JP3673632B2 - Non-uniformity inspection method and apparatus for translucent material, and transparent substrate - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides a non-transparent material that can detect optical non-uniformities (defects) of a transparent material such as a transparent substrate for a photomask and a transparent substrate for a liquid crystal display with high accuracy and high speed. The present invention relates to a uniformity inspection method and apparatus, and a transparent substrate to be subjected to non-uniformity inspection.
[0002]
[Prior art]
In the manufacturing process of a semiconductor integrated circuit, a photomask, and the like, a photolithography method is used for forming a fine pattern. For example, when manufacturing a semiconductor integrated circuit, a pattern is transferred using a photomask in which a pattern is formed by a light-shielding film (for example, a chromium film) on a transparent substrate that has been polished with high precision and mirror-finished. Yes. An inspection method for a photomask, which can be said to be a master of this pattern, collects light in a very small area of the pattern surface as seen in the surface state inspection apparatus described in Japanese Patent Application Laid-Open No. 58-162038. A method for comparing reflected output and transmitted output is known.
[0003]
[Problems to be solved by the invention]
However, in recent years, with the increase in pattern density, not only the inspection of the pattern surface as in the above method, but also the minute defect of the transparent substrate itself that has been polished and mirror-finished with high accuracy becomes the object of defect detection. ing. In the above-described method, since light is collected in a minute area of the pattern surface, it is necessary to scan the light using some means when the inspection area covers a wide range, which is proportional to the area of the inspection area. Therefore, the inspection time is long, and the change in the amount of reflected / transmitted light with respect to the pattern itself and the transparent substrate is not so large depending on the presence or absence of defects, so that it is difficult to apply to the detection of minute defects on the transparent substrate.
[0004]
Therefore, in order to solve such problems, the present inventor has developed a non-uniformity inspection method for a translucent substance that can detect optical nonuniformity of the translucent substance with high sensitivity and high speed, and the method thereof. The device was previously proposed (Japanese Patent Application No. 9-192863).
[0005]
The present invention inspects for the presence or absence of a non-uniform portion of a translucent material having a mirror-finished surface. When the optical path of the translucent material is optically uniform, the surface is totally reflected. When light is introduced into the light-transmitting material so that the light is introduced, and there is a non-uniform portion in the optical path of the light introduced and propagated in the light-transmitting material, the light is leaked from the surface. It is characterized by detecting non-uniformity of a sex substance.
[0006]
In other words, the light introduced into the translucent material repeats total reflection on the surface and is confined inside the translucent material, and if the translucent material has uneven portions such as scratches on the surface, the total reflection condition is satisfied. However, non-uniformity is detected because light leaks from the surface of the translucent material. In this way, since geometric optical total reflection, which is a physical critical phenomenon, is used, non-uniformity appears with dramatic contrast, and minute scratches and the like can be detected with high sensitivity.
[0007]
In the said invention, as shown to Fig.7 (a), the laser beam L is introduce | transduced from the C surface (chamfering part) of the one side with respect to the transparent substrate 1 as a translucent substance, for example. By the way, a normal laser beam emitted from a laser has a beam diameter of 1 mm and a beam divergence angle of about 1 mrad. When the laser beam is emitted from the laser and reaches the transparent substrate 1 through an optical system such as a mirror, The beam diameter is about 2 mm. On the other hand, when the transparent substrate 1 is a glass substrate for photomask (glass substrate), the width of the C surface serving as the introduction surface of the laser light L is, for example, about 0.1 mm to 0.6 mm.
[0008]
For this reason, as shown in FIGS. 7A and 7B, of the laser light L irradiated to the transparent substrate 1, a part of the laser light L incident on the C plane (shaded portion of FIG. 7B). However, most of the remaining laser light L was wasted and could not be used effectively for inspection. In addition, most of the laser light L that could not be introduced into the transparent substrate 1 is reflected by the main surface H and the end surface T of the transparent substrate 1 and is incident on a detection system that detects non-uniformity (defect) detection light. As a result, the contrast of the defect detection light is lowered.
