JPH0120483B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for detecting defects on the surface of a disk that records video information, etc., and more particularly, to a device for detecting defects caused by scratches, dust, etc. that occur on the surface of a disk after recording video information, etc. It is.

For disk-shaped disks used as video disks, etc., if there are scratches or dust on the disk surface before recording video information, accurate video information recording will not be possible, so the disk surface is inspected for defects. It is already known that the disk surface is irradiated with a constant amount of laser light and the reflected light amount is compared with a preset threshold value for measurement and inspection, and this is sufficient for inspection.

However, the reality is that disks that have been measured and inspected using such a method and on which video information is recorded are visually inspected for defects. This is because the information grooves recorded and formed on the disk scatter reflected light in the same way as defects, making it impossible to distinguish between the information grooves and disk defects, and therefore cannot be inspected using the above-mentioned optical device.

SUMMARY OF THE INVENTION An object of the present invention is to provide a micro-defect inspection device that can measure and inspect even micro-defects on the disk surface after information has been recorded.

The present invention allows either diffracted light or scattered light that reaches a condensing lens out of the light reflected from the disk surface to pass through a slit provided in the condensing path of the condensing lens, thereby changing the amount of light. By detecting this with a photodetector, it is possible to detect defects on the disk surface after information has been recorded.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is an overall view for explaining the principle of the present invention, and shows a laser light source 11, a first lens 13 that focuses laser light 12 generated from the source and irradiates it onto a disk 14, and a a second lens 17 that collects the reflected light 16 on the surface; and a lens 1
a slit 18 through which only regular diffracted light (described later) obtained through the slit 18 passes through the slit 18;
A photodetector 1 that detects the diffracted light focused through the
9. Here, the disk 14 is installed on a turntable (not shown), and the other devices are configured to be able to move and scan along the disk groove. Note that 15 is the irradiation point of the laser beam.

Figures 2 and 3 are explanatory diagrams of the diffraction phenomenon when a laser beam is irradiated on the disk surface with information grooves.If there are no scratches on the disk surface, the reflected light will be reflected as shown in the enlarged view in Figure 3. can get.

Moreover, FIGS. 4 and 5 are explanatory diagrams of changes in the amount of reflected light when there is a defect due to a scratch on the disk surface, and the same reference numerals as in FIG. 1 above indicate the same items. However, numeral 31 indicates a scratch caused on the disk surface, and numeral 32 indicates scattered light received by the scratch 31, which is indicated by a broken line.

Hereinafter, the case of defect detection will be described according to these figures.

First, the laser beam 12 emitted from the laser light source 11 is focused to an arbitrary size by the first lens 13 whose spot diameter can be freely changed by position setting, and then an irradiation point 15 is created on the surface of the disk 14. . The light reflected on the disk surface spreads as diffracted light 16 and scattered light 22 as shown in FIG. 1, and after reaching the second lens 17, only one of the diffracted lights 16 passes through the hole of the slit 18. The light is then focused on the photodetector 19.

Next, the diffracted light 1 generated by reflecting off the disk surface
6 will be explained with reference to FIGS. 2 and 3. In the figure, regular information grooves 20 are recorded on a disk 14 with dimensions slightly larger than the wavelength of the laser beam used. When this disk surface is irradiated with laser light 12, a diffraction phenomenon occurs at the edge portion 21 at the apex of the information groove 20.
The reflected lights interfere with each other and become a plurality of diffracted lights 16. Next, as shown in FIGS. 4 and 5, the scratch 31
When a certain disk surface is irradiated with laser light 12, a diffraction phenomenon occurs at the edge portion 21 of the information groove 20.
Since diffuse reflection occurs at the disk scratch 31, diffracted light 16 and scattered light 32 due to the scratch 31 are generated. In this case, since the diffracted light 16 is caused by light interference, the amount of the diffracted light 16 changes by the amount of light in the edge portion 21 occupied by the disk scratch 31. On the contrary, scattered light 32
is simply diffuse reflection and has no regularity like the diffracted light 16, so it is diffused in various directions. For these reasons, the disk scratch 31 is detected by detecting the change in the amount of diffracted light 16, but in this embodiment, the second lens 17 and the photodetector 19 are used.
A photodetector 19 detects a change in the amount of diffracted light 16 through a slit 18 provided between the slit 18 and confirms a scratch 31 on the disk surface. In addition,
Changes in the amount of diffracted light can be easily confirmed by displaying it on a screen or the like.

Furthermore, in the above-described embodiment, the slit 18 installed between the second lens 17 and the photodetector 19 is provided with a hole through which only the diffracted light of the reflected light received by the disk surface passes through. However, in addition to this, a hole is provided that allows only the scattered light 22 to pass through (a hole is formed opposite to the case of diffracted light), and the scattered light 22 is passed through.
Similar actions and effects can be obtained by detecting the change in the amount of light in step 2.

According to the above-mentioned embodiment, a laser beam is irradiated onto the disk surface after information has been recorded, and detection is performed through a slit that allows only the diffracted light reflected by the disk to pass, and scratches on the disk surface can be detected from the detection results. Since the device is designed to have a slit in the optical system for inspecting scratches on the disk before information is recorded, it can be used almost as is, and has a great economical effect. Additionally, by changing the size of the spot diameter of the laser beam irradiated onto the disk, the size of defects on the disk surface that can be detected can be changed. It is sufficient to reduce the diameter and re-inspect, and the time required to detect the defect can be shortened.

As another method, the same result can be expected by keeping the spot diameter of the laser beam constant and changing the rotation speed of the turntable.

As is clear from the above description, according to the present invention, only either the diffracted light or the scattered light passes between the lens that collects the reflected light from the disk and the detector that detects the reflected light. This method detects defects on the disk surface by providing a slit and detecting changes in the amount of light that passes through the slit, so it is possible to detect defects on the disk surface after information has been recorded, which was extremely difficult to detect. Defects can be detected extremely easily, and the optical system used for detecting defects before information recording can be used almost as is, resulting in great economical effects.

[Brief explanation of drawings]

The attached drawings are diagrams for explaining one embodiment of the present invention, in which Fig. 1 is a principle diagram of an apparatus for detecting defects on the surface of a disk having information recording grooves, and Fig. 2 is a diagram showing the principle of an apparatus for detecting defects on the surface of a disk having information recording grooves. A diagram explaining the diffraction phenomenon when irradiated, Figure 3 is an enlarged diagram, Figure 4 is a diagram explaining the change in the amount of reflected light when there is a scratch on the disk surface, and Figure 5 is a partially enlarged diagram. . 11... Laser light source, 12... Laser light,
13...first lens, 14...disc, 15...
...Irradiation point, 16...Diffracted light, 17...Second lens, 18...Slit, 19...Photodetector, 20
... Information groove, 21 ... Edge part, 22 ... Scattered light.

Claims (1)

[Claims] 1 a light source, a first lens for focusing the light emitted from the light source onto the disk surface, a second lens for focusing the light reflected by the information recording groove on the disk surface onto the photodetector; and a photodetector for detecting changes in the amount of light that has reached the second lens, the device inspects for defects on the disk based on the changes in the amount of light reflected on the disk surface, the device comprising: A slit is provided between the lens and the photodetector to allow only either the diffracted light or the scattered light to pass through, and the photodetector detects changes in the amount of light that has passed through the slit, thereby creating an information recording groove. 1. An apparatus for detecting defects on a disk surface, characterized in that the device is configured to detect defects on the surface of a disk.