| 摘要 |
PURPOSE:To obtain a high-accuracy measuring instrument which measures film thickness accurately by adjusting the size of the spot of a laser light source on a film surface. CONSTITUTION:A projector 14 consists of an expander which expands measurement luminous flux 15 and a cylindrical lens which reduces the size of the luminous flux and projects the measurement light 15 on a formed film at an angle of incidence larger than a Brewster angle so that the luminous flux is adjustable. A photodetector 17 photodetects reflected light 16 or transmitted light and converts it photoelectrically. A detecting means detects the film thickness property of the film based on an electrical signal outputted by the photodetector 17. At this time, the film surface is projected with laser light 15 at an angle of incidence larger than the Brewster angle and reflected light 16 of a P and an S component obtained as mentioned above is photodetected 17, so that an interference waveform is formed by an arithmetic part 25. Consequently, intervals of troughs of the signal, the number of the troughs, and the phase of starting are found to measure the film thickness variation and the width of trough tips is found to measure an irregularity in thickness.
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