[0009]
In order to improve this, it is conceivable that the parallel laser light L is condensed using a condensing lens and irradiated onto the C surface. In this case, the light introduced into the transparent substrate 1 is absorbed in the substrate 1. After focusing, the light becomes divergent light, so that there is almost no light that satisfies the condition of being confined in the substrate 1 by repeating total reflection on the surface of the transparent substrate 1, and effective inspection cannot be performed. In addition, a method of increasing the width of the C surface and facilitating the introduction of light into the transparent substrate 1 can be considered, but in this method, the light can be introduced into the substrate 1, but the introduced light is transmitted to the substrate. Although the light is totally reflected on one surface and returns to the introduced C-plane side, the returned light immediately exits from the C-plane, and it is difficult to confine the light in the substrate 1.
[0010]
Therefore, in order to solve the above problems, the present invention can effectively introduce the irradiation light to the translucent substance into the translucent substance, and eliminate the fine non-uniformity (defect) existing in the translucent substance. It is an object of the present invention to provide a non-uniformity inspection method and apparatus for a translucent substance that can be detected with high accuracy and high speed, and a transparent substrate suitable for these inspections.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, a non-uniformity inspection method for a translucent substrate according to the present invention inspects nonuniformity of a translucent substrate having at least a pair of main surfaces and a pair of end surfaces that are mirror-finished. A method for inspecting a non-uniformity of a light-transmitting substrate, wherein the light-transmitting substrate has an optically uniform optical path when laser light is introduced into the light-transmitting substrate. The total reflection between the main surface and the end surface can be repeated to make it almost confined in the translucent substrate, and the optical path of the translucent substrate is optically uniform in the translucent substrate. In this case, the laser beam is introduced so as to be almost confined in the translucent substrate by repeating total reflection between the main surface and the end surface, and is introduced into the translucent substrate and propagates. When there is a non-uniform part in the laser beam path By utilizing the fact that a part of the introduced laser light leaks outside without being totally reflected by the main surface or end face of the translucent substrate, the leakage of the translucent substrate is detected by detecting the leaked light. The translucent substrate has an introduction surface for introducing laser light, and the introduction surface reduces the laser light introduced from the introduction surface by condensing the laser light. In addition, it is characterized in that it is formed in a concave cross section so as to be substantially parallel light.
[0012]
If the translucent material does not have non-uniform portions such as scratches and cracks on the surface, the light introduced into the translucent material is totally reflected on the surface and does not leak to the outside, but if there is a non-uniform portion, it is totally reflected. The conditions are not satisfied, and light leaks from the surface of the translucent material. In this way, since geometric optical total reflection, which is a physical critical phenomenon, is used, the response to light (inspection light) in the non-uniform part and uniform part of the translucent material to be inspected is also critical. And non-uniformity appears with dramatic contrast. In addition to the non-uniformity of the surface of the translucent material, it is also related to the detection of defects with the same transmittance but different refractive index, which are characteristic of internal defects such as bubbles and foreign matter, or glass striae. In a place where there is a foreign substance or a place where the refractive index is different, if it is essentially uniform, the light path (path) that passes through will be removed, and it will leak out of the translucent substance, so that it can be detected.
[0013]
Based on the above principle, the non-uniformity of the translucent material is inspected. In the present invention, the light introduced into the translucent material is condensed according to the size of the introduction surface of the translucent material. In addition, the introduction light (focused light) that is condensed and reduced is introduced into the translucent substance as almost parallel light by the introduction surface formed in a concave cross section. Even if the light introduced into the light-transmitting substance has a beam diameter larger than that of the translucent material introduction surface, most of the light introduced is effectively transmitted as parallel light with a cross-sectional shape that matches the size of the introduction surface. It can be introduced into the sex substance.
[0014]
In addition, the non-uniformity inspection apparatus for a translucent substrate according to the present invention is the non-uniformity of the translucent substrate for inspecting the non-uniformity of the translucent substrate having at least a pair of mirror-finished main surfaces and a pair of end surfaces. A method for inspecting uniformity , wherein the light-transmitting substrate has a light path between the main surface and the end face when the light path is optically uniform when laser light is introduced into the light-transmitting substrate. When the optical path of the translucent substrate is optically uniform with the translucent substrate, the main reflection can be achieved. Laser light is introduced so as to be totally confined in the translucent substrate by repeating total reflection between the surface and the end surface, and the optical paths of the respective laser beams introduced and propagated in the translucent substrate When there are non-uniform portions in the Non-uniformity of the translucent substrate by detecting the leaked light by utilizing a part of the laser beam leaked outside without being totally reflected by the main surface or end face of the translucent substrate The laser beam to be introduced is reduced in accordance with the size of the introduction surface with respect to the introduction surface for introducing the laser beam into the translucent substrate and is incident as almost parallel light. It is characterized by that.
[0015]
The introduction light is reduced in accordance with the size of the introduction surface with respect to the planar introduction surface for introducing light into the translucent material, and is incident as almost parallel light. Even if the introduced light has a beam diameter larger than that of the translucent material introduction surface, it can be irradiated as parallel light having a cross-sectional shape that matches the size of the introduction surface, and most of the introduced light is effectively transmitted as it is. It can be introduced into the sex substance.
[0017]
A non-uniformity inspection apparatus for a translucent substance according to the present invention is for carrying out the non-uniformity inspection method , and has a mirror-finished at least pair of main surfaces and a pair of end surfaces. An apparatus for inspecting non-uniformity of a light-transmitting substrate for inspecting non-uniformity of a light-transmitting substrate, wherein the light-transmitting substrate has an optical path optically introduced when laser light is introduced into the light-transmitting substrate. When uniform, the laser beam can be made to be in a state where it is confined within the light-transmitting substrate by repeating total reflection between the main surface and the end surface. Irradiation that introduces laser light so that when the optical path of the optical substrate is optically uniform, total reflection is repeated between the main surface and the end face so that the optical substrate is almost confined in the transparent substrate. Means and a laser which is introduced into the translucent substrate and propagates Utilizing the fact that when there is a non-uniform portion in the optical path of the light, a part of the introduced laser light leaks outside without being totally reflected by the main surface or end surface of the translucent substrate, The light detection means for detecting the leaked light and the introduction surface for introducing the laser light into the translucent substrate reduce the laser light introduced corresponding to the size of the introduction surface and make it almost parallel light And an optical system that makes the light incident.
[0018]
The transparent substrate of the present invention is suitable for the inspection method and apparatus described above, and is a transparent substrate having a mirror-finished surface. When the optical path of the transparent substrate is optically uniform, In order to introduce light into the transparent substrate so as to propagate the total reflection repeatedly, an introduction surface having a concave cross section is formed.
[0019]
In the inspection apparatus, it is desirable to provide an angle adjusting means for changing the incident angle of light with respect to the translucent substance. Since light having different incident angles propagates little by little while being totally reflected in the translucent material, the light reaches all corners of the translucent material without leakage. In addition, it is desirable to provide moving means for moving the light incident position on the surface of the translucent substance. When the incident position of the light is moved by the moving means, the light can be scanned quickly and without leaking over the entire area of the translucent material. Further, it is desirable to provide a detection means for detecting light leaking from the surface of the translucent substance without being totally reflected. Providing the detection means can automate the inspection of the non-uniformity of the translucent substance, shorten the inspection time, and improve the reliability of the inspection.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an embodiment of a non-uniformity inspection apparatus for translucent substances according to the present invention.
[0021]
In FIG. 1, reference numeral 1 denotes a rectangular flat plate transparent substrate made of optical glass or the like to be inspected. As shown in FIG. 2, the transparent substrate 1 has a main surface (front surface and back surface) H and an end surface (side surface) T, and the main surface H and the end surface T are mirror-polished. Each side (excluding one side a) of the transparent substrate 1 is a C-surface that is chamfered by chamfering so as to form 45 degrees with respect to the main surface H and the end surface T. In order to confine light introduced into the transparent substrate 1 into the substrate 1 by repeating total reflection several times on the surface of the transparent substrate 1, the width of the C surface is preferably as small as 0.4 mm. In the following, it is more preferable that the thickness is 0.2 mm or less. However, if it is extremely small (less than 0.1 mm), chipping occurs at the edge of the substrate during mirror polishing, which is not preferable.
[0022]
The transparent substrate 1 is held horizontally with as few contacts as possible by a folder (not shown) so that total reflection on the surface is not hindered and leakage light can be easily inspected.
[0023]
The transparent substrate 1 is provided with irradiation means for introducing laser light for inspecting non-uniformity into the transparent substrate 1. The irradiation means includes a laser 2 that emits a laser beam L, and mirrors 3 and 4 for irradiating the laser beam L to the introduction surface 6 on one side a of the transparent substrate 1 at a predetermined angle.
[0024]
The mirrors 3 and 4 are provided with an angle adjusting means 5 for adjusting the incident angle with respect to the transparent substrate 1, and the incident angle is varied within a range where the laser light introduced into the transparent substrate 1 causes total reflection. Can be incident. In addition, driving means (not shown) for horizontally moving the transparent substrate 1 held in the folder in the direction of one side a (introduction surface 6) is provided. By moving, the laser beam is scanned along one side a (introduction surface 6) of the transparent substrate 1.
[0025]
One side a of the transparent substrate 1 is an introduction surface 6 for introducing laser light into the transparent substrate 1, and the introduction surface 6 has a groove shape whose cross section is recessed in an arc shape as shown in FIGS. Is formed. For example, as shown in FIG. 3, the processing of the introduction light 6 is performed by arranging an axis of a cylindrical grindstone 7 along one side of the transparent substrate 1 installed horizontally, and rotating the grindstone 7 about the axis. It can be formed by descending.
[0026]
As shown in FIGS. 1 and 2, a condensing lens 8 that condenses the laser light L is provided between the introduction surface 6 and the mirror 5. As shown in FIG. 2 or FIG. 4, the condensing lens 8 condenses the laser light L having a circular cross section reflected by the mirror 5 in the width direction of the introduction surface 6 and condensing the laser light L having an elliptical cross section. ₁ is a cylindrical lens. The length in the minor axis direction of the laser beam L ₁ having an elliptical cross section irradiated on the introduction surface 6 is focused by the condenser lens 8 so as to substantially match the width of the introduction surface 6 as shown in FIG. . In order to introduce the laser beam L ₁ focused in the width direction of the introduction surface 6 as a parallel laser beam L ₂ into the transparent substrate 1 as shown in FIG. 2, the curvature of the introduction surface 6 having an arc-shaped cross section is introduced. Is set.
[0027]
Below the transparent substrate 1, detection means for detecting light leaking from the transparent substrate 1 is provided. The detection means includes a CCD 10 and an imaging lens 9 that forms an image on the CCD 10 with light leaked from the substrate 1. The optical sensor that detects the light leaking from the transparent substrate 1 is not limited to the CCD, and a photomultiplier or the like may be used. The CCD 10 analyzes the detected light information (light quantity, intensity distribution, etc.) to determine the type of non-uniformity (scratches and cracks on the surface, internal striae and bubbles), size, and non-uniformity of the transparent substrate 1. An image processing apparatus 11 for obtaining the position of the uniform portion is connected.
[0028]
Next, a method for inspecting the non-uniformity of the transparent substrate 1 using the above inspection apparatus will be described. First, the laser beam L emitted from the laser 2 is reflected by the mirrors 3 and 4 and applied to the introduction surface 6 of the transparent substrate 1. As the laser 2, a He—Ne laser having a beam diameter of 0.7 mm, a beam divergence angle of 1 mrad, a laser power of 0.5 mW, and a wavelength of 543.5 nm was used. When the condenser lens 8 is incident, the laser beam L having a circular cross section has a beam diameter of about 2 mm. The laser light L having the circular cross section is condensed by the condenser lens 8 in the width direction of the introduction surface 6. Then, the laser beam L ₁ is contracted and deformed to have an elliptical cross section so that the minor axis dimension of the laser light L ₁ having an elliptical section substantially matches the width (0.4 mm) of the introduction surface 6. Since the introduction surface 6 has a cross-sectional shape curved in an arc shape with a predetermined curvature in the width direction, it has a diverging action in the width direction of the introduction surface 6 and is focused and incident in the width direction of the introduction surface 6. The light L ₁ is introduced into the transparent substrate 1 and propagated as parallel laser light L ₂ having an elliptical cross section.
[0029]
In this way, the laser beam L having a beam diameter larger than the width of the introduction surface 6 can be introduced into the transparent substrate 1 as parallel light having a cross-sectional shape that matches the shape of the introduction surface 6. Most of the introduced light) can be effectively introduced into the substrate 1 and the laser light introduced into the substrate 1 is almost parallel light, so that many of the introduced lights have good conditions for total reflection on the surface of the substrate 1. Satisfied and well confined in the substrate 1. Further, a lot of light introduced into the substrate 1 is effectively confined in the substrate 1 and used, and is reflected on the surface of the substrate 1 without being introduced, or is introduced into the substrate 1 from the surface of the substrate 1. The amount of light that is immediately transmitted or incident on the detection means is reduced, and the contrast of the non-uniform detection light can be increased.
[0030]
As shown in FIG. 2, the parallel laser light L ₂ incident on the transparent substrate 1 propagates while repeating total reflection on the main surface H and the end surface T of the transparent substrate 1, and passes through the substrate 1 on a side orthogonal to the side a. The laser light L ₂ is almost confined in a single flat (thin plate) region cut along b. At this time, since the incident angle of the laser light L ₂ is continuously changed within the range satisfying the total reflection on the surface of the substrate 1 using the angle adjusting means 5, the inside of the substrate 1 is changed according to the change of the incident angle. The beam trajectory passing through the beam also shifts little by little, and the laser beam L ₂ propagates so as to cover the entire area of the one-dimensional irradiation region in the substrate 1 without omission.
[0031]
If the transparent substrate 1 has surface irregularities such as scratches or cracks, or internal irregularities such as striae or bubbles, light leaks from the surface of the transparent substrate 1 without being totally reflected by the uneven portions of the surface. In addition, since the light path (orbit) of the light is not uniform at the non-uniform portion inside the substrate 1, light leaks to the outside without satisfying the total reflection condition on the surface of the substrate 1. The leaked light is imaged on the CCD 10 by the imaging lens 9 and detected. In this way, when the substrate 1 is viewed from the main surface H side (detection means side), it is possible to inspect a one-line irradiation region. In this one-line inspection process, the transparent substrate 1 is sequentially moved in the direction of one side a (introduction surface 6) by the driving means, and laser light is scanned along one side a (introduction surface 6) of the transparent substrate 1. Thus, the nonuniformity of the entire area of the transparent substrate 1 can be inspected.
[0032]
FIG. 5 shows an embodiment in which, as another embodiment, a C-plane ground into a transparent substrate 1 is used as an introduction surface, and laser light L is introduced into the C-plane as parallel light with a reduced diameter. The laser light L has been circular cross section emitted from the laser is condensed by the convex lens 12, the laser beam L ₃ which is the focused laser beam L ₄ of the parallel light by the concave lens 13 installed in front of the focal point of the convex lens 12 ( (It has a spread of several mrad) and is incident on the C plane almost perpendicularly. The focal lengths of the convex lens 12 and the concave lens 13 to be used are determined so that the diameter of the laser beam L _{4 having} a circular cross section substantially matches the width of the C surface.
[0033]
FIG. 6 shows another embodiment in which light is introduced from a corner portion of the transparent substrate 1 and light is propagated throughout the entire area of the substrate 1. In this embodiment, the corner surface (introduction surface) 14 at the corner portion of the substrate 1 is recessed into a spherical shape to have a function of a concave lens, and the corner surface 14 is irradiated with laser light condensed by the convex lens 15. . The laser light focused to the size of the corner surface 14 by the convex lens 15 is returned to parallel light by the corner surface 14 and introduced into the substrate 1.
[0034]
In the above embodiment, a lens is used as an optical system for focusing the light introduced to the introduction surface of the transparent substrate. However, the introduction light is converged and diverged using a mirror such as a concave mirror or a convex mirror. It may be configured. In addition, it is preferable to use a zoom lens as an optical system that focuses and diverges light introduced to the introduction surface of the transparent substrate, because the introduction light can be adjusted according to the curvature and size of the introduction surface.
[0035]
By using the inspection method of the above-described embodiment, it is possible to quickly and appropriately eliminate defective transparent substrates and improve the productivity of transparent substrates. Note that a glass transparent substrate having defects such as scratches on the surface can be mirror-polished and cleaned again to obtain a substrate that falls within the range of specifications for various applications.
[0036]
Moreover, in the said embodiment, although the transparent substrate made from glass was mentioned as a translucent substance which has the mirror-finished surface, not only glass but optical plastics, such as an acrylic resin, optical crystals, such as a crystal | crystallization, test | inspections Any material that can transmit light may be used.
