JPH04344446A - Detecting method for abrasion of disc-shaped contact type information recording medium - Google Patents

Abstract

PURPOSE:To automatically detect the degree of abrasion of a disc-shaped contact type information recording medium with high accuracy. CONSTITUTION:When the board surface 1a of a recording medium 1 abrades, the opening edge portions 5a, 5b of each pit 5 opposing each other in the circumferential direction of movement of the pit during R/W take different shapes due to plastic deformation, and when the board surface 1s is illuminated with light quantities of light scattered at the portions 5a, 5b are different because of the deformation. Then two light quantity detecting portions 2, 3 each disposed along the direction of the tangent of a rack detect quantities of light scattered at the group of pits existing in the tanget area 1a between the track and the tangent and the difference between values detected by the detecting portions 2, 3 is found by a light quantity comparing portion 4 and used as a value corresponding to the abrasion loss of the recording medium 1a so as to measure the degree of the abrasion.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a method for detecting wear on disc-shaped contact type information recording media, and in particular, it is possible to automatically detect the degree of wear occurring on storage media such as contact type video discs with high precision by optical means. The purpose is to provide a method.

0002

[Prior Art] In a disc-shaped recording medium such as a capacitive video disk in which recorded information is read/written using a contact pickup, when the storage medium itself wears out, the pickup side also wears out rapidly. , worn recording media must be replaced as soon as possible.

[0003] Therefore, it is necessary to check the state of wear on the surface of the recording medium at appropriate intervals, and visual observation has conventionally been the simplest inspection method. That is, pits representing recorded information are formed concentrically on the surface of the recording medium, and when observing the recording medium 51 from diagonally above as shown in FIG. However, as the wear of the disc surface progresses, the gloss of each concentric area 52 changes subtly, and the degree of wear is determined empirically from the changed state. There is also a method of determining the state of wear by looking at the surface roughness of the recording medium, deformation of the pits themselves, etc. using a metallurgical microscope, but this is not generally practiced except in special cases.

On the other hand, when recorded information is read from the above-mentioned recording medium with a pickup, if the disk surface is worn out, the electrical characteristics such as signal loss rate and signal output will change, so it is difficult to observe changes in the characteristics. It is thought that the degree of wear can be measured by It is inappropriate as a means of detecting

[0005]

[Problems to be Solved by the Invention] However, as mentioned above, the methods using visual means or metallurgical microscopes involve manual work and empirical judgment, which is troublesome and does not allow accurate measurement of the degree of wear. It is not possible to obtain quantitative data.

Furthermore, when light is irradiated onto the surface of a recording medium, if there is foreign matter 53 attached to the surface, scratches 54 or deformation 55, as shown in FIG. Light is reflected. As shown in FIG. 8, the microscattered light reflected from the vicinity of each pit 56 serves as a measure of the degree of wear, but the scattered light is due to the above-mentioned scattered light caused by the adhesion of foreign matter, etc. In comparison, it is extremely weak, and it is not possible to distinguish changes due to wear from changes due to adhesion of foreign matter or the like just by looking at the reflected light.

Therefore, the present invention focuses on the influence that the deformation of the opening edge portion of each pit due to wear has on the scattered light, and by optically detecting this, automatically and accurately determines the degree of wear on the surface of the recording medium. It was created with the purpose of providing a method to measure the

[0008]

Means for Solving the Problems The present invention has a basic configuration as shown in FIG. Light amount detection units 2 and 3 are respectively disposed diagonally upward at the front and back of the recording medium 1, and each light amount detection unit detects the amount of scattered light reflected at the contact area 1a while the disk surface 1s of the recording medium 1 is irradiated with light. Detected by parts 2 and 3,
The present invention relates to a method for detecting wear on a disk-shaped contact type information recording medium 1, which is characterized in that the degree of wear on the disk surface 1s of the recording medium 1 is detected by determining the difference between the detected amounts of light (L2, L3).

[0009]

[Operation] The disc-shaped contact type information recording medium 1 is rubbed and worn by the sensor part of the pickup during R/W, but if we look at this phenomenon in detail, the lubricant layer on the disc surface 1s disappears, and the surface Plastic flow occurs and the opening edge of each pit 5 becomes deformed. That is, as shown in FIG.
During R/W, the opening edge 5a on the moving circumferential side undergoes shearing deformation such that it protrudes toward the center of the pit 5, while the opening edge 5b on the opposite side has a larger radius of curvature due to shearing deformation. It becomes a curved surface.

As a result, when light is irradiated onto the disc surface 1s, the reflection at the aperture edge 5a becomes smaller, and conversely the reflection at the aperture edge 5b becomes larger, so that the light is reflected in the tangential direction to the track of the recording medium 1. The amount of scattered light that diffuses diagonally upward on the board surface 1s becomes larger when viewed from the front in the moving circumferential direction.
Conversely, it becomes smaller when viewed from the rear in the moving circumferential direction.

By the way, in the initial state (state before wear) as shown in FIG. 2, when light is irradiated perpendicularly to the board surface 1s, the light irradiates around the entire circumference of the opening edge of each pit 5. The light is reflected almost evenly, and the amount of scattered light from each pit 5 is uniform over the entire board surface.

