JP2001208517A - Optical disc inspecting instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disc inspecting instrument which accomplishes an inspection to determine whether the width and depth of a track groove of an inspection disc meet an allowable range or not based on the results obtained from the detection of primary to higher order diffraction light by a photo detector as generated when the inspection disc is irradiated with an inspection laser. SOLUTION: An inspecting instrument 1a performs an inspection to determine whether the width P1 and the depth D of a track groove 6 in an optical disc 2 having a side 2b with the groove 6 formed at a pitch P are within an allowable range or not and is provided with an irradiation means 4, a photo detector 7, a transfer means, a judging means and control means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk inspection apparatus for inspecting whether or not a groove width and a depth of a track groove formed on an optical disk are within an allowable range.

[0002]

2. Description of the Related Art In the following, what is inspected by an optical disk inspection apparatus is an optical disk substrate or an optical disk master (glass master, glass master) for copying a large number of such optical disk substrates. Grooves (grooves, track grooves) are formed concentrically or spirally on the optical disk substrate and the optical disk master at a predetermined track pitch. In addition, a dielectric layer, a recording layer, a dielectric layer, a reflective layer,
A recordable optical disk can be obtained by sequentially forming the protective layers. Furthermore, a reproduction type optical disk can be obtained by sequentially forming a reflective layer and a protective layer on the signal surface of the optical disk substrate. By irradiating the recording or reproducing laser beam to the track grooves (grooves) or between the track grooves (lands) formed on the signal surface from the signal surface side or the reading surface side opposite to the signal surface, the information signal is irradiated. Can be recorded or reproduced.

FIG. 4 is a diagram for explaining a configuration of a main part of a conventional optical disk inspection device, and FIG. 5 is a diagram for explaining an inspection operation of the conventional optical disk inspection device. FIG. 6 is a diagram for explaining the state when θ <90 °, and FIG. 6 is a diagram for explaining the inspection operation of the conventional optical disk inspection device. It is a figure for explaining the state when it became.

[0004] In the mastering process of the glass master as the optical disk master, the track grooves are cut by a master recording device (cutting machine) on a glass master (resist master) coated with a resist. At this time, the recording is performed by the exposure power of the laser beam. Thereafter, by developing, a glass master having a track groove formed thereon is manufactured. In the production of this glass master, it is required that the track pitch of the track grooves be formed with high precision. Therefore, stable cutting can be maintained by controlling the exposure power and controlling the groove width and the groove width.

Therefore, an optical disk inspection device, which will be described later, is required as an inspection device for managing the groove width of the track groove shape. By feeding back a highly reliable inspection measurement value at the time of cutting, the groove can be formed with higher accuracy. The width can be formed. Here, a conventional optical disk inspection apparatus will be described with reference to the drawings.

As shown in FIG. 4, a groove shape inspection apparatus 1 which is a conventional optical disk inspection apparatus has a laser beam irradiating means 4 for emitting an inspection laser beam 3, a mirror 5, and a light receiving device having photodetectors 7a, 7b and 7c. An element 7 and an arithmetic processing means 8 are provided. In FIG. 4, reference numeral 2 denotes an optical disc master on which a track groove to be inspected is cut;
Is a track groove.

[0007] The laser beam irradiating means 4 irradiates the laser beam 3 perpendicularly to one surface (incident surface) 2a of the master optical disk 2 via the mirror 5. As a result, the laser beam 3 passes through the optical disk master 2 and then travels straight from the other surface (emission surface) 2b of the optical disk master 2 to be emitted. Thereby, the zero-order diffracted light d ₀ of the laser light 3 from the emission surface 2b,
The first order diffracted light d ₁ and the higher order diffracted light (second order diffracted light d ₂ ) are emitted. Here, 1 is order diffracted light d ₁ occurs clearly, for the second-order diffracted light d _2, that although the contour can recognize somehow, the high-order diffracted light d ₃ to d _n of the third-order after its contour I can hardly see it. The first-order diffracted light d ₁ is inclined with respect to the _zero- order diffracted light d _{0 at} an angle θ ₁
And the second-order diffracted light d ₂ is emitted with an inclination angle θ ₂ with respect to the _zero- order diffracted light d ₀ .

[0008] photodetector 7a, 7b, 7c is a 0-order diffracted light d _0, 1 order diffracted light d _1, 2-order diffracted light d ₂ emitted from the emitting surface 2b of the optical disk original 2, which can be incident at right angles to the light receiving surface Position. Thus, the photodetectors 7a, 7b, 7c are
0-order diffracted light d ₀ , first-order diffracted light d ₁ , and second-order diffracted light d ₂ emitted from the emission surface 2b corresponding to the irradiation range position of the spot light of the laser light 3 formed on the incident surface 2a. The received light signal is output to the arithmetic processing means 8.

