JPS634462A - Storage information readout circuit - Google Patents

Abstract

PURPOSE:To attain noise rejection on a base line and accurate peak position detection by eliminating a DC component of a reproduced analog signal, applying half-wave rectification to the result, extracting only a half wave in the peak polarity direction only, and using the resulting signal for an object of peak detection by a differentiation circuit and a comparator circuit. CONSTITUTION:A read analog signal (a) is fed to a half wave rectifier circuit 4, where only a positive half waveform is detected based on a zero level corresponding to a peak direction polarity of the read analog signal (a) to obtain a detection signal (b). Then the detection signal (b) is subject to time differentiation by a differentiation circuit 5 and a differentiation signal (c) being its output has a waveform in which a peak point of the read analog signal (a) is converted into a zero cross point. That is, the positive peak point of the read analog signal (b) being '1' information is coincident with a positive peak point of the detection signal (b) and further coincident with a position crossing the zero level from the positive to the negative level of the differentiation signal (c). Since the differentiation signal (c) is fed to one input of the comparator circuit 6 and a prescribed threshold valve -VTH is fed to the other input, a peak signal (d) being the result of comparison goes to a logical signal of level '1' when the differential signal (c) reaches the value -VTH or below.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a storage information readout circuit, and more particularly to a storage information readout circuit suitable for an optical storage device such as an optical disk device.

[Conventional technology]

In optical storage devices such as optical disk devices, optical sensors detect that when a storage medium is irradiated with a laser beam focused on a very small spot, the intensity of reflected light changes depending on the presence or absence of bits formed on the surface of the medium. Detection is performed and the information is reproduced. The reproduced analog signal obtained from the optical sensor has a waveform whose peak corresponds to the center of bit 7 on the medium, as shown in waveform (e) in FIG. 4, for example. Therefore, the readout circuit is configured to read out information by detecting the peak point of the reproduced analog signal. As a means for detecting the peak point, a method is generally used in which a differentiation circuit and a zero-cross comparison circuit are combined to detect a cross point between the differentiated reproduced analog signal and the zero level.

However, in this type of device, the medium noise etc. are large and it is not possible to obtain a sufficient S/N ratio.
As shown in the block diagram in Figure 4 and the operation waveform diagram in Figure 4, a simple circuit configuration is used to reproduce the reproduced analog signal for the purpose of preventing erroneous detection of XX1 data due to noise at the ``0'' position where there is no bit. A method has been used in which the comparison level of the comparison circuit 6 which obtains the peak signal (g) from the differential signal (f) obtained by differentiating (e) is set to a predetermined threshold value -1 instead of the zero level.

[Problem that the invention seeks to solve]

The conventional readout circuit described above uses a differentiation circuit to detect the peak point of the reproduced analog signal.
The /N ratio is lower than the S/N ratio of the reproduced analog signal.

In order to prevent false detection at the "0" data position for a differential signal whose S/N ratio has deteriorated more than the reproduced analog signal, it is necessary to set the value larger than the threshold value VrHk. (2) When rH is increased, the detection position of the peak signal deviates from the true peak point, and the amplitude and waveform variation of the reproduced analog signal becomes the detection position variation (bit shift) of "1" data.

Due to the problem of false detection of "1" data due to noise at the 90" data position and the problem of "1" data shift, conventional readout circuits have a small margin for setting the threshold value VTI (on the contrary). Due to the above-mentioned problem, conventional readout circuits have the disadvantage that the error rate during readout cannot be reduced.

[Means for solving problems]

The storage information readout circuit of the present invention is a readout circuit that obtains readout data that is a binary digital signal by detecting peak positions of n reproduction analog signals obtained from storage information detection means. A high-pass filter removes the read analog signal and detects the half-wave waveform of the polarity in the peak direction of the read analog signal.
A half-wave rectifier circuit that obtains a differential signal, a differentiation circuit that differentiates a detected signal and obtains a differential signal, a comparison circuit that compares the level of the differential signal with a predetermined threshold and obtains a peak signal based on the comparison result, It is characterized by:

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.
2 is a reading optical head, 2 is a high-pass filter, 3 is an amplifier circuit, 4 is a half-wave rectifier circuit, 5 is a differentiation circuit, and 6 is a comparison circuit.

FIG. 2 is an operation waveform diagram of the embodiment shown in FIG. 1, and (a) to
The waveforms in (d) show examples of operating waveforms of the signals (a) to (d) in FIG. 1.

The DC component of the reproduced analog signal regenerated by the readout light 1 is removed by a high-pass filter 2, and since this signal is weak, it is amplified by an amplifier circuit 3 and becomes a readout analog signal (a) 3. The read analog signal (a) is supplied to the half-wave rectifier circuit 4, where the read analog signal (a)
) is detected, and a detected signal (b) is obtained by detecting only the half-wave waveform on the positive side of the zero level corresponding to the polarity in the peak direction. Next, the detected signal (b) is time-differentiated by the differentiating circuit 5, and its output, the differential signal (C), has a waveform in which the peak point of the read analog signal (a) is converted to a zero-crossing point. That is, the peak point on the positive side of the read analog signal (a), which is information '1'', coincides with the peak point on the positive side of the detected signal (b), and the differential (from the positive level of No. i (C) to the negative level This corresponds to the position where the zero level is crossed.In the comparator circuit 6, one input is supplied with the differential signal (C), and the other input is supplied with a predetermined threshold value -VTR, so that the comparison result is the peak. The signal (d) becomes a logical signal of "1" when the differential signal (C) becomes less than -VTR.The change of the peak signal (d) from "O" to "91" is due to the change in the read analog signal (a). Corresponds to the peak point, and the rising edge of this signal is XX
This is read data indicating 1" information.

According to the above embodiment, the read analog signal (a) is
All the noise on the baseline corresponding to the 10" data has been removed, and even if the detection signal (b), which is the output of the half-wave rectifier circuit 4, is differentiated by the differentiator 5, it is already differentiating a signal with no baseline noise. There is no increase in the baseline noise to be differentiated because it is used as a target. Therefore, the threshold value V'l'' of the comparator circuit 6! (The setting of () does not require the purpose of removing baseline noise on the input signal as in the conventional circuit shown in Fig. 3, but is merely for the purpose of determining the comparison output when the differential signal (C) is at zero level. Therefore, it is only necessary to give a sufficiently small value compared to the conventional circuit.As a result, the problem of 11" data shift caused by the detection deviation from the true peak point, which was a problem in the conventional circuit, is also solved.

The embodiment shown in Figure 1 uses a high-pass filter 2 and an amplifier circuit 3, but since the high-pass filter 3 only has the function of removing direct current, the same purpose can be achieved even if an alternating current amplifier circuit is used in place of both. be done.

〔Effect of the invention〕

As explained above, the present invention provides a readout circuit that obtains readout data by detecting the peak position of a reproduced analog signal. By extracting this signal and subjecting it to peak detection using a differentiating circuit and a comparison circuit, noise removal on the baseline and accurate peak position detection can be achieved despite the simple circuit configuration, and the readout error rate can be reduced. effective.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one practical example of the present invention, FIG. 2 is an operation waveform diagram of the embodiment shown in FIG. 1, FIG. 3 is a block diagram showing the prior art, and FIG. FIG. 3 is a diagram showing the correspondence between operation waveforms, pits on the medium, and reproduced analog signals. 1°゛゛°°reading source head, 2...°...° high-pass filter, 3...... amplifier circuit, 4...-half wave rectifier circuit, 5...... differential circuit , 6...Comparison circuit, 7...--Pit. Agent Patent Attorney Oto Uchihara. X, 5 Hayabusa 4th Ward 82 Prisoners 83rd Ward Diagram 4

Claims (1)

[Claims] A storage device comprising storage information detection means for obtaining a reproduced analog signal having a peak waveform corresponding to stored information on a storage medium, and obtaining read data as a binary digital signal by detecting a peak position of the reproduced analog signal. In the information reading circuit, a high-pass filter removes a DC component of the reproduced analog signal to obtain a read analog signal; a half-wave rectifier circuit detects a half-wave waveform of peak direction polarity of the read analog signal to obtain a detected signal; It has a differentiating circuit that obtains a differential signal from a detected signal, and a comparing circuit that compares the level of the differential signal with a predetermined threshold value and obtains a peak signal based on the comparison result, and is configured to use the peak signal as the read data. A storage information reading circuit characterized by: