| 摘要 |
<p>PURPOSE:To surely detect a body to be detected in the same manner as a blank having a light-shielding property such as a sheet of paper or the like even in the case of a transparent body such as a transparent sheet or the like by a method wherein two polarization plates are installed in a light path so as to keep an interval where the body to be detected is marched in the middle. CONSTITUTION:When a body 20 to be detected is a transparent body of a non-isotropic material, linearly polarized light which has passed a first polarization plate 12 is rotated optically by a birefringence phenomenon when it is transmitted through the body 20 to be detected, and has a light-wave component parallel to the polarization direction of a second polarization plate 14. Consequently, the body 20 to be detected is situated in the middle between the first polarization plate 12 and the second polarization plate 14, light waves are passed through the second polarization plate 14, an optical signal is detected by a photodetection part 16 and the existence of the body 20 to be detected is detected. Although the optical rotation degree of the body 20 to be detected is changed by the property of a refractive index of the body 20 to be detected and by the thickness of the body 20 to be detected, the light-wave component which passes the second polarization plate 14 is formed when the object 20 to be detected is formed of the non-isotropic material. Thereby, an optical signal can be detected.</p> |