[0037]
Moreover, in the said embodiment, although the transparent substrate which has the surface by which mirror finishing was given was mentioned, it is not restricted to this, You may be a transparent substrate which has the surface by which part or the whole surface is not mirror finishing (however, In the above embodiment, when the introduction surface has a concave cross-sectional shape, it is preferably mirror-finished.) In that case, by applying a liquid such as matching oil onto a surface that is not mirror-finished, the surface becomes a surface that is mirror-finished (liquid free surface). Can inspect non-uniform portions.
The case where the entire surface of the transparent substrate is not mirror-finished means, for example, a case where only the non-uniformity (streaks, bubbles, foreign matters, etc.) inside the transparent substrate is inspected. In this case, if there is a non-uniform portion inside, it becomes a fatal defect. For example, in the case of a glass substrate for phase shift mask, defective products can be excluded by inspecting at the stage before mirror finishing. Therefore, the manufacturing cost can be reduced.
[0038]
Furthermore, the shape of the translucent substance is not limited to a square (rectangular) or circular substrate, but may be a block shape or a curved surface. The substrate can be applied to inspection of various substrates such as a photomask (phase shift mask) glass substrate, a liquid crystal glass substrate, and an information recording glass substrate (magnetic disk, optical disk, etc.). Since the information recording glass substrate is disk-shaped, when actually inspecting, laser light is incident from a polished outer peripheral or inner peripheral end surface (for example, a chamfered portion). When inspection on both sides of the substrate is necessary, detection means may be provided on both sides of the substrate, respectively, so that inspection on both sides of the substrate is performed at once.
[0039]
In the above embodiment, a gas laser (He-Ne laser) is used as the laser. However, the laser is not limited to this, and a laser in the visible region such as a semiconductor laser or a light-transmitting substance has little absorption. If so, an ultraviolet excimer laser, an infrared Nd-YAG laser, a CO2 laser, or the like can be used as an inspection light source. In particular, it is preferable to use an ultraviolet laser (for example, an excimer laser or a YAG laser harmonic) because foreign substances adhering to the substrate surface can be expected to be removed by an action such as evaporation or transpiration.
[0040]
In the above embodiment, the angle adjusting means 5 for changing the incident angle with respect to the substrate is provided on the mirrors 3 and 4 between the laser 2 and the transparent substrate 1. As long as the angle can be changed, any configuration may be used, and angle adjusting means may be provided in the laser itself. Alternatively, for example, by using a multi-line of Ar laser, laser light of a plurality of wavelengths is simultaneously incident on the introduction surface of the transparent substrate or the like from the same direction, and is introduced into the transparent substrate or the like due to a difference in refractive index depending on the wavelength You may comprise so that light may inject with a different incident angle. Further, the laser light may be guided using an optical fiber instead of a mirror as in the above embodiment.
[0041]
In the embodiment shown in FIG. 1 (or FIG. 5), the example in which the laser beam L is introduced from one side a (introduction surface) of the transparent substrate 1 has been described. The inspection may be performed by introducing light from one side b as the introduction surface or by introducing light from two directions from side a and side b. It is preferable to inspect by introducing light from two directions because it is effective for detecting a directional defect and the like, and a highly accurate inspection can be performed.
[0042]
【The invention's effect】
As described above in detail, according to the present invention, the introduction light is reduced in accordance with the size of the introduction surface of the translucent substance, and is introduced into the translucent substance as almost parallel light. Therefore, most of the introduced light can be effectively used as non-uniform inspection light. In addition, a large amount of light introduced into the translucent material can be effectively confined in the translucent material, and reflected from the surface of the translucent material without being introduced. Therefore, the contrast of the non-uniformity detection light can be increased, and the fine non-uniformity can be detected with higher accuracy.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an embodiment of a non-uniformity inspection apparatus for translucent substances according to the present invention.
2 is an enlarged cross-sectional view showing a state of light introduction into the transparent substrate of FIG. 1 and light propagation in the transparent substrate.
FIG. 3 is a perspective view showing an example of a method of forming an introduction surface having an arc-shaped cross section on a transparent substrate.
FIG. 4 is a perspective view showing an embodiment in which laser light is condensed on an introduction surface having an arcuate cross section by a condensing lens.
FIG. 5 is a cross-sectional view showing another embodiment in which laser light is incident on a planar introduction surface of a transparent substrate.
FIG. 6 is a perspective view showing another embodiment in which laser light is introduced from a corner portion of a transparent substrate.
FIG. 7 is a view for explaining a state when laser light having a larger diameter than the introduction surface is introduced into the introduction surface of the transparent substrate.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Laser 3, 4 Mirror 5 Angle adjustment means 6 Introduction surface 8 Condensing lens 12 Convex lens 13 Concave lens 15 Convex lens L Laser light

Claims (5)

A method for inspecting non-uniformity of a translucent substrate for inspecting non-uniformity of a translucent substrate having at least a pair of mirror-finished main surfaces and at least a pair of end surfaces ,
When the optical path is optically uniform when laser light is introduced into the translucent substrate, the translucent substrate repeats total reflection between the main surface and the end surface and substantially transmits the laser light. It can be in a state of being confined in the optical substrate,
When the optical path of the translucent substrate is optically uniform, the translucent substrate repeats total reflection between the main surface and the end surface and is almost confined in the translucent substrate. Introduce laser light so that
When there is a non-uniform portion in the optical path of the laser beam introduced and propagated into the translucent substrate, a part of the introduced laser beam is not totally reflected at the main surface or end surface of the translucent substrate. Inspecting the non-uniformity of the light-transmitting substrate by detecting the leaked light by utilizing leakage to the outside,
The translucent substrate has an introduction surface for introducing laser light, and the introduction surface is recessed so as to condense and reduce the laser light introduced from the introduction surface to be substantially parallel light. A method for inspecting non-uniformity of a light-transmitting substrate, characterized by being formed in a cross-sectional shape. A method for inspecting non-uniformity of a translucent substrate for inspecting non-uniformity of a translucent substrate having at least a pair of mirror-finished main surfaces and at least a pair of end surfaces ,
When the light path is optically uniform when laser light is introduced into the light transmissive substrate, the light transmissive substrate totally reflects the laser light between the pair of main surfaces and the pair of end surfaces. Repeatedly, it can be in a state where it is almost confined in a translucent substrate,
When the optical path of the translucent substrate is optically uniform, the translucent substrate repeats total reflection between the main surface and the end surface and is almost confined in the translucent substrate. Introduce laser light so that
When there is a non-uniform portion in the optical path of the laser beam introduced and propagated into the translucent substrate, a part of the introduced laser beam is not totally reflected at the main surface or end surface of the translucent substrate. Inspecting the non-uniformity of the light-transmitting substrate by detecting the leaked light by utilizing leakage to the outside,
A laser beam introduced into the translucent substrate for introducing the laser beam is reduced in size so as to correspond to the size of the introduction surface and is incident as substantially parallel light. Non-uniformity inspection method for optical substrates. The non-uniformity inspection of a translucent substrate according to claim 1, wherein the introduction surface is a chamfered surface formed on each side where a main surface and an end surface of the translucent substrate intersect. Method. A non-uniformity inspection apparatus for a translucent substrate for inspecting non-uniformity of a translucent substrate having at least a pair of main surfaces and at least a pair of end surfaces mirror-finished ,
When the optical path is optically uniform when laser light is introduced into the translucent substrate, the translucent substrate repeats total reflection between the main surface and the end surface and substantially transmits the laser light. It can be in a state of being confined in the optical substrate,
When the optical path of the translucent substrate is optically uniform, the translucent substrate repeats total reflection between the main surface and the end surface and is almost confined in the translucent substrate. An irradiation means for introducing a laser beam,
When there is a non-uniform portion in the optical path of the laser beam introduced and propagated into the translucent substrate, a part of the introduced laser beam is not totally reflected at the main surface or end surface of the translucent substrate. A light detecting means for detecting the leaked light by making use of leaking to the outside;
An optical system for reducing the laser light to be introduced in accordance with the size of the introduction surface and making it incident as substantially parallel light with respect to the introduction surface for introducing the laser light into the translucent substrate. A non-uniformity inspection apparatus for a light-transmitting substrate. A translucent substrate having at least a pair of mirror-finished main surfaces and at least a pair of end faces,
When the optical path is optically uniform when laser light is introduced into the translucent substrate, the translucent substrate propagates the laser light by repeating total reflection between the main surface and the end surface. Thus, in order to introduce a laser beam into the translucent substrate, a concave introduction surface is formed.

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