JPS6353453A - Defect inspecting device for disc - Google Patents

Abstract

PURPOSE:To optimize quality control based on a reference corresponding to a defect condition, by projecting light from the back of a disc while receives for reflected lights and transmission lights are provided to enable highly accurate inspection without being adversely affected by interference. CONSTITUTION:A disc D is irradiated with a laser light L at an angle theta and the reflected light L3 and the transmission light L1 are incident into light receivers 33 and 34 respectively. As defects B1-B3 reach an irradiating position, the quantity of the light L changes, the waveform of an output signal (a) of a differentiation amplifier 35' varies accordingly and is sliced with a comparator 38 to be sent to an exclusive OR element 41 as signal (b). As a defect B3 on the back reaches the irradiating position, the quantity of the light L3 changes and an output signal (c) of a differentiation amplifier 35 varies in response the to defect B to be sent to the element 41 as signal (d) through a comparator 37. The defect B1 on a surface D1 and the defect B2 or B3 inside D2 are detected depending on a defect signal (e) from the element 41.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a defect inspection device for inspecting defects such as defects and scratches on optical discs and the like.

(Prior Art) Conventionally, as shown in FIGS. 5 and 6, a device for inspecting defects in a sheet-like object is composed of a light emitter, a light receiver, and a control section. In the figure, 1 is a light emitter. 2 is a laser, 3 is a vibrating mirror, 4 is a light receiver, 5 is a diffuser plate 6 is a photomultiplier, 7 is a preamplifier, 8 is a summing amplifier, 9 is a driver, 1
0 is a high voltage power supply, 20 is a control unit, and 11 is SPAIN
Adjustment section, 12 is a slice level setting section, 13 is a comparator, 14 is an edge control section, 15 is ~1PU, 16 is a printer, 17 is a defect number setting section, 18 is a display, 19 is an alarm, 21 is a rotary encoder It is.

This device is used as a light source for the projector port, and it is a single-wavelength light that produces a light beam with a small divergence angle (in a straight line in one direction. A photomultiplier tube is used as the light and the photoreceiver 4, which has a good S/N ratio, a large output, is suitable for weak light detection, and has a fast response speed.

This equipment uses a flying spot method to thoroughly inspect the surface of the sheet.

As shown in the figure, this method uses a vibrating mirror 3 or a rotating mirror to scan the laser beam L at a frequency corresponding to the speed at which the object to be inspected Δ flows, thereby eliminating detection errors.

Now, considering the state in which the reflected light from the object to be inspected is entering the light receiver 4 in Fig. 5, if there is a scattering defect (foreign object, (i), If there is a defect (such as a sunspot), a slight change will occur in the incident light.The change is converted into an electrical signal by the photomultiplier 6, which is then differentiated and amplified by the differential amplifier 11 through the addition amplifier 8 and driver 9. becomes a video signal, and when the slice level exceeds the slice level preset in the slice level setting unit]2, the detection signal is set to 1q.

Then, based on the signal, the number of defects can be counted, outputted by relay contact when detected, and if necessary, the detected position and the number of defects can be printed on the printer 6, and the product can be printed. It is now possible to easily obtain information on the shortcomings of In addition, depending on the object to be inspected and the defect to be detected, the most suitable 99 constant must be selected, but the method shown in the table in Figure 7 should be selected in advance, and the position of the emitter and receiver and the angle between It is now possible to get to the best point with practical savings.

(Problem to be Solved by the Invention) However, when inspecting an object to be inspected with an uneven surface, such as an optical disk, with the conventional 83iU as described above, conventionally, the reflected light from the object to be inspected (σ8 Therefore, there is a problem in that the unevenness of the group etc. causes interference between the laser beams and reduces the S/\ ratio (see Figure 8), making it impossible to perform accurate inspection. By using the transmitted laser beam of the inspection object, it is possible to prevent the adverse effects of interference, as shown in FIG. 9.

However, when using transmitted light, the surface of the disk,
Defects on the back side and inside g3 (Fig. 3 B 7゜82, B
3) is uniformly applied to HHL, which poses the following problems. That is, in the case of a disk, defects 81. on its surface and inside. For B2, for example, it is necessary to detect even a small defect of the order of 0 μ, but for defect B3 on the back side, it is sufficient to detect a defect of the order of 100 μ, for example, but if we perform uniform detection. , on the back side, there are defects of large size that do not need to be detected (e.g.
Even if there is a defect (on the order of 0μ), this is detected, and there is a problem in that it is considered to be a good product even if it is originally a good product.

The purpose of the present invention is to solve the following two problems, and to avoid the adverse effects of laser beam interference even when inspecting objects with uneven surfaces, and to avoid the problem of preventing the disk surface from being adversely affected by laser beam interference. The purpose of the present invention is to provide an inspection device that can change the inspection method (1) for detecting defects on the inside (or on the inside) and defects on the back side.

[Means for Solving the Problem] In order to achieve the above object, the present invention provides a disc with the following features:
a light emitter that emits light from the rear opening] 11, a transmitted light receiver that receives the transmitted light of the disc, a reflected light receiver that receives the reflected light of the disc, and these transmitted light receivers. and a defect signal generation section that generates a defect signal based on changes in the amount of light received by the reflected light receiver.

(Function) Since the device of the present invention has the above configuration, it functions as follows.

In other words, the light emitted from the projector to the disk is
Part of it is reflected by the back surface of the disc, and the other part passes through the disc and is transmitted to the front side.

Since the light receiver is provided with one for reflected light and one for transmitted light, the reflected light is received by the light receiver for reflected light,
The transmitted light is received by a light receiver for transmitted light. At this time, since the light is projected from the front side of the disk which has no irregularities, no interference occurs in the reflected light and a high S/N ratio is maintained. In addition, since there is a receiver for reflected light and a receiver for transmitted light, defects on the disk surface or inside can be detected by changes in the amount of transmitted light, and defects on the back surface of the disk can be detected by changing the amount of foul light. Because it can be detected by change, defects on the front or inside and defects on the back can be detected by 1i N,%
It can be detected by changing the

'(Example) The illustrated embodiment will be described below.

In FIG. 1, 29 is a light projector, and 30 is a laser similar to the conventional one, which emits laser light from the back side D3 of the disk D, which is the object to be inspected, through a konometer 31 and a turbulence mirror 32. The projected laser beam (- indicates that part of it is on the back side of the disc D3.
The reflected light becomes 3, and the other part is the disk D.
It passes through the inside and is transmitted to the surface D1 side to become transmitted light L1.

33 is a reflected light receiver that receives the reflected light L3;
4 is a transmitted light receiver that receives the transmitted light L1.

These light receivers 33 and 34 are all temporary diffuser light receivers, and their light receiving windows are disposed perpendicularly to the disk flow direction C, as shown in FIG. These, receiver 3
3.34 are the received reflected light L3 and A passing light L1, respectively.
The change in the amount of light is expressed as an electric signal f3. f1 and outputs it to the defect signal generation section 36 through differential amplifiers 35, 35-. Then, the defect signal generation section 36
generates a defect signal e based on a change in the amount of light received by the transmitted light receiver 34 and the reflected light receiver 33 (that is, a change in the electrical signal F3.fl). In this embodiment, the defect signal generation unit 36 includes a comparator 37 that inputs the output from the reflected light receiver 33, and a transmitted light receiver 34.
a comparator 38 that inputs the output from the comparator 38, a slice level setting section 39.40 that can arbitrarily set the slice level of these comparators 37 and 38, and a comparator 38 that receives the output from the comparator 3;
7 and 38.

Now, as shown in FIG. 3, the operation of the present apparatus will be described in the case where there are defects B1, B2 and B3 on the front surface Di, inside D2 and back surface D3 of the disk D, respectively. First, as shown in FIG. 1, disk D is moving in the direction of arrow C.
On the other hand, the laser beam is vertical and θ (for example, 10°
), and the reflected light L3 and transmitted light L1 enter respective light receivers 33 and 34. Therefore, as disk D moves, defect B1. .

