JPS62128044A - Photomagnetic disc reproducing device - Google Patents

Abstract

PURPOSE:To constitute a waveform shaping circuit and following circuits as one system without degrading a ratio of signal to noise by cutting off the output of an adding amplifier when a photomagnetic signal is reproduced. CONSTITUTION:The output of an adding amplifier 3 which takes out a header signal is cut off when the photomagnetic signal is outputted from a differential amplifier 2 which takes out the photomagnetic signal, and the output of the differential amplifier 2 which takes out the photomagnetic signal is cut off when the header signal is outputted from the adding amplifier 3 which takes out the header signal. Thus, the output of the adding amplifier 3 which takes out the header signal and that of the differential amplifier 2 which takes out a data signal are prevented from being noise to each other to suppress the degradation in ratio of signal to noise.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magneto-optical disk reproducing apparatus for reproducing information using a magneto-optical disk.

Conventional technology In recent years, magneto-optical disks with guide grooves for tracking have become commonplace, and hard-sector disks, in which address information on the disk is recorded using bits made of uneven surfaces, are generally used. It has become.

Below, a conventional magneto-optical disk reproducing apparatus for reproducing a magneto-optical disk having hard sectors will be described.

FIG. 3 is a block diagram of a conventional magneto-optical disk reproducing apparatus. In Fig. 3, 1a and 1b are light receivers that receive reflected light from the disk and convert it into electrical signals, 2 is a differential amplifier that subtracts the outputs of the two light receivers 1a and 1b, and 3 is two light receivers. an adder/amplifier that adds the outputs of 1a and 1b;
4 is a summing amplifier that adds the output of the differential amplifier 2 and the output of the summing amplifier 3; 6 is a waveform shaping circuit that binarizes the output of the summing amplifier 4; and 6 detects information from the output of the waveform shaping circuit 6. This is a signal processing circuit that performs

The operation of the magneto-optical disk remaster device configured as described above will be described below.

The reflected light from the disk is incident on the two light receivers 1a and 1b without being separated. The outputs of the two light receivers 1a and 1b are input to a differential amplifier 2 and a summing amplifier 3. The differential amplifier 2 outputs a magneto-optical signal, that is, a reproduced data signal. The output of the summing amplifier 3 is a header signal due to changes in the intensity of reflected light from the disk, that is, unevenness.

Although there is a method of demodulating these header signals and data signals using separate waveform shaping circuits and signal processing circuits, the waveform shaping circuit and signal processing circuit are usually shared in order to simplify the circuit. To share circuits.

The header signal and the data signal are added in a summing amplifier 4,
It is output as a signal consisting of a header signal and a data signal, and is input to a waveform shaping circuit. The waveform shaping circuit 5 outputs a signal consisting of a binary header signal and a data signal. The output of the waveform shaping circuit 5 is input to the signal processing circuit 6, where the address and data are demodulated and sent to the next stage as a demodulated address signal and a demodulated data signal.

Problems to be Solved by the Invention However, in the above-mentioned conventional configuration, at the input of the summing amplifier 4, ideally signals would not be output simultaneously from the differential amplifier 2 and the summing amplifier 3 in the previous stage, but in reality, When reading data, noise may be output from the summing amplifier 3 where the header signal is not recorded due to a defect on the disk, or conversely, noise may be output from the differential amplifier 2 when reading the header signal, causing the signal pair to deteriorate. This has the problem of deteriorating the noise ratio.

The present invention solves the above-mentioned conventional problems.

It is an object of the present invention to provide a magneto-optical disk reproducing device that does not suffer from deterioration in signal-to-noise ratio due to sharing a circuit for demodulating a header signal and a data signal.

Means for Solving the Problems To achieve this object, the magneto-optical disk reproducing apparatus of the present invention includes a differential amplifier that extracts magneto-optical signals by differentially amplifying signals from a plurality of light receivers; and a summing amplifier that extracts a header signal due to unevenness on the disk surface by adding and amplifying the signals from the plurality of light receivers, and sends the outputs of the differential amplifier and summing amplifier to the signal demodulation circuit of the next stage and subsequent stages. The apparatus further includes means for cutting off the outputs from the differential amplifier and the summing amplifier, and is configured to cut off the output from the summing amplifier at least when reproducing the magneto-optical signal.

With this configuration, when a magneto-optical signal is being output from the differential amplifier that takes out the magneto-optical signal, the output of the summing amplifier that takes out the header signal is output, and when a header signal is being output from the summing amplifier that takes out the header signal, , the output of the differential amplifier that takes out the magneto-optical signal can be blocked, and therefore the output of the summing amplifier that takes out the header signal and the output of the differential amplifier that takes out the data signal can be prevented from becoming noise, and the signal pair Deterioration of the noise ratio can be suppressed.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows the configuration of a magneto-optical disk reproducing apparatus in a first embodiment of the present invention. In Figure 1, 1
a and 1b are light receivers that are subjected to predetermined processing such as an analyzer and are provided to obtain header signals and data signals; 2;
3 is a differential amplifier whose output is the difference between the outputs of the light receivers 1a and 1b; 3 is a summing amplifier whose output is the sum of the outputs of the light receivers 11L and 1b; 6 is a waveform shaping circuit for binarization; 7 is a signal processing circuit, and 8 is a changeover switch.

The operation of the magneto-optical disk reproducing apparatus configured as described above will be described below.

First, the reflected light from the disk that is incident on the light receivers 1a and 1b is converted into an electrical signal, and the header signal is inputted to the waveform shaping circuit 6 via the changeover switch 8 by the summing amplifier 3, where it is binarized. The binarized header signal is demodulated by the signal processing circuit 7.

Address information is read out. At the same time as reading of the address information is completed, the signal processing circuit 7 sends a signal to the selector switch 8.
A control signal is output to switch the selector switch 8 to the differential amplifier 2.

As a result, the differential amplifier 2 and the waveform shaping circuit 5 are connected, and the data signal output from the differential amplifier 2 passes through the waveform shaping circuit 6 and is demodulated by the signal processing circuit 7. At the same time as data reading is completed, the signal processing circuit 7 again sends out a signal for controlling the changeover switch 8 to switch the state in which the summing amplifier 3 and the waveform shaping circuit 5 are connected, that is, the state in which address information is read. The methods of creating the timing for switching between the differential amplifier 2 and the summing amplifier 3 are as follows: (1) Add a synchronization signal to the tail of the header signal or data signal and detect the synchronization signal. (2) Demodulate the header signal as an initial state. For example, it is managed by the time of the header signal or data signal.

As described above, according to this embodiment, the magneto-optical signal output obtained by differentially amplifying the signals from the plurality of light receivers that receive reflected light from the magneto-optical disk, and the plurality of light receivers A changeover switch is provided as a means for cutting off one output before sending the header signal output obtained by adding and amplifying the signals from the header to the subsequent signal demodulation circuit. With this configuration, deterioration of the signal-to-noise ratio can be suppressed even if the circuits from the next stage onward are shared.

A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram of a magneto-optical disk reproducing apparatus showing a second embodiment of the present invention. In the figure, 1a and 1b are light receivers that receive reflected light from the disk and convert it into electrical signals, 5 is a waveform shaping circuit, and 7 is a signal processing circuit, which has the same configuration as in FIG. 1. . The difference from the configuration shown in FIG. 1 is that the differential amplifier for subtracting the outputs of the photodetectors 1a and 1b is a variable gain differential amplifier 9, and the photodetector 1N
.

A summing amplifier 1o that adds the outputs of the variable gain differential amplifier 1b is a variable gain summing amplifier 1o, and a summing amplifier 4 that adds the outputs of the variable gain differential amplifier 9 and the variable gain summing amplifier 10.
The point is that

The operation of the magneto-optical disk reproducing apparatus configured as described above will be described below.

First, the reflected light from the disk is received by the light receiver 11L.

