JP3511745B2 - Method and apparatus for detecting substrate crack in disk-shaped information recording medium - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a detection method and a substrate crack detection device for detecting a substrate crack that occurs in a disc-shaped information recording medium in which an information recording section is provided on a transparent substrate.

[0002]

2. Description of the Related Art Disc-shaped information recording media such as optical discs and magneto-optical discs are subjected to the following inspections at the manufacturing stage. In order to guarantee the durability of the disc, it is inspected whether the protective film is normally applied to the molded or formed disc. Alternatively, it is necessary to inspect whether the substrate itself has a defect such as a scratch or a crack. In order to ensure that the operation of recording information on the information recording section of the disc and reproducing the information recorded in the information recording section can be performed smoothly, a magnetic film is normally formed on the disc. In addition, it is necessary to inspect whether there are scratches, foreign matters, or defects such as pinholes during film formation.

When inspecting for defects as described above, laser light is irradiated from the reading surface of the disk (the surface opposite to the surface having the magnetic film), and the disk is driven to rotate. Therefore, a method of scanning the entire surface of the disk with laser light is generally known. In such a system of scanning with laser light, when the disk is irradiated with the laser light, reflected light (transmitted light in the case of a pinhole) from the disk is received by, for example, a photodetector. For the electrical signal converted from this photodetector, set the slice level to a level slightly lower or slightly higher than this electrical signal, and recognize the presence or absence of a defect on the disk by comparing the electrical signal with the slice level. To do.

[0004]

However, the cracks that occur in the substrate may exist from the center hole of the substrate to the inner peripheral transparent portion due to its nature, and may not reach the range where the magnetic film is formed. Therefore, the method of inspecting the magnetic film from the reading surface of the disk as described above cannot inspect the cracks generated in such a substrate. Therefore, conventionally, when inspecting a crack in the substrate itself, it is general that an inspector visually inspects or uses an image processing device to inspect whether or not there is a substrate crack formed in the inner peripheral transparent portion. However, these methods have a problem that the labor cost of the worker and the construction cost of the system of the image processing apparatus are high.
There is also a problem that the detection time for performing image processing is relatively long. Therefore, it is desired to propose a substrate crack detection method that is inexpensive, has a short inspection time, and is easily adaptable to existing equipment. Therefore, the present invention has been made to solve the above-mentioned problems, and is a method and a device for detecting a substrate crack of a disc-shaped information recording medium that can detect a substrate crack of a disc-shaped information recording medium at low cost and at high speed. Is intended to provide.

According to the present invention, a method for detecting cracks in a substrate which is generated in an inner transparent portion of a disc-shaped information recording medium in which an information recording portion is provided on a transparent substrate is used. The cracks in the substrate are detected by irradiating the cracks in the transparent portion on the inner circumference of the substrate and receiving the reflected light.

According to the present invention, when a substrate of a disk-shaped information recording medium is cracked, the substrate is cracked by irradiating the substrate with a light and receiving the reflected light. You can This eliminates the need for the operator to visually check for cracks in the substrate or use advanced processing techniques such as image processing.

The above-mentioned object is, in the invention, a detection device for detecting a crack of a substrate which occurs in a disc-shaped information recording medium in which an information recording portion is provided on a translucent substrate. A setting unit for setting the medium to be removable, a driving unit for rotating the setting unit for setting the disc-shaped information recording medium, and irradiating light to the crack of the substrate of the rotating disc-shaped information recording medium, This is achieved by a substrate crack detection device for a disc-shaped information recording medium, which includes a light detection unit for detecting a crack in the substrate by receiving the reflected light. According to the present invention, the setting unit sets the disc-shaped information recording medium to be removable. The drive means rotates a setting unit in which a disc-shaped information recording medium is set. The light detecting means irradiates a crack on the substrate of the rotating disc-shaped information recording medium with light and receives the reflected light to detect the crack on the substrate. This eliminates the need for the operator to visually check for cracks in the substrate or use advanced processing techniques such as image processing.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The embodiment described below is a preferred specific example of the present invention,
Although various technically preferable limitations are given, the scope of the present invention is not limited to these forms unless otherwise specified in the description below.