The arithmetic processing means 8 measures the intensity level of each light receiving signal corresponding to the _0th-order diffracted light d ₀ , the 1st-order diffracted light d ₁ , and the 2nd-order diffracted light d ₂ . The 0-order diffracted light d ₀ for 1 intensity ratio of the diffracted light d ₁ (first intensity ratio), and obtains the 0 intensity ratio of the second-order diffracted light d ₂ for order diffracted light d ₀ (second intensity ratio). The arithmetic processing means 8 performs the first
The value of the track pitch P of the track width 6 (the length of the track groove in the disk radial direction) and the value of the depth D of the track width 6, which are uniquely determined according to the two values of the intensity ratio and the second intensity ratio. (Thickness of a resist layer serving as a carved track groove). by this,
The arithmetic processing means 8 converts the two values of the first intensity ratio and the second intensity ratio stored in the data table into the first intensity ratio based on the light receiving signals supplied from the photodetectors 7a to 7c. By comparing the two values with the second intensity ratio, the values of the track pitch P and the depth D can be derived from the collated values.

FIG. 5 is a view for explaining a state in which the angle θ of generation of higher-order diffracted light with respect to 0-order diffracted light is θ <90 °. The same components as those described above are denoted by the same reference numerals, and description thereof will be omitted.

The glass master, which is the optical disk master 2, is formed by forming a resist film having a predetermined thickness on a well-polished glass plate, exposing the resist film with a laser beam from a cutting machine, and developing the resist film. Be produced. In the manufactured glass master 2, the exposed and developed portions of the resist film are removed, and the other portions are left with the resist film remaining. Therefore, the removed portions serve as the track grooves 6. Such track grooves 6 are formed in a plurality (at a constant interval track pitch P) in the radial direction of the glass master.

The laser light 3 emitted from the laser light irradiating means 4 and applied to the optical disk master 2 is not condensed on the incident surface 2a and is formed on the incident surface 2a because it does not pass through an objective lens or the like. The spot diameter is 1-2 mm. Accordingly, a plurality of track grooves 6 are present at a predetermined track pitch P on the emission surface 2b corresponding to the spot area of the laser beam 3.

Thus, the incidence surface 2a of the optical disk master 2
When the laser light 3 is irradiated upward, the laser light 3 is transmitted through the inside of the optical disk master 2 and is guided to the emission surface 2b side. At this time, the laser beam 3 is diffracted on the emission surface 2b because the track grooves 6 formed on the emission surface 2b side function as fine slits.

Laser light 3 transmitted through optical disk master 2
Is the diffracted light d. The diffracted light d is 0-order diffracted light d ₀ which is transmitted at right angles to the exit surface 2b of the track groove 6, from the diffracted light d ₀ perpendicular, and a 0-order with respect to the tangential direction of the track grooves 6 as viewed from the irradiation direction predetermined inclination angle theta ₁ inclined by 1-order diffracted light d _1, occurs as the inclination angle theta ₂ inclined second order in the same direction diffracted light d ₂ ~n order diffracted light d _n.

Each order diffracted light d (first order diffracted light d ₁ , second order diffracted light d ₂ , n order diffracted light d _n ) other than the ₀ order diffracted light d ₀ has a plus side (−) and a minus side (+), each of which is symmetric with respect to zero-order diffracted light d _0. The first-order diffracted light d ₁
Although clearly occurs, for the second-order diffracted light d _2, that although the contour can recognize somehow, the high-order diffracted light d ₃ to d _n of the third-order after its contour can not be hardly visible.

The inclination angle θ of each of the above-mentioned diffracted lights can be expressed by the following [Equation 1].

(Equation 1) Where λ: wavelength of laser beam 3 P: track pitch n: order

[0017] than the [Formula 1], when the laser wavelength λ is constant, the type of the material of the optical disc master 2, the track pitch P of the track grooves 6, the inclination angle theta ₁ ~ to each order diffracted light d ₁ to d _n occurs θ _n will be different.

For example, a CD using λ = 690 nm
(Compact disc) (Track pitch P = 1.6μ)
In the case of the optical disk substrate of m), the respective inclination angles θ _{1 to} θ ₃ by the respective order diffracted lights d _{1 to} d ₃ are as shown in Table 1.

[0019]

[Table 1]

According to Table 1, each of the inclination angles θ ₁ to θ ₃ is θ ₁
Θ ₃ <90 °, and as shown in FIG.
Appears on the exit surface 2b side. The same can be said even if the laser wavelength λ changes.

FIG. 6 is a diagram for explaining a state in which the generation angle θ of the higher-order diffracted light with respect to the zero-order diffracted light is θ> 90 °. The same components as those described above are denoted by the same reference numerals, and description thereof will be omitted.

In the system having the above-mentioned structure (FIG. 5), the optical disk substrate of the CD is replaced with a DVD (digital video disk or digital versatile disk).
(Track pitch P = 0.74 μm) and the laser wavelength λ is constant (λ = 690 nm), the inclination angles θ _{1 to} θ ₃ of the respective order diffracted lights d _{1 to} d ₃ are as shown in Table 2. become.

[0023]

[Table 2]

[0024] [Table 2] of the inclined angle theta ₁ through? ₃ by the inclination angle theta _2, theta ₃ is theta _2, theta _3> is approximately 90 °. This is the incident surface 2a of the optical disk master 2 as shown in FIG.
It can be seen that both appear on the side and the exit surface 2b side. Therefore,
Each of the inclination angles θ _{1 to} θ ₃ is approximately 90 ° (θ _{1 to} θ ₃ > 9).
0 °) is determined by the relational condition of the combination of the wavelength λ of the laser beam and the track pitch P according to the above [Equation 1]. Until now, in the case of an optical disk substrate of a CD (P = 1.6 μm), as can be seen from Table 1, each of the above inclination angles θ _{1 to} θ ₃ does not exceed approximately 90 °, and the optical disk substrate of this CD This was not a problem because it occurred in the in-plane range on the incident surface 2a side of the optical disk master 2 for duplicating the data, and the measurement was possible.

