JPH01184667A - Waveform shaping circuit - Google Patents

Abstract

PURPOSE:To speed up follow-up of a peak detecting means and to accurately restore a digital signal by switching the offset voltage of the peak detecting means to the voltage change of the digital signal to input to a waveform shaping circuit inside in advance. CONSTITUTION:An offset switching signal (f) a RF detecting circuit is changed from a high level to a low level by moving through a recording starting position to a recording track, a transistor 31 is turned off, and the offset voltage of a peak detecting circuit 1 is changed over. Consequently, even when the voltage of an address signal (d) changes remarkably, the peak detecting circuit 1 follows-up the peak of the address signal (d) quickly. Consequently, in a comparator 4, the address signal (d) is compared with a threshold voltage to follow-up the address signal (d), and a digital signal (e) waveform shaped can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a waveform shaping circuit, and particularly to a waveform shaping circuit suitable for use when reproduction signal voltages differ significantly, such as address signals of an optical recording/reproduction device. It is related to.

[Conventional technology]

When reproducing a digital signal optically or magnetically recorded on a recording medium, conventionally the signal reading unit amplifies the detected reproduced signal and after death, performs waveform shaping by comparing it with a predetermined threshold voltage. , I was getting a playback digital signal. For this reason, there is a problem in that due to the voltage drop of the reproduced signal, data may be lost due to waveform shaping without exceeding a predetermined threshold voltage.

Therefore, as described in Japanese Unexamined Patent Publication No. 159981/1981, a signal reading section generates a round threshold voltage by following the peak voltage of the detected reproduced signal and compares it with the reproduced signal. proposed a waveform shaping circuit for obtaining a reproduced digital signal.

[Problem to be solved by the invention]

However, the waveform shaping circuit is basically a circuit proposed for voltage fluctuations of a reproduced signal reproduced at the same voltage. Consideration should be given to the case where the voltage of the reproduced signal detected by the information reading unit is significantly different between the unrecorded track and the recorded track, such as an address signal recorded in advance on a spiral guide track. It wasn't. That is, when moving from an unrecorded track to a recorded track or from a recorded track to an unrecorded track,
Since the voltage of the reproduced signal changes significantly, the means for detecting the peak voltage of the reproduced signal cannot follow the changes, and as a result, the deity of the digital signal after waveform shaping is different from the deity of the recorded digital signal. However, problems may occur in subsequent signal processing.

SUMMARY OF THE INVENTION An object of the present invention is to provide a waveform shaping circuit that can accurately restore a recorded digital signal even when the reproduced signal voltage is fundamentally different, such as a regular address signal. be.

[Means to solve the problem]

In order to achieve the above object, in the present invention, a digital signal is recorded in a part of a first area where a certain signal is recorded and a part of a second area where the signal is not recorded. inputting the digital signal obtained by separating from the reproduced signal out of the reproduced signal obtained by reproducing from the recorded recording medium, and outputting a voltage that is higher than the offset voltage and follows the peak voltage of the digital signal. a threshold voltage generator that generates and outputs a threshold voltage from the peak voltage output by the peak detector; A waveform shaping circuit comprises a comparing means for comparing and outputting a companion pulse signal according to the magnitude relationship thereof, and obtains the pulse signal as the waveform-shaped digital signal. A switching means is provided for switching, and the switching means causes the reproduction signal to change at least in the peak detecting means when the reproduction signal is being reproduced from the first region and when the reproduction signal is being reproduced from the second region. 9. To switch the value of offset voltage.

[Effect]

The voltage of the digital signal obtained separately from the reproduced signal is significantly different when the reproduced signal is reproduced from the first area and when it is reproduced from the second area.

Therefore, the switching means changes the offset voltage value of the peak detecting means so that the reproduction signal
By switching between when reproducing from the region and when reproducing from the second region, the voltage followed by the peak detecting means can be set in advance to a minimum value s fj kC.

It is possible to speed up tracking when a signal is input from a no-signal state.

As a result, the comparison means Wb can quickly follow the threshold voltage to be compared with the digital signal and perform waveform shaping, and the digital signal recorded on the recording medium can be accurately restored. @Thereby, malfunctions can be eliminated in signal processing after waveform shaping.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings, taking as an example a case in which a waveform shaping circuit is employed in an address signal demodulation circuit of an optical recording/reproducing device.

FIG. 1 is a block diagram showing a waveform shaping circuit as an embodiment of the present invention.

