| 摘要 |
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. |