Therefore, as in the present invention, two light quantity detection sections 2 and 3 are arranged diagonally above in the tangential direction to the track of the recording medium 1, and before and after the contact area 1a between the tangential line and the track. , the light intensity of the scattered light of the pit group existing in the contact area 1a (L2
. can. In other words, the greater the difference (|L2-L3|) between the respective light quantities detected by the light quantity detectors 2 and 3, the more the wear of the recording medium 1 has progressed, and the wear of the recording medium 1 is progressing. It becomes possible to detect the difference in light amount as a value corresponding to the amount of wear on the recording medium 1.

[0013]

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 3 to 5. FIG. 3 shows a schematic configuration diagram of a wear detection device for a disc-shaped contact type information recording medium (hereinafter referred to as a "disk"). In the figure, 11 is a disk, 12 is a motor that rotates the disk 11, and 13 is a detection unit (30
; 14 is a drive belt for moving the carrier base 13 in the radial direction of the disk 11; 15 is a pulley for driving the belt 14;
6 is a driven pulley, 17 is a sliding guide shaft of carrier base 13, 18 is a support roller of carrier base 13, 19 is a guide rail of support roller 18, 20 is a motor that rotates drive pulley 15, 21 is motor 12 ,2
1 shows a motor control unit that controls 0.

The configuration of the detection unit 30 mounted on the carrier base 13 is shown in FIG. A condensing lens 31a is mounted to condense the light into a spot with a constant width on the surface of the disc 11, and a light irradiation system 31,
There are two light amount detection units 32 at target positions on both sides of 31a,
33 and a condenser lens 3 for condensing light onto the detection surface.
2a and 33a are installed. Note that the two detection systems [32, 32a] and [33, 3
3a] is perpendicular to the center line of the disk 11, passes through the center of the irradiation spot area on the disk surface of the disk 11 by the condenser lens 31a, and is at an angle of θ with respect to the disk surface. It forms an angle. As shown in FIG. 3, the light source lamp 31 is ON/OFF controlled by the light source control section 34, and the detection signals from the light amount detection sections 32 and 33 are input to the wear measurement section 35, so that the wear of the disk 11 is controlled. Data is created.

[0015] Here, to explain in detail each of the above-mentioned optical system elements, it is natural that a compact mechanical configuration is desirable, but it is also desirable that they have the following characteristics or performance. desirable. First, regarding the light source lamp 31, the brightness of the light beam is high, the infrared region is cut to prevent heat damage to the disk 11, and the wavelength thereof is within the high sensitivity wavelength range of the light amount detection sections 32 and 33. can be,
In addition, it is necessary that the wavelength of the light be such that the amount of scattered light on the surface of the disk 11 is as large as possible. In addition, for the optical system including the condensing lens 31a, it is desirable that the irradiation spot area can be configured as narrow as possible (for example, an irradiation spot area of about 5 mm in diameter), and that there is less noise due to stray light, and the scattered light reflected on the surface of the disk 11 is desirable. It is necessary to have a focal length that allows the light to enter the light amount detection units 32 and 33 without blocking the light. Based on the above conditions, the light source lamp 31 is a high-intensity red LED (for example, a 2000mcd high-intensity GaA
lAs-LED (center wavelength 660 nm), a cold cathode fluorescent tube, a light guide using an optical fiber and a halogen lamp, etc. can be used, and by applying the light amount detection units 32 and 33 that have these wavelengths as a highly sensitive wavelength range. good. Also, if the angle of incidence of the irradiation light on the disk 11 is perpendicular, one light source is sufficient, but if the illuminance is insufficient, two light sources may be installed at symmetrical positions with respect to the center line of the disk 11. In this case, if an optical fiber is used, it becomes possible to arrange the optical fiber at a substantially coaxial position with the light amount detection sections 32 and 33. On the other hand, regarding the light amount detection units 32 and 33,
It is necessary that the detection sensitivity be high, that the center wavelength of the light source lamp 31 be in a high sensitivity region, that the output voltage be large, that the detection area be small, and that its spatial resolution be high. Based on this condition, silicon photodiodes whose detection surfaces are narrow in one direction can be used as the light amount detection sections 32 and 33. In addition, the condenser lenses 32a, 3
The optical system including 3a must have a high aperture ratio and be bright, a lateral magnification that is compatible with the detection area of the light amount detection sections 32 and 33, and an angle at which the diffracted light does not enter the pits of the disk 11 (in FIG. 4). θ), and it is necessary to reduce noise due to return light within the optical system.

Furthermore, the wear measuring section 35 incorporates a circuit as shown in FIG. 5 in relation to the light amount detecting sections 32 and 33 described above. In this circuit, each light amount detection section 32,
33 silicon photodiodes (D
2, D3) generates a current by receiving scattered light from the irradiation spot area, but both light amount detection units 32
, 33, the difference is detected,
The potential difference on the input side caused by the current difference is inverted and amplified by the low-noise operational amplifier 40, thereby obtaining an output voltage corresponding to the difference in the amount of received light.