Further, FIG. 2 is a diagram showing an example of an optical recording/reproducing apparatus in which the waveform shaping circuit of FIG. 1 is used.

In Fig. 2, 6 is a disk, 1o is a photosensor for monthly detection of recording position alignment, 11 is a detection circuit, 12 is a disk motor, and 13 is a disk motor so that 12601 revolutions correspond to one frame of the video signal. 12 is a disk motor drive circuit that controls 12, 14 is an optical head,
15 is a slider drive circuit for moving the optical head 14 in the disk radial direction; 16 is a laser drive circuit built into the optical head 14; 17 is a t-V conversion processing circuit;
18 is a preamplifier, 19 is a focus/tracking control circuit, 20 is a recording/playback signal processing circuit, and 21 is a playback R.
From K, by frequency detection or envelope detection of the F signal,
22 is an address demodulation circuit having a waveform shaping circuit according to the present invention; 25 is a recording control circuit; and 24 is a micro combinator or the like. 6 with the configured system controller.

First, one disk 6 will be explained.

FIG. 3 is a plan view schematically showing a specific example of the disk in FIG. 2. FIG.

As shown in FIG. 3, the disk 6, which is a disc-shaped or cylindrical recording medium, has guide tracks 7 formed in a spiral or concentric shape during manufacture (FIG. 3 shows a spiral guide track).

), an address signal unique to each guide truck is digitally recorded in the address area 8 as a concave-convex phase structure. Also, marks 9 are formed for use in recording start position alignment for each guide track.

Next, the operation shown in FIG. 2 will be explained.

The signal α to be recorded on the disk 6 is processed by the signal processing circuit 20 as F.
The signal is M-modulated and input into the laser drive circuit 16 as an RF multiplied signal. The laser drive circuit 16 modulates the intensity of the output light of the laser mounted on the optical head 14 according to the input RF signal and irradiates the disk 6 with the intensity modulated output light of the laser mounted on the optical head 14 to record information as a change in the reflectance of the laser beam from the first diagnosis disk 6. Let's do it.

Further, during reproduction, the laser drive circuit 16 irradiates the disk 6 with a low-output light beam of -constant intensity, and detects the recorded information via the t-V conversion processing circuit 17,
The reproduced RF signal 6 amplified by the preamplifier 18 is FM demodulated by the signal processing circuit 20, and a reproduced signal C is output.

The address signal recorded on disk 6 is 1 of disk 6.
Once per rotation, the signal is reproduced superimposed on the reproduced R and F signals 4, and demodulated by the address demodulation circuit 22.

FIG. 4 shows a block diagram of the address demodulation circuit 22.

As shown in FIG. 4, the reproduced RF signal 6 is passed through an equalizer 25 and a low pass filter (L, P, F)
6 and then amplified by an amplifier 27 to obtain the superimposed address signal d. The waveform shaping circuit 2B shapes the address signal d into a digital signal 1, which is then stored in the shift register 30 as address data by the digital signal processing circuit 29.

By the way, in the case of the optical recording/reproducing apparatus shown in FIG. 2, since information is also recorded on the address area 8 as a change in the reflectance of the disk 60 as described above, as shown in FIG. The voltage of the address signal d input to the recording track is significantly higher than that of the unrecorded track.

Therefore, the waveform shaping circuit shown in FIG. 1 is used as the waveform shaping circuit 28 for waveform shaping the address signal d to obtain a digital signal -.

In FIG. 1, 1 is a peak detection circuit that inputs the address signal d and outputs a voltage that follows a peak voltage higher than the offset voltage, and 2 is the FLF detection circuit 21 shown in FIG.
An offset voltage switching circuit 3 switches the offset voltage of the peak detection circuit 1 according to an offset switching signal f from the peak detection circuit 1; In the threshold generation circuit, 5 is a pull-up resistor.

FIG. 6 shows a specific example of this circuit. Fig. 7 shows the signal waveforms of each part.

In the unrecorded track, OR-1 from the RF detection circuit 21
The voltage switching signal M becomes high level, turns on the transistor 31 of the offset voltage switching circuit 2, and changes the offset voltage to the resistor 52. Resistance 33. Resistance 54. transistor 31
The voltage is determined by . (9) On the recording track, the offset switching signal f from the RF detection circuit 21 becomes low level, turns off the transistor 31, and transfers the offset voltage to the resistor 32. Switch to the voltage determined by the resistor 34.

