JPH11258172A - Method and apparatus for inspection of heterogeneity of translucent substance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method and an apparatus in which the optical heterogeneity of a translucent substance can be detected with high sensitivity and at high speed. SOLUTION: Laser light L is introduced into a transparent substrate 1 from one side (a) of the transparent substrate 1. On the other hand, an ultrasonic beam U whose frequency is changed is propagated inside the transparent substrate 1 from one side (b) of the substrate 1. When the laser light L is incident on a region whose refractive index is changed due to the ultrasonic beam U, first-order diffracted light L1 , first-order diffracted light L2 ,... due to the Bragg diffraction are generated in addition to zero-order light L0 which travels straight without being diffracted. The zero-order light L0 , the first-order diffracted light L1 , the first-order diffracted light L2 ,... are propagated while the total reflection is being repeated on the main surfaces H and the edge T of the transparent substrate 1, they are set to a state that the light is confined mostly inside the substrate 1, and the light is spread everywhere inside the substrate 1. When a heterogeneous part such as a flaw or the like exists in the transparent substrate 1, the light is not reflected totally on the surface of the substrate 1, and the light is leaked from the surface of the substrate 1. When the leaked light is detected, the heterogeneity of the transparent substrate 1 can be inspected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for inspecting optical nonuniformity (defect) of a transparent material such as a transparent substrate for a photomask and a transparent substrate for a liquid crystal display. The present invention relates to a method and an apparatus for inspecting the non-uniformity of a light-transmitting material, which can detect the non-uniformity of the light-transmitting material with high sensitivity and high speed by utilizing the total reflection on the surface of the light-transmitting material. It is.

[0002]

2. Description of the Related Art In a process of manufacturing 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 highly polished and mirror-finished transparent substrate. . An inspection method for a photomask, which can be said to be a master of this pattern, involves collecting light in a small area of the pattern surface, as seen in a surface state inspection apparatus described in Japanese Patent Application Laid-Open No. 58-162038. A method of comparing a reflection output and a transmission output is known.

[0003]

However, in recent years, with the increase in the density of patterns, not only the inspection of the pattern surface as in the above-mentioned method, but also the fineness of the highly polished and mirror-finished transparent substrate itself has been achieved. Defects are also targeted for defect detection. In addition, in the above-described method, since light is collected in a minute area on the pattern surface, if the inspection area is over a wide range, it is necessary to scan the light using some means, and the light is scanned in proportion to the area of the inspection area. The change in the amount of reflected light and transmitted light with respect to the pattern itself and the transparent substrate is not so large depending on the time required for inspection and the presence or absence of a defect, and it is difficult to apply the method to detection of fine defects in the transparent substrate.

In order to solve such a problem, the present inventor has proposed a non-uniformity inspection of a light-transmitting substance capable of detecting the optical non-uniformity of the light-transmitting substance with high sensitivity and high speed. A method and an apparatus have been proposed (Japanese Patent Application No. 9-192763).

The present invention inspects the presence or absence of a non-uniform portion of a light-transmitting substance having a mirror-finished surface. When the light path of the light-transmitting substance is optically uniform, the surface is checked. When light is introduced into the light-transmitting material so that total reflection occurs, light leaks from the surface when there is a non-uniform part in the optical path of light that is introduced and propagated into the light-transmitting material. And detecting the non-uniformity of the light-transmitting substance.

That is, light introduced into the light-transmitting material is repeatedly total reflected on the surface so as to be confined inside the light-transmitting material. If the light-transmitting material has an uneven portion such as a scratch on the surface, the total reflection occurs. Since the condition is not satisfied and light leaks from the surface of the light-transmitting substance, non-uniformity is detected. in this way,
Since geometrical 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.

The above inspection method and apparatus are used, for example, in an inspection step after a manufacturing step of a glass substrate which is a transparent substrate for a photomask. (The length of the transparent substrate for the photomask is usually about ± 0.4 mm in length and about ± 0.1 mm in thickness), and the size of the glass substrate having the dispersion is one sheet. Inspection after grasping one sheet and finding the optimum total reflection conditions for each glass substrate took an enormous amount of time, which was not practical.

