JPH07270332A - Inspection device for memory medium - Google Patents

Abstract

PURPOSE:To detect a defect having an optical anisotropy in an optical disk. CONSTITUTION:A first polarizer 2 and a second polarizer 4 are disposed between a light source 1 and a photodetector 5 so that vibration directions of polarized lights thereof are perpendicular to each other. An optical disk 3 is disposed between both of the polarizers 2, 4. When the optical disk 3 does not have a defect of an optical anisotropy, the light does not reach the photodetector 5. When it has a defect, birefringence occurs in the position so that the vibration directions are varied, then a part of the light can reach the photodetector 5.

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 a storage medium such as an optical disc represented by a compact disc (CD) or a laser disc (LD).

[0002]

2. Description of the Related Art Conventionally, optical discs represented by compact discs and laser discs have been manufactured by molding plastic. In this case, a defect having optical anisotropy may occur in the optical disc in the manufacturing process, but the inspection of the manufactured storage medium such as the disc is mainly related to the physical shape, and The fact is that it has not reached the inspection of defects having optical anisotropy. That is, when a defect having optical anisotropy is generated on the optical disc, the defective portion is different from the non-defect portion only in the optical property and the other physical properties are exactly the same. It was difficult to detect a defect having optical anisotropy only by inspecting the physical characteristics of the.

[0003]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an inspection apparatus capable of detecting a defect having optical anisotropy in a storage medium such as an optical disk.

[0004]

Therefore, in the inspection apparatus for a storage medium according to the present invention, the first polarizer 2 and the second polarizer 4 are arranged between the light source 1 and the photodetector 5, and the first polarizer is provided. A storage medium 3, which is an inspection object, is arranged between the polarizer 2 and the second polarizer 4, and the first polarizer 2 and the second polarizer 4 are arranged.
Is arranged such that the vibration directions of the polarized light intersect, the light from the light source 1 is converted into linearly polarized light via the first polarizer 2, and the linearly polarized light is stored in the storage medium 3 and After sequentially passing through the second polarizer 4, the photodetector 5
It is characterized in that it has a structure for incident on.

[0005]

As a result of the above, the linearly polarized light that has passed through the defective portion having optical anisotropy on the storage medium 3 such as an optical disk is directed to the polarized light different from that when there is no defect.
As a result, the light passing through the second polarizer 4 changes depending on the presence / absence of a defect, which appears as a difference in light intensity in the photodetector 5.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the storage medium inspection apparatus of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a perspective view showing the structure of an embodiment of the storage medium inspection apparatus of the present invention, FIG. 2 is a sectional view of the above embodiment, and FIG. 3 is a case where the storage medium has no defects having optical anisotropy. Pattern diagram,
FIG. 4 is a schematic diagram showing the operation of this embodiment when there is a defect having optical anisotropy.

In FIGS. 1 and 2, as a structure of a storage medium inspection apparatus, a first polarizer 2 and a second polarizer 4 are arranged between a light source 1 and a photodetector 5, and a first polarized light is further provided. A storage medium as an inspection target, for example, an optical disk 3 is arranged between the child 2 and the second polarizer 4. Where light source 1
For example, a light bulb, a fluorescent lamp, or a laser beam is used, but it may be natural light. In addition, the first polarizer 2 and the second polarizer 4
For this, a polarizing prism or a polaroid that converts natural light or the like into linearly polarized light is used. The photodetector 5 includes a photodiode or C for converting the intensity of light into the intensity of an electric signal.
A CD or the like is used. Then, the first polarizer 2 and the second polarizer 4 are arranged such that the vibration directions of the polarized light are at right angles to each other.

Next, the operation of the above embodiment will be described with reference to FIGS. First, in the above structure, the light 7 from the light source 1 is linearly polarized by passing through the first polarizer 2, passes through the optical disc 3 as the transmitted light 8 of the first polarizer 2, and the transmitted light 9 of the optical disc 3 becomes After passing through the second polarizer 4, the light is incident on the photodetector 5 as transmitted light 10.

At this time, if the optical disk 3 does not have the defect portion 6 having optical anisotropy, the transmitted light 8 which is linearly polarized light in FIG. Since it becomes the transmitted light 9 of 3,
This transmitted light 9 remains the same linearly polarized light as the transmitted light 8 of the first polarizer 2. Therefore, the transmitted light 9 from the optical disk 3
Is blocked by the second polarizer 4 having a vibration direction different from the polarization direction of the first polarizer 2 by 90 °, and almost no transmitted light 10 from the second polarizer 4 is generated. Therefore, the photodetector 5 The intensity of light detected at is zero or very weak.

On the other hand, if the optical disk 3 has a defective portion 6 having optical anisotropy, the transmitted light 8 from the first polarizer 2 which is linearly polarized light in FIG. When passing through the defect portion 6 having optical anisotropy, due to the birefringence characteristic of the substance having optical anisotropy, the transmitted light 8 from the first polarizer 2 becomes a linearly polarized light having a different vibration direction. It is converted into the transmitted light 9 from the optical disc 3. Therefore, at least a part of the transmitted light 9 passes through the second polarizer 4 and enters the photodetector 5 as the transmitted light 10. Therefore, the intensity of the light detected by the detection detector 5 becomes stronger than that in the case where there is no defective portion 6, whereby the defective portion 6 having optical anisotropy can be detected.

In the above embodiment, the first polarizer 2 and the second polarizer 4 are arranged so that the vibration directions of the polarized lights thereof are at right angles to each other, but the invention is not limited to this. It can also be arranged at other angles.

[0012]

As described above, in the storage medium inspection apparatus of the present invention, it is possible to detect a defective portion having optical anisotropy on the storage medium, and the storage medium can be inspected more completely. .

[Brief description of drawings]

FIG. 1 is a perspective view showing the configuration of an embodiment of a storage medium inspection device of the present invention.

FIG. 2 is a cross-sectional view of the above embodiment.

FIG. 3 is a schematic diagram when the storage medium has no defects having optical anisotropy.

FIG. 4 is a schematic diagram showing the operation of this example when there is a defect having optical anisotropy.

[Explanation of symbols]

 1 Light Source 2 1st Polarizer 3 Storage Medium 4 2nd Polarizer 5 Photodetector

Claims (1)

[Claims] 1. A first polarizer (2) and a second polarizer (4) are arranged between a light source (1) and a photodetector (5), and the first polarizer (2) and the above A storage medium (3) as an inspection object is arranged between the second polarizer (4) and the first polarizer.
The polarizer (2) and the second polarizer (4) are arranged so that the vibration directions of the polarized light intersect, and the light from the light source (1) is supplied to the first polarizer (2). The linearly polarized light is converted to linearly polarized light through the storage medium (3) and the second polarizer (4) in this order, and then is incident on the photodetector (5). Characteristic storage medium inspection device.