JPS59215039A - Device for detecting defect of picture information disc - Google Patents

Abstract

PURPOSE:To detect stably a defect signal existing on a disc face and a defect signal mixed in a picture signal by detecting an envelope from the picture signal including a pulselike defect signal and detecting only a pulse corresponding to the defect signal through circuits such as delay, addition and differentiation or the like. CONSTITUTION:A reproducing signal supplied to an input terminal 21 and including a synchronizing signal a1, a positive defect signal a2, a negative defect signal a3 and a positive defect signal a4 existing on the synchronizing signal is envelope-detected by an envelope detecting circuit 22, delayed by a delay circuit 23 only for a prescribed time tauD1 and outputted to a positive output terminal 33 as defect detected outputs h1, h2 by a positive defect detecting circuit 36 comprising an adder circuit 24 and a differentiating circuit 25 or the like. On the other hand, the reproducing signal supplied to the input terminal 21 is inputted also to an inverse circuit 34 and outputted to a negative defect output terminal 37 as a defect pulse h3 by a negative defect pulse detecting circuit 35.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an image information disc defect detection apparatus during a video disc manufacturing process.

[Technical background of the invention and its problems]

In recent years, image information disks have come to be used as video recording and reproducing systems. There are optical reading methods, needle reading methods, etc., but both of them have advantages such as the disks that serve as image sources can be mass-produced at low cost using a press, and high-speed image access is possible compared to conventional VTR devices. It is excellent. However, since information is recorded by adding uneven shapes to the disk surface or reflective surface, defects in the shape on the recording surface thicken (deteriorate) the image quality.Therefore, defects occurring on the recording surface can be detected. This is particularly important in the manufacturing process.

The conventional method for detecting defects in image information disks is to play back one track at a time in the same way as normal screen playback, and the playback signal is
Since the signal is M-modulated, a method is used that detects the envelope of the signal and detects every point in time when the envelope drops. However, this method takes a long time to inspect because it inspects one truck at a time.

Therefore, a method is used in which information on several tracks is extracted at once by, for example, shining a light beam on the disc, and all defects are inspected in a short time. However, in this case, because several tracks are detected at once, the detection signal is different from the FM modulated signal obtained when only one track is detected, and the synchronization signal and control signal for tracking are pulses that correspond to defects. It appears mixed with similar signals. For this reason, it was not possible to lower the defect detection level to the level of the synchronizing signal, and therefore it was not possible to detect defective signals at a level lower than the synchronizing signal level.

A conceivable method for alleviating this problem is to detect a defective signal at a level lower than the synchronizing signal level without performing detection in the synchronizing signal portion. However, in this case, it was impossible to detect a defective signal in the sync signal portion. Furthermore, since the frequency component of a defect signal is generally a little higher than that of a synchronization signal, a method of performing all defect detection by frequency discrimination has been considered. However, since the synchronization signal and control signal are in a frequency band very close to that of the defective signal, it has been difficult to detect only the defective signal by simply using a frequency discrimination method.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image information disc defect detection device that can stably detect defect signals on the image information disc surface and defect signals mixed in the image signals in a short time.

[Summary of the invention]

The present invention detects all image signals including pulse-like defect signals from a reflected beam obtained from a disk on which image information is recorded, inputs this image signal to a total envelope detection circuit, extracts the envelope signal, and delays the output of the entire image signal. This is added to the original envelope signal, differentially shaped, and a pulse train containing the defect signal is created and delayed. At the same time, a further delayed version of the above-mentioned delayed envelope signal is subtracted from the original envelope signal,
By fully opening and closing the switch leading to the defective output terminal in response to this output signal, one of the four extended pulse trains mentioned above is generated.
It detects only the pulses corresponding to defect number Iro.

[Effect of revelation]

According to the present invention, it is possible to detect defects on the recording surface of an image information disk in a short time and stably, and in particular, it is also possible to detect defects on the synchronization signal and control signal. The image information obtained can be used to inspect disks for defects with high efficiency.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described in detail using the drawings.

FIG. 1 is a diagram showing an optical system from which a reproduction signal is obtained from reflected light from an image information disk. The laser beam output from the laser oscillation device (11) is sent to the beam splitter (12).
A small light sporatra is connected to the image circular engraving 14) through the lens (13). At this time, the disk (14) is moved by the motor (
15). In order to perform the inspection in a short time, the light spot is sufficiently thick (focused) on the recording pits and tracks on the disk (14), and several tracks (for example, 5 tracks) are reproduced at once. (14) The reflected beam that is reflected by the surface and contains image signals and defect information is sent back to the lens (13) 'e beam splitter (12)
) and is received by a photodetector (16). Here, the optical signal becomes an electrical signal and is output to the output terminal (17).

Also, the focus adjuster (18) receives a signal from the photodetector (16) and operates the lens (3) so that the shape of the light spot on the board is always the optimum size.

FIG. 2 shows an embodiment of the defect detection circuit according to the present invention,
FIG. 3 is a diagram showing the trough waveform of FIG. 2. A reproduced signal from the optical detection device shown in FIG. 1 is supplied to the reproduced signal input terminal (21) in FIG. A diagram showing all the waveforms of this reproduced signal is shown in Fig. 3 (at, synchronization signal a1, positive direction defect signal at, negative direction defect signal a8 m).
It includes a positive direction defect signal a4 present on the synchronization signal. Note that since the video signal □ detects several tracks at once, it is averaged and does not appear as a large imaging width at the fourth detection point. The envelope of this reproduced signal is detected by the envelope detection circuit (22), and the entire waveform is shown in FIG. 3 (1), and in FIG. Frequency components close to the defect signal appearing in the defect signal a1 in the negative direction and the synchronization signal are removed.The output of this envelope detection circuit (22) is input to the delay circuit (23), and its output is delayed for a certain period of time τD1. This output waveform is shown in FIG. 3 (cl). At this time, the delay time τD is made shorter than the length of the synchronizing signal and longer than the length of the defective signal.

Here, the signal output from the delay circuit (23) is combined with the signal output from the envelope detection circuit (22) and the addition circuit (24).
) is added. FIG. 3 (dl) is a diagram showing the output waveform of this adder circuit (24).

Here, the defect signal is two pulses separated by a certain time τD, but a signal 2, such as a synchronization signal, having a length of τD1 or more is one pulse. The output of the adder circuit (24) is divided into one unit by a differentiating circuit (25), and further, only the rising pulse in the positive direction is shaped by a pulse shaping circuit (26).

This pulse total delay circuit (27)'! The waveform delayed by τD2 is shown in FIG. 3 (tel).

Here, both positive pulses are two pulses separated by a certain time τD1. The delay time τD2 is used to ensure that all pulses generated in the synchronizing signal section are masked by a switch opening/closing signal, which will be described later, and its length is approximately half the pulse width of the synchronizing signal. On the other hand, the delay circuit (2
The output of 3) is further input to the delay circuit (28) and τD
Delayed by 3. That is, the output delayed by .tau.D, +.tau.D3 is input to the summation circuit (29) together with the output of the envelope detection circuit (22).

This subtraction circuit (29) subtracts the delayed envelope signal shown in FIG. 3 (fl) from the envelope signal shown in FIG. 3 (bl), and the waveform shown in FIG. can get.

This delay time τD3 is for slightly delaying the falling part of the switch opening/closing signal, which will be described later, and for masking the latter pulse of the pair of pulses corresponding to the synchronizing signal part shown in FIG. 3(e). , and its length is approximately twice τDt. The output of the subtraction circuit (29) is input to a comparator (30). In this comparator (30), the comparison voltage input from the comparison voltage input terminal (31) (3111g
The output of the subtraction circuit (29) is compared with the output of the subtraction circuit (29), and only when the output of the subtraction circuit (29) is greater than the comparison voltage, the switch (32) k is opened (.This switch (32) ) is the opening/closing signal in Figure 3 (hl).The positive pulse output from the delay circuit (27) mentioned above is the switch (
32) is closed, the positive defect output terminal (3
3) is output. When the switch opening/closing signal shown in Fig. 3 is a long pulse like a synchronization signal, the delay time τD1
It has a length of +τD8. Also, as mentioned above, the pulse delay time τD! is smaller than τDa. Therefore, among the outputs of the pulse shaping circuit (26), a set of two pulse all switches (32
) is not allowed. Further, in the case of a pulse-like defect signal having a shorter width than the delay time τD, the switch opening/closing signal does not have the length of the delay time τD. For this purpose, the output signal of the pulse shaping circuit (26) shown in FIG.
o's out of fl.

f, is a switch (32) k does not pass, but fl,, f, I
is passed through the switch (32) and the positive output terminal (33) is the defect detection output shown in FIG. 3 (1), h.
is output to. At this time, even if a defect pulse is on the synchronization signal, all defects can be detected as a problem (ht).

