Strain inspection apparatus for transparent materials

摘要

A strain inspection apparatus (1) for inspecting strain in an object includes a first polarizing plate (7); a second polarizing plate (8) opposing to the first polarizing plate (7) with a predetermined distance being provided therebetween, the second polarizing plate (8) forming on one surface thereof at the side of the first polarizing plate a test surface on which an object to be inspected is placed; a diffusion plate (9) arranged at the other surface of the second polarizing plate (8); an illumination device (10) for irradiating light on the diffusion plate (9) from a side opposite to the side where the second polarizing plate (8) is arranged; a holder (11) for accommodating therein the illumination device (10); and a light source (12) arranged at a bottom surface of the holder (11). The light source (12) is constituted by an LED; and the illumination device constitutes a surface illumination device which is adapted to produce uniform light from light emitted by the LED. The illumination device (10) includes a reflection plate having a plurality of small holes (14) therein.