However, in the case of a DVD (P = 0.74 μm) optical disk substrate, as can be seen from Table 2, each of the above-mentioned conditions depends on the combination of the wavelength λ of the laser beam 3 and the track pitch P. Some of the inclination angles θ _{1 to} θ ₃ exceed about 90 °. This DVD
In order to vertically irradiate the incident surface 2a side of the optical disk master 2 for duplicating the optical disk substrate, each order diffracted light d
_{1 to} d ₃ are near the position where the optical disk master 2 is located, that is, at an angle (approximately 90 °) at which the size and installation range of the photodetectors 7a, 7b, 7c cannot be measured, and not at the exit surface 2b side of the optical disk master 2. The optical disk master 2, the laser beam irradiating means 4, and the photodetectors 7 a, 7 b, and 7 c appear on the opposite incident surface 2 a side.
Due to the structural surface described above, it is impossible to perform measurement on the exit surface 2b side of the optical disk master 2.

Further, if the wavelength of the laser beam 3 is shortened by the relational condition of the combination of the wavelength λ of the laser beam 3 and the track pitch P, the inclination angle θ can be reduced to about 90 °.
Can be suppressed within a range not exceeding the value, but it is not desirable in relation to the sensitivity of the resist.

[0027]

The above problems can be summarized as the following (1) to (4). (1) Due to the vertical irradiation of laser light and the fixation of the light-receiving element (detector), even if it is possible to measure only the first-order diffracted light, it may not be possible to measure the higher-order diffracted light after the second-order diffracted light. there were. (2) The first-order diffracted light and the second-order diffracted light shift depending on how the glass disc as the optical disc master is placed, causing an offset, which may cause a variation in measured values. (3) The influence of the drift of the optical axis of the laser light caused variations in the measured values. (4) In the system configuration of the conventional optical disk inspection device,
The mechanical structure was large and required a large space, and thus it was necessary to reduce the size.

[0028]

In order to solve the above-mentioned problems, the present invention provides an optical disk inspection apparatus having the following constitutions (1) and (2). (1) As shown in FIG. 1, an optical disk (optical disk master, glass master) 2 having one surface (emission surface) 2b in which track grooves 6 are formed concentrically or spirally at a predetermined track pitch P is provided. An optical disk inspection device (groove shape inspection device) 1a for inspecting whether or not a groove width P1 in the radial direction of the track groove 6 and a depth D of the track groove 6 are within an allowable range; A laser beam irradiating unit 4 for irradiating the surface (incident surface) 2a obliquely with the inspection laser beam 3 at a predetermined incident angle α, and the laser beam irradiating unit 4 located on the other surface 2a side of the optical disk 2; diffracted by the track grooves 6 formed on one surface 2b by emitting zero-order diffracted light d ₀ to high-order diffracted light (first order diffracted light d _1, 2-order diffracted light d ₂₎ 1 of the diffracted light detection hand for detecting the (Light-receiving element, a photodetector)
7 and 0th order diffracted light d _{0 to} higher order diffracted light (first order diffracted light d ₁ ,
A transferring means for transferring the first diffracted light detecting means 7 to a light receiving position capable of receiving the _second-order diffracted light d ₂ ); and a spot light generated on the other surface 2 a when the inspection laser light 3 is irradiated. The one surface 2b corresponding to the irradiation position 2a1
Generated by the track grooves 6 of the upper, 0 high relative-order high-order diffracted light with respect to diffracted light d ₀ (1-order diffracted light d _1, 2-order diffracted light d ₂₎ tilt angle theta ₁ through? ₂ 0-order diffracted light d ₀ by measuring the The intensity ratio of the _second-order diffracted light (first-order diffracted light d ₁ , second-order diffracted light d ₂ ) is determined, and the groove width P1 and the depth D of the track groove 6 are obtained from the intensity ratio.
And determination means for determining whether or not each of the calculated values is within an allowable range; and a higher order diffracted light (first order diffracted light d ₁ , second order diffracted light d ₂ ) with respect to the ₀ order diffracted light d ₀ . When the inclination angles θ _{1 to} θ ₂ exceed 90 °, the incident angle α of the inspection laser beam 3 is changed to change the inclination angle θ ₁
An optical disk inspection apparatus comprising: a control unit that controls the laser beam irradiation unit 4 so that? ₂ is less than 90 degrees. (2) As shown in FIG. 2, one surface (emission surface) 2b in which track grooves 6 are formed concentrically or spirally at a predetermined track pitch P, and an opposite surface to the one surface 2b. It has another surface (incident surface) 2a, which is a surface, and a reflective film (metal film) 2c laminated on the one surface 2b and totally reflecting transmitted light transmitted from the other surface 2a side. An optical disk inspection device (a groove shape inspection device) 10a for inspecting whether or not a groove width P1 and a depth D of the track groove 6 in a radial direction of the track groove 6 of the optical disk 20 are within an allowable range. The other side 2a of
A laser beam irradiating means 4 for irradiating the inspection laser beam 3 obliquely at a predetermined incident angle α, and the other side 2a of the optical disk 20, wherein the inspection laser beam 3 is The 0th-order diffracted light that is transmitted through the surface 2a and then reflected by the reflective film 2c to the other surface 2a, thereby being diffracted and reflected by the track groove 6 formed on the one surface 2b of the optical disc 20. d _{0 to} higher order diffracted light (first order diffracted light d ₁ , second order diffracted light d ₂ )
The first diffracted light detecting means (light receiving element, photodetector) 7 for detecting the first and second order diffracted lights d _{0 to} d ₁ and the second order diffracted light d ₂ . A transfer means for transferring the diffracted light detection means 7; and a track groove on the one surface 2b corresponding to the irradiation position 2a1 of the spot light generated on the other surface 2a when the inspection laser light 3 is irradiated. 6, higher-order diffracted light (first-order diffracted light d ₁ , second-order diffracted light d) with respect to the _0- order diffracted light d _0
2 ) measuring the inclination angles θ _{1 to} θ ₂ to determine the intensity ratio of the higher-order diffracted light (first-order diffracted light d ₁ , second-order diffracted light d ₂ ) to the _zero- order diffracted light d ₀ , and from the intensity ratio, Determining means for calculating the groove width P1 and the depth D, and determining whether the calculated values are within an allowable range;
When the inclination angle theta ₁ through? ₂ of the high-order diffracted light (first order diffracted light d _1, 2-order diffracted light d ₂₎ exceeds 90 ° relative to _0,
Control means for controlling the laser light irradiation means 4 such that the incident angle α of the inspection laser light 3 is changed so that the inclination angles θ _{1 to} θ ₂ are less than 90 °. Optical disk inspection device.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an optical disk inspection apparatus according to the present invention will be described with reference to the drawings.