On the other hand, the reproduced signal supplied to the input terminal (21) is also input to the inverting circuit (34), and the inverting circuit (34)
Negative defective pulse detection circuit (35) with reversed pulse polarity
Enter. This negative defective pulse detection circuit (35) is a circuit similar to the circuit (36) surrounded by the dotted line in FIG. In this way, the negative defect signal a shown in FIG.
, is outputted to the negative defect output terminal (37) as a defect pulse h3 shown in FIG. A defective output can be obtained at the output terminal (39).

FIG. 3 (k+ is a diagram showing the defective output of this defective output terminal (39).

A. As stated above, the present invention is characterized in that it focuses only on the rising portion of the waveform of the output signal, and does not depend on the shape of other portions of the waveform. In fact, the above is effective because it is easy to faithfully reproduce the rising part of a waveform in an envelope detection circuit, but the reproduced waveform of the small falling part tends to be rounded.

In addition, in the process of bias force processing, the difference-differentiation of the signal, the force, and the DC component (average value of the input signal) are removed, so stability can be maintained regardless of the input signal level.

In addition, according to the above embodiment, optical information can be obtained in several tracks at a time.
I showed you how to read everything, but even with a contact type needle that is large enough to span several tracks? It is also possible to conveniently obtain a reproduced signal. Also, without inverting the reproduced signal with an inverting circuit,
A circuit to detect the lower envelope? It is also possible to completely detect only the defect signals in the negative direction.

Furthermore, in steps 2 to 3, the output of the delay circuit and the output of the envelope detection circuit are completely added together, then differentiated and pulse-shaped to obtain a pulse train.The envelope output is differentiated and shaped to form a digital signal. It is also possible to obtain a pulse train by digitally delaying the pulses. Also, the output of the subtraction circuit is input to a comparator to operate the switch, but the switch open/close signal can also be generated by attenuating the envelope output relative to the delay output and inputting it as is to the comparator and comparing the signals. It is possible to obtain 01).

[Brief explanation of drawings]

FIG. 1 is a diagram showing an optical system up to obtaining the reproduction token, FIG. 2 is a diagram showing an embodiment of the present invention, and FIG. 3 is a diagram showing all the waveforms of each part in FIG. 2. 11... Laser oscillation device degree, 12... Beam splitter, 13... Lens, 14... Image information disk,
15...Nana-ta, 16...Yuan) disaster relief device, 17...
Output terminal, 18... Focus adjuster, 21... F'4 raw signal input terminal, 22... Envelope detection circuit, 23, 27
, 28... Delay circuit % 24... Addition circuit, 25...
... Differential circuit, 26... (Russ forming circuit, 29...
- Subtraction circuit, 30... Comparison circuit, 31... Comparison pressure input terminal, 32... Switch, 33... Positive direction defect output terminal, 34... Inverting circuit, 35... Negative direction Defect detection circuit, 36... Positive direction defect detection circuit, 37...
Negative direction defect output terminal, 38...OR circuit, 39...
Defective output terminal. Representative Patent Attorney Noriyuki Chika (and 1 other person) (12)

Claims (1)

[Claims] means for detecting an envelope of a reproduced signal including a pulse-like defect signal obtained from a recording medium on which all image information is recorded; and a first means for delaying the envelope signal obtained from the envelope detecting means.
a delay means, a means for adding the delayed signal obtained from the first delay means and the envelope signal, a means for differentiating the output obtained from the adding means, and an output obtained from the differentiating means. means for detecting positive pulses of
a second delay means for delaying the output obtained from the means for detecting the positive pulse; a third delay means for further delaying the n delayed signal obtained from the first delay means; means for subtracting the delayed signal obtained from the four extension means from the envelope signal; means for comparing the output obtained from the subtracting means with a constant voltage; 2. An image information disc defect detection apparatus characterized by comprising means for passing all of the pulses obtained from the delay means of item 2.