JPH0618442A - Inspection device - Google Patents

Abstract

PURPOSE:To ensure a waveform signal from a sensor to match a reference level waveform in terms of time, and accurately detect the abnormality of an inspection object. CONSTITUTION:A delay circuit 11 is provided to delay a waveform signal for keeping a reference level waveform and a waveform signal from a sensor 8 at an identical phase. Pulses contained in a waveform signal from a CCD sensor 8 are restrained with a low pass filter 13a and the restrained signals are formed to have a reference level waveform relative to the waveform signal from the sensor 8 via a level setting section 15. Also, the reference level waveform is delayed, relative to the waveform signal from the CCD sensor 8 due to the low pass filter 13. Then, the waveform signal is delayed through the delay circuit 11, thereby maintaining the matching of the reference level waveform inputted from the level setting section 15 and the waveform signal from the CCD sensor 8 in terms of time, at the input side of a comparison means 41. As a result, the abnormality of an inspection object A can be accurately detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inspection device for optically and electrically detecting defects such as scratches, stains and foreign substances on an optical disk by using a CCD linear image sensor.

[0002]

2. Description of the Related Art Conventionally, there has been provided an apparatus for detecting foreign matters, pinholes and the like by using reflected light or transmitted light from an object to be inspected such as a glass plate and a compact disk using a CCD sensor. In this device, a threshold level waveform for the waveform signal from the CCD sensor is formed from the waveform signal. In other words, when the threshold for the waveform signal from the CCD sensor is set to an absolute constant value, the waveform signal of the CCD sensor itself fluctuates. Therefore, it is necessary to use a threshold value with the same fluctuation as the waveform signal.

Therefore, a reference level waveform (threshold level waveform) is added to the CC by adding a predetermined coefficient to the above waveform signal.
It is the threshold level for the waveform signal from the D sensor. Since the waveform signal from the CCD sensor becomes a signal including a sharp edge pulse when a flaw, a pinhole or the like is detected on the object to be inspected, it is necessary to blunt this pulse, so that a reference level waveform is formed. Before that, a low-pass filter is interposed to remove the high frequency component of the pulse.

[0004]

However, in such a conventional example, since the reference level waveform is formed by providing the low-pass filter, the presence of this low-pass filter causes the reference level waveform to be a waveform signal from the CCD sensor. There is a problem that the phases become out of phase, that is, the reference level waveform is delayed with respect to the waveform signal, and an abnormality such as a scratch or a pinhole on the inspection object cannot be accurately detected.

The present invention has been made in order to solve the above-mentioned conventional drawbacks, and an object thereof is to achieve time alignment between a waveform signal from a sensor and a reference level waveform to accurately detect an abnormality of an object to be inspected. It is to provide an inspection device capable of detecting the above.

[0006]

Therefore, in the inspection apparatus according to the first aspect, the sensor 8 for receiving the transmitted light or the reflected light from the inspection object A and the inspection object A included in the waveform signal from the sensor 8 are provided. And a low-pass filter 13 for suppressing a pulse component as an abnormality detection signal of
A level setting unit 15 that forms a reference level waveform for the waveform signal by multiplying the output signal from 3 by a certain coefficient;
A comparison unit 41 for comparing the reference level waveform from the level setting unit 15 with the waveform signal from the sensor 8 is provided between the comparison unit 41 and the sensor 8, and the comparison unit 41 causes the reference level waveform and the sensor 8 to be compared. The delay means 11 for delaying the waveform signal so as to match the phase with the waveform signal from No. 1 and the determination means 42 for determining the abnormality of the inspection object A by the signal from the comparison means 41 are provided.

The inspection apparatus according to claim 2 further comprises a delay circuit 4 for further delaying the reference level waveform with respect to the waveform signal.
It is characterized by having 3.

