DOUBLE REFRACTION MEASURING APPARATUS FOR DISC

摘要

PURPOSE:To enable automatic measurement of double refraction with the setting of a disc, by taking out a transmission light or a reflected light of the disc through a rotary type analyzer. CONSTITUTION:Linearly polarized component of light from a semiconductor laser 10 is taken out with a polarized beam splitter 11 and the light is turned to a parallel light with a collimator lens 12 to be converted into a circularly polarized light with a lambda/4 plate 13. The circularly polarized light 13a is turned to a light 13b passing through an optical disc substrate 2 to be applied to a rotary optical analyzer 14 and a laser light 14a on the output side thereof is applied to a photo sensor 15. A sensor 15 detects modulation (double refraction) of the circularly polarized light 13a attributed to the substrate 2. The substrate 2 rotates intermittently by a specified angle with a step motor 21 and the motor 21 is moved along a slit guide 22 during the suspension of the rotation thereby making the irradiation of the laser light radial.