FIG. 1 shows a substrate crack detecting device for a disc-shaped information recording medium according to the present invention. In FIG. 1, the disc-shaped information recording medium 4 to be inspected is an optical disc such as a compact disc. The information recording medium 4 is detachably attached to the spindle 1 which is preferably made of brass. The brass spindle 1 is rotated by a spindle motor 5 at a predetermined speed. The spindle motor 5 is controlled by a command from the motor controller 6. The spindle 1 is a setting unit that sets the disc-shaped information recording medium 4 to be removable. The spindle motor 5 is a driving means for rotating the spindle 1 together with the disc-shaped information recording medium.

On the upper part of the information recording medium 4, the light detecting means 2 is provided.
Are arranged. The light detecting means 2 is connected to the substrate crack determination processing section 7 via an amplifier 3. The light detecting means 2 is, for example, a semiconductor laser 2a and a photodetector 2b.
It has and. The laser beam L emitted from the semiconductor laser 2a irradiates the information recording medium 4 at an angle of θ. This angle θ is nearly 40 ° about. The spindle 1 is preferably made of, for example, brass so that diffuse reflection of the laser light L does not occur. By using this brass spindle 1, the diffused reflection of the laser light L is prevented, and the photodetector 2 of the light detecting means 2 is prevented.
The accuracy of receiving the reflected light at b is ensured.

FIG. 2 is a plan view of the information recording medium 4.
The information recording medium 4 includes a center hole 11 and an inner transparent portion 1.
Have three. A part of the spindle 1 is fitted in the center hole 11, and the information recording medium 4 can be fixed to the spindle 1 by vacuum suction, for example.

As shown in FIG. 3, an information recording medium 4 such as a compact disc is a transparent plastic substrate 3.
0, a reflective layer 31 and a protective layer 32. As shown in FIG. 2, the reflective layer 31 and the protective layer 32 are substantially formed on the portion excluding the inner peripheral transparent portion 13. The substrate 30 is made of polycarbonate, for example. Reflective layer 31
Is, for example, an aluminum thin film, and information is recorded on the reflective layer 31. The protective layer 32 is formed to protect the reflective layer 31.

An example of the substrate crack 12 is shown in FIG. Due to the nature of the substrate crack 12, the inner peripheral transparent portion 13
In most cases, it is generated radially from the center hole 11 to the inner peripheral portion thereof. In the embodiment of the present invention, attention is paid to the shape and location of such a substrate crack. That is, since the substrate crack 12 is formed in the inner peripheral transparent portion 13 in the radial direction from the center hole 11 side, the protective layer 32, the reflective layer 31, and the like are not formed as shown in FIG. It is difficult to detect in the conventional inspection process. However, in the embodiment of the present invention, unlike the so-called conventional method of detecting defects in the magnetic film, the inner peripheral transparent portion 13 is formed by using the photodetector 2.
The substrate crack 12 of this kind is detected by irradiating the substrate with the laser light L.

In the conventional method for detecting defects in the magnetic film,
The defective portion of the magnetic film is irradiated with the laser light from the laser diode, and the reflected light (transmitted light) is received by the photodetector. Therefore, the defect of the magnetic film is detected by converting the intensity of light entering the photodetector into an electric signal and comparing it with a reference signal.
However, in the embodiment of the present invention, unlike the conventional method of detecting defects in the magnetic film, the semiconductor laser 2 shown in FIG.
When the laser light L emitted from a is applied to the substrate crack 12 in FIG. 2, the photodetector 2b receives the reflected light reflected by the substrate crack 12. That is, whether or not the substrate crack 12 is present in the inner peripheral transparent portion 13 is determined only by determining whether or not the reflected light is incident on the photodetector 2b.