Accordingly, the present invention has been made to solve the above-mentioned problem, and even if a light-transmitting substance such as a glass substrate has a variation in dimensions due to processing accuracy or the like, the optical property of the light-transmitting substance is not improved. An object of the present invention is to provide a highly practical method for inspecting non-uniformity of a light-transmitting substance, which can detect non-uniformity with high sensitivity and high speed, and an apparatus therefor.

[0009]

To achieve the above object, a first method for inspecting non-uniformity of a light-transmitting substance according to the present invention is a method for inspecting non-uniformity of a light-transmitting substance. So,
Light is introduced into the light-transmitting substance from the surface of the light-transmitting substance,
The optical path of the translucent material is obtained by utilizing the acousto-optic effect of the light introduced into the translucent material and the ultrasonic beam generated by the ultrasonic wave generating means and propagating in the translucent material. When the light is optically uniform, the angle of incidence of light on the surface is changed within a range in which total reflection can occur on the surface, and unevenness occurs in the optical path of light introduced and propagated in the translucent material. When a part is present, non-uniformity of the light-transmitting substance is detected from light leaking from the surface. Specifically, it is preferable that the change in the incident angle of the light be caused when the light first enters the main surface after the light enters the translucent material.

If there is no non-uniform part such as a scratch on the surface of the translucent substance, the light introduced into the translucent substance is totally reflected by the surface and does not leak to the outside. The reflection condition is not satisfied, and light leaks from the surface of the light transmitting material. As described above, since the geometrical optical total reflection, which is a physical critical phenomenon, is used, the response to the inspection light in the non-uniform part and the uniform part of the translucent material to be inspected is also critical. , Non-uniformities appear with dramatic contrast. Also,
Characteristic not only for the non-uniformity of the surface of the translucent material, but also for defects due to foreign matter and impurities inside, or striae of glass, etc.
Regarding the detection of defects with the same transmittance but different refractive index, even if there is a foreign substance or the refractive index is different, the light path (path) that is originally uniform will deviate and leak to the outside of the translucent substance. Therefore, it becomes detectable.

The non-uniformity of the light-transmitting material is inspected based on the above principle. The light introduced into the light-transmitting material and the ultrasonic wave generated by the ultrasonic wave generating means are used to inspect the light-transmitting material. Utilizing the acousto-optic effect with the ultrasonic beam propagating in the substance, when the optical path of the translucent substance is optically uniform, the light is transmitted to the translucent substance surface within a range where total reflection can occur on the surface. Since the incident angle of light is changed, the size of the translucent material to be inspected varies, and even if there is some difference in the optimal total reflection condition for each translucent material, Different light propagates through different paths while being totally reflected on the surface of the light-transmitting material, and light can be transmitted to every corner of the light-transmitting material without leakage.

In the above invention, the ultrasonic beam can be easily propagated into the light-transmitting material by, for example, bringing the transducer (piezoelectric element) into contact with the surface of the light-transmitting material. When an ultrasonic beam is propagated in a translucent material, a periodic change in the refractive index appears in proportion to the period of the ultrasonic wave, and the periodic change in the refractive index functions as a diffraction grating. For this reason, when light enters the region where the ultrasonic beam has propagated, in addition to undiffracted light that travels straight, deflected diffracted light is generated, and light with a different incident angle is incident on the surface of the translucent material. Will be.

When the frequency of the ultrasonic wave generated from the transducer is changed and the ultrasonic beam having the changed frequency is introduced into the translucent material, the period of the refractive index of the translucent material changes. As a result, the diffraction angle (deflection angle) of the diffracted light changes, so that various lights having slightly different incident angles on the surface of the light-transmitting material can be transmitted.

In the second method for inspecting non-uniformity of a light-transmitting substance according to the present invention, when the light path of the light-transmitting substance is optically uniform, total reflection occurs on the surface of the light-transmitting substance. Within the obtainable range, the light whose traveling direction is changed by the acousto-optic effect is introduced into the translucent material from the introduction surface for introducing light into the translucent material, and is introduced into the translucent material. When an uneven portion is present in the optical path of the propagating light, the light leaks from the surface to detect the non-uniformity of the light-transmitting substance. In the second inspection method, when light is introduced from the surface of the translucent material, the traveling direction of the light is changed by the acousto-optic effect within a range satisfying the condition of total reflection on the surface of the translucent material. Light (that is, light having a different incident angle to the surface) is introduced. Specifically, the traveling direction of light is changed by an acousto-optic polarizer.

An apparatus for inspecting non-uniformity of a light-transmitting substance according to the present invention is for performing the above-described first or second method for inspecting non-uniformity. Irradiation means for introducing light at a predetermined angle into the light-transmitting substance, and when the optical path of the light-transmitting substance is optically uniform, the light propagates into the light-transmitting substance within a range where total reflection can occur on the surface. Ultrasonic wave generating means for changing the traveling direction of light by an acousto-optic effect.

[0016] In the above apparatus, a moving means for moving the incident position of the light on the translucent substance is further provided, so that the light can be quickly scanned without leaking over the entire area of the translucent substance. It becomes possible. Further, if a detecting means for detecting light leaking from the surface of the light-transmitting substance without being totally reflected from the surface is further provided, the inspection of the non-uniformity of the light-transmitting substance can be automated, and the inspection time can be shortened. Reliability can be improved.

[0017]

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 device for testing non-uniformity of a translucent substance according to the present invention.

In FIG. 1, reference numeral 1 denotes a rectangular flat transparent substrate made of quartz glass to be inspected. Transparent substrate 1
As shown in FIG. 2, has a main surface (front and back surfaces) H and an end surface (side surface) T, and the main surface H and the end surface T are mirror-polished. Each side of the transparent substrate 1 has a main surface H and an end surface T
The surface is ground and chamfered to form an angle of 45 degrees with respect to the C surface.

Irradiation means for introducing a laser beam for inspecting non-uniformity into the transparent substrate 1 is provided on the transparent substrate 1. Irradiation means is laser light L
And mirrors 3 and 4 for irradiating the laser light L to the C-plane of one side a of the transparent substrate 1 at a predetermined angle.

A transducer 5 is provided in contact with a side b (C plane) of the transparent substrate 1 which is parallel to the side a and immediately below the side a. The transducer 5 is for generating an ultrasonic beam U in the transparent substrate 1 by inputting a high-frequency voltage from a driver (high-frequency oscillator) 6 connected thereto. The ultrasonic beam U is incident from the side b at a predetermined angle. Further, the transducer 5 also constitutes a part of a folder for holding the transparent substrate 1 horizontally.

The transparent substrate 1 held in the folder
A driving means (not shown) for moving the transparent substrate 1 horizontally in the direction of one side a of the transparent substrate 1 is provided.
Is configured to scan with the laser light L along.

Below the transparent substrate 1, a detecting means for detecting light leaking from the transparent substrate 1 is provided.
The detecting means detects the CCD 8 and the light leaked from the substrate 1
And an imaging lens 7 that forms an image on D8. In addition, as an optical sensor for detecting light leaked from the transparent substrate 1, C
Not limited to a CD, a photomultiplier or the like may be used. The CCD 8 analyzes the information of the detected light (light amount, intensity distribution, etc.) and detects the type of non-uniformity of the transparent substrate 1 (scratch or crack on the surface, internal striae and bubbles), the size, An image processing device 9 for obtaining the position of the uniform portion is connected.

Next, a method for inspecting the non-uniformity of the transparent substrate 1 by the above-described inspection apparatus will be described. First, the laser light L emitted from the laser 2 is reflected by the mirrors 3 and 4 so that the transparent substrate 1
And the laser light L is introduced into the transparent substrate 1. As laser 2, beam diameter 0.7mm, beam divergence angle 1mrad, laser power 0.5mW,
A He-Ne laser with a wavelength of 543.5 nm was used.

On the other hand, the tuning DC voltage of the driver 6 is varied so that the center frequency 110
Ultrasonic waves are generated by applying a high-frequency voltage that fluctuates at ± 25 MHz around the MHz, and the ultrasonic beam U whose frequency fluctuates at 110 MHz ± 25 MHz from one side b of the transparent substrate 1 is propagated into the transparent substrate 1.