1b and is converted into an electric signal, and the converted electric signal is input to a variable gain differential amplifier 9 and a variable gain summing amplifier 10. The gains of the variable gain differential amplifier 9 and the variable gain summing amplifier 10 are in a reciprocal relationship, and at the timing when the header signal is output from the variable gain summing amplifier 1o, the gain of the variable gain differential amplifier 9 is set to zero, and the gain of the variable gain differential amplifier 9 is set to zero. At the timing when the magneto-optical signal, that is, the data signal, is output from the variable gain differential amplifier 9, the gain of the variable gain summing amplifier 10 becomes zero. The outputs of the variable gain differential amplifier 9 and the variable gain summing amplifier 1o are input to the summing amplifier 4. The output of the summing amplifier 4 is binarized by a waveform shaping circuit 6 and demodulated by a signal processing circuit 7.

The signal processing circuit 7 demodulates the header signal and the data signal to generate a timing signal for controlling the gains of the variable gain summing amplifier 1° and the variable gain differential amplifier 9.
This timing signal is input to the variable gain summing amplifier 10 and the variable gain differential amplifier 9. The timing signal for controlling the gain is created using the method for creating the timing for controlling the changeover switch 8 of the first embodiment of the present invention.

As described above, by making the gains of the summing amplifier that takes out the header signal and the differential amplifier that takes out the data signal in a reciprocal relationship, even if the summing amplifier output and the differential amplifier output are added, the summing amplifier output and the differential amplifier output are The outputs do not interact with each other as noise, and the same effects as in the first embodiment of the present invention can be obtained.

In the second embodiment, the variable gain differential amplifier 9 and the variable gain summing amplifier 1o are used as the differential amplifier for extracting the data signal and the summing amplifier for extracting the header signal. When the output of the variable gain differential amplifier 9 is small, the deterioration of the signal-to-noise ratio is small, so the variable gain differential amplifier 9 may be a differential amplifier with a constant gain.

In the second embodiment, the variable gain differential amplifier 9
Although the outputs of the variable gain type summing amplifier 1o are summed by the summing amplifier 4, it is needless to say that they may be added without using the summing amplifier 4.

Effects of the Invention As described above, the present invention provides a differential amplifier for extracting a magneto-optical signal and a summing amplifier for extracting a header signal due to unevenness on the disk surface. By providing a means for cutting off the signal from the amplifier and, at least when reproducing the magneto-optical signal, for cutting off the output of the summing amplifier, the circuits after the waveform shaping circuit can be integrated into one system without deteriorating the signal-to-noise ratio. Accordingly, it is possible to realize an excellent magneto-optical disk reproducing apparatus that can perform the following functions.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a magneto-optical disk reproducing apparatus in a first embodiment of the present invention, FIG. 2 is a block diagram showing the configuration of a magneto-optical disk reproducing apparatus in a second embodiment of the present invention, FIG. 3 is a block diagram showing the configuration of a conventional magneto-optical disk reproducing apparatus. 1a, 1b...Photodetector, 2...Differential amplifier, 3...Summing amplifier, 4...Summing amplifier,
5...Waveform shaping circuit, 7...Signal processing circuit, 8...Fall) changeover switch, 9...
...Variable gain differential amplifier, 1o...Variable gain summing amplifier.

Claims (1)

[Claims] a plurality of light receivers that receive reflected light from the magneto-optical disk;
A differential amplifier extracts a magneto-optical signal by differentially amplifying the signals from the plurality of photoreceivers, and a header signal due to unevenness on the disk surface is added and amplified by adding and amplifying the signals from the plurality of photoreceivers. and a summing amplifier for taking out the signal, and before sending the outputs of the differential amplifier and summing amplifier to the subsequent signal demodulation circuit, means is provided to cut off the signals from the differential amplifier and summing amplifier, and at least the output of the summing amplifier is A magneto-optical disk reproducing apparatus characterized in that the output of the summing amplifier is cut off during magnetic signal reproduction.