Next, the operation of the substrate crack detecting device for the optical disc-shaped information recording medium shown in FIG. 1 will be described. The information recording medium 4 of FIG. 1 is loaded by a transporting machine (not shown) so that the center hole 11 fits into the protruding portion 1a of the spindle 1. This makes spindle 1
For example, vacuum chucks the inner peripheral transparent portion 13 of the information recording medium 4 using, for example, a vacuum suction force. Then, the motor drive unit 6 gives a drive signal to the spindle motor 5. The spindle motor 5 rotationally drives the spindle 1 based on the drive signal. This causes the information recording medium 4 to rotate. The rotation speed of the spindle 1 can be adjusted, for example, between about 30 and 120 rpm. The number of rotations of the spindle 1 can be adjusted in this manner in order to ensure the light receiving reaction of the photodetector 2b of the light detecting means (sensor) 2. That is, excessive high-speed rotation of the information recording medium 4 may cause the photodetector 2b of the photodetector 2 to stop reacting, and excessive low-speed rotation leads to delay of inspection time. For this reason, it is necessary to determine the number of rotations of the spindle 1 in consideration of the optimum detection sensitivity of the photodetector 2b and the inspection time.

Next, the laser driving source 21 is the semiconductor laser 2b.
To drive. As a result, the semiconductor laser 2b emits red laser light L having a wavelength of 670 nm, for example. As shown in FIG. 4, this laser light L irradiates the substrate crack 12 on the innermost peripheral side of the information recording medium 4 so as to form an angle of about 90 °. This is done so that if there is a substrate crack 12 in the inner peripheral transparent portion 13 of the information recording medium 4 to be inspected, the laser beam L is surely reflected by the substrate crack 12. In this case, the irradiation time is set in order to reliably detect the substrate crack 12.
At least the information recording medium 4 needs time for one rotation.

When the information recording medium 4 is a non-defective information recording medium 4 having no substrate cracks 12, the laser beam L forms an angle θ of about 40 ° from the horizontal plane of the spindle 1 as shown in FIG.
Incident on the horizontal plane 1a of the spindle 1 at a reflection angle of 40 ° (θ). Therefore, in this case, the laser beam L never returns to the photodetector 2b. That is, the photodetector 2b is in the off state, and this state is transmitted to the substrate crack determination processing section 7 via the amplifier 3. The substrate crack determination processing unit 7 determines that the information recording medium 4 has no substrate crack 12 based on the absence of a signal from the photodetector 2b.

On the other hand, in the case of the defective information recording medium 4 in which the substrate crack 12 exists in the information recording medium 4 as shown in FIG. 6, the laser beam L emitted from the semiconductor laser 2a passes through the spindle 1. The light enters the horizontal plane 1a at an angle of about 40 °, is reflected by the substrate crack 12, and returns as reflected light L1 to the photodetector 2b side. In this case, since the reflected light L1 can be received by the photodetector 2b,
The photodetector 2b is amplified by the amplifier 3 of FIG. 1 and sent to the substrate crack determination processing unit 7. Substrate crack determination processing unit 7
Can determine that the substrate crack 12 exists based on the light reception signal from the photo detector 2b.

As described above, by using the photodetector 2 for the substrate crack generated on the substrate of the information recording medium, for example, the optical disc such as the compact disc, the reflected light from the substrate crack is used, so that it is fast and inexpensive. It is possible to detect board cracks.

Further, it is preferable to use a spindle 1 made of brass so that the laser beam L irradiated on the spindle 1
Since the laser beam L is not diffusely reflected, it is possible to reflect the laser beam L in a direction different from the direction in which the photodetector 2b exists, particularly when there is no substrate crack 12 in FIG. Therefore, the photodetector 2b will not erroneously receive light when there is no substrate crack 12.