The ultrasonic beam U causes the transparent substrate 1
Within, the refractive index fluctuation with the period of the ultrasonic wave occurs,
This acts as a diffraction grating. Therefore, when the laser beam is incident on the refractive index fluctuation region due to the ultrasonic waves, the first-order diffracted lights L ₁ , L ₂ ,... Due to Bragg diffraction are generated in addition to the zero-order light L _{0 that} travels straight without receiving diffraction. Although the diffraction angle (deflection angle) of the first-order diffracted light in Bragg diffraction is almost proportional to the ultrasonic frequency, in the present embodiment, since the frequency of the ultrasonic wave is changed, the first-order diffracted light in which the deflection angle continuously changes is used. L
₁ , L ₂ ,... Occur. Zero-order light L ₀ , first-order diffracted light L ₁ , L
₂ ,... Enter the main surface H at an incident angle satisfying the condition of total reflection.

The zero-order light L ₀ , the first-order diffracted lights L ₁ , L ₂ ,.
One-plane shape (thin plate shape) that propagates while repeating total reflection on the main surface H and the end surface T of the transparent substrate 1 and cuts the substrate 1 along the direction of one side c orthogonal to one side a of the transparent substrate 1
Is almost confined within the region.

If the surface of the transparent substrate 1 is uneven such as scratches or cracks, or if the inside of the substrate such as striae or bubbles is present, the surface of the transparent substrate 1 is not totally reflected by the uneven part of the surface but is not reflected. Since the light leaks out and deviates from the optical path when the optical path (trajectory) of the light is uniform in the uneven portion inside the substrate 1,
Light leaks outside without satisfying the condition of total reflection on the surface of the substrate 1. The leaked light is imaged on the CCD 8 by the imaging lens 7 and detected. In this way, when the substrate 1 is viewed from the main surface H side (detection means side), a one-line irradiation area can be inspected. In this one-line inspection process, the transparent substrate 1 is sequentially moved in the direction of one side a by the driving means, and the laser beam is scanned along the one side a of the transparent substrate 1 so that the entire area of the transparent substrate 1 is scanned. Inspection of non-uniformity can be performed.

In this embodiment, the first-order diffracted lights L ₁ , L ₂ ,.
Is continuously changed within a range that satisfies the total reflection on the surface of the substrate 1, so that many lights having different incident angles are incident on the main surface H of the transparent substrate 1. The trajectory of the light beam passing through the substrate 1 shifts little by little according to the change, and the introduced light propagates so as to completely cover the entire one-plane irradiation region in the substrate 1.

For this reason, each transparent substrate (glass substrate)
Even if you do not input the laser beam after grasping the incident condition that causes more total reflection, it is highly practical by changing the incident angle within the range of the incident angle that satisfies the certain total reflection condition. Inspection of non-uniformity of the glass substrate can be performed. Therefore, in the process of inspecting a plurality of glass substrates, even if each glass substrate slightly varies in size due to a difference in processing accuracy, a ray trajectory propagating in the glass substrate by changing the incident angle of light. Is also shifted little by little, so that the entire area in the substrate is inspected. This means that unevenness of the glass substrate can be inspected by absorbing variations in the processing accuracy of the glass substrate.

Here, in the process of inspecting a plurality of glass substrates, the exact dimensions of the glass substrates are measured as described in Japanese Patent Application No. 9-192763, and the incident conditions under which more total reflection is performed are set. If the inspection method of injecting laser light after grasping is adopted, extra time before inspection is performed, {(time for measuring the dimensions of the glass substrate) + (simulation time)} × (number of inspections) It is not practical because it will take.

FIG. 3 shows an example in which the acousto-optic deflector 10 is used to change the incident angle from the C-plane of the transparent substrate 1 within the range where total reflection can occur on the surface of the transparent substrate 1 so that the laser light can enter the substrate 1. 5 shows an embodiment for introducing L. As shown in FIG.
The acousto-optic deflector 10 has a transducer 11 adhered to one end of an acousto-optic medium 12 and an absorber 13 attached to the other end.
The ultrasonic beam U is transmitted from the transducer 11 to the absorber 13 to the acousto-optic medium 12 by a high frequency signal from the driver 14. The laser light L from the irradiating means is irradiated toward one side b (C plane) of the transparent substrate 1. In order to deflect the laser light L, the acousto-optic medium 1
2 are provided in contact with the side b (C plane) of the transparent substrate 1. Also in this embodiment, the frequency of the ultrasonic beam U is changed, and the laser beam L applied to the side b (C plane) of the transparent substrate 1 is diffracted by passing through the acousto-optic medium 12. In addition to the zero-order light L _{0 that} travels straight without receiving, the first-order diffracted lights L ₁ , L ₂ , whose deflection angle changes little by little,
Are generated, and the zero-order light L ₀ and the first-order diffracted lights L ₁ , L ₂ ,.
Goes to the main surface H at an incident angle that satisfies the condition of total reflection.