When B2.83 sequentially reaches the laser beam irradiation point, the amount of transmitted light L1 changes, and therefore the differential amplifier 3
The waveform of the output signal a of 5' also corresponds to the defects B1, B2, B
3, it changes as shown in FIG. 4(a). Then, this signal a is sliced by a comparator 38 based on a preset slice level and outputted to the exclusive OR element 41 as a signal b (see FIG. 4(b)). On the other hand, when the defect B3 on the back surface reaches the laser beam irradiation point, the extinction of the reflected light L3 also changes, and the differential amplifier 35
The waveform of the output signal C in FIG. 4 (C) also corresponds to the defect B3.
This signal C is sliced by a comparator 37 based on a preset slice level and outputted to the exclusive OR element 41 as a signal d (see FIG. 4(d)). and exclusive logic m element 41
calculates the exclusive OR of the signals S and d, and calculates the
) outputs a defect signal e as shown in FIG. As can be seen from this signal e, only the defect B1 on the disk surface D1 and the defect B2 on the inside D2 were detected. However, this is a case where the defect B3 on the back side D3 does not reach the size that should be detected, and when the defect B3 is of a size that should be detected, the slice level setting section 39 and 40 are adjusted and the comparator 3
By setting the slice level of 8 and the slice level of the comparator 37 to predetermined large serrations, the corresponding waveform d' of defect B3 in the signal gd and the corresponding waveform d' of the defect B'3 in the signal gd are set as conditions. It is now possible to set the defect B3.

As described above, this embodiment provides the following effects. ′? (1) A portion of the laser beam projected from the projector 29 onto the disk D is reflected by the back surface D3 of the disk,
The other portion passes through the disk D2 and is transmitted to the surface D1 side. Since a light receiver 33 for the reflected light L3 and a light receiver 34 for the transmitted light L1 are provided, the reflected light L3 is received by the light receiver 33, and the transmitted light L1 is received by the light receiver 34. At this time, since the light is projected from the back side ff', ID3 of the disc, which has no irregularities, no interference occurs with the reflected light, and a high S/N ratio can be obtained.

(n) Since a light receiver 33 for reflected light and a light receiver 34 for transmitted light are provided, defects B1 or B2 on the disk surface D1 or inside D2 can be detected by changes in the amount of transmitted light, and defects B1 or B2 on the disk back surface D3 can be detected. Since a certain defect B3 can be detected by a change in the amount of reflected light, a defect B on the surface or inside D2, or a defect B3 on B2 and the back surface D3 can be detected by changing the detection criteria.

(III) Since the light receiver 34 for transmitted light and the light receiver 33 for reflected light are installed at the same time and the signal sword is illuminated at the same time, the inspection time is shortened compared to inspecting the front and back sides separately. be able to. Furthermore, if the front and back sides are inspected separately, the position of the defect will not be known if it is an optical disc, but since the front and back sides are inspected at the same time, positioning is not a hassle.

(IV) By taking the exclusive logic of transmission and reflection ■1, defects Bz on the disk surface and inside.

It is possible to detect only B2.

(V) Slice level 3 of front side comparator 37
By changing 9, the size of the back surface defect B2 to be detected can be arbitrarily set.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and can be modified as appropriate within the scope of the gist.

For example, the light projection is not limited to a laser; any focused light may be used, and any light that can be used with an optical sensor may be used.

Further, the setting method for defect detection is not limited to that of the above embodiment, but is effective for any en-setting method (see FIG. 7).

[Effects of the Invention] As described above, according to the present invention, since light is emitted from the back side of the disk, accurate inspection can be performed without being adversely affected by light interference, and it is possible to Since a light receiver and a light receiver for transmission are installed, the inspection standards are different for defects that occur on the surface or inside and defects that occur on the back surface.
Appropriate quality control can be performed.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing an example of the device of the present invention, Figure 2 is a diagram showing a light receiving window, Figure 3 is a diagram showing defects, and Figure 4 (a).
The waveform diagrams from (e) to (e) are waveform diagrams for explaining the operation, and FIG. 5 is the conventional example 1! ! ! 6 is a block diagram of the same as above, FIG. 7 is a surface showing an example of use of the same, and FIGS. 8 and 9 are diagrams of the same as above. 2... Emitter, 33... Receiver for reflected light, 34...
...Receiver for transmitted light, 36...Defective beam generation section, D.
··disk.

Claims (1)

[Claims] a light projector that projects light onto the disk from the back side thereof; a transmitted light receiver that receives the transmitted light of the disk;
It is characterized by comprising a reflected light receiver that receives reflected light from the disk, and a defect signal generation unit that generates a defect signal based on changes in the amount of light received by the transmitted light receiver and the reflected light receiver. Defect inspection equipment for disks.