JPS61233470A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To detect gate signals stably and accurately with a simple circuit constitution by clamping inputted edge signals in the recording section without passing a differentiation circuit, comparing at a specified level and outputting gate signals. CONSTITUTION:Edge signals 13 are amplified by an amplifier 31 and inputted to a clamping circuit and the differentiation circuit 4. Clampled signals are compared with a fixed DC level inputted from a terminal 6 by a comparator circuit 3 and gate signals 15 are obtained. On the other hand, differentiated signals 16 are compared with OV level and zero cross signals 17 are obtained. The gate signals 15 are inputted to JK input of JK flip flop of a signal processing circuit 7 and the zero cross signals 17 are inputted to a clock and output 8 is obtained as demodulation signals.

Description

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

BACKGROUND OF THE INVENTION FIG. 4 is a diagram showing the most common reproducing system in the case of differential recording in a conventional optical information recording/reproducing apparatus. The edge signal 18 reproduced from the optical recording disk is differentiated through a differentiating circuit 19, and this differential signal 24 is supplied to a comparator circuit 2o for gate signal detection and a comparator circuit 21 for zero cross signal detection, respectively. The gate signal 29 and zero cross signal 3o detected by the circuit are processed by the signal processing circuit 22 and a demodulated signal 23 is output. Here, the gate signal 29 is a differential signal 24 differentiated by the differentiating circuit 19, as shown in the waveform diagram of FIG.
Then compare the signals at the levels shown in Figure 5 25, create the signals shown in Figure 6 27, and compare them in the same way at the levels shown in Figure 6 26.
The gate signal shown in FIG. 6 is generated by detecting the rise and fall of these two signals. The differential signal 24 is also input to a comparator circuit 21, which compares the differential signal 24 at Ov level and sends out a zero cross signal 3o shown in FIG. 630. The gate signal 29 and the zero cross signal 30 are sent to the signal processing circuit 2.
2 and outputs the demodulated signal shown in FIG. 623.

Problems to be Solved by the Invention In such a conventional circuit, as shown at 25 and 26 in Fig. 6, comparison must be made using a comparator circuit at two levels, which makes the circuit that much more complicated. Furthermore, when comparing two levels, the S/N margin is twice as large as when comparing once to create a gate. Furthermore, since the envelope changes due to surface runout of the disk, it is difficult to stably detect the gate signal.

The present invention has been made in view of the above, and an object of the present invention is to provide an optical information recording/reproducing device with a simple circuit and a large S/N margin when generating a gate signal.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention generates a gate signal by clamping the input edge signal at a recording section in the edge signal without passing it through a differentiation circuit. , a comparison is made at a predetermined level and a gate signal is output.

Effects of the present invention With the above-described configuration, a gate signal can be generated in a comparator circuit by one comparison, and the circuit is simpler than the conventional comparator circuit for gate signal detection, and at the same time, the S/N ratio is reduced. The gate signal can be detected stably by the clamp circuit.

Embodiment FIG. 1 is a block diagram showing an embodiment of the optical information recording/reproducing apparatus of the present invention during reproduction. In FIG. 1, an edge signal 1, which is a reproduced signal, is supplied to a clamp circuit 2 and a differentiation circuit 4. In the clamp circuit 2, the input edge signal is clamped at a recording section where information is recorded. The clamped signal 14 is input to a comparator circuit 3 for gate signal detection, and a gate signal 16 is generated by comparing it with a fixed DC level e.

On the other hand, the signal 16 differentiated by the differentiating circuit 4 is input to the comparator circuit 6 for zero cross signal detection, and the zero cross signal 1
Generate 7. Each of the zero cross signal 17 and gate signal 16 is processed by a signal processing circuit 7 and a demodulated signal 8 is output. FIG. 2 is a waveform diagram of each part of the embodiment shown in FIG. 1. A edge signal 10 is generated from the data signal 9 to be recorded. This edge signal of 1° is then recorded on an optical recording disk. 11 is a recording pit made on the disc. When the recorded pit 11 is reproduced, an edge signal 1 is obtained. However, edge signal 1 is an ideal waveform,
In reality, when influenced by the frequency characteristics of recording and reproduction, the waveform becomes as shown in 12. Furthermore, due to surface runout and eccentricity of the disk, the signal level of the recording section changes as shown in 13. Here, the signal in signal 13 is the recording section, ■
indicates an unrecorded part. When clamping is applied at the recording section level (2), the waveform shown in 14 is obtained. By comparing this signal 14 and the fixed DC level shown at O, the gate signal 15 is
Detect. On the other hand, by differentiating the edge signal 13, a differential signal 18 is obtained, and by comparing this signal with the OvC level, a zero cross signal 17 is generated.

Demodulated signal 8 is generated using gate signal 16 and zero cross signal 17.
can be generated.

FIG. 3 is a specific configuration diagram of the embodiment shown in FIG. 1.

First, the edge signal 13 is amplified by the amplifier 31 and input to the clamp circuit 2 and the differentiator circuit 4, and the clamped signal is compared with the fixed DC level input to the terminal 6 by the comparator circuit 3 to obtain the gate signal 15. . On the other hand, the differentiated signal 16 is compared in ovC level by a comparator circuit 6 to obtain a zero cross signal 17. The gate signal 16 is input to the IK input of the JK flip-flop of the signal processing circuit 7, and the zero cross signal 17 is input to the clock to obtain an output 8 as a demodulated signal.

As described in detail, according to the present invention, an envelope detection circuit or the like is not required as a level signal for comparison in a comparator circuit, and comparison can always be made at a fixed DC level, resulting in an extremely simple circuit. With this configuration, the gate signal can be detected stably and accurately, and the signal can be regenerated reliably, which has great practical effects.

[Brief explanation of drawings]

Figure 1 is a block diagram of a reproduction system in an embodiment of the present invention, Figure 2 is a signal waveform diagram in the same embodiment, Figure 3 is a specific circuit diagram of the embodiment, and Figure 4 is a conventional reproduction system. The block diagram and FIG. 6 are signal waveform diagrams thereof. 2... Franz circuit, 3, 6... Con/< rail circuit, 4... Differential circuit, 7...
...Name of agent for signal processing circuit 0 Patent attorney Toshio Nakao and one other person
e Fig. 4 Fig. 5 Similar end 23

Claims (1)

[Claims] A clamp circuit that clamps the information recording part in the signal reproduced from the signal differentially recorded on the optical recording disk, and a comparator circuit that compares a predetermined voltage with the output signal of the clamp circuit, and is used to retrieve information. An optical information recording/reproducing device characterized in that it generates a gate signal.