JP2663525B2 - Strain inspection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a distortion inspection apparatus, and more particularly, to a method for quantifying a warp distortion of an optical disk stamper having a glossy and thin surface and having a warp distortion, such as a stamper for an optical disk. The present invention relates to a distortion inspection device that calculates a distance.

[Conventional technology]

A conventional distortion inspection device will be described. FIG. 8 is a schematic view showing an example of a conventional distortion inspection apparatus.

In the distortion inspection apparatus shown in FIG. 8, the light generated from the light source 2 is collected by the condenser lens 3 and passes through the pinhole 4, so that the wavefronts of the light are aligned. The light is irradiated on the sample 1 by changing its traveling direction by the reflecting mirror 5. The sample 1 is placed on a sample table 11 covered with a black cloth so as not to reflect light. The light reflected from the sample 1 is transmitted through a diffused screen 8.
It is projected to.

In the above configuration, if there is a concave portion on the surface of the sample 1, light is collected, so that the light becomes bright on the screen. If there is a convex portion on the surface of the sample 1, the light is scattered, so that it looks dark on the screen.

Therefore, irregularities on the surface of the sample are exaggerated by the intensity of light, so that the observer can sensibly grasp the irregularities on the surface.

[Problems to be solved by the invention]

However, such a conventional strain inspection apparatus described above generally observes the surface distortion of a thick, non-warped sample. However, in a thin, warped sample, the size of an image shown on a screen is large. However, it is difficult to compare each sample because the size of the sample becomes larger or smaller depending on the warpage of the sample, and the fact that the image on the screen is enlarged or reduced makes it difficult to grasp the exact position of the irregularities on the sample surface. is there.

In addition, in the conventional distortion inspection apparatus, since the image on the screen is distorted due to the setting of the angle of the screen, there is a demand to rotate and observe the sample, but the sample table is fixed,
In addition, there is a disadvantage that handling is inconvenient due to the inclination.

[Means for solving the problem]

The distortion inspection apparatus according to the present invention includes an optical system that produces light with a uniform wavefront, a sample stage that horizontally mounts the sample and rotates the sample, and irradiates the sample with light generated by the optical system and receives reflected light from the sample. It comprises a screen, a photodetector provided above the screen, and a calculator for measuring the brightness of an image shown on the screen and quantitatively calculating the magnitude of the warpage of the sample based on the measured brightness.

In addition, the distortion inspection apparatus of the present invention includes an optical system that produces light having a uniform wavefront, a sample stage on which a sample is placed horizontally and a sample is rotated, and a light generated by the optical system is irradiated on the sample and reflected from the sample. A screen for receiving light, a photodetector above the screen and movable horizontally with respect to the screen, a linear sensor for measuring the position from the center of the screen to the photodetector, and an image on the screen. And a calculator for measuring the size of the image and quantitatively calculating the magnitude of the warpage of the sample.

In addition, the distortion inspection apparatus of the present invention includes an optical system that produces light with a uniform wavefront, a sample table on which the sample can be placed horizontally and the sample can be rotated, and a light generated by the optical system that irradiates the sample and reflects the light from the sample. A screen for receiving light, a photodetector above the screen and movable horizontally with respect to the screen, a linear sensor for measuring a position from the center of the screen to the photodetector, and an image on the screen. And a calculator for measuring the brightness of the entire surface of the image and quantitatively calculating the rate of change of the displacement of the strain on the sample surface from the measured value.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

 FIG. 1 is a schematic diagram showing a first embodiment of the present invention.

In the distortion inspection apparatus shown in FIG. 1, light generated from the light source 2 is collected by the condenser lens 3 and
To align the wavefront of light. Sample 1 with this light placed horizontally
Is irradiated by the reflecting mirror 5. A back plate 6 covered with a black cloth is provided below the sample 1 to prevent reflected light from components other than the sample 1. The sample 1 can be rotated by a pulse motor 7. The light reflected by the sample 1 is displayed on a transmission-scattering screen 8. Also, a photodetector 9 is placed above the screen to measure the brightness of the image, and a photodetection signal p
Is output to the arithmetic unit 10.

Next, an example in which a thin, donut-shaped nickel stamper for an optical disk is used as the sample 1 will be described.

In the above configuration, the brightness _S of the image on the screen can be simply expressed by the following equation (1).

_S is the brightness of the image on the screen per unit area is the brightness of the incident light on the test surface per unit area A _S is the area of the image on the screen A _O is the area of the sample λ is the sample area Is the light transmittance of the screen. Since the incident light and screen are the same in the same device, φ is the same. Here when the area of the sample A _O, and the state of the surface λ is compared for the same sample, _S is thus inversely proportional to A _S. That is, if λ, A _O , and φ are the same, the brightness per unit area of the image shown on the screen is inversely proportional to the area of the image shown on the screen (the square of the diameter of the image).

FIG. 2 is an illustration showing the relationship between the sample and the path of light in the embodiment shown in FIG.

In FIG. 2, the solid line indicates the case where the sample 1 does not warp with respect to the incident light path A, that is, the reflected light path Ba when the sample 1 is located at the sample position 1a, and the dotted line indicates that the sample 1 is warped and the outside of the sample 1 is lowered. Path of reflected light when located at sample position 1b
Bb indicates the reflected light path Bc when the sample 1 is located at the sample position 1c in which the sample 1 is warped and rises outward.

As is apparent from the figure, when the sample 1 is at the sample position 1b having a downwardly warped sample position, the image on the screen 8 is larger than that at the non-warped sample position. The image above is small.

Therefore, in the case of the sample 1 having the outwardly curving, the image on the screen 8 becomes large, and the brightness per unit area of the image becomes dark. Conversely, in the case of the sample 1 having a warp whose outside rises, the image on the screen 8 becomes small, and the brightness per unit area of the image becomes bright.

FIG. 3 is a graph showing the relationship between the sample and the light detection signal in the embodiment shown in FIG.

In FIG. 3, the solid line indicates the sample position where the sample 1 is not warped.
The output of the light detection signal p from the photodetector 9 in the case of 1a is shown.
The alternate long and short dash line shows the case of the sample position 1c having a warp whose outside rises.

As can be seen from the figure, when the outside has a downward warp, the size of the image on the screen 8 is large and the brightness per unit area of the image is dark, so that the output of the light detection signal p is small. Conversely, in the case of a sample having a warp whose outer side rises, the output value of the light detection signal p increases because the brightness per unit area increases.

Therefore, the amount of warpage of the sample can be quantitatively determined from the output value of the light detection signal p.

If the image on the screen has uneven brightness in the circumferential direction, rotate the sample with a pulse motor,
It is also possible to measure as an average value of several places.

 FIG. 4 is a schematic view showing a first embodiment of the present invention.

In the distortion inspection apparatus shown in FIG. 4, light generated from the light source 2 is collected by the condenser lens 3 and passed through the pinhole 4 to make the wavefront of the light uniform. This light is applied to the sample 1 placed horizontally by the reflecting mirror 5. A back plate 6 covered with a black cloth is arranged below the sample 1 to prevent reflected light from components other than the sample 1. The sample 1 can be rotated by a pulse motor 7. The light reflected by the sample 1 is projected onto a transmission-scattering screen 8 which is detected by a light detector 9 which can move horizontally with respect to the screen 8 to output a light detection signal p. The position of No. 9 is measured by the linear sensor 11 that outputs the position signal a.

Next, an example in which a thin, donut-shaped nickel stamper for an optical disk is used as the sample 1 will be described.

In the above configuration, when the image shown on the screen is viewed from the outside to the inside by the photodetector 9, the output level of the light detection signal p rises sharply at a position corresponding to the outer diameter of the sample 1, Falls suddenly at the location corresponding to the inside diameter of

Therefore, when the output level of the light detection signal p exceeds a certain threshold level when the light detector 9 starts to move from the outside, the center can be determined as the outer diameter position, and the position of the light detector 9 at this time is determined by a linear sensor. By measuring at 11, the size of the image on the screen 8 can be determined.

FIG. 5 is an explanatory diagram showing the relationship between the sample and the light path in the embodiment shown in FIG.

In FIG. 5, the solid line represents the sample 1 with respect to the incident light path A.
Shows the reflected light path Ba in the case of the sample position 1a having no warp,
The dotted line indicates the reflected light path Bb in the case of the sample position 1b in which the outer peripheral portion is warped, and the dashed line indicates the reflected light path Bc in the case of the sample position 1c in which the outer peripheral portion is warped. .

As is clear from the figure, the size of the image on the screen 8 is larger in the case of the sample 1 having a warp in which the outer side is lowered and the inner side is raised (a convex shape when viewed in cross section), and the reverse. In the case of having the warpage, it becomes smaller.

Therefore, the screen 8 is detected by using the light detection signal p from the light detector 9, the position signal a from the linear sensor 11 and the arithmetic unit 12.
By calculating the size of the image on the sample, the size of the warpage of the sample 1 can be quantitatively obtained from the size of the image.

In some cases, the image shown on the screen 8 is not a perfect circle but is distorted. In this case, the sample 1 is rotated by the pulse motor 7 to measure several outside diameters and to take an average value. The amount of warpage can be obtained by the following.

 FIG. 6 is a schematic view showing a third embodiment of the present invention.

In the distortion inspection apparatus shown in FIG. 6, light generated from the light source 2 is collected by the condenser lens 3 and passed through the pinhole 4 to make the light wavefront uniform. This light is applied to the sample 1 placed horizontally by the reflecting mirror 5. A back plate 6 covered with a black cloth is disposed below the sample 1 to prevent light reflected from other than the sample. The sample 1 can be rotated by a pulse motor 7. The light reflected by the sample 1 is displayed on a transmission-scattering screen 8. Above the screen 8, a photodetector 9 that can move horizontally with respect to the screen 8 and a linear sensor 11 that measures the position of the photodetector 9 are provided.

Next, an example in which a thin donut type nickel stamper for an optical disk is used as the sample 1 will be described.

In the above configuration, the brightness of the image shown on the screen 8 is measured by the photodetector 9 and a photodetection signal p is output. At this time, the photodetector 9 is moved outward from the center of the screen 8, and the sample 1 is moved by the pulse motor 7.
Is rotated, the entire surface of the image captured on the screen 8 can be measured by the photodetector 9.

When the surface of the sample 1 has a concave portion, the light is collected and thus looks bright on the screen 8, and when there is a convex portion, the light is scattered and becomes dark. The degree of light and darkness is also affected by the amount of displacement of the surface irregularities, but rather, the degree of light and darkness is largely changed by the shape of the surface irregularities.

FIG. 7 is a graph conceptually showing the relationship between the uneven shape of the sample surface and the output of the photodetector in the embodiment shown in FIG.

In FIG. 7, the convex portions PA and PB have the same maximum displacement but different shapes. Although the maximum displacement amounts are the same in the concave portions PC and PD, their shapes are different. The convex portion PA and the concave portion PD have a sharp change in displacement and a sharp central portion, and the convex portion PB and the concave portion PC have a round shape with a gradual change in displacement.

As can be seen from the figure, the convex part PA and concave part that change rapidly
In the PD, the output value of the photodetector 9 also changes greatly, and the change in the light detection signal p is small in the convex portion PB and the concave portion PC that change gradually.

Accordingly, the change rate of the uneven displacement of the sample surface can be obtained from the output of the light detection signal p.

〔The invention's effect〕

The distortion inspection apparatus of the present invention irradiates a sample with a uniform wavefront, copies the distortion of the sample on a screen, and measures the brightness of this image with a photodetector. This has the effect that the warp distortion of can be obtained quantitatively.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a first embodiment of the present invention, FIG. 2 is an explanatory diagram showing a relationship between a sample and a light path in the embodiment shown in FIG. 1, and FIG. 3 is a diagram in FIG. FIG. 4 is a graph showing the relationship between a sample and a photodetection signal in the embodiment shown in FIG. 4; FIG. 4 is a schematic diagram showing a second embodiment of the present invention; Explanatory diagram showing the relationship with
FIG. 7 is a schematic view showing a third embodiment of the present invention, and FIG.
FIG. 8 is a graph showing the relationship between a sample and a light detection signal in the embodiment shown in FIG. 8, and FIG. 1 ... sample, 2 ... light source, 3 ... condenser lens,
4 ... pinhole, 5 ... reflector, 6 ... back plate, 7 ... pulse motor, 8 ... screen, 9 ... photodetector, 10,12,13 ... calculator, 11 ... linear sensor,
14: Sample table, A: Incident light path, B, Ba, Bb, Bc: Reflected light path, 1a, 1b, 1c: Sample device, 8a, 8b, 8c ... Outer diameter position, d ...
Inner diameter position, r: radius, PA, PB: convex portion, PC, PD: concave portion, p: light detection signal, s: surface displacement, a: position signal.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-294904 (JP, A) JP-A-62-284248 (JP, A) JP-A-53-118070 (JP, A) 153109 (JP, U) Japanese Utility Model 63-131648 (JP, U) Japanese Utility Model 57-134612 (JP, U)

Claims (3)

(57) [Claims] 1. An optical system for producing light with a uniform wavefront, a sample stage processed in black, a pulse motor below the sample stage and capable of rotating the sample stage, and a light generated from the optical system being applied to a sample. A screen that irradiates and receives reflected light, a photodetector that is located above the screen and that can move horizontally with respect to the screen and outputs a photodetection signal, and a position from the center of the screen to the photodetector. A linear sensor that measures and outputs a position signal, and measures the brightness of the front of the image reflected on the screen,
And a calculator for quantitatively calculating the rate of change of the displacement of the sample surface and the amount of warpage of the entire sample based on the measured value and the position signal. 2. An optical system comprising a light source, a condenser lens, and a pinhole, wherein light emitted from the light source is collected by a condenser lens and passed through the pinhole to generate light having a uniform wavefront. The distortion inspection apparatus according to claim 1, wherein the distortion inspection apparatus is characterized in that: 3. The sample table according to claim 1, wherein said sample table is constituted by a sample table having a surface processed in black, and said sample table, and said sample table prevents reflected light from an object other than the sample. 3. The distortion inspection apparatus according to claim 2.