On the other hand, the peak detection circuit 1 detects the voltage that follows the peak voltage of the address signal d, which is higher than the offset voltage determined as above, as the peak detection voltage! If there is no peak voltage higher than the offset voltage, the offset voltage is output as the peak detection voltage! Output as .

For example, when moving from an unrecorded track to a recorded track by normal feed, as shown in FIG.
When the offset switching signal f from the detection circuit 21 changes from high level to low level, the transistor 31 is turned off and the offset voltage of the peak detection circuit 1 is switched. Therefore, even if the voltage of the address signal d changes significantly, the peak detection circuit 1 quickly follows the peak of the address signal d. Therefore, in the comparator 4, the address signal d is compared with the threshold voltage input that follows the address signal d, and a waveform-shaped digital signal can be obtained.

Similarly, when moving from a recorded track to an unrecorded track, the 1 offset switching signal f changes from low level to high level, the transistor 31 turns on, the offset voltage of the peak detection circuit 1 is switched, and the comparator 4 By comparing the address signal d with a threshold voltage that follows the address signal dK, a waveform-shaped digital signal can be obtained.

According to this embodiment, the address signal d, which has a significantly different voltage reproduced from the disk 6 between a recorded track and an unrecorded track, is compared using a threshold voltage that always follows the peak of the address signal d. As a result, a waveform-shaped digital signal can be obtained, and the digital signal recorded on the disk 6 can be accurately restored.In addition, in this embodiment, a transistor is used in the offset voltage switching circuit 2. However, it goes without saying that it may be constructed using analog switches, D/A converters, and the like.

(9) In this embodiment, the offset voltage switching is performed in two stages: recorded track and unrecorded track, but it is of course possible to switch the offset voltage in three or more stages.

〔Effect of the invention〕

According to the present invention, the offset voltage of the peak detection means is switched in advance with respect to the voltage change of the reproduced digital signal inputted into the waveform shaping circuit, thereby detecting the peak in response to the voltage change of the digital signal. Since the tracking means can be fast tracked, even if the voltages of the digital signals are significantly different, the threshold voltage can be generated from the peak voltage output from the peak detection means. It is possible to perform single waveform shaping by comparing with a threshold value that follows the peak voltage of , and it is possible to accurately restore the digital signal recorded on the recording medium.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a waveform shaping circuit as an embodiment of the present invention, FIG. 2 is a block diagram showing an example of an optical recording/reproducing device in which the waveform shaping circuit of FIG. 1 is used, and FIG. FIG. 2 is a plan view schematically showing a specific example of the disk, FIG. 4 is a block diagram showing the address demodulation circuit of FIG. 2, and FIG. Figure 6 is a waveform diagram showing the difference between
FIG. 7 is a circuit diagram showing a specific example of the waveform shaping circuit shown in the figure, and FIG. 7 is a waveform diagram showing signal waveforms at various parts in FIG. Explanation of symbols 1... Peak detection circuit -% 2... Offset voltage switching circuit, 3... Threshold generation circuit, 4... Comparator, 6... Disk, 8... Address area, 1
4...Optical head, 16...Laser drive circuit, 17
・・Tsukasa-■ Conversion circuit, 18... Preamplifier, 21...
・RF detection circuit, 22...address demodulation circuit, 25.
・Equalizer, 26...L, P, F127
...Amplifier, 28...Waveform shaping circuit, 31...Transistor, 32-34...Resistor.

Claims (1)

[Claims] 1. A recording medium in which a digital signal is recorded in a part of a first area where a certain signal is recorded and a part of a second area where the signal is not recorded. peak detection means for inputting the digital signal obtained by separating the reproduced signal from the reproduced signal obtained by reproducing the signal, and outputting a voltage that is higher than an offset voltage and follows a peak voltage of the digital signal; , threshold generation means for generating and outputting a threshold voltage from the peak voltage output by the peak detection means; and comparing the voltage of the separated digital signal with the threshold voltage. a comparison means for outputting a pulse signal according to a magnitude relationship, and a waveform shaping circuit for obtaining the pulse signal as the waveform-shaped digital signal, further comprising a switching means for switching an offset voltage in the peak detection means; The switching means switches at least the value of the offset voltage in the peak detection means between when the reproduction signal is being reproduced from the first region and when the reproduction signal is being reproduced from the second region. A waveform shaping circuit characterized by: