JPH0877611A - Reference disk for optical system calibration - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a reference disc for optical system calibration that can accurately stipulate the defect detection accuracy and the reflectance of the defect area according to the direction and calibrate the optical system of the optical disc defect inspection apparatus. To aim. A defect pattern 2 is formed on a signal reading surface side 1a of a protective film layer 1 on which a laser beam is incident. A so-called pit 3 is formed on the protective film layer 1 on the signal reading surface side 1a.
Also, a projection portion called a is formed. Λ / 4 of the wavelength of the laser light incident from the pit surface 3a at the top of this pit
The area depressed by the amount is called a land. In this way, the defect pattern is formed in the same layer as the layer in which the pits 3 and the lands 4 are formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reference disc for calibrating an optical system, which is used for calibrating an apparatus for inspecting a defect generated in an optical disc in manufacturing the optical disc.

[0002]

2. Description of the Related Art Since an optical disk can store a large amount of information, it is used as a storage medium for recording image information, database information and the like. One optical disc has a large capacity as compared with the storage capacity of a conventional magnetic recording medium or the like, and high processing accuracy is required. Since the fine processing is performed in this manner, various inspections are performed at the time of manufacturing in order to maintain high quality of the optical disc. Therefore, the optical disk provided to the user is a product that has been subjected to various kinds of strict inspections at the time of manufacture. There is a defect pattern inspection apparatus as an apparatus for inspecting an optical disk to be inspected for the presence or absence of defects as one of the inspections performed during manufacturing of an optical disk.

An optical disk defect inspection apparatus in an optical disk manufacturing line detects the reflected light of the laser beam applied to the signal reading surface side of the optical disk to be inspected, and detects the signal pattern of the defect generated in the optical disk due to, for example, a scratch. The presence or absence of defects is determined by comparison. In order to make this comparison, the optical disk defect inspection apparatus calibrates the apparatus using a reference disk for optical system calibration in which a known defect pattern is formed in advance. The reference disc for calibrating the optical system is commercially available from, for example, ABEX.
For example, in a reference disc for calibrating an optical system manufactured by ABEX, the above-described defect pattern is arranged on the signal reading surface side of the disc. Further, the shape of the defect pattern is formed so as to be parallel to the circumferential direction of the optical disc. In the reference disc, a defect pattern is formed in a black or scratched pattern on the defect pattern formation region, for example, the disc surface.

[0004]

By the way, when the optical disc defect inspection apparatus calibrates using the above-mentioned optical system calibration reference disc, as shown in FIG. 14, for example,
Even if there is a scratch on the surface of the disc on the signal reading surface side, if the size of the laser beam LB passing through this surface is larger than the scratch IP, the irradiated laser beam LB is transmitted to the base surface 1a for signal reading. I will end up. As a result, the optical disc defect inspection apparatus, when using this optical system calibration reference disc, is unlikely to affect the return light reflected by the pit surface 3a, and the size of the flaw IP is also affected by the light interference. The amount of reflected light may not be accurate. Furthermore, since this optical system calibration reference disk is a defect pattern formed on the disk surface 11a, it may be damaged due to aging.

Further, the defect pattern formed on the optical system calibration reference disk has a pattern array in which the defect pattern is aligned parallel to the circumferential direction. This pattern array is an array for rotating and viewing the reference disc for optical system calibration, but nothing can be specified for detection of scratches extending in the direction perpendicular to the circumferential direction, that is, the radial direction of the disc. It will be.

Further, since the reflectance of the defective area in the optical system calibration reference disk is not specified in the conventional reference disk, the conventional reference disk also has a problem as the reference disk in this respect. .
Therefore, the present invention has been made in view of the above-mentioned circumstances, and calibrates the optical system of the optical disc defect inspection apparatus by accurately defining the detection accuracy of a defect and the reflectance of a defect area according to the direction. It is an object of the present invention to provide a reference disc for calibrating an optical system.

[0007]

An optical system calibration reference disk according to the present invention is an optical system calibration reference disk used for calibration of an apparatus for inspecting a defect generated in an optical disk during manufacturing of the optical disk. The feature is that a defect pattern is formed in the pit formation layer on the side.

Here, the defect patterns are arranged at regular intervals in the radial direction of the disc, and for example, the recording area of the disc is divided into 15 equal intervals in the radial direction from the inner circumference side to the outer circumference side as constant intervals. Form. As for the shape of this defect pattern, for example, the width in the shape is set to 50 μm as the size in which the aspect ratio is changed, and the length is set to 1 μm and 5 μm in order from the inner peripheral side.
After that, 10 pieces are increased from 10 μm to 100 μm by 10 μm, and the last two lengths are set to 200 μm and 1 mm, respectively. Each length may be set in the circumferential direction or the radial direction of the optical disc.

In the area where the defect pattern is formed, the reflectance with respect to the incident light applied is made different from that in the other areas. For this reason, a dielectric multilayer film of chromium or the like is used as a black spot film. The black spot film made of chromium is uniformly formed by applying dielectrics in multiple layers by etching or the like.

[0010]

The reference disc for calibrating the optical system according to the present invention has a defect pattern formed in the pit forming layer on the signal reading surface side of the optical disc to enhance the optical correlation with the optical disc to be measured. The detection accuracy is improved compared to the detection accuracy of. By arranging the defect patterns in the radial direction of the disc with the aspect ratio changed at regular intervals, the defect pattern is generated at each position in the radial direction of the optical disc in the circumference of the optical disc, that is, in the rotation direction or the radial direction of the disc. The accuracy of detection for scratches or the length of scratches is specified.

In the defect pattern formation region, the reflectance with respect to the incident light applied is made different from that of the other regions, whereby the defect region is accurately defined and the recognition of the defect region is improved. Defect patterns are formed by coating dielectric layers in multiple layers, so that, for example, when inspecting a reflection type optical disk, the film thickness is controlled to reflect only light of a specific wavelength, and the amount of reflected light is controlled to allow transmission. When inspecting a type of optical disc, the optical system is calibrated based on the detected light amount of the transmitted light amount which is inspected at a wavelength other than the specific wavelength and is made a non-reflection region and attenuated.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an optical system calibration reference disk according to the present invention will be described below with reference to the drawings.
Here, the reference disc for optical system calibration is a defect pattern which is preliminarily provided to calibrate an optical system of an optical disc defect inspection apparatus for inspecting an optical disc to be measured, that is, a light incident system and a light emitting system. It is a disc.

On the reference disc for calibrating the optical system, defect patterns having a shape in which the aspect ratio is changed at regular intervals are arranged in the radial direction of the disc. This arranged area is a data recording area on a normal optical disk, that is, an area corresponding to the area DT shown in FIGS. As the defect pattern, for example, two patterns are provided as shown in FIG. One defect pattern is a first pattern whose length is changed so as to be parallel to the circumferential direction of this disc shown in the region DP1, and another defect pattern is the radial direction of this disc shown in the region DP2. The second pattern has different lengths. In both patterns, a defect pattern is formed and arranged one by one in an area obtained by dividing the data recording area at equal intervals from the center of the disc toward the outer peripheral direction.

The defect pattern will be briefly described with reference to the schematic diagrams of FIGS. 2 and 3 in which the essential parts of the first pattern and the second pattern are enlarged, respectively. These schematic diagrams show pattern shapes by ignoring the equally spaced scales. The first pattern of FIG. 2 is the area DP1 shown in FIG. 1A, and the second pattern of FIG. 3 is the area of FIG.
The patterns of the area DP2 shown in FIG. This first pattern is formed at this radial position by a quadrilateral (mainly rectangular) pattern that is parallel to the concentric circles at the radial position of the disk forming this pattern. Therefore, each pattern has the same length A corresponding to the width of the quadrangle shown in FIG. 2, and is changed according to the position where the other length B of the quadrangle is formed.
Specific numerical values will be described later in detail.

Further, the second pattern forms a quadrilateral pattern which is changed in the radial direction. Also in this case, the length C corresponding to the width of the quadrangle shown in FIG. 3 is set to be the same for all the patterns, and the length D of the other is gradually increased from the inner peripheral side to the outer peripheral side, for example. It is set. Specific numerical values will be described later in detail. Next, a layer forming a defect pattern in this optical system calibration reference disk will be described with reference to FIGS.

The reference disc for calibrating the optical system is shown in FIG.
When cut along the fracture line X shown in, the cross section becomes as shown in FIG. FIG. 3 is an enlarged view of the position corresponding to the region DP2 of this cross section. In the optical system calibration reference disk, as shown in FIG. 4, for example, a defect pattern 2 is formed on the signal reading surface side 1a of the protective film layer 1 on which the laser light is incident. A protrusion called a pit 3 is also formed on the protective film layer 1 on the signal reading surface side 1a. A region recessed by λ / 4 of the wavelength of the laser light incident from the pit surface 3a at the top of the pit is called a land. In this way, the defect pattern is formed in the same layer as the layer in which the pits 3 and the lands 4 are formed.

Further, in the optical system calibration reference disk, the protective film layer 1 on the signal reading surface side 1a is covered with polycarbonate. As a result, the polycarbonate layer 5 is formed on the protective film layer 1 in the optical system calibration reference disk. In the reference disc for optical system calibration, when the laser beam is incident from the disc surface 6, the laser beam is irradiated onto the pit 3 through the polycarbonate layer 5. Further, a part of the laser light is also applied to the land 4. The reflected light from the pit 3 and the reflected light from this land 4
Since the heights of the surface positions of the pits 3 and the lands 4 are different by λ / 4 of the wavelength of the laser light, a strong portion and a weak portion are generated due to the diffraction phenomenon. The optical disc defect inspection device detects the intensity of the reflected light with an optical head of the optical disc defect inspection device and uses it as a change in the electric signal level.

The size of the laser beam supplied from the optical disk defect inspection device is much larger than the size of the pit 3 because it is not focused on the focus on the disk surface 6. Therefore, even if the disc surface 6 is scratched, the laser light passes through it, and it is difficult to affect the return light reflected by the pit surface 3a. This is because the phenomenon that the intensity of the return light is weak occurs for the first time due to the height of the pits 3 and the lands 4, and therefore scratches are provided on the surface of the disc located on the layer where the pits 3 and the lands 4 are formed. Hard to influence. As a result, it can be seen that the scratch on the disk surface cannot be a fatal defect. In addition to this, because of the influence of light interference and the fact that an accurate reflected light amount cannot be obtained, the size of the scratch that is occurring cannot be accurately known.

Therefore, the reference discs provided so far can cause a fatal defect even if the optical system of the optical disc defect inspection apparatus is adjusted by the defect pattern, that is, the scratch provided on the disc surface. I can't. The reference disk is required to detect not only the above-mentioned defects on the disk surface but also defects on the signal surface. In order to provide the reference disc in which the defects on the signal surface are also taken into consideration, the optical system calibration reference disc of the present invention has the defect pattern 2 formed on the protective film layer 1 on the signal reading surface side 1a where the pits 3 are formed. To do. In this way, the defect of the reference disc is detected, for example, in the case of a reflection type optical disc, assuming that the reflective film is missing, and in the case of a transmission type optical disc, assuming that the pit 3 is missing. When this optical system calibration reference disk is used, a signal amount depending on the size of the missing portion is obtained as a change in the reflected light amount.

Here, the optical system of the optical disc defect inspection apparatus is calibrated using the reference disc for calibrating the optical system. When the optical disc defect inspection device detects a defect in the optical disc to be inspected, the optical disc defect inspection device compares the information such as the size of the defect, that is, the length, with a known defect pattern of the reference disc to obtain accurate detection accuracy. Can be specified in. According to this definition, not only the length of the defect in the rotation direction but also the length of the defect pattern in the radial direction of the disk can be measured.

Further, the optical system calibration reference disk has conventionally been recognized only to the extent that the defective portion is different from the other portions of the disk, and there are many types of defects that actually occur in the optical disk, and the internal defect It was not possible to determine the condition etc. with a uniform regulation. Therefore, in the defect pattern formed on the optical system calibration reference disk, the reflectance from the defect pattern is changed by changing the film thickness of the pattern.

This reflectance is made different from other disk portions by coating a dielectric multi-layered film having a constant dielectric constant in multiple layers. Examples of the dielectric multilayer film include silicon dioxide SiO ₂ and chromium Cr. This dielectric multilayer film has a specific wavelength λ depending on the layer thickness.
Has a property of strongly reflecting only the light and absorbing light in a wavelength region other than the wavelength λ indicated by diagonal lines (see the reflection characteristic curve of FIG. 5). By utilizing this property, it is possible to reflect only the specific wavelength λ and adjust the amount of reflected light by adjusting the film thickness of the defect pattern. In particular, it is effective to use a reflection type optical disk. This defect pattern can also be used for a transmission type optical system calibration reference disk. When the reflective film formed in this region is irradiated with a laser beam having a wavelength other than the wavelength λ, the defect pattern absorbs the incident light, so that the film thickness is adjusted to be similar to the reflective type. The amount of transmitted light can also be adjusted.

Next, a specific example of the defect pattern of the optical system calibration reference disk will be described with reference to FIGS. 6 and 7. Here, the reference disk for calibrating the optical system is made of a material having a condition that the refractive index of polycarbonate is 1.55 at the wavelength λ = 780 nm, that is, the birefringence for so-called SK5 = 0. This optical system calibration reference disk has a base portion made of so-called SK5, and a black spot film is formed as a defect pattern on a signal reading surface where pits of the base portion are formed. Chromium is used as the dielectric used for the black spot film. Figure 6
The optical system calibration reference disk of FIG. 7 is for a transmission type optical disk in which no reflective film is formed. The optical system calibration reference disk is made of a single-sided anti-reflection (AR) material on the base portion and the black spot film. It is coated. A layer of the protective film 5 is formed on this.

This disc has a diameter 2R of 64.8 mm.
Up to the size of, and at least the radius R is applied to a disk having a size of 31.6 mm or more. The length r from the center of the disc to the innermost circumference is 14.5 mm. Each defect pattern will be briefly described. The defect pattern shown here is for a transmissive type without a reflective film. The defect pattern is formed in each area obtained by dividing the area DT from the innermost circumference to the outermost circumference in the radial direction of the disk at 15 equal intervals.

In the case of FIG. 6, a defect pattern is formed in each area along the circumference. The defect pattern to be formed has a shape in which the aspect ratio is changed, for example, the width in the shape is set to 50 μm, and the length is set to 1 μm and 5 μm in order from the inner circumference side. . After that, 10 pieces were increased by 10 μm from 10 μm to 100 μm, and the last two lengths were 200 μm and 1 m, respectively.
Set to m. These defect patterns are arranged at the midpoint of each interval.

In the case of FIG. 7, as in the defect pattern shown in FIG. 6, all the widths in the shape are set to 50 μm, and the lengths of the two are 1 μm and 5 μm respectively from the inner peripheral side.
Set to. Subsequent defect patterns are 10 μm to 100 μm
The last two lengths are set to 200 μm and 1 mm, respectively, by increasing 10 by 10 μm to m. This defect pattern is formed in the radial direction orthogonal to the defect pattern formed in the circumferential direction of FIG. Further, the defect pattern is arranged so that the midpoint position of each interval and the midpoint of the length of the defect pattern match.

In FIGS. 6 and 7, four defect patterns are shown in a region including 10 in increments of 10 μm in order to simplify the drawings. By forming a defect pattern on the disk surface in this way, not only detection of scratches and stains on the disk surface but also adjustment of the optical disk defect inspection apparatus can be performed assuming defects due to missing reflection. Further, the two defect patterns may be simultaneously formed in one optical system calibration reference disk. Thereby, not only the conventional circumferential direction but also the radial length of the defect can be defined.

By providing a difference in reflectance,
It becomes possible to recognize the defects existing on the disk to be measured, and it becomes possible to easily determine whether or not there is a defect, and it is also possible to measure the defects quantitatively. In this more specific embodiment, the optical system calibration reference disk for the transmission type has been described, but the optical system calibration reference disk is formed as the reflective type to form the above-mentioned defect pattern. By calibrating, the optical disk defect inspection apparatus can also perform the defect detection accuracy and the quantitative defect measurement of the defects generated in the optical disk to be measured.

Next, an optical disk defect inspection apparatus calibrated by this optical system calibration reference disk will be described with reference to FIGS.
This will be described with reference to FIG. This optical disc defect inspection device is a device that detects dust adhering to an optical disc and a scratch formed on the optical disc, and compares the measured degree of failure with a reference value to determine whether it is a non-defective product.

As shown in FIG. 8, for example, the optical disk defect inspection apparatus includes a spindle motor 12 for rotating an optical disk 11 to be measured mounted on a mounting table 10 and a slide motor for moving the spindle motor 12 in a radial direction. 13, a servo circuit 14 for controlling the operations of the spindle motor 12 and the slide motor 13, a laser light emitting circuit 15 for supplying a light emitting signal to a laser light emitting element, and a laser light according to a light emitting signal from the laser light emitting circuit 15. An optical unit 1 having an emitting laser emitting element and an optical system for detecting return light reflected by the surface of the optical disk 11 on the signal reading side or light transmitted through the optical disk 11.
6, an IV amplifier section 17 for amplifying an output signal from the optical unit 16 to an appropriate level, and an IV amplifier section 17
A defect detection circuit 18 for detecting a defect of the optical disk 11 based on an output signal from the optical disc 11, and a center for determining whether or not a defect for the entire circumference is acceptable based on the signal of the defective portion distinguished by the defect detection circuit 18. And an arithmetic circuit (hereinafter referred to as CPU) 19.

The CPU 19 sends, for example, a determination result to the external computer 20 to store data, and processes data on the output signal from the defect detection circuit 18. In this way, the external computer 20
Is an apparatus that supports the optical disc defect inspection by the optical disc defect inspection apparatus. The optical unit 16
There are two types of units depending on whether the optical disk 11 to be inspected has a reflective film or not.

The optical unit 16 has laser elements for emitting a plurality of laser beams arranged in the radial direction of the disc, for example, and emits the laser beams to the optical disc 11. When the optical disk 11 has a reflective film, this optical unit 1
For example, as shown schematically in FIG. 9, laser light 6 is offset by 5 ° slightly oblique to the perpendicular of the optical disk 11 and is incident on the signal reading surface. Optical disc 1
Of the return light reflected from 1, the 0th order light is the optical unit 1
Two photodetectors P _A and P _B in 6 detect. In this way, a plurality of photodetectors P _A and P _B are provided for each laser beam emitted.

The primary light is, for example, the optical unit 16
The photodetector is provided outside the detector. Therefore, one optical system in the optical unit 16 will be described with reference to FIG. This optical unit 16
Emits laser light from, for example, the laser light emitting element LD ₁ in accordance with the light emission signal supplied from the laser light emitting circuit 15. This laser light is collimated through the collimator lens 16a and supplied to the polarization beam splitter 16b. The polarization beam splitter 16b reflects the incident light by 90 ° with respect to the optical path. The polarization beam splitter 16b converts the laser light into circularly polarized light through the λ / 4 plate 16c and makes it enter the reflection film of the optical disk 11 at a slightly oblique angle. Zero-order diffracted light and first-order diffracted light are generated in the return light reflected by the signal reading surface of the optical disc 11.

The 0th-order diffracted light of this is reflected in the direction of the condenser lens 16f. The condenser lens 16f includes the photodetectors P _RA and P _RA .
_The focus is focused on the light receiving surface of _RB . Since the influence of other light is removed and the 0th-order diffracted light is introduced into the optical unit 16, a slit 16g is provided in the housing of the optical unit 16.
Is provided. This slit 16g
Is transmitted to the polarization beam splitter 16h via. The polarization beam splitter 16h divides the reflected 0th-order diffracted light into P-polarized light and S-polarized linearly polarized light, respectively. The polarization beam splitter 16h sends the transmitted light, which has been converted into the light of only the P-polarized component parallel to the incident surface, to the photodetector P _RA . In addition, the polarization beam splitter 16h converts the light into an S-polarized component light that is perpendicular to the incident surface at the junction surface of the prism, bends the optical path at a right angle, and sends the light to the photodetector P _RB .

When the optical disk 11 does not have a reflective film, the optical unit 16 emits laser light from the optical unit 16A arranged on one side of the optical disk 11 to the perpendicular of the optical disk 11, as shown in FIG. It is made to enter the signal reading surface with a slight offset of 5 °. This laser light passes through the optical disc 11 and is detected by the optical unit 16B on the other side. In this case, two photodetectors P _TA and P _TB are provided for each laser beam.

An optical system for one of the laser light emitting elements arranged in the optical unit 16A will be described with reference to FIG. Here, in order to make the optical path offset by 5 ° in FIG. 11 easy to see in FIG. 12, the optical axis of the incident light is drawn along the center. In the optical unit 16A, for example, laser light is emitted from the laser light emitting element LD ₁ according to the light emission signal supplied from the laser light emitting circuit 15. This laser light is sent to the polarization beam splitter 163 via the lenses 161 and 162. The polarization beam splitter 163 reflects the incident light by 90 ° with respect to the optical path. Laser light is emitted by the polarization beam splitter 163.
Circularly polarized light is passed through the λ / 4 plate 164 and is incident on the reflection film of the optical disk 11 at a slightly oblique angle. This optical disc 1
The laser transmitted through 1, that is, the 0th-order diffracted light is sent to the condenser lens 165. The condenser lens 165 is adapted to form an image on the light receiving surfaces of the photodetectors P _TA and P _TB . Further, a slit 166 is provided in the housing of the optical unit 16B in order to introduce the 0th-order diffracted light into the optical unit 16 by removing the influence of other light.

This transmitted light is sent to the polarization beam splitter 167 in the optical unit 16B via the slit 166. The polarization beam splitter 167 divides the transmitted light into linearly polarized waves of P polarization and S polarization, respectively. The polarization beam splitter 167 sends to the photodetector P _TA the transmitted light that has been converted into the light of only the P-polarized component parallel to the incident surface. Further, the polarization beam splitter 167 turns the light path of the S-polarized light component, which is perpendicular to the incident surface at the junction surface of the prism, into a light path, and sends it to the photodetector P _TB .

As described above, the optical unit 16 includes the reflection type photodetectors P _RA and P _RB , and the transmission type photodetectors P _TA and P _TA .
The output signal from P _TB is output to the IV amplifier unit 17.
This output signal contains information regarding the defect of the optical disk 11. The IV amplifier section 17 amplifies these received light signals to appropriate signal levels and supplies them to the defect detection circuit 18.

The defect detection circuit 18 performs the calculation result based on the preset threshold level TH and the supplied signal level regardless of the case of the reflection type optical disk 11 or the transmission type optical disk 11. Compare with the value of. As shown in FIG. 13 in the subsequent stage, when the value of the low calculation result is equal to or lower than the threshold level TH, it is determined that there is a defect. Further, when a value larger than the threshold level TH is detected, it is regarded as normal. The defect detection circuit 18 supplies the CPU 19 with the presence or absence of a defect in the area scanned by the optical unit 16 and information quantifying the defect.

The CPU 19 judges the quality of the optical disk 11 to be inspected, for example, based on the number of defects detected from the defect detection circuit 18 and the preset number of times of defect detection. In addition, since it is possible to detect scratches quantitatively, that is, to detect the length and area of defects, etc., it is also possible to determine whether or not the size of one scratch on the optical disk is a fatal defect based on this information. You will be able to.

The operation of this optical disc defect inspection apparatus will be described. First, the optical disk 11 to be measured is placed on the mounting table 10.
Place on top. In response to the “start” command supplied from the external computer 20, the CPU 19 decodes this “start” command and outputs a “spindle motor rotation start” command to the servo circuit 14. In response to this command, the spindle motor 12 starts rotating. When the CPU 19 detects that the spindle motor 12 has reached the specified rotation speed, the “laser emission” command is supplied to the laser emission circuit 15. The laser light emitting circuit 15 supplies a light emission signal as a drive signal to each laser light emitting element in the optical unit 16.

The optical unit 16 includes information about the shapes of the pits 3 and the lands 4 formed on the signal reading surface side of the optical disc 11 while changing the configuration of the optical system according to the presence or absence of the reflection film of the optical disc 11. Respectively detect reflected light and transmitted light by photoelectric conversion. The optical unit 16 supplies the detection signal to the defect detection circuit 18 via the IV amplifier section 17.

The defect detection circuit 18 detects the presence / absence of a defect of the optical disk 11 while performing arithmetic processing and the like using the supplied signal. For example, in the defect detection circuit 18, when the optical system calibration reference disk on which the defect pattern is arranged is used, for example, waveforms as shown in FIG. 13 are obtained. In the waveform corresponding to the defect pattern obtained from the conventional reference disk, there are many phenomena in which the waveform violates at the position of the defect pattern as shown in FIG. When the presence / absence of a defect (defect) is discriminated by using this waveform at a predetermined threshold level TH, a waveform as shown in FIG. 13B is obtained. This waveform ramp-up phenomenon (eg, Figure 1
Due to the occurrence of the region L ₁ and the region L ₂ in 3 (b), the information regarding the defect such as the length of the defect pattern cannot be accurately obtained. Such a phenomenon is mainly caused by uneven coating when forming a black spot for forming a non-reflective area, and an optical system was adjusted by using such a disk as a reference disk. It was caused by something.

However, in the reference disc for optical system calibration of the present invention, the surface of the black spot can be uniformly formed by forming the dielectric multilayer film by using, for example, etching treatment. According to the optical disc defect inspection apparatus calibrated by using the optical system calibration reference disc, the waveform corresponding to the defect pattern can be obtained as shown in FIG. 13C without the conventional ramp-up phenomenon. In addition, this waveform can be obtained such that the threshold level TH is almost exactly passed at the start end and the end end of the defect pattern. Therefore, the discrimination signal shown in FIG. 13D can improve the accuracy of defect detection.

The defect detection circuit 18 sends information about the defect detection to the CPU 19. The CPU 19 uses the defect detection circuit 1
The defect inspection in the entire circumference corresponding to the signal reading area of the optical disc 11 is performed while accumulating the sampling supplied when there is a defect in 8. By the defect inspection by the CPU 19, the quality of the optical disk 11 is finally judged. This C
In the PU 19, not only the above-described mere quality judgment based on the number of defects with respect to the whole, but also a multi-faceted defect inspection by quantitatively considering the size of the defect and categorizing into various inspection types such as whether or not the defect is fatal. It can be carried out. In addition, the CPU 19
Also performs system control of the entire optical disc defect inspection device while communicating with the external computer 20. The external computer 20 stores defect signals and optical disc defect information.

With the above-mentioned structure, it is possible to detect a defect in a layer for reading a signal, which is more resistant to aging than a conventional reference disk, and it is possible to improve detection accuracy. As a result, the quality of non-defective optical disks to be shipped can be further improved. Furthermore, by preparing a plurality of similar optical systems, it is possible to simultaneously measure the optical disks to be measured for each area and shorten the measurement time, and it is possible to provide a more preferable configuration.

Further, in the defect pattern formation region, the reflectance with respect to the incident light applied is made different from that of the other regions to accurately define the defect region and improve the recognition of the defect region, thereby improving the detection accuracy. Not only can information on various defect inspections be obtained, but the quality of inspections can be improved. The defect pattern can be formed by coating dielectrics in multiple layers, controlling the film thickness to reflect only light of a specific wavelength, and controlling the amount of reflected light, so that a defect can be inspected with a desired amount of light. The degree of freedom can be increased. Further, the waveform quality of the defect detection signal can be improved and the detection accuracy can be improved.

[0048]

According to the reference disc for calibrating an optical system according to the present invention, it is possible to detect a defect in a layer for reading a signal, which is more resistant to aging than a conventional reference disc, and to improve detection accuracy. You can As a result, the quality of non-defective optical disks to be shipped can be further improved.

Further, by preparing a plurality of similar optical systems, it is possible to simultaneously measure the optical disc to be measured for each area and shorten the measurement time, and it is possible to provide a more preferable configuration. . Further, the defect pattern forming region not only improves the detection accuracy by differentiating the reflectance with respect to the irradiated incident light from other regions to accurately define the defect region and improve the recognition of the defect region. Information on various defect inspections can be obtained, and the quality of inspection can be improved.

A defect pattern can be inspected with a desired light quantity by forming dielectric layers in multiple layers, controlling the film thickness to reflect only light of a specific wavelength, and controlling the quantity of reflected light. , The degree of freedom of inspection can be increased.
Further, the waveform quality of the defect detection signal can be improved and the detection accuracy can be improved.

[Brief description of drawings]

FIG. 1 is a plan view seen from the signal reading surface side of a reference disc for calibrating an optical system according to the present invention, and a sectional view taken along a broken line.

FIG. 2 is a schematic enlarged view of a main part of a defect pattern formed on the reference disc for optical system calibration.

FIG. 3 is a schematic enlarged view of a main part of a defect pattern formed on the optical system calibration reference disk.

FIG. 4 is a schematic enlarged sectional view of a main part of a defect pattern formed on the reference disc for optical system calibration.

FIG. 5 is a graph showing a reflectance characteristic curve with respect to wavelength of a material used for a defect pattern of the optical system calibration reference disk.

FIG. 6 is a schematic plan view showing a more specific example of the case where defect patterns of the optical system calibration reference disk are arranged in the circumferential direction.

FIG. 7 is a schematic plan view showing a more specific example when the defect patterns of the optical system calibration reference disk are arranged in the radial direction.

FIG. 8 is a block diagram showing a schematic configuration of an optical disc defect inspection apparatus that calibrates with the optical system calibration reference disc.

FIG. 9 is a diagram showing a schematic relationship between a reflection type optical unit used in the optical disc defect inspection apparatus and an optical disc.

FIG. 10 is a diagram schematically showing a configuration of an optical system used when the optical disc is a reflection type.

FIG. 11 is a diagram showing a schematic relationship between a transmission type optical unit used in the optical disc defect inspection apparatus and an optical disc.

FIG. 12 is a diagram schematically showing a configuration of an optical system used when the optical disc is a transmission type.

FIG. 13 is a diagram showing a signal waveform obtained when the optical disc defect inspection apparatus is calibrated using the optical system calibration reference disc and the conventional reference disc.

FIG. 14 is a cross-sectional view illustrating a state when performing calibration using a conventional reference disk.

[Explanation of symbols]

 1 Protective Layer 2 Defect Pattern 3 Pit 4 Land 5 Polycarbonate Layer 3a Pit Surface

Claims (4)

[Claims] 1. A reference disc for calibrating an optical system, which is used for calibrating an apparatus for inspecting defects generated in an optical disc during manufacturing of the optical disc, wherein a defect pattern is formed in a pit forming layer on a signal reading surface side of the optical disc. Reference disc for optical system calibration. 2. The reference disc for calibrating an optical system according to claim 1, wherein the defect patterns are arranged in a shape in which the aspect ratio is changed at regular intervals in the radial direction of the disc. 3. The optical system calibration reference disk according to claim 1, wherein the defect pattern forming region has a reflectance with respect to the incident light that is irradiated different from that of the other regions. 4. The reference disc for optical system calibration according to claim 1, wherein the defect pattern is formed by coating dielectrics in multiple layers.