In the embodiments of the invention described above, an optical disc, particularly a compact disc, is taken as an example of the information recording medium. However, the present invention is not limited to this, and a magneto-optical disk as shown in FIG. 7, for example, can also be used as an information recording medium to be inspected. The magneto-optical disk shown in FIG. 7 is, for example, a read-only mini disk, and the information recording medium 104 includes a center hole 111 and a reflective layer 13.
1, a protective layer 132, a pit 140, and a transparent plastic substrate 130. The substrate 130 is made of polycarbonate, for example. The inner transparent portion 113 of the information recording medium 104 such as this type of magneto-optical disk.
Even if the substrate crack 112 occurs, the substrate crack 112 can be detected at high speed and at low cost by the substrate crack detecting device for the disc-shaped information recording medium shown in FIG.

The present invention is not limited to the above embodiment. For example, the above-described information recording medium is exemplified by an optical disk such as a read-only compact disk and a read-only magneto-optical disk. However, the present invention is not limited to this, and it is also possible to detect a crack in the substrate of a magneto-optical disk capable of recording / reproducing or a next-generation optical recording medium, a so-called digital video disk (DVD).

[0023]

As described above, according to the present invention,
It is possible to detect cracks in the substrate of a disc-shaped information recording medium at low cost and at high speed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a preferred embodiment of a substrate crack detection device for a disc-shaped information recording medium of the present invention.

FIG. 2 is a plan view of the information recording medium of FIG.

3 is a sectional view showing a part of the information recording medium of FIG.

FIG. 4 is a diagram showing an example of irradiating a laser beam on a substrate crack of an information recording medium.

FIG. 5 is a diagram showing a reflection path of a laser beam when the laser beam is applied to a non-defective disc having no substrate crack.

FIG. 6 is a diagram showing a laser light reflection path when a defective disk having an information recording medium having a substrate crack is irradiated with laser light.

7 is a diagram showing an example of an information recording medium of a different type from the information recording medium of FIG.

[Explanation of symbols]

1 spindle (setting section) 2 Light detection means 2a Semiconductor laser (light emitting part) 2b Photodetector (light receiving part) 4,104 Information recording medium (disc) 5 Spindle motor (driving means) 12 Board crack 13 Inner circumference transparent part

Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01N 21/84-21/958 G01B 11/00-11/30 G11B 23/00

Claims (2)

(57) [Claims] 1. A substrate crack detection of a disc-shaped information recording medium for detecting a substrate crack generated in an inner transparent portion of a transparent substrate of a disc-shaped information recording medium having an information recording portion.
A method of fixing the optical recording medium to a spindle and rotating the optical recording medium, the optical recording medium being provided on an inner transparent portion of a substrate of the optical recording medium.
The laser diode and the photodetector placed on top of the
A laser beam is emitted from the photodetector having the optical recording medium.
At an angle of approximately 90 ° to the radial direction of the substrate , and
The information recording medium is illuminated at an angle of about 40 ° with respect to the horizontal plane of the substrate, the laser light is reflected by the inner transparent portion of the substrate , and reflected from the inner transparent portion of the substrate. the light, in the photodetector
A substrate crack detection method for a disc-shaped information recording medium, characterized by detecting a substrate crack in an inner peripheral transparent portion of the substrate by receiving light . 2. A device for detecting a substrate breakage that has occurred in an inner peripheral transparent portion of a transparent substrate of a disc-shaped information recording medium having an information recording portion, wherein the optical recording medium is set to be removable. A setting unit, a driving unit for rotating the setting unit, the optical recording medium is fixed in the setting unit, and is rotated by the driving unit, the inner transparent portion of the substrate of the optical recording medium. And a photodetector for detecting a substrate crack by receiving the reflected light, the photodetector having a semiconductor laser and a photodetector, and emitted from the semiconductor laser. The laser light is
Almost 90 ° with respect to the radial direction of the inner transparent part of the substrate of the recording medium
Angle and the horizontal plane of the substrate of the optical recording medium.
URN is irradiated at an angle of 40 °, by the laser light is to be reflected by the inner circumferential transparent portion of the substrate, the reflected light from the inner peripheral transparent portion of the substrate, is received by the photodetector of the light detection means, A substrate breakage detection device for a disc-shaped information recording medium, which detects a substrate breakage in an inner peripheral transparent portion of the substrate.