In the configuration shown in FIGS. 3 to 5, when detecting wear of the disk 11, the motor control section 21 first controls the motor 20, and moves the carrier base 13 to the peripheral edge of the disk 11 via the drive belt 14. Set it in the section. After the light source control section 34 turns on the light source lamp 31, the motor control section 21 activates the motor 12 to rotate the disk 11, and while controlling the motor 20, moves the carrier base 13 onto the disk 11. Move it to the center. By the above operation, carrier base 1
The detection unit 30 mounted on the disk 11 can sequentially scan the disk 11 from the track portion on the outer circumferential side, and the degree of wear on the entire surface of the disk 11 can be detected.

During the above scanning, the light source lamp 31
A predetermined irradiation spot area is formed on the surface of the rotating disk 11 by converging the irradiation light with the condensing lens 31a, and the scattered light from the irradiation spot area is condensed as shown in FIG. Lenses 32a and 33a converge the light onto detection surfaces (silicon photodiodes) of light amount detection units 32 and 33. As a result, the light amount detection units 32 and 33 can detect the scattered light of the pit group existing in the irradiation spot area, but if the disk 11 is worn out, the opening edge of each pit 11a During R/W, the moving circumferential direction side protrudes toward the center, and the opposite side is rounded, so as seen in FIG. 4, the output of the light amount detection section 32 is It becomes larger than the output of 33. This is because the light amount detection section 32 receives the scattered light that is strongly reflected on the rounded side of the opening edge, and the light amount detection section 33 receives the scattered light that is attenuated on the protruding side of the opening edge. It is from.

Each of the above detection outputs is sent to the wear measuring section 3.
5, the output difference is detected and amplified by the circuit shown in FIG. 5, and detected as a voltage value corresponding to the degree of wear. In this case, the output values of the respective quantity detectors 32 and 33 also include strong scattered light components due to deposits, scratches, and deformations on the disk 11. Taking the output difference of 32 and 33,
and because the irradiation spot area is set small, changes in the strongly scattered light based on these factors appear in the output of each light amount detection unit 32, 33 in the same phase, so the output due to the strongly scattered light is They are mutually canceled by the circuit No. 5, and only the change in the scattered light due to the deformation of the opening edge of the pit 11a is detected. That is, it is possible to exclude changes in the scattered light due to the above-mentioned factors and detect only changes in the scattered light due to the wear of the disk 11, thereby making it possible to accurately measure the degree of wear of the disk 11.

By the above-described operation, in this embodiment device, the wear measurement section 35 is moved while the carrier base 13 is moved.
The degree of wear of the entire disk surface of the disk 11 can be measured in this way.The wear measuring section 35 A/D converts the output difference signal, and the data is converted into control data of the motor control section 21 (rotational speed of the disk 11, When stored in the memory together with the phase data and the movement amount data of the carrier base 13,
By analyzing these data, the wear distribution on the surface of the disk 11 can be accurately determined.

[0021]

As described above, the present invention makes it possible to automatically detect the degree of wear of a disc-shaped contact type information recording medium with high precision by optical means. In addition, in the detection process, only the degree of wear is detected purely without being affected by deposits, scratches, deformation, etc. on the surface of the recording medium. As a result, compared to the conventional method, which relied on empirical judgment using visual means or observation means using a metallurgical microscope, this method not only eliminates troublesome work but also enables quantitative detection of the degree of wear. This allows highly reliable wear data to be obtained. In addition, it becomes possible to confirm the appropriate time to replace a capacitive video disk or the like based on its wear data, and it is possible to effectively prevent wear on the pickup side that accompanies wear of the disk.

[Brief explanation of the drawing]

FIG. 1 is a principle diagram showing a wear detection method for a disc-shaped contact type information recording medium according to the present invention.

FIG. 2 is a sectional view showing the state of the surface of the recording medium before wear.

FIG. 3 is a schematic configuration diagram of a wear detection device according to an embodiment.

FIG. 4 is a diagram showing an optical configuration of a detection unit.

FIG. 5 is an electrical circuit diagram of the wear measuring section.

FIG. 6 is a diagram illustrating a method of visually determining wear of a recording medium.

FIG. 7 is a diagram showing a state in which strong scattered light is generated on the surface of a recording medium.

FIG. 8 is a diagram showing a state in which weak scattered light is generated on the surface of a worn recording medium.

[Explanation of symbols]

1... Disc-shaped contact type information recording medium, 1a... Contact area, 1
s...Disc surface, 2, 3...Light amount detection section, 4...Light amount comparison section, 5...
Pit, 5a...Aperture edge on the moving circumferential direction side during R/W, 5b...Aperture edge on the opposite side to the moving circumferential direction during R/W, L2, L3...Light amount.

Claims (1)

[Claims] 1. A light amount detection unit is provided in a tangential direction to a track of a disc-shaped contact type information recording medium, and diagonally above a contact area between the tangential line and the track, respectively, and Detecting the degree of wear on the surface of the recording medium by detecting the amount of scattered light reflected at the contact area with each light amount detection section while irradiating the contact area with light, and finding the difference between the two detected light amount values. A method for detecting wear of a disc-shaped contact type information recording medium, characterized by: