JPS61104440A - Method and device for detecting deffect of recording medium with no contact - Google Patents

Abstract

PURPOSE:To secure the assured and quick detection for shallow, small and narrow defects respectively by projecting a check beam to a disk forming a recording medium, catching the reflected check beam for detection of the form change and detecting the information on the defects based on the form change signal. CONSTITUTION:When a defective area enters a check beam during revolutions of a disk, the signal S2 rises greatly up to a level LC. The level of the signal S2 is set again at level 0 when the detective area passes through the check beam. The width of the level LC is decided unconditionally by the scale of the defect and the revolvingnumber of the disk and equal to the width WS of a level L8. The 1st waveform shaping unit 28 extracts the level fluctuation part, i.e., the area of the width WB of a sum signal S1. This extracted part undergoes the binary coding and the conversion into the single polarity. While the level fluctuation part, i.e., the area of the width WB of a difference signal S2 is extracted by the 2nd waveform shaping unit 29 and undergoes the binary coding and the conversion into the single polarity. These two binary coded outputs are added together through an OR circuit 30 and turned into a high-level defect signal DS of the width WB. This signal DS is applied to a defect deciding unit 31.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a defect detection method for non-contact detecting defects existing in a recording medium, and an apparatus used to carry out the method, and more particularly, to a compact disc. When an inspection beam with a predetermined cross-sectional shape is projected onto a disk constituting a recording medium such as a video disk or a video disk, the level and cross-sectional shape of the reflected beam change depending on the defects present in the disk. The present invention relates to a non-contact defect detection method for a recording medium for detecting defects present in a disk, and an apparatus used to carry out the method.

[Conventional technology and problems]

When detecting defects in recording media such as compact discs and video discs, non-contact defect detection methods are used to prevent damage to the recording media during detection.
In particular, an optical non-contact defect detection method is used.

The optical non-contact defect detection method projects inspection light onto a recording medium, and uses a photodetector to detect the state of scattering and absorption of the inspection light caused by the presence of defects as level fluctuations in the amount of light received.
This method uses this as a defect signal and detects that the level fluctuation exceeds a predetermined amount to determine the presence or absence of a defect.

However, this conventional optical non-contact defect detection method detects the presence or absence of defects by capturing level fluctuations in the amount of light received by the photodetector, so fluctuations exceeding a certain level exceeding the noise level and measurement error may occur. If it does not exist, defects cannot be detected accurately. Therefore, defects with small level fluctuations, such as large but shallow defects, small defects, narrow defects, defects due to bubbles existing inside the recording medium, etc., may have a large impact on recording and playback processing. There was a problem that it could not be detected regardless of the situation.

Additionally, knowing the state of a defect is important information in determining the cause of the defect, but conventional methods of detecting defects based only on level fluctuations However, there was a problem that the state of the defect could not be detected accurately.

[Object of the invention and means for achieving it]

The present invention solves the above-mentioned problems in the conventional non-contact defect detection method for recording media, and can detect not only defects that cause large level fluctuations that exist on the disk, but also shallow defects and small defects that do not appear as large level fluctuations. It is an object of the present invention to provide a non-contact defect detection method for a recording medium that can detect narrow defects reliably and at high speed, and can also accurately determine the state of the defect.

In order to achieve the above object, the present invention provides a non-contact defect detection method for a recording medium, in which an inspection beam having a predetermined cross-sectional shape is projected onto a disk constituting the recording medium, and The reflected beam of the recording medium is captured, the shape change that occurs in the cross section of the reflected beam is detected, and information regarding the disc ← existing defect is detected based on the detected shape change signal, or the recording medium is A test beam with a predetermined cross-sectional shape is projected onto the constituent disks, and a reflected beam of the test beam from the disk is captured to detect a change in the level of the reflected beam and a change in shape that occurs in the cross section. It is configured to detect information regarding defects existing in the disk based on both the signal and the shape change signal, and the apparatus for carrying out the detection includes a disk constituting a recording medium, inspection beam generating means for projecting an inspection beam with a predetermined cross-sectional shape onto the disk; beam detection means for capturing reflected beams of the inspection beam from the disk by a plurality of detection elements and generating detection signals for each; logical operation means for generating a shape change signal corresponding to the shape change of the reflected beam by logically operating the detection signal from the detection element; and means for detecting information regarding a defect existing in the disk based on the shape change signal. Alternatively, the configuration may include a disk constituting a recording medium, an inspection beam generating means for projecting an inspection beam having a predetermined cross-sectional shape onto the disk, and a plurality of detection elements for detecting the reflected beam of the inspection beam from the disk. a beam detecting means for generating a detection signal by capturing each detection signal, and logically operating the detection signals from the plurality of detection elements to generate a level change signal corresponding to a change in the level of the reflected beam and a change in the cross-sectional shape of the reflected beam. logical operation means for generating a shape change signal;
The present invention is configured to include means for detecting information regarding defects existing in the disk based on both the level change signal and the shape change signal.

〔Example〕

Each embodiment of the present invention will be described in detail with reference to the drawings.

Fig. 1 is an explanatory diagram of an embodiment of the present invention, Fig. 2 is an explanatory diagram of an example of a beam detector used in the embodiment, and Fig. 3 is an explanatory diagram of an example of a defect detector used in the embodiment. 4 is an explanatory diagram of operation waveforms of the same embodiment, FIG. 5 is an explanatory diagram of specific experimental data according to the same embodiment, and FIG. 6 is an explanatory diagram of another embodiment of the present invention.

In FIG. 1, reference numeral 11 denotes a disk constituting a recording medium, such as an optical disk on which a reflective film is deposited, or a transparent disk immediately after molding, that is, before the reflective film is deposited. Optical discs include compact discs, video discs, and the like. A spindle 12 rotates the disk 11 using a CLV or CAV method using a drive device (not shown). Reference numeral 13 denotes an inspection beam generator, which generates a sufficiently narrow inspection beam with reflection characteristics for the disk drive 1. For example, a laser light source is suitable as such an inspection beam.

14A is a half mirror that separates the inspection beam and the reflected beam. Reference numeral 14B is a focusing thread that further narrows down the inspection beam generated from the inspection beam generator 13 and forms an inspection beam 5 having a predetermined cross-sectional shape.
Project to 1. In the following description of the embodiment, it is assumed that the inspection beam 15 is formed into a perfect circle as a predetermined cross-sectional shape. The thickness of the inspection beam 150, that is, the diameter of the perfect circle, is determined in consideration of the resolution of detectable defects, inspection speed, etc., and in the embodiment, a diameter of about 50μ is used. 16 is a reflected beam, inspection beam 1
5 is formed by reflecting off the disk 11. 1
A beam detector 7 detects the reflected beam and converts it into an electrical signal. A defect detector 18 detects information regarding the defect, such as the presence or absence of a defect, its size, and condition, based on the signal from the beam detection a17.

2nd F again! ! In the beam detector 17 shown in J,
19A to 19D are four-division detection elements, 16A to 16G
shows the shapes of various projected reflected beams. As the detection element 19, in addition to a type in which it is divided into four parts as shown in the figure, a multi-divided type in which it is divided into a plurality of parts in the circumferential direction, a type in which it is further divided into multiple parts in the radial direction, etc. can be used.

Next, the operations shown in FIGS. 1 and 2 will be explained.

In the following description, He-N is used as the inspection beam 15.
Using a laser beam such as an e-laser with a completely circular surface, a four-segment detection element 1 is used as the beam detector 17.
9A to 19D will be used as an example, but the present invention is not limited to these cases. When a laser beam is used as the inspection beam 15, an optical fiber is used as the focusing thread 14B. A focusing thread is used, and a light receiving element is used as a detection element.

The inspection beam 15 formed by the inspection beam generator 13 and the focusing thread 14 has a perfect circular cross section and is attached to the disk 1.
Projected to 1. This projected inspection beam is reflected by the disk 11 to become a reflected beam 16, and the focusing thread 14
The beam is incident on the detection elements 19A to 190 of the beam detector 17 via the beam B and the half mirror 14A.

If there is no defect on the disk 11, the shape of the reflected beam 16 incident on the detection elements 19A to 19D is the same as that of the second
As shown in Figure (A), the reflected beam 16A has the same perfect circular shape as the inspection beam 15.

Note that the reflected beam 16A is adjusted so as to be located at the center of the four-split detection elements 19A to 19D as shown in the figure. Therefore, in the case of FIG. 2(A), each detection element 19A to
The detection outputs a w d of 19D are equal.

By the way, if there are defects such as scratches or blank spots (so-called "stains") on the surface of the disk 11, or if there are defects such as bubbles inside, the inspection beam will be scattered or absorbed depending on the state of the defect. As the amount of reflection changes, the output level of each detection element changes.Furthermore, the cross-sectional shape of the reflected beam 16 changes from the cross-sectional shape of the inspection beam 15, corresponding to the state of the defect, and becomes a perfect circle. The detection elements 19A to 19D of the beam detector 17
is incident on the

For example, if there is a flaw extending in the scanning direction of the inspection beam (the straight line connecting the detection elements 19B and 19D in FIG. 2(A)), the reflected beam 16 will be reflected as shown in FIG. 2(B). The light changes into a long elliptical shape in the direction perpendicular to the scanning direction and enters the detection elements 19A to 19D. Furthermore, in the case of a flaw extending perpendicular to the scanning direction of the inspection beam, the flaw changes into an elliptical shape that is elongated in the scanning direction, as shown in FIG. 2(C).

The present invention focuses on the phenomenon that when there is a defect in the disk 11, the reflected beam 16 not only changes in level but also changes in shape in response to the state of the defect, and makes use of this phenomenon. This makes it possible to detect defects in oak that could not be detected using conventional defect detection methods that utilize only level fluctuations, and also to detect the state of the defects.

Referring to FIG. 3, a defect detection method using the four-division detection elements 19A to 19D will be described.

In the defect detector 18 shown in FIG. 3, a preamplifier 20 surrounded by a chain line is a current/voltage converter (
CV converter) 21A to 21D and preamplifier 22A to 2
It has 2D.

The preamplifiers 22A-22D are connected to the detection elements 19A-19D and the current/voltage converters 21A-
21D output and gain are corrected, and the disc 11
Each preamplifier 22A-22D when no defects exist in
Adjust so that the outputs A-D of the two are equal. Note that the resistor R connected to the beam detector 17 is connected to each detection element 1.
This is a bias resistor for optimizing the detection efficiency of 9A to 19D.

23 surrounded by a chain line is an arithmetic unit, which includes a first adder 24 and a second adder 24;
It has an adder 25, a third adder 26, and a subtracter 2'7,
A logical operation is performed on the outputs A-D of each preamplifier to output a level change signal corresponding to a change in the level of the reflected beam and a shape change signal corresponding to a change in the cross-sectional shape of the reflected beam. 1st
Adder 24 adds outputs A and C of preamplifiers 22A and 22C. The second adder 25 is a preamplifier 22B.
and the outputs B and D of 22D are added. Third adder 26
is the sum signal S1 by adding the outputs of the first and second adders 24 and 25, that is, S1=(A +"'B +C+D
) is output. The subtracter 27 is the first and second adder 24
and 25 outputs to obtain the difference signal S2, i.e. 32
= (A+C) (B+D) is output. The sum signal S+ created in this way is a level change signal,
The difference signal S2 is used as a shape change signal.

Reference numeral 28 denotes a first waveform shaper which binarizes a variation above a certain level from the sum signal S1, and then converts it into a unipolar signal and outputs it. 29 is a second waveform shaper which binarizes the variation above a certain level from the difference signal S2 and then outputs it as a unipolar signal. 30 is an OR circuit which adds the outputs of the first and second waveform shapers and outputs a defect signal DS. 31 is a defect determiner which receives a defect signal DS applied from the OR circuit 30;
The presence or absence of a defect and the size of the defect are determined by measuring the pulse width. Reference numeral 32 denotes a defective state determiner, which connects the preamplifiers 22A to 22A.
The state of the defect is determined from the output of 22D. Reference numeral 33 denotes a clock source for determination, which supplies the defect determiner 31 and the defect state determiner 32 with a clock used to determine the presence or absence and state of a defect.

Next, the operation shown in FIG. 3 will be explained with reference to the operation waveform diagram for the fourth factor, with and without a defect in the disk 11.

(A) When there is no defect on the disk When there is no defect on the disk 11, the detection elements 19A to 19D of the beam detector 17 receive a perfectly circular reflected beam 16A as shown in FIG. 2(A). are incident evenly. Therefore, the outputs a % d of the detection elements 19A to 19D and the outputs A to D of the preamplifiers 22A to 22D are all at the same level.

Sum signal Sl (=A+
B+C+D) is a constant bell LA which is four times the output of one preamplifier, as shown in FIG. The output state of the constant bell L^ is connected. Subtractor 27
The difference signal S2 (=(A+G)-(B+D)) is A
-B-C Since it is snowy, as shown in Figure 4 (A),
This zero level output state is maintained even if time passes.

The first and second waveform shapers 28 and 29 binarize only the level fluctuation portion in which the level has changed by a certain value or more using a bipolar variable threshold circuit, and then convert it into a unipolar signal and output it. . Therefore, in the case of FIG. 4A where there is no defect in the disk 11, no output is generated from either the first or second waveform shaper 28 or 29, and the defect signal is output from the OR circuit 30. DS becomes a zero level state as shown in FIG. 4(A).

In this case, the defect determiner 31 and the defect state determiner 32 are
In either case, it is determined that no defect exists.

Note that the operation of both dividers will be explained in detail in the operation when a defect exists in the next disk.

(B) When there is a defect on the disk When there is a defect on the disk 11, for example, when there is a scratch in the scanning direction of the inspection beam 15, the perfect circular inspection beam 15 is As shown in , the reflected beam 16B is transformed into an elliptical reflected beam 16B that is elongated in the direction perpendicular to the scanning direction, and is incident on the detection elements 19A to 19D.

Sum signal S1 of the third adder 26 for the reflected beam 16B
The level L8 in Figure 4 (
As shown in B), the sum signal S for the transmitted beam 16A
It becomes lower than the level L^ of s.

When the disk 11 rotates, assuming that there is no defect at first, the level of the sum signal 51 is Lll, but when a portion with a defect enters the inspection beam 15, the sum signal Sl
The level of decreases to Le. The defective part is the inspection beam 15
When passing through, the level of the sum signal S1 returns to L^ again.

, the width Ws of this level L11 is uniquely determined by the size of the defect and the number of rotations of the disk 11.

2 (B
), (A+C) is much larger than CB+D). Once, the difference signal S of the subtractor 27
2, the level Lc becomes much higher than zero, as shown in FIG. 4 (B).

When the disk 11 rotates, the level of the difference signal S2 is zero level, assuming that there is no defect at first, but the part with the defect enters the inspection beam 15 (then the difference signal S2
The level of increases significantly to Lc. When the defective part passes through the inspection beam 15, the level of the difference signal S2 returns to zero level again. The width of this level Lc is uniquely determined by the size of the defect and the number of rotations of the disk 11, and the width of the level L8
corresponds to the width W@.

The first waveform shaper 28 extracts the level fluctuation portion of the sum signal SI, that is, the width Ws portion, and converts it into binarization and unipolarization, and the second waveform shaper 29 extracts the level fluctuation portion of the difference signal S2, that is, the width Ws. The W8 portion is extracted and binarized and unipolarized.

These two binary outputs are added by the OR circuit 30, and as shown in FIG. 4(B), a high level defect signal DS with a width of We is
and is added to the defect determiner 31.

The defect determiner 31 measures the width We of the defect signal DS, detects the presence or absence of a defect, and the size of the defect in the scanning direction, and outputs the detected value. The width W8, which indicates the magnitude of the defect signal DS, can be obtained by, for example, adding a clock applied from the determination clock source 33 to a counter (not shown) and counting the number of clocks within the width W++. In the case of the CLV method, a clock with a constant period is added, and in the case of the CAV method, a clock with a period inversely proportional to the size of the radius from the center of the disk 11 to the scanning position of the inspection beam 15 is added.

If the scratch is shallow or small, the level change of the reflected beam will be slight, but the shape change will clearly occur. Therefore, according to the present invention, shallow flaws, small flaws, etc. that cannot be detected by conventional defect detection methods that detect only level fluctuations of reflected beams can be reliably detected.

FIG. 2(C) shows the state of the reflected beam 16G when a defect exists in a direction perpendicular to the scanning direction. In this case, as shown in the figure, the shape changes from a perfect circle to an ellipse that is elongated in the scanning direction.

FIG. 4(C) shows the third adder 26 in the case of FIG. 2(C).
sum signal Sr, difference signal S2 of the subtracter 27, OR circuit 30
This figure shows the state of the defect signal DS. Figure 2 (C
) is narrower than the width of the defect in the case of FIG. 2(B), so the width WC of the sum signal S1 and the difference signal S2 in FIG. 4(C) is It appears narrower than the width W8 of the sum and difference signals in B). Since the defect detection operation is the same as that in FIGS. 2(B) and 4(B), the description thereof will be omitted.

Next, a defect state detection method will be explained.

As can be clearly seen when comparing (A) to (C) in FIG. 2 and FIG. (See also Figure 5). Therefore, by using these signals, the state of the defect can be determined.

The defect state determiner 32 uses the clock from the determination clock source 33 and the position information of the inspection beam 15 from the disk drive device (not shown) to determine the sum signal Sl and difference signal S2 obtained when the disk 11 is scanned. level value,
The information is stored individually in a storage device (not shown). When the scanning of the disk is completed, the pattern of defects present in the di-warp 11 is stored in the storage device as a sum signal Sl and a difference signal S2, respectively. If the contents of the storage device are read out and displayed on the display, each defect pattern will be displayed on the display and the state of the defect can be observed. Furthermore, it is also possible to recognize the state of the defect using a known pattern recognition or image recognition method.

For example, by preparing patterns for various states of defects as reference patterns for the sum signal Sl and difference signal S2, and comparing them with these, it is possible to detect various states of defects in detail. Detection element 19
If the inspection beam 15 is further divided into multiple parts and the inspection beam 15 is further made thinner, the shape of the defect can be detected in more detail. Note that such pattern recognition or image recognition techniques themselves are well known, so a description thereof will be omitted.

In this manner, according to the present invention, it is possible to detect in detail the state of various defects that exist in the circumferential direction (scanning direction) and/or the radial direction of the disk 11.

FIG. 5 shows the sum signal Sl of the third adder 26 and the difference signal S of the subtracter 27 for various defect states observed by the non-contact defect detection device for storage media shown in FIGS. 1 to 3.
2 is shown. CAV of inspection 2400rpm
This is the case with the method.

FIG. 5(A) shows a defect caused by a black spot (scorch) with a length of 80 μm in the scanning direction of the inspection beam. FIG. 5(B) shows the case of a defect caused by a flaw with a length of 150 μm in the scanning direction of the inspection beam. FIG. 5(C) shows the case of a shallow spiral-shaped defect with a length in the inspection beam direction of 30 μm. Same figure (A)
and (B), the level of the sum signal S1 is the difference signal S2
(For example, in case (B), the difference signal S2 is about eight times as large as the sum signal S1), and in the case (C), the sum signal S1 cannot be detected.

In the case of defects as shown in (A) to (C) in Figure 5,
Since the level of the sum signal S1 is low, it is impossible or difficult to detect it reliably, so it is impossible or difficult to detect the presence or absence of a defect using conventional defect detection methods that utilize only level fluctuations of the reflected beam. However, according to the present invention, which also utilizes the difference signal S2, that is, the shape change of the reflected beam, it is possible to easily and reliably detect any of the cases shown in FIGS. 5(A) to 5(C).

The defect detector 18 in FIG. 3 has a sum signal S! This method uses both the sum signal S1, the difference signal S2, and the defect signal S2, but as is clear from the explanation so far, the sum signal S1, the difference signal S2, and the defect signal DS form a pulse signal with the same width in principle. Therefore, even if only the difference signal S2 is used instead of the defect signal DS, information regarding the defect, such as the presence or absence of a defect, the size of the defect, and the state of the defect, can be detected.

When detecting information regarding a defect using the difference signal S2, the third adder 26, first waveform shaper 28, and OR circuit 30
is no longer necessary, and the storage device of the defect status determiner 32 can be halved, so the overall configuration can be simplified. The method of determining the presence or absence of a defect and its condition using only the difference signal S2 is as follows:
Since this is clear from the above-described determination method using the sum signal Sl and difference signal S2, a detailed explanation thereof will be omitted.

FIG. 6 shows another embodiment of the invention. In the embodiment shown in FIGS. 1-4, the inspection beam 1
5 is shown, but in this case, since there is only one inspection beam, it takes time to scan the entire surface of the disk 11, and there is a problem that defect inspection takes time. The embodiment shown in FIG. 6 aims to shorten the defect inspection time by using a plurality of inspection beams.

A suitable multiple inspection beam generator used in this embodiment is, for example, the multiple inspection beam generator disclosed in the same application filed by the same applicant. To simply explain the configuration of this multiple inspection beam generator with reference to FIG. 6, in the figure, He
-N e The light projected from the light source 41 such as a laser is split by a light distribution 842 and guided to the light projection/reception head 44 by a plurality of optical fibers 43, respectively. A plurality of optical focusing systems 45 are provided within the light emitting/receiving head 44 .

Each optical focusing system 45 converts the light from the optical fiber 43 into parallel light using a collimator lens 46 integrally attached to the optical fiber 43, and outputs the light into parallel light.Furthermore, after being reflected by a half mirror 47A, a convex lens 47B converts the light into a circle of an appropriate diameter. The shape inspection beam 48 is focused and projected onto the disk 11. Each inspection beam reflected from the disk 11, that is, each reflected light beam 49, spreads out again after passing the focal point and reaches the light emitting/receiving head.

The light is incident on a plurality of photodetectors 50 provided at 44.

The configuration of the photodetector 50 is the same as the beam detector 1 of the above-mentioned embodiment.
In addition, since the defect detector (not shown) and its operation for detecting information regarding the defect, such as the presence or absence, size, and condition of the defect, are the same as in the previous embodiment, a description thereof will be omitted. .

In the embodiment of FIG. 6, the disk 11 is rotated,
Furthermore, by scanning the radiation emitting/receiving head 44 in the radial direction of the disk 11, or by fixing the emitting/receiving head 44 and moving the disk 11 in the radial direction, only the radial section up to the next inspection beam can be scanned. In this way, the entire surface of the disk 11 can be inspected in a spiral manner. for example,
If N inspection beams are used, defect inspection can be completed in 1/N of the time required using one inspection beam.

Further, since a plurality of inspection beams are ordered by distributing one laser light source using a plurality of optical fibers, the multiple inspection beam generator can be simplified.

〔Effect of the invention〕

As explained above, according to the present invention, defects are detected by capturing both the level change and the shape change, or the shape change, of the reflected beam caused by a defect existing on the disk. It is possible to easily and reliably detect the presence or absence of defects due to shallow scratches, small scratches, etc., which could not be detected using conventional defect detection methods that capture only level fluctuations. In addition, the state of defects can be detected easily and reliably, and the state of all defects present on the disk can be detected in detail, so that the cause of the defect can be quickly and reliably investigated. Furthermore, the use of multiple inspection beam generators can significantly reduce defect inspection time.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of an embodiment of the present invention, Fig. 2 is an explanatory diagram of an example of a beam detector used in the embodiment, and Fig. 3 is an explanatory diagram of an example of a defect detector used in the embodiment. 4 is an explanatory diagram of operation waveforms of the same embodiment, FIG. 5 is an explanatory diagram of specific experimental data according to the same embodiment, and FIG. 6 is an explanatory diagram of another embodiment of the present invention. 11...Disk, 12...Spindle, 13...
・Inspection beam generator, 14A... Focusing system, 14B...
- Half mirror 115... inspection beam, ]6... reflected beam, 17... beam detector, 18... defect detector, 19... detection element, 20... preamplifier, 2
1... Current/voltage converter (CV converter), 22...
Preamplifier, 23... Arithmetic unit, 24... First adder, 25... Second adder, 26... Third adder, 27
...Subtractor, 28...First waveform shaper, 29...
2nd waveform shaper, 3o... OR circuit, 31... Defect determiner, 32... Defect state determiner, 33... Clock source for determination, and 41... Laser light source, 42...・・・
Optical distributor, 43... Optical fiber, 44... Light emitting/receiving head, 45... Optical focusing system, 46... Collimator lens, 47A... Half mirror 147B... Convex lens, 48...・Inspection beam, 49...Reflected light, 50
...Photodetector.

Claims (8)

[Claims] (1) A test beam with a predetermined cross-sectional shape is projected onto a disk constituting a recording medium, and a reflected beam of the test beam from the disk is captured to detect a change in shape that occurs in the cross section of the reflected beam. A non-contact defect detection method for a recording medium, characterized in that information regarding a defect existing in a disk is detected based on a shape change signal. (2) A non-contact defect detection method for a recording medium according to claim 1, wherein the inspection beam is projected at a plurality of different positions in the radial direction of the disk. (3) Projecting an inspection beam with a predetermined cross-sectional shape onto a disk constituting a recording medium, capturing the reflected beam of this inspection beam from the disk, and detecting changes in the level of the reflected beam and changes in shape that occur in its cross section. A non-contact defect detection method for a recording medium, characterized in that information regarding a defect existing in a disk is detected based on both the detected level change signal and shape change signal. (4) A non-contact defect detection method for a recording medium according to claim 3, characterized in that the inspection beam is projected at a plurality of different positions in the radial direction of the disk. (5) A disk constituting a recording medium, a test beam generating means for projecting a test beam with a predetermined cross-sectional shape onto the disk, and a plurality of detection elements that capture and detect the reflected beams of the test beam from the disk, respectively. beam detection means for generating a signal; logical operation means for generating a shape change signal corresponding to a change in the shape of the reflected beam by performing a logical operation on the detection signals from the plurality of detection elements; 1. A non-contact defect detection device for a recording medium, comprising means for detecting information regarding defects existing in the recording medium. (6) Non-contact defect detection of a recording medium according to claim 5, wherein the inspection beam generating means projects an inspection beam at a plurality of different positions in the radial direction of the disk. Device. (7) A disk constituting a recording medium, a test beam generating means for projecting a test beam with a predetermined cross-sectional shape onto the disk, and a plurality of detection elements that capture and detect the reflected beams of the test beam from the disk, respectively. a beam detection means for generating a signal; and a logical operation of the detection signals from the plurality of detection elements to generate a level change signal corresponding to a change in the level of the reflected beam and a shape change signal corresponding to a change in the cross-sectional shape of the reflected beam. A non-contact defect detection device for a recording medium, comprising a logic operation means and a means for detecting information regarding a defect existing in a disk based on both the level change signal and the shape change signal. (8) Non-contact defect detection of a recording medium according to claim 7, wherein the inspection beam generating means projects an inspection beam at a plurality of different positions in the radial direction of the disk. Device.