JPS62202360A - Signal detection circuit of optical memory device - Google Patents

Abstract

PURPOSE:To improve the locking of a PLL and the reliability of detection of synchronization by adding the voltage of a level to an unrecorded part to a reproducing signal, or the prescribed position of a comparison voltage generating circuit or a comparison voltage and using a comparison voltage obtained in this way so as to detect a digital information signal. CONSTITUTION:In adding a signal 102 to the DC component of a reproducing signal 101, the DC component of a signal 103 (broken lines) is obtd. Thus, a digital information signal 105 detected by comparing the reproducing signal 101 with a comparison voltage being the output of a low pass filter 3 from the DC component of the signal 103 has no random noise signal at the unrecorded part and the duty is improved just after the start of a recorded area. Further, the signal 102 is added to the reproducing signal 101 in this case, but in adding the signal 102 to the comparison voltage 104, only the random noise signal at the unrecorded part is avoided. Thus, the locking of the PLL and the reliability of synchronization detection in a sector mark are improved.

Description

[Detailed Description of the Invention] Technical Field> The present invention relates to an optical memory device that records, reproduces, or erases information by irradiating an optical information recording medium with a light beam such as a laser beam. The present invention relates to a signal detection circuit that detects a signal.

<Prior Art> A signal detection circuit in a magneto-optical disk memory device will be described as an example of a signal detection circuit in a conventional optical memory device. A magneto-optical disk memory device is an optical memory device in which a magnetic film with an axis of easy magnetization perpendicular to the film surface is used as a recording medium, and recording, reproduction, or erasing is performed by irradiating the film with a laser beam.0 This magneto-optical disk memory First, the recording/reproducing method of the device will be explained.

During recording, when a laser beam focused to about 1 μm is intensity-modulated according to the recording signal and irradiated onto the magnetic film surface of the magneto-optical disk, the temperature of the magnetic film locally rises. The coercive force decreases in the area where the temperature has risen, so if an auxiliary magnetic field is applied from the outside at the same time, the direction of magnetization is reversed and information is recorded.

During reproduction, the surface of the recorded magnetic film is irradiated with linearly polarized laser light of a weaker intensity than during recording. Then, the reflected light causes a tilt in the plane of polarization due to the magneto-optical effect (Kerr effect) of the magnetic film. This slope is detected by an analyzer and converted into light intensity, which is then detected by a photodetector and information is reproduced.

FIG. 5 shows a block diagram of an information reproducing device of a magneto-optical disk device, FIG. 6 shows a signal detection circuit, and FIG. 7 shows a signal waveform in FIG. 6. Note that the same reference numerals shown in FIG. 5, FIG. 6, and FIG. 7 indicate the same thing.

In FIG. 5, an analog signal reproduced by an optical head 21 becomes a reproduced signal 101 via an amplifier 22 and a waveform processing circuit 23, and a digital information signal 205 is detected by a signal detection circuit 24.

The digital information signal 205 is the PLL and synchronization detection circuit 2
5. Introduced digital information signal 205
Based on this, the PLL generates a phase-synchronized clock signal, and the synchronization detection circuit detects synchronization in units of sectors such as sector marks.

Conventionally, the signal detection circuit 24rfi shown in FIG. 5 has the configuration shown in FIG. 6. That is, the reproduced signal 101 comparator l
It is led to one side of the circuit as an input, and is also led to the comparison voltage generation circuit 31 (the part surrounded by the broken line). In this example, a low-pass filter 32 is used as the comparison voltage generation circuit 31.

Comparison voltage 2 obtained as an output from the comparison voltage generation circuit 31
04 is led to the other input of the comparator 1, and a digital information signal 205 is obtained as the output of the comparator 1.

FIG. 7 shows the waveform in FIG. 6. As shown in FIG. 7, the reproduced signal 101 corresponds to the recording marks only in the recorded area. This playback signal +01 DC
Components are indicated by dashed lines. The output of the low-pass filter 32 in the comparison voltage generation circuit 31, ie, the comparison voltage 204, has a waveform exhibiting transient response characteristics with respect to the DC component of the reproduced signal 101. Hence the playback signal! The digital information signal 205 obtained by comparing the comparison voltage 204 with the comparison voltage 204 becomes a random noise signal in the unrecorded area as shown in FIG. This will result in a signal with a shift in duty.

The digital information signal 205 shown above is converted to P1 as shown in FIG. When input to the L and synchronization detection circuit, random noise signals generated in the unrecorded area and signals with deviations in the data immediately after the start of the recording area will reduce the reliability of the PLL pull-in operation and the synchronization detection of sector marks, etc. Deteriorated. In other words, the PLL tends to respond to random noise signals, and the synchronization detection circuit may erroneously detect synchronization. Duty
A signal that is deviated from the synchronization detection circuit may degrade the PLL pull-in response and may not be detected by the synchronization detection circuit. Therefore, a signal detection circuit that detects reliable digital information signals for PLL pull-in operation and synchronization detection has been desired.

In this example, a magneto-optical disk memory device is used as the optical memory device, but the above-mentioned problems are the same in write-once type optical disk memory devices and the like.

<Object of the invention> In view of the problems of the prior art described above, the object of the present invention is to
It is an object of the present invention to provide a signal detection circuit that detects a digital information signal with reliability for pull-in operation and synchronization detection in sector marks and the like.

<Embodiment> An embodiment of a signal detection circuit for an optical memory device according to the present invention will be described below by taking a signal detection circuit for a magneto-optical disk memory device as an example. FIG. 1 shows a signal detection circuit according to an embodiment of the present invention. FIG. 2 is a diagram showing the waveform in FIG. 1.

In FIG. 1, a reproduced signal 101 is led to one side input of a comparator 10 and an adder 2. In FIG. On the other hand, the voltage vO is set by variable resistor 4
A signal 10 is obtained by switching the voltage divided by and the ground voltage in the switching circuit 5 based on the timing signal +06.
2 is led to adder 2. In this adder 2, a signal 102 is added to the reproduced signal +01. The output signal 103 of the adder 2 is guided to the comparison voltage generation circuit 3I using the low-pass filter 3 as the zero comparison voltage generation circuit 31.

The comparison voltage +04 obtained here is led to the other input of the comparator 1, and the digital information signal 105 is detected. FIG. 2 shows the signal waveform in FIG. 1. Playback signal +0
signal +02 based on timing signal 106 for 1
is added. In other words, considering only the unrecorded area, the reproduction signal 1
Add a certain level to 01. Focusing on the DC component,
As shown in FIG. 2, a signal 1 is added to the DC component of the reproduced signal 101.
When adding 02, the DC component of signal 103 (shown by the dashed line)
is obtained. Therefore, the digital information signal 105 detected by comparing the comparison voltage 104 outputted through the low-pass filter 3 with the reproduced signal 101 can avoid the generation of random noise signals in the unrecorded area, and Immediately after starting, the duty can be improved. In this example, if the signal +02 is added to the reproduced signal +01 and then the signal +02 is added to the comparison voltage 104, only the generation of random noise signals in the unrecorded area can be avoided.

Next, a second embodiment will be described using FIG. 3.

The reproduced signal +01 is guided to one side of the input of the comparator I and the second comparison voltage generation circuit 31 (the part surrounded by the broken line).

First, this second comparison voltage generation circuit 31 will be explained. The reproduced signal 101 is guided to a positive direction peak hold circuit 11 and a negative direction peak hold circuit I2, and the respective output signals II+ and +12 are sent to an adder +3. Multiplier 1
4 (T times). That is, this circuit detects the envelope of the reproduced signal 101 and sets the center level of the envelope to the second level.
This is a second comparison voltage generation circuit that outputs a comparison voltage of . Now, the voltage obtained by dividing VQ by the variable resistor 14 and the ground voltage are used in the switching circuit 15 as a timing signal 10.
6, a signal +14 is obtained.0 The signal +15 obtained by adding this signal 114 and signal +13 in the adder 16 is outputted via the low-pass filter 7, and the first
A comparison voltage of +16 is obtained. A digital information signal 105 is detected by comparing the reproduction signal +01 and the first comparison voltage +16 in the comparator l.

The signal waveform in FIG. 3 will be explained using FIG. 4. The DC component of the second comparison voltage 113 is shown in FIG.
A signal +14 is added to the second comparison voltage 113 based on . Therefore, the output signal 115 of the adder 16 shown in FIG.
A first comparison voltage of +16 is obtained for the DC component (waveform shown by a broken line). A digital information signal 105 is obtained by comparing the output signal +01 with the first comparison voltage 116. Similar to the example shown in FIG. 2, this digital information signal 105 can avoid generating random noise in the unrecorded area, and can improve the duty immediately after the start of the recorded area.

In this example, the signal +14 is added to the second comparison voltage 113, but the reproduced signal +01 is added instead of the second comparison voltage +13.
and input it to the second comparison voltage generation circuit 31,
A similar effect can be obtained by comparing the second comparison voltage and the reproduced signal. Further, even if the signal 114 is added to the output signal of the low-pass filter 17 instead of the second comparison voltage 113, only the generation of random noise in the unrecorded portion can be avoided.

As shown above, a voltage of a certain level is added in the unrecorded area to the reproduced signal or the output of the second comparison voltage generation circuit or the comparison voltage input to the comparator, and the comparison voltage obtained thereby is used. If the digital information signal is detected using the same method, the generation of random noise signals in the unrecorded portion can be avoided, and the duty immediately after the recording portion starts can be improved. Therefore, it is possible to improve the reliability of the PLL pull-in operation and the synchronization detection in the synchronization detection circuit based on this digital information signal.

In the above two embodiments, a magneto-optical disk memory device was taken as an example of the optical memory device, and an example of the signal generation circuit thereof was shown. It is also applicable in

<Effects of the Invention> According to the present invention, a voltage of a certain level is added to the predetermined position or comparison voltage of the reproduced signal or comparison voltage generation circuit in the unrecorded area, and the comparison voltage obtained thereby is used. By detecting the digital information signal, the generation of random noise signals in the unrecorded portion can be avoided, and the duty immediately after the recording portion starts can be improved. Therefore, the reliability of the pull-in operation of the PLL and the synchronization detection of the synchronization detection circuit can be improved based on this digital information signal.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a signal detection circuit of a magneto-optical disk memory device according to an embodiment of the present invention, FIG. 2 is a signal waveform diagram in FIG. 1, and FIG. 3 is an embodiment of the present invention. The second signal detection circuit of the magneto-optical disk memory device according to the example
4 is a signal waveform diagram in FIG. 3, FIG. 5 is a block diagram of an information reproducing device, FIG. 6 is a circuit diagram showing a conventional signal detection circuit, and FIG. 7 is a diagram showing a conventional signal detection circuit. 6 is a signal waveform diagram in FIG. 6. FIG. In the figure, 1... Comparator 2, 13.16... Adder
3゜17.32...Low pass filter 4,14...
・Possible f resistance 5.15...Switching circuit 11...
- Positive direction peak hold circuit 12... Negative direction peak hold circuit 14... Multiplier 21... Optical head 22... Amplifier 23... Waveform processing circuit
24...Signal detection circuit 25...PLL and synchronization detection circuit 31...Comparison voltage generation circuit Agent: Patent attorney Tsuyoshi Sugiyama (and 1 other person) Area N, Figure 2, Kouki Shinto is a.

Claims (1)

[Claims] 1) In an optical memory device that records, reproduces, or erases information by irradiating an optical information recording medium with a light beam such as a laser beam, a digital information signal is generated by comparing a reproduction signal with a comparison voltage. The apparatus includes a comparator for detection, an adder that adds a voltage of a certain level to the reproduced signal based on a timing signal, and a comparison voltage generation circuit that generates the comparison voltage from the output of the adder, and includes a comparator for detecting the reproduced signal. A signal detection circuit for an optical memory device, characterized in that the comparison voltage is compared in the comparator to detect a digital information signal. 2) In an optical memory device that records, reproduces, or erases information by irradiating an optical information recording medium with a light beam such as a laser beam, a digital information signal is detected by comparing a reproduction signal with a first comparison voltage. a second comparison voltage generation circuit that generates a second comparison voltage from the reproduced signal, and an adder that adds a voltage of a certain level to the second comparison voltage based on a timing signal. A signal detection circuit for an optical memory device, characterized in that the adder output is used as the first comparison voltage, and the reproduced signal and the first comparison voltage are compared in the comparator to detect a digital information signal.