| 摘要 |
PURPOSE:To measure film thickness accurately by observing the beat frequency of frequencies of two laser oscillators which are obtained by moving a substrate having a film whose thickness is to be measured. CONSTITUTION:The film 6 which transmits laser light and whose thickness is to be measured is formed on the substrate 7, and an annular laser resonator having the surface of the substrate 7 as part of a reflecting surface is provided. The substrate 7 is moved by a driving source 11 in a specific direction at a constant speed to divide the laser oscillation frequencies of the laser resonator into two frequencies by an optical path difference. Then, the two laser oscillation frequencies are put together by a half-mirror 5 and inputted to a detector 12 to obtain a signal of beat frequency. This signal is amplified by an amplifier 13 and inputted to a counter 15 through a filter 14 to observe and display it. The thickness of the coating film is known accurately and easily from the observation result. |
