| 摘要 |
PROBLEM TO BE SOLVED: To obtain a thickness measuring apparatus which has a simple constitution, which can perform a measurement at a high speed, with high accuracy and stability, and whose maintenance is easy. SOLUTION: A coherent light, which is emitted from a light source 31, is converted into desired linearly polarized light by a polarizer 32. The linearly polarized light is made incident on a birefringent specimen 33 to extract a beam of ordinary light and a beam of abnormal light. The extracted beams of light are made incident on a wedge prism 34. A beam of light, which is transmitted through the incident position of the specimen 33 and which has phase difference changed according to a thickness obtained, by adding the thickness of the specimen 33 to the thickness of the wedge prism 34 is extracted. The extracted beam of light is received by an analyzer 35. Components in one polarization direction is extracted regarding the beam of normal light and the beam of abnormal light. The component of the beam of normal light and the component of the beam of abnormal light in one polarization direction are made to interfere, and the interference generated is projected to the imaging screen of an imaging device 36 as interference fringes. By observing projected interference fringes, the thickness of the specimen 33, which depends on the displacement of the interference fringes, is measured by an image processor 37.
|
