereof can be stably detected. The comparator (2) 16 uses the comparator (1
) Set the detection level higher than 15. FIG. 6 shows the envelope voltage and detection level in one embodiment of the present invention.
The relationship between envelope binary signals is shown. A is the reproduction signal,
B is the input signal of the comparator. a is the detection level of the comparator (1), and C is the output signal of the comparator (1). Although the envelope is detected even in the data unrecorded section due to noise and crosstalk, here it is sufficient to detect the address signal section and edges C and C' indicating the end of the address signal section. b is the detection level of the comparator (2), and D is the output signal of the comparator (rumored).Although the envelope is not detected in the address signal section, it is sufficient to be able to distinguish between recorded and unrecorded data signal sections.

In FIG. 1, according to the output of the comparator (2) 16, the recorded/unrecorded discriminator 17 outputs the signal from the data signal processing circuit 12 only in the recorded period. This signal and address signal processing circuit 11
is switched by the address/data switcher based on the output of comparator 0), and the signal from the address signal processing circuit is demodulated in the address signal section, and the signal from the data signal processing circuit is demodulated in the data section. sent to the vessel.

Effects of the Invention As described above, according to the present invention, it is possible to distinguish between address data and recorded/unrecorded data by detecting envelopes of address signals and data signals of an optical disk reproducing apparatus using a light source such as a semiconductor laser. It can be performed stably over a long period of time without being affected by noise or crosstalk, and is extremely useful in practice.

[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 envelope binarization.
Figure 4 shows envelope 2 of the optical disc regeneration device in Figure 2.
FIG. 6 is a waveform diagram showing envelope binarization in the embodiment of FIG. 1. 1... Semiconductor laser, 8... Optical disk, 14... Envelope detection circuit, 15.1
6... Comparator, 17... Recorded/unrecorded discriminator, 18... Address/data switch. Name of agent: Patent attorney Toshio Nakao and one other person
. Ward ■ Ward

Claims (1)

[Claims] An apparatus for reproducing signals from an optical disk in which address signals and data signals are provided in different areas, comprising means for removing a DC component of a reproduced signal to obtain an AC signal, and means for detecting an envelope of the AC signal to obtain an envelope signal. and means for comparing the envelope signal at a first detection level to distinguish between an address signal and a data signal, and comparing the envelope signal at a second detection level to distinguish between a data recorded section and a data unrecorded section. An optical disc playback device comprising means.