| 摘要 |
PROBLEM TO BE SOLVED: To highly precisely measure a film thicknesses of first and second layers formed on a base film layer with simultaneous multilayer application. SOLUTION: Lights with mutually different center wavelengthsλ1,λ2 are respectively projected from projectors 10A, 10C to a base film and the lights transmitted through the base film are respectively detected by light receivers 20A, 20C. Two projected lights are projected from projectors 10A-10D to a magnetic recording medium 1 and the lights transmitted through the magnetic recording medium 1 are respectively