By using the inspection method of the above-described embodiment, a transparent substrate having a defect can be quickly and appropriately eliminated, and the productivity of the transparent substrate can be improved. Note that a glass transparent substrate having a defect such as a scratch on the surface is again subjected to precise mirror polishing and cleaning treatment, whereby a substrate falling within the range of specifications for various applications can be obtained.

In the above embodiment, the frequency of the ultrasonic beam is changed, but an ultrasonic beam having a constant frequency may be used. Further, in the embodiment of FIG. 1 described above, the transducer 5 is brought into direct contact with the transparent substrate 1, but an acousto-optic medium such as acousto-optic glass is adhered to the transducer 5 and the inside of the transparent substrate 1 is inserted through the acousto-optic medium. An ultrasonic beam may be introduced. further,
Ultrasonic waves may be introduced from other than the C-plane of the transparent substrate 1.

In the above embodiment, a transparent substrate made of quartz glass is used as the light-transmitting material having a mirror-finished surface. However, the present invention is not limited to quartz glass, and other types of glass, optical plastic, and quartz may be used. Any material may be used as long as the inspection light can be transmitted and an acousto-optic effect can be obtained, such as an optical crystal.

In the above embodiment, a transparent substrate having a mirror-finished surface has been described. However, the present invention is not limited to this, and a transparent substrate having a partially or entirely non-mirror-finished surface may be used. . In this case, by applying a liquid such as matching oil on a surface that has not been mirror-finished, the surface becomes a mirror-finished surface (free surface of the liquid). This allows inspection of non-uniform portions.

The case where the entire surface of the transparent substrate is not mirror-finished refers to, for example, a case where only non-uniformity (striae, bubbles, foreign matter, etc.) inside the transparent substrate is inspected. In this case, if there is a non-uniform part inside, it will be a fatal defect.For example, in the case of a glass substrate for a phase shift mask, it is necessary to exclude defective products by inspecting it before mirror finishing. The manufacturing cost can be reduced.

Further, the shape of the light-transmitting substance is not limited to a square (rectangular) or circular substrate, but may be a block or a curved surface. Further, as the substrate, it is applicable to inspection of various substrates such as a glass substrate for a photomask (phase shift mask), a glass substrate for a liquid crystal, and a glass substrate for information recording (magnetic disk, optical disk, etc.). Since the glass substrate for information recording has a disk shape, the actual inspection is performed by irradiating a laser beam from a polished outer or inner peripheral end surface (for example, a chamfered portion). If inspection of both sides of the substrate is required, detection means may be provided on both sides of the substrate, and inspection of both sides of the substrate may be performed at once.

In the above embodiment, a gas laser (He-Ne laser) is used as the laser.
Not limited to this, an excimer laser in the ultraviolet region or an Nd-YA in the infrared region, as long as the laser is in the visible region, such as a semiconductor laser, or has a low absorption for a light-transmitting substance.
A G laser, a CO2 laser or the like can be used as a light source for inspection. In particular, it is preferable to use an ultraviolet laser (for example, a harmonic of an excimer laser or a YAG laser) because foreign substances or the like adhering to the substrate surface can be expected to be removed by an action such as evaporation or evaporation.

Further, in the embodiment shown in FIG. 1, an example in which the laser light L is introduced from one side a of the transparent substrate 1 has been described.
For example, the inspection may be performed by introducing light from the side c of the transparent substrate 1 or by introducing light from the side a and the side c in two directions. It is preferable to perform inspection by introducing light from two directions, because it is effective for detecting a directional defect and the like, and a more accurate inspection can be performed. When laser beams are simultaneously incident from two directions, it is preferable to introduce ultrasonic waves also from the side parallel to the side c. Further, the laser beam may be incident from the C plane at the corner of the transparent substrate instead of the C plane on the side a or the side c.

In the above embodiment, the laser beam is scanned while moving on the transparent substrate side. However, the laser beam is scanned by moving on the laser irradiation system side including the laser 2, the mirrors 3, 4 and the like. You may.

Although not shown in the above embodiment,
In order to actually inspect a plurality of light-transmitting substances (such as a glass substrate), it is necessary to introduce light to a predetermined position of the light-transmitting substance. Detecting means for detecting a positional relationship, for example, a laser scanning measurement system (manufactured by Canon), a precision distance measuring device (manufactured by YHP)
Also, it is possible to provide a laser interferometer or the like, or to provide a device such as a TV camera, a CCD image sensor, or the like for observing the surface state of a translucent material and removing an object that has not been mirror-finished, for example. Good. Note that the above information may be captured as data in a computer or the like, and control may be performed by transmitting a control signal to an irradiation unit, a moving unit, or the like.

[0042]

As described in detail above, according to the present invention,
The acousto-optic effect of the light introduced into the translucent material and the ultrasonic beam propagated into the translucent material, or the light introduced into the translucent material and propagated into the acousto-optic medium Since the direction of light propagating in the translucent material is changed using the acousto-optic effect with the ultrasonic beam, the size of the translucent material to be inspected varies, and the Even if there is a slight difference in the optimal total reflection condition for a substance, for example, light that has a different incident angle on the main surface that strikes first after light is incident on the translucent substance is totally reflected on the surface of the translucent substance. In this way, the light propagates through different paths, so that light can be transmitted to every corner of the translucent material without leakage. For this reason,
The non-uniformity of the translucent substance can be reliably inspected with high accuracy, and the utility is high. Moreover, since the light is deflected using the acousto-optic effect, the inspection can be performed easily and at a high speed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a non-uniformity inspection apparatus for a translucent substance according to the present invention.

FIG. 2 is an enlarged side sectional view showing an end face portion where a laser beam and an ultrasonic beam are introduced into the transparent substrate of FIG. 1;

FIG. 3 is a side sectional view showing another embodiment in which laser beams having different incident angles are introduced from the surface of a transparent substrate.

[Explanation of symbols]

Mirror 1 transparent substrate 2 laser 3, 4 5 transducer 6 Driver seventh imaging lens 8 CCD 10 acoustooptic deflector 11 transducer 12 acoustooptic medium L laser beam L ₀ 0 order light L _1, L ₂ 1-order diffracted light U ultrasonic beam

Claims (5)

[Claims] 1. A method for inspecting non-uniformity of a light-transmitting substance, comprising: introducing light into the light-transmitting substance from a surface of the light-transmitting substance; The ultrasonic wave generated by the generating means utilizes an acousto-optic effect with an ultrasonic beam propagating in the translucent material, and the optical path of the translucent material is optically uniform when the optical path is optically uniform. The incident angle of light on the surface is changed within a range where total reflection can occur, and when there is a non-uniform part in the optical path of light that is introduced and propagated in the translucent material, light is emitted from the surface. A method for inspecting non-uniformity of a light-transmitting substance, wherein the non-uniformity of the light-transmitting substance is detected from leakage. 2. The method according to claim 1, wherein said ultrasonic wave generating means is a transducer. 3. The translucent light according to claim 2, wherein the frequency of the ultrasonic wave generated from said transducer is changed, and the ultrasonic beam having the changed frequency is propagated in said translucent material. Testing method for non-uniformity of chemical substances. 4. A method for inspecting non-uniformity of a light-transmitting substance, wherein the optical path of the light-transmitting substance is optically uniform within a range where total reflection can occur on the surface of the light-transmitting substance. Introducing light whose traveling direction has been changed by an acousto-optic effect from an introduction surface for introducing light into the light-transmitting substance, and unevenness in an optical path of light introduced and propagated into the light-transmitting substance. A method for inspecting non-uniformity of a light-transmitting substance, wherein light non-uniformity of the light-transmitting substance is detected from light leaking from the surface when a part is present. 5. An apparatus for inspecting non-uniformity of a light-transmitting substance, comprising: an irradiating means for introducing light at a predetermined angle from a surface of the light-transmitting substance into the light-transmitting substance; Ultrasonic wave generating means for changing the traveling direction of light propagating in the translucent material by an acousto-optic effect within a range where total reflection can occur on the surface when the optical path is optically uniform. A non-uniformity inspection device for a light-transmitting substance.