FIGS. 1 and 2 are diagrams for explaining the main parts of the first and second embodiments of the optical disk inspection apparatus of the present invention, respectively.
FIG. 3 is a diagram for explaining a state in which an offset has occurred by irradiating the laser beam onto the master optical disc. The same components as those described above are denoted by the same reference numerals, and description thereof will be omitted.

The features of the optical disk inspection apparatus of the present invention are as follows. By obliquely irradiating the laser light, the 0th-order diffracted light and the 1st-order diffracted light of the laser light and the 2nd-order diffracted light (only one of the generated diffracted lights in two directions) are generated within the range of the light transmitted through the resist master disk. The groove width and groove depth in the track direction and pitch direction of the pit shape of the master optical disc can be adjusted by using the second-order diffracted light / first-order diffracted light,
It can be obtained from the intensity ratio of the 1st-order diffracted light / 0th-order diffracted light.

Further, in order to reduce the influence of the displacement of the optical axis due to the placement of the glass disk, one light receiving element (photodetector) is rotated in a pendulum manner to convert the 0th-order diffracted light to the 1st-order diffracted light and the 2nd-order diffracted light. The laser light peak value is received by one light receiving element (photodetector).

Further, by adopting a configuration in which a convex lens or a flat lens is interposed on the optical path in front of the light receiving element (photodetector), a stable collection even if an optical axis shift, a wobble due to an offset, or a positional shift occurs. Light becomes possible.

Further, in order to reduce the influence of the variation in the measured value due to the optical axis drift of the laser light, the size of the laser is reduced by using a semiconductor laser. By installing, the optical path length can be considerably reduced (to 1/10).

Furthermore, although a large space was required for the apparatus structure, the glass master to be measured was fixedly installed, the optical path was shortened by using a small semiconductor laser, and the light receiving element (photodetector) for receiving light was made movable. As a result, the mechanical volume can be reduced to 1/4, and a compact and small inspection system can be realized.

The optical disc inspection apparatus of the present invention may have the following configuration and operation. (A) Mastering Step The groove width and groove depth, which are the pit widths of the optical disk master after development, are accurately measured and managed based on the intensity distribution of diffraction fringes by the slits. The resist layer of the resist glass disk is transmitted through the resist layer by means of a laser beam irradiating means for irradiating a parallel light beam using a laser that emits light having a uniform phase (coherent light) as a light source, vertically or obliquely. At this time, an angle at which the zero-order diffracted light is generated and an angle at which the first-order diffracted light or the higher-order diffracted light is generated are detected. When a metal film (such as sputtering) is applied to the resist layer surface of the optical disk (resist glass disk) in order to enhance the preservability, a parallel light beam using a laser that emits light with uniform phase (coherent light) as a light source Is reflected by laser light irradiation means for vertically or obliquely irradiating, and the angle at which the zero-order diffracted light occurs and the angle at which the first-order or high-order diffracted light occurs are detected. A laser light detecting means for detecting the diffracted light generated by the laser light irradiating means and the track groove at the measuring point; and a movable means for moving the laser light detecting means in a pendulum manner in a direction in which the diffracted light is generated with respect to the optical disk. And the angle at which the zero-order diffracted light occurs and the first-order diffracted light, or
An optical disc comprising: an inspection method which is an arithmetic means for calculating an intensity ratio of diffracted light in a track groove from a difference in angle at which high-order diffracted light is generated, and calculating a groove width and a groove depth. Groove shape inspection equipment.

(B) The laser beam detecting means for detecting the diffracted light generated by the track grooves of the optical disc is a photodetector, and a lens is provided on the optical path after passing through a resist layer or a reflective film (metal film). An optical disc groove shape inspection apparatus having an interposed structure.

(C) Further, under the condition where the tilt angle θ of the diffracted light exceeds about 90 ° (θ> 90 °), the laser light irradiating means is tilted by a predetermined angle, whereby the glass A configuration in which diffracted light can be generated within the in-plane range of the transmitted light of the master and combined with movable means that can move in the direction in which the diffracted light is generated by one laser light detection means Thus, the optical disk groove shape inspection apparatus has a feature that can be extended to a measurement target range that could not be measured until now.

Next, a first specific example of the optical disk inspection apparatus of the present invention will be described. (First Embodiment) As will be described later, the optical disk inspection apparatus of the present invention has the following configuration. That is, as shown in FIG. 1, one surface (emission surface) in which track grooves 6 are formed concentrically or spirally at a predetermined track pitch P.
An optical disk inspection device (groove shape) for inspecting whether or not the groove width P1 and the depth D of the track groove 6 in the radial direction of the track groove 6 of the optical disk (master optical disk or glass master) 2 having 2b are within allowable ranges. An inspection device) 1a, a laser beam irradiating means 4 for irradiating the other surface (incident surface) 2a of the optical disk 2 with the inspection laser beam 3 obliquely at a predetermined incident angle α, located on the other surface 2a side, emits is diffracted by the track grooves 6, wherein formed on one surface 2b of the optical disc 2 0-order diffracted light d ₀ to high-order diffracted light (first order diffracted light d _1, 2 next order diffracted light d ₂₎ 1 of the diffracted light detecting means for detecting (light receiving element, a photodetector) and 7, zero-order diffracted light d ₀
A transfer means for transferring the first diffracted light detecting means 7 to a light receiving position capable of receiving (the strongest) high-order diffracted light (first-order diffracted light d ₁ , second-order diffracted light d ₂ );
Generated by the track grooves 6 on the one surface 2b in correspondence with the spot irradiation position of the light 2a1 generated in the other surface on 2a when irradiated with, zero-order high-order diffracted light with respect to diffracted light d ₀ (1-order diffracted light d _1, 2 determine the intensity ratio of the inclination angle theta ₁ through? ₂ measurement to 0-order diffracted light with respect to order diffracted light d ₀ (1-order diffracted light d _1, 2-order diffracted light d ₂₎ of the diffracted light d _2), wherein calculates the groove width P1 and the depth D of the track grooves 6 from the intensity ratio, determining means for whether or not each value thus calculated is within the allowable range, 0-order diffracted light with respect to order diffracted light d ₀ ( The inclination angles θ _{1 to} θ _{2 of the first-} order diffracted light d ₁ and the second-order diffracted light d ₂ )
Is greater than 90 °, control means for changing the incident angle α of the inspection laser light 3 and controlling the laser light irradiation means 4 so that the inclination angles θ _{1 to} θ ₂ are less than 90 °. An optical disk inspection device, comprising:

FIG. 1 shows a groove shape inspection apparatus for an optical disk master according to a first embodiment of the present invention, in which a case where the angle of generation of higher-order diffracted light becomes θ> about 90 ° depending on the constitutional conditions is shown. It is a side view.

As an optical disk, after a resist film is formed on a glass disk, the track grooves 6 are formed by cutting.
Is used, and the glass master 2 is a transmissive optical disc as described later.

In the first embodiment, as shown in FIG.
The intensity ratio of the diffracted light in the track groove 6 engraved on the glass master 2, the groove width and the groove depth are controlled and inspected, and the exposure power of the laser beam at the time of cutting is adjusted based on the inspection result. In addition, in order to form a track groove 6 with higher accuracy by feeding back to the entire mastering process, an indirect management inspection is performed.

The groove shape inspection apparatus 1a is used as a laser beam irradiating means 4 for irradiating the laser beam 3 obliquely to the glass master 2 and a laser beam detecting means for detecting the laser beam 3 transmitted through the track groove 6 of the glass master 2. A light detector (photodetector) 7 having a lens 9 interposed on the optical path after passing through the track groove 6; Movable means for swinging (swing arm) in a pendulum type in the direction in which

The laser beam irradiating means 4 irradiates the irradiated laser beam 3 to the glass master 2 at a predetermined angle (obliquely upward), and the zero-order diffracted light d ₀ is generated in a state inclined with respect to the glass master 2. The _second- order diffracted light d ₂ (higher-order diffracted light d _n ) that could not be measured angularly can be expressed within the range of the transmitted light side of the glass master 2. in other words, 0-order diffracted light d ₀ and the plus side or minus side in two directions of the other hand (generated symmetrically one) only of each order diffracted light d _n within the transmitted light side of the glass master 2 of each order diffracted light d _n Can be generated within the range.

This can be known by calculating the difference θ ₁ (θ _n ) between the angle at which the _zero-order diffracted light d ₀ is generated and the angle at which the first-order diffracted light d ₁ is generated. This can be confirmed by the example of the result table in which θ was calculated from [Equation 1] described above.

For example, the DVD having the largest value from the above-mentioned result table
In order to make it possible to measure the _second-order diffracted light d ₂ in the above case, if the laser 4 is tilted by a predetermined angle, the second-order diffracted light d ₂ can be taken into the transmitted light side surface of the glass master 2. You can check.

The laser beam irradiating means 4 is characterized in that the glass master 2 is fixedly mounted and a compact semiconductor laser is used to reduce the space and shorten the optical path length. I also have

The light receiving element (photodetector) 7 detects the intensity of the incident laser light (diffraction light d). If the laser light (diffraction light d) has the same intensity, the light receiving element (photodetector) 7 is used. Are more strongly detected as the intensity when they are incident at a right angle to the light receiving surface.

The spot diameter is condensed by interposing a lens 9 on the optical path of the laser light (diffracted light d) after passing through the glass master 2 and the track groove 6 (in front of the photodetector), and the light is received at a right angle by the light receiving surface. As shown in the enlarged schematic perspective view of FIG.
Laser light detecting means characterized in that it can receive light even when f set δ (δ ₀ , δ ₁ ) is present.

This light receiving element (photo detector) 7
It is movable (swing arm) in a pendulum direction with respect to the glass master 2 in a direction in which the diffracted light d is generated, so that each order diffracted light d _n can be received at a right angle on the light receiving surface, and furthermore, received from a part where the diffracted light d is emitted. The distance to the element (photodetector) 7 does not change. Therefore, it is possible to detect the respective following diffracted light d _n by one light receiving element (photodetector) 7. (See Fig. 1)

The movable means is for moving the light receiving element (photodetector) 7 in the movable direction, and has a drive section for swing arm and an angle detecting section for detecting an inclination angle with respect to the glass master.

The movable means can control the movement of the glass master 2 in the direction in which the diffracted light d is generated in the entire range within the transmitted light side surface of the glass master 2 by detecting the tilt angle.
That is, each angle θ of occurrence of the following diffracted light d _n, can be determined by the angle detection means, 0 angle-order diffracted light d ₀ occurs angle θ and 1-order diffracted light d _1, or the high-order diffracted light d _n occurs θ Can be calculated from the detected difference between the two angles, and positioning is performed.

The light receiving element (photodetector) 7 at that time
Diffracted light d at the angle at which the light intensity incident on
The light intensity is measured. The ratio is obtained from the intensity of the diffracted light d obtained by the measurement, and the ratio is derived by calculating the groove width and the groove depth from the intensity ratio. This inspection method is the same in a second embodiment described later.

Next, a specific second embodiment of the optical disk inspection apparatus of the present invention will be described. (Second Embodiment) As will be described later, the optical disk inspection apparatus of the present invention has the following configuration. That is, as shown in FIG. 2, one surface (emission surface) in which track grooves 6 are formed concentrically or spirally at a predetermined track pitch P.
2b, the other surface (incident surface) 2a opposite to the one surface 2b, and transmitted light laminated on the one surface 2b and transmitted from the other surface 2a. Optical disc 20 having reflective film (metal film) 2c that totally reflects
An optical disk inspection device (groove shape inspection device) 10a for inspecting whether the groove width P1 in the radial direction of the track groove 6 and the depth D of the track groove 6 are within an allowable range. A laser beam irradiating means 4 for irradiating the inspection laser beam 3 obliquely at a predetermined incident angle α to the surface 2a of the optical disk 20, and the inspection laser beam 3 located on the other surface 2a side of the optical disc 20; After being transmitted from the other surface 2a side, the light is reflected (total reflection) by the reflection film 2c to the other surface 2a side, so that the light is diffracted by the track groove 6 formed on the one surface 2b of the optical disc 20. One diffracted light detecting means (light receiving element, photodetector) 7 for detecting the _0th order diffracted light d _{0 to} higher order diffracted light (first order diffracted light d ₁ and second order diffracted light d ₂ ) reflected
And 0th order diffracted light d _{0 to} higher order diffracted light (first order diffracted light d ₁ , 2
Transport means for transporting the first diffracted light detecting means 7 to a position where it can receive the next diffracted light d ₂ );
Generated by the track grooves 6 on the one surface 2b corresponding to the irradiation position 2a1 of the spot light generated on the other surface 2a when irradiated with, 0-order diffracted light with respect to order diffracted light d ₀ (1-order diffracted light d _1, 2 determine the intensity ratio of the order of diffracted light d ₂₎ tilt angle theta ₁ through? ₂ of measured 0-order diffracted light with respect to order diffracted light d ₀ (1-order diffracted light d _1, 2-order diffracted light d _2), the intensity calculates the groove width P1 and the depth D of the track grooves 6, respectively from the ratio, a determination unit configured to whether or not each value thus calculated is within the allowable range, 0-order diffracted light with respect to order diffracted light d ₀ ( 1-order diffracted light d _1, 2 next time the inclination angle theta ₁ through? ₂ of the diffracted light d ₂₎ exceeds 90 °, the inclination angle theta ₁ through? ₂ by changing the angle of incidence α of the inspection laser light 3 Control means for controlling the laser beam irradiation means 4 so that the angle is less than 90 °. Optical inspection apparatus characterized by comprising and.

The optical disk 20 is a reflection film (metal film)
2c, a comparison between the second embodiment and the first embodiment shows that the first embodiment is a transmissive optical disc 2, whereas the second embodiment is a reflection type optical disc 2. The difference is that the optical disc 20 is of the mold type. In the second embodiment, the laser light detecting means 4 for receiving the diffracted light d is located on the same side of the optical disc 20 as the laser light irradiating means 4 (incident surface 2a side). The first embodiment is different from the first embodiment in that the laser light detecting means 4 for receiving the diffracted light d is located on the side opposite to the laser light irradiating means 4 with respect to the optical disk 2 (on the exit surface 2b side). Therefore, in describing the second embodiment, portions different from the first embodiment will be mainly described, and the same portions will be denoted by the same reference numerals and description thereof will be omitted.

FIG. 2 shows a groove shape inspection apparatus for an optical disk master according to a second embodiment of the present invention, in which a case where the angle of generation of higher-order diffracted light is θ> about 90 ° depending on the constitutional conditions is shown. It is a side view. As in the apparatus of the first embodiment, the apparatus includes a laser beam irradiation unit 4, a photodetector 7, and a movable unit.

As in the first embodiment, the irradiation laser beam 3 is applied to the optical disc 20 at a predetermined angle (oblique) α, the laser light 3 is reflected by the reflection film 2c of the optical disc 20, and the diffracted light d occurs as reflected light. That is, the diffracted light d is directed toward the laser light irradiating means 4 on the side opposite to that in the first embodiment, and the first-order diffracted light d ₁ and the higher-order diffracted light d _n are tangential to the track groove 6. And is reflected at a right angle and bent at a predetermined angle with respect to the _zero- order diffracted light d0.

The photodetector 7 and the movable means for supporting the photodetector 7 are arranged in the side (upper side) of the reflected light of the optical disk 20 and, as in the first embodiment, move the photodetector 7 in the direction in which the diffracted light d is generated. It is movable.

Accordingly, the diffracted light d can be received by the light receiving surface of the photodetector 7, whereby the intensity of the diffracted light d in the spot range is detected in the same manner as in the first embodiment.
By obtaining this strength ratio, the groove width and groove depth can be derived.

[0060] Further, in the groove shape inspection, generation angle and the first or higher order diffracted light d, 1-order diffracted light d ₁ and the measurement of the intensity ratio in the spot range 2 but utilizing diffracted light d _2, 2 using the diffracted light d _n of the next higher order may be measured.

[0061]

As is apparent from the above description, according to the present invention, a laser beam is transmitted through an optical disc, and the angle generated between the 0th-order diffracted light and the 1st-order or higher-order diffracted light. The intensity ratio in each spot range can be obtained from the difference between the two, and the groove width and groove depth can be measured and inspected from this. Therefore, the management inspection can be performed at an early stage in the optical disk manufacturing process. The generation of non-defective products (optical disks) can be prevented. In addition, by tilting the laser beam irradiating means for irradiating the optical disk with laser beam at a predetermined angle, the angle θ at which high-order diffracted light is generated becomes θ.
Even if it exceeds> 90 °, it is generated in the transmitted light side surface of the glass master so that measurement and inspection can be performed. Therefore, inspection can be performed even if the type of the optical disk, the track pitch, and the conditions of the laser beam are changed. Also,
A movable means for moving the laser light detecting means for detecting the diffracted light generated by the track grooves of the optical disc in a direction in which the diffracted light is generated with respect to the optical disc is provided, and the movable means is provided between the diffracted lights measured by these laser light detecting means Based on the generated angle, the intensity ratio and the groove width and groove depth of the track groove are calculated by the calculation means from the intensity of the diffracted light in the spot range.
It is possible to provide a device that does not rely on human vision and therefore does not require skill, and that can simplify the inspection and improve the inspection accuracy. Further, by combining the above-described configurations, the moving space is eliminated and the size of the apparatus can be reduced. Further, since the laser light detecting means for detecting the diffracted light generated by the track grooves of the optical disk is a photodetector, the detection of the laser light can be facilitated. Furthermore, by providing a lens on the diffracted light path after passing through the track groove of the optical disc and in front of the laser light detecting means, even if an offset such as a shift of the laser light occurs during the measurement, it is always present. Stable beam light can be condensed and received on the photodetector surface, thereby increasing inspection accuracy. On the other hand, laser light is reflected by an optical disk (coated with a metal film), and the laser light irradiation means is inclined to generate reflected light (diffraction light) in the side surface of the reflected light. . Then, the 0th-order diffracted light and 1
An optical disc as in claim 1, wherein the intensity ratio in each spot range can be determined from the difference in angle between the diffracted light of the next or higher order, and the groove width and groove depth can be measured and inspected from this. Management inspection at each stage of the manufacturing process,
The occurrence of defects at each manufacturing stage can be prevented. Further, in the problem to be solved by the invention, for a problem in which the measured value varies due to each of the influence factors, the inspection apparatus system is configured to reduce the variation of the measured value for each of the influence factors. By designing, it is possible to improve detection accuracy and obtain stable data in which a measured value to be obtained is not affected by an influence factor. This makes it possible to manage the groove shape stably, to control the exposure power and the like during cutting, and to considerably improve the reliability of the entire system. Furthermore, this system structure increases the number of target disks that can be measured, so that inspection can be performed. Furthermore, since the size is reduced at each point, the inspection apparatus as a whole can be reduced in space.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a main part of a first embodiment of an optical disk inspection apparatus according to the present invention.

FIG. 2 is a diagram for explaining a main part of a second embodiment of the optical disk inspection apparatus of the present invention.

FIG. 3 is a diagram for explaining a state in which an offset has occurred by irradiating a laser beam onto a glass master.

FIG. 4 is a diagram for explaining a conventional optical disk inspection device.

FIG. 5 is a diagram for explaining the operation of a conventional optical disk inspection device.

FIG. 6 is a diagram for explaining the operation of a conventional optical disk inspection device.

[Explanation of symbols]

1a, 10a Groove shape inspection device (optical disk inspection device) 2, 20 Optical disk master, glass master (optical disk) 2a Incident surface (other surface) 2a1 Irradiation position 2b1 Range position 2b Emission surface (one surface) 2c Metal film (reflection) Film) 3 inspection laser beam 4 laser beam irradiation means 6 track groove 7 light receiving element, photodetector (diffraction light detection means) d ₀ 0th-order diffraction light d1 _1st-order diffraction light d2 _2nd-order diffraction light D Track groove depth P track pitch P1 Groove width of track groove α Incident angle θ ₁ , θ ₂ Tilt angle

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hiroyoshi Yoshikawa 3-12 Moriyacho, Kanagawa-ku, Yokohama-shi, Kanagawa Japan F-term (reference) 2F065 AA23 AA25 AA49 BB02 BB03 BB18 CC03 DD02 FF44 FF48 FF65 GG06 HH04 HH12 HH15 JJ01 JJ05 JJ08 JJ09 JJ15 MM25 PP05 QQ25 QQ26 RR08 5D121 AA02 HH09

Claims (2)

[Claims] An optical disk having one surface on which concentric or spiral track grooves are formed at a predetermined track pitch has a groove width in the radial direction of the track grooves and a depth of the track grooves within an allowable range. An optical disk inspection device for inspecting whether or not there is a laser beam irradiating means for irradiating the other surface of the optical disk with a laser beam for inspection obliquely at a predetermined incident angle, and the other surface side of the optical disk A first diffracted light detecting means for detecting 0th order diffracted light or higher order diffracted light which is diffracted and emitted by a track groove formed on the one surface of the optical disc; Transferring means for transferring the one diffracted light detecting means to a light receiving position at which light can be received, and spot light generated on the other surface when the inspection laser light is irradiated. The inclination ratio of the higher-order diffracted light to the zero-order diffracted light generated by the track groove on the one surface corresponding to the irradiation position is measured to determine the intensity ratio of the higher-order diffracted light to the zero-order diffracted light, and the track is determined from the intensity ratio. Determining means for calculating the groove width and depth of the groove, respectively, and determining whether the calculated values are within an allowable range; and the inclination angle of the higher-order diffracted light with respect to the zero-order diffracted light exceeds 90 °. An optical disk inspection apparatus, comprising: control means for controlling the laser light irradiation means such that the angle of incidence of the inspection laser light is changed so that the inclination angle is less than 90 °. 2. One surface on which track grooves are formed concentrically or spirally at a predetermined track pitch,
An optical disc having a surface opposite to the one surface and a reflective film that is stacked on the one surface and totally reflects transmitted light transmitted from the other surface.
An optical disk inspection device for inspecting whether a groove width and a depth of a track groove in a radial direction of a track groove are within an allowable range, wherein the inspection is performed obliquely at a predetermined incident angle with respect to the other surface of the optical disk. A laser beam irradiating means for irradiating a laser beam for inspection, the inspection laser beam being located on the other surface side of the optical disc, being reflected by the reflection film to the other surface side after transmitting from the other surface side. As a result, 0-order diffracted light or higher-order diffracted light that is diffracted and reflected by a track groove formed on the one surface of the optical disc is detected.
Diffracted light detecting means, transferring means for transferring the one diffracted light detecting means to a light receiving position capable of receiving 0th order diffracted light or higher order diffracted light, and on the other surface when the inspection laser light is irradiated The inclination ratio of the high-order diffracted light with respect to the zero-order diffracted light is determined by measuring the inclination angle of the high-order diffracted light with respect to the zero-order diffracted light, which is generated by the track groove on the one surface corresponding to the irradiation position of the spot light generated in the Determining means for calculating the groove width and the depth of the track groove from the intensity ratio, and determining whether or not the calculated values are within an allowable range; and the inclination angle of the high-order diffracted light with respect to the zero-order diffracted light is Control means for controlling the laser light irradiation means so as to change the incident angle of the inspection laser light when the angle exceeds 90 ° so that the inclination angle is less than 90 °. Light day Screen inspection device.