| 摘要 |
PROBLEM TO BE SOLVED: To provide a film thickness measuring method and a device capable of measuring online accurately even if irregularities exist on the surface. SOLUTION: This film thickness measuring device 1 is characterized by having a first light source 2 for irradiating a film to be measured with light having a first wavelength, a first incident light photodetector 8 for measuring the intensity of incident light having the first wavelength, a first transmitted light photodetector 8 for measuring the intensity of transmitted light having the first wavelength, a first comparator for determining a first ratio which is the ratio between the intensity of incident light having the first wavelength and the intensity of transmitted light, a second light source 4 for irradiating light having a second wavelength different from the first wavelength, a second incident light photodetector 10 for measuring the intensity of incident light having the second wavelength, a second transmitted light photodetector 10 for measuring the intensity of transmitted light having the second wavelength, a second comparator for determining a second ratio which is the ratio between the intensity of incident light having the second wavelength and the intensity of transmitted light, and a film thickness calculator 12 for determining the film thickness based on the first ratio and the second ratio.
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