APPARATUS FOR MEASURING EXTINCTION RATIO OF POLARIZED OPTICAL ELEMENT

摘要

PURPOSE:To make it possible to measure the extinction ratio of a polarized optical element without a mechanical rotating element and without a high-power light source by providing a light source, a Faraday element, a magnetic field generating means and a photodetector. CONSTITUTION:A laser light source 10 emits laser light 32. The laser light 32 is made to be the parallel light through a collimator lens 12. The laser light 32 is made to be the linear polarized light which is in parallel with an optical axis 30 and has high linearity through a polarizer 14. The light is inputted into a Faraday element 16. An electromagnet 18 which is arranged around the element 16 generates a magnetic field by current conduction so that the magnetic field is applied on the element 16. The element 16 rotates the plane of polarization of the incident laser light 32 in response to the magnetic field. A photodetector 22 receives the laser light transmitted through a specimen to be measured 20 and generates the electric output corresponding to the amount of light. In this way, a rotating mechanism is omitted, and elements characterized by much optical loss such as a 1/4 wavelength plate can be omitted. A high-power light source is not required. Many specimens can be efficiently measured with the simple constitution.