[0008]

In the inspection apparatus of the first aspect, as shown in FIG. 1, the light from the inspection object A is received by the sensor 8, and the waveform signal from the sensor 8 is sent to the delay means 11 and the low pass filter 13. The low-pass filter 13 suppresses the pulse contained in the waveform signal from the sensor 8, and the suppressed signal is formed by the level setting unit 15 into a reference level waveform for the waveform signal from the sensor 8. Since the reference level waveform is delayed by the low-pass filter 13 with respect to the waveform signal from the sensor 8, the waveform signal is delayed by the delay means 11 and input from the level setting section 15 at the input side of the comparison means 41. By comparing the waveform of the reference level and the waveform signal from the sensor 8 in time, the comparison unit 41 compares and detects whether or not there is an abnormality in the inspection object A.
The signal from the comparison means 41 is sent to the determination means 42,
The determination means 42 determines whether or not the inspection object A has an abnormality such as a scratch or a pinhole. In this way, by matching the waveform signal from the sensor 8 and the reference level waveform on the input side of the comparison means 41, it is possible to accurately detect the abnormality of the inspection object A.

In the inspection apparatus of the second aspect, the delay circuit 43 further delays the reference level waveform with respect to the waveform signal, so that the signal passing through the low-pass filter 13 includes a pulse having a large sharp edge. However, since that part lags behind the pulse part of the waveform signal to be compared, the abnormality of the inspection object A can be accurately detected.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, specific embodiments of the inspection apparatus of the present invention will be described in detail with reference to the drawings. First, the overall schematic configuration of the surface inspection apparatus of the present invention and the principle of signal processing will be described with reference to FIGS.

In FIG. 5, A is an inspection object, and this inspection object A is, for example, a compact disc. The inspection object A is a motor 1 including, for example, a step motor.
The motor 1 is rotationally controlled by the motor drive unit 2. In the present invention, light is applied to the surface of the object A to be inspected, and defects such as scratches, dirt, foreign matter, and pinholes on the disk surface are optically and electrically detected from the reflected light. The light from the lamp 3 is totally reflected by the reflection mirror 5 via the light projecting optical system 4 and projected onto the surface of the inspection object A. Then, the light reflected on the surface of the inspection object A is totally reflected by the reflection mirror 6, and the light receiving optical system 7
The light is received by the CCD sensor 8 via. Here, for example, a tungsten halogen lamp is used as the lamp 3 and a condenser lens system or a collimator lens system is used for the optical systems 4 and 7. And CCD
A high-speed drive type CCD linear image sensor is used as the sensor 8.

The output of the CCD sensor 8 is signal-amplified by the CCD driver 9 and input to the A / D converter 10 and the low-pass filter (LPF) 13 in the next stage. The output signal of the CCD driver 9 fluctuates up and down with respect to the reference level when a foreign substance or a pinhole is detected. The threshold level is used to detect the signal that fluctuates up and down, but since the detection signal itself fluctuates, if the threshold level is set to an absolute constant value, there is a risk of erroneous detection. The threshold level is also changed according to the change of the detection signal from the CCD sensor 8.

A low pass filter 13 is used to generate the varying threshold level. That is C
Since the output of the CD sensor 8 includes a pulse-like signal that projects vertically when a pinhole or a foreign substance is detected, a low-pass filter 13 is used to control the threshold level that smoothly changes in order to suppress this sharp fluctuation. Is generating.

By using the low-pass filter 13 to generate the threshold level, the threshold level will be delayed in time. Therefore C
The output signal from the CD sensor 8 cannot correspond to the threshold level compared with this output signal.

Therefore, a delay circuit (digital delay line) 11 is provided at the next stage of the A / D converter 10, and C
By eliminating the time delay between the output signal of the CD sensor 8 and the threshold level, the two are accurately corresponded. The digital signal output from the delay circuit 11 is converted into an analog signal by the D / A converter 12, and the output signal from the D / A converter 12 and the signal from the low pass filter 13 are sent to the signal processing circuit 14. Each of the above circuits 10
The control unit 31 is constituted by 14.

The signal processing circuit 14 composed of a microcomputer or the like has a structure as shown in FIG. 6, and comprises a level setting section 15 for setting the threshold level to a predetermined level and a level setting section 15. Comparing the set threshold level with the output signal from the CCD sensor 8, and the comparators 16 to 19 and the binary values corresponding to the scratches, pinholes, foreign matters, etc. of the inspection object A by obtaining the outputs of these comparators 16 to 19. Input / output for inputting / outputting data to / from the personal computer 23; It is composed of an output interface (I / O) 22 and the like.

The binarized pulse train data of the judgment result of the judgment unit 20 is stored in the memory 21, and the data is processed while being sequentially read by the personal computer 23, and the color CRT 24 almost simultaneously detects the defective portion of the defective portion. Mapping images are displayed so that the image of the defect can be known instantly. Further, the printer 26 can output the above determination result and the like. 25 is a keyboard. 5 corresponds to that of FIG.

Next, the principle of signal processing for generating a binarized pulse for detecting defects such as scratches, pinholes and foreign matters will be described with reference to FIGS. 5, 6 and 7. First, in the optical system C
When an image is formed on the CD sensor 8, the CCD driver 9
Video data is output by the internal processing. Based on this video data, signal processing is performed in real time to a level at which the controller 31 can perform computer processing. Binary pulse (scratch binary pulse) after capturing this video data
The principle up to the occurrence will be described below.

As a concrete example, a case where an audio compact disc is modeled as the inspection object A will be described. The SH pulse (source signal) in FIG.
It is a signal indicating the scan timing for one line of the CCD sensor 8 and is a waveform at the input end of the control unit 31.

SH pulse shown in FIG. 7B (after correction)
When performing various waveform processing in the process of extracting various binary pulses (scratch binary pulses), the waveform is inevitably delayed each time it is processed.
The SH pulse is obtained by delaying one equivalent by the shift register and correcting the relationship with the binarized pulse position.

FIG. 7C shows a raw video waveform output from the CCD driver 9, and the control unit 3 is the same as FIG. 7A.
It is a waveform at the input end of 1. FIG. 7D shows a sampling interval pulse, which is a pulse for determining the sampling interval when the raw video waveform of FIG. 7C is sampled in order to follow the background level of the video waveform.

FIG. 7 (e) shows a sampling video waveform, which is a basic waveform for generating various threshold waveforms. Then, in the section in which the sampling section pulse is not output as shown in FIG. 7D, as a hold level section, the level sampled at the sampling tail position of the previous scan is held up to the sampling head position of the next scan. .

The present inspection apparatus has three modes of inspection method according to the type of the object A to be inspected, such as scratches and pinholes, and generates a binarized pulse corresponding to the inspection result. The signal processing is performed in the above three modes (A mode, K mode, D mode). The three types of modes can be inspected separately for each mode and can be inspected at the same time for each mode.

The waveform shown in FIG. 7 (f) is an A / K mode waveform and is a waveform to be inspected which is input to the comparator when the A mode binarization pulse and the K mode binarization pulse are generated. Is. Then, as in the case of (b) above, a delay time T1 corresponding to the most delayed threshold waveform is delayed by the digital delay line (delay circuit 11), and the video waveform is corrected in relation to the binarized pulse position. is there.

FIG. 7 (g) shows a K-mode threshold waveform, which is a threshold level waveform input to the comparator 16 when the K-mode binarizing pulse is generated. Here, this K-mode threshold waveform is AK
1 for background level of mode video waveform
It is used in the range of 00% or more and less than 200%. This K
The mode threshold waveform is generated by the level setting unit 15 of the signal processing circuit 14. And comparator 1
At 6, the AK mode video waveform and the K mode threshold waveform are compared to generate the K mode binarization pulse described above.

FIG. 7 (h) shows an A-mode threshold waveform, which is a threshold level waveform input to the comparator 17 when the A-mode binarizing pulse is generated. Further, the A mode threshold level is used at 100% or less with respect to the background level of the A / K mode video waveform. The A-mode threshold waveform is generated by the level setting unit 15, and the comparator 17 compares the A / K-mode video waveform with the A-mode threshold waveform to generate the A-mode binarizing pulse. .

FIG. 7 (i) shows a K mode binarizing pulse, which is a pulse which becomes H level when the A / K video waveform level becomes higher than the K mode threshold level. This is detected in the portion of the surface of the inspection object A where the reflectance is high due to scratches or the like, and a K mode binarizing pulse is generated. It should be noted that, in the K mode, a portion having a high reflectance, such as a mirror surface portion on the inner and outer circumferences of the compact disc, is regarded as a scratch. ), But excluded from the scope of wound inspection.

FIG. 7 (j) shows an A-mode binarization pulse, which is an H-level pulse when the AK video waveform level becomes lower than the A-mode threshold level. When there is a pinhole in the inspection object A, light is not reflected, so that the AK video waveform level becomes low in this block 2, so that an A mode binarization pulse is generated.

Here, when the binarized pulse in the D mode is taken out, the threshold waveform is held, but in order to generate the hold pulse, there is provided a mode called D'mode which precedes the D mode. Therefore, FIG.
The D'mode video waveform shown in (k) is used only to generate a hold pulse.

The D'mode threshold waveform shown in FIG. 7A is used to generate a hold pulse, as in the case of (k) above.

The D'mode binarization pulse (hold pulse) shown in FIG. 7 (m) is a pulse which becomes H level when the D'mode video waveform level becomes lower than the D'mode threshold level. is there. In this case, the D mode threshold waveform is temporarily held. This D'mode threshold level is set by the level setting unit 15
Is generated in, is input to the comparator 18, and is compared,
A D'mode binarization pulse is generated when the D'mode threshold level is higher than the D'mode video waveform.

D of the D-mode video waveform shown in FIG.
The mode is a mode for detecting a wide scratch having a shallow drop in the video waveform, which is difficult to detect in the A mode, for example, a scratch commonly called silver. In order to extract only this shallow and wide flaw component, the waveform that has passed through the low-pass filter 32 (FIG. 6) is used as the video waveform for the A / K mode video waveform of FIG. 7 (f).

The D-mode video waveform passed through the low-pass filter 32 and the D-mode threshold waveform formed by the level setting section 15 are compared by the comparator 19, and D
When the mode threshold waveform is higher than the D mode video waveform, the D mode binarization pulse shown in FIG. 7 (p) is generated.

Further, FIG. 7 (o) shows a D-mode threshold waveform, and a threshold waveform whose phase is delayed from that of the video waveform is used in order to threshold the shallow and wide drop of the D-mode video waveform. The difference from other threshold waveforms is that once the drop of the video waveform becomes lower than the threshold level, the D'mode hold pulse temporarily stops the tracking operation of the video waveform at the threshold waveform level (holds). ), Maintain a horizontal level (Fig. 7
(See (n) and (o)). Then, when the drop of the video waveform ends and it becomes higher than the threshold level, the threshold level again follows the video waveform by the hold release pulse described below. The D-mode threshold waveform is used at 100% or less of the background level of the D-mode video waveform.

FIG. 7 (p) shows a D mode binarization pulse (hold release pulse), which is a pulse that becomes H level when the D mode video waveform level becomes lower than the D mode threshold level. Further, the falling edge of the pulse plays a role in releasing the hold of the threshold level.

The software compulsory mask shown in FIG. 7 will now be described. In the video output of the CCD sensor 8, there are always dummy pixels before and after the SH pulse, where the video waveform does not appear at all and where it does not appear reliable. Since the number of dummy pixels differs depending on the CCD format, the CCD format is automatically read by software, and the dummy pixel section corresponding to the format is forcibly masked. This mask area is common to the K mode, A mode, and D mode.

The user mask is the following mask. That is, the area outside the inspection target is automatically masked by inputting the inner diameter dimension and the outer diameter dimension, which are the inspection target range of the disk, with the keyboard of the personal computer, and this is called a user mask. Also, this mask area is common to the K mode, A mode, and D mode, as in the above.

In the block diagram shown in FIG. 5, the inspection of the inspection object A by light is shown as a so-called reflection type, but it may be configured as a transmission type. Further, although the incident angle to the inspection object A is inclined with respect to the vertical (for example, 10 ° with respect to the vertical), the incident angle may be vertical and the inspection may be performed by a reflection type or a transmission type.

Next, the gist of the present invention will be described in more detail. 1 shows the schematic system diagram of FIG. 5, in which the delay means 11 of FIG. 1 corresponds to the delay circuit 11 of FIG. 5, and the comparator 16 corresponds to the comparison means 41. A as above
By providing the digital delay circuit 11 between the / D converter 10 and the D / A converter 12, the output waveform of the CCD sensor 8 is not blunted (while a signal from a defect featuring a sharp edge is maintained. ) The signal is delayed, and the signal of the sharp edge is temporally killed through the low-pass filter 13, so that it is possible to achieve time matching with the delayed threshold waveform (reference level waveform).

FIG. 2A shows a waveform signal (video waveform) which is an output signal of the delay circuit 11, and FIG. 2B shows a threshold waveform (reference waveform) obtained by removing the sharp edge portion through the low pass filter 13 from the CCD sensor 8. Level waveform). If the delay circuit 11 is not provided,
The waveform signal shown in FIG. 2A is a signal earlier in time than the reference level waveform shown in FIG. However, in the present invention, since the delay circuit 11 is provided, the waveform signal of FIG. 2A and the reference level waveform of FIG. 2B have the same phase.

Here, by multiplying the waveform shown in FIG. 2B by a coefficient in the level setting section 15, the waveform shown in FIG.
The predetermined reference level waveform shown in is formed to form a threshold waveform for the waveform signal.

As shown in FIG. 2C, the waveform signal and the reference level waveform are compared, and a binarized pulse as shown in FIG. 2D is generated at a portion where the waveform signal is lower than the reference level waveform. However, defects of the inspection object A such as scratches and pinholes will be detected.

(Embodiment 2) FIGS. 3 and 5 show Embodiment 2, in which the portion of the waveform signal from the CCD sensor 8 having a large sharp edge is also shown in FIG.
As shown in (b), the influence remains and unevenness corresponding to the original sharp edge is formed.

In this case, as shown in FIG.
Even when the waveform signal from the D sensor 8 is compared with the reference level waveform, the level of the reference level waveform also drops at a portion where the sharp edge is large, like the waveform signal, and the defect cannot be accurately detected.

Therefore, as shown in FIG. 4, a delay circuit 43 is provided to delay the reference level waveform from the state shown in FIG. 3B with respect to time as shown in FIG. Therefore, as shown in FIGS. 3D and 3E, it is possible to accurately generate a binarized pulse even in a portion having a large sharp edge and to accurately detect a defect of the inspection object A. Is.

Although the delay circuit 43 is provided after the level setting unit 15 in FIG. 4, it may be provided before the level setting unit 15. The delay circuits 11 and 43 may have any circuit configuration as long as they can be temporally matched with the reference level waveform. Further, in the present invention, the A mode has been described for the sake of description, but it goes without saying that the same applies to the above K mode and D mode.

[0047]

According to the inspection apparatus of the first aspect, since the reference level waveform is delayed by the low-pass filter with respect to the waveform signal from the sensor, the waveform signal is delayed by the delay means, and the comparison means of the comparison means. By making a time-wise match between the reference level waveform input from the level setting unit and the waveform signal from the sensor on the input side, it is possible to accurately detect the abnormality of the inspection object.

Further, in the inspection apparatus according to the second aspect, the reference level waveform is further delayed with respect to the waveform signal by the delay circuit, so that the signal passed through the low pass filter includes a pulse having a large sharp edge. Since that portion lags behind the pulse portion of the waveform signal to be compared, the abnormality of the object to be inspected can be detected more accurately.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of an embodiment of the present invention.

FIG. 2 is an operation waveform diagram of the embodiment.

FIG. 3 is an operation waveform diagram of the second embodiment.

FIG. 4 is a schematic block diagram of a second embodiment.

FIG. 5 is a schematic system configuration diagram of the entire inspection apparatus of the embodiment.

FIG. 6 is a block diagram of a signal processing circuit according to an embodiment.

FIG. 7 is a timing chart for explaining the principle of signal processing for binarized pulse generation according to the embodiment.

[Explanation of symbols]

 8 CCD Sensor 11 Delay Circuit (Delaying Means) 13 Low Pass Filter 15 Level Setting Unit 41 Comparing Means 42 Judging Means

Claims (2)

[Claims] 1. A sensor (8) for receiving transmitted light or reflected light from an inspection object (A) and an abnormality detection signal of the inspection object (A) included in a waveform signal from the sensor (8). Low-pass filter (1
3), a level setting unit (15) that forms a reference level waveform for the waveform signal by multiplying the output signal from the low pass filter (13) by a certain coefficient, and a reference level waveform from the level setting unit (15) And a comparison means (41) for comparing the waveform signal from the sensor (8) and between the comparison means (41) and the sensor (8). The delay means (11) for delaying the waveform signal so as to match the phase with the waveform signal from (8), and the determination means (42) for determining abnormality of the inspection object (A) by the signal from the comparison means (41). An inspection device characterized by being provided with. 2. The inspection apparatus according to claim 1, further comprising a delay circuit (43) for further delaying the reference level waveform with respect to the waveform signal.