| 摘要 |
PURPOSE:To ensure the measurement of the thickness of a film, by forming two sets of interference fringes by combining two light waves having different light-path lengths, inserting a rotatable sample film, which can be rotated into the direction where the light path length is changed, in one light path, and detecting the rotary angle of the sample. CONSTITUTION:Light from a laser light source 4 is divided into reflected luminous flux 13 and transmitted light 14 by a reference surface 7. The light 14 is further divided into a part alpha, which is directly inputted to a mirror 8, and a part beta, which is inputted to the mirror 8 after transmission through a sample 16. The light beams 13, alpha and beta go backward on the light path and are projected on a screen 12 through a half mirror 5 and a lens 11. On the screen 12, interference fringes Aalpha, which are formed by combining the reflected light A and the transmitted light alpha, and interference fringes Bbeta, which are formed by the reflected light B and the transmitted light beta, are formed. The interference fringes Aalpha are reference fringes. Bbeta are deviated by the difference in light paths owing to the sample. Based on the amount of deviation, the phase difference of the interference fringes is obtained. Namely, based on the distances between the interference fringes and the amount of deviation DELTAS, which are shown in a monitoring TV25, a ratio DELTAS/S is obtained. A rotary table 15 is rotated by a processor, and the incident angle to the sample 16 is changed. The phases difference of the interference fringes is obtained again and inputted to the processor 17. Thus the thick ness of the sample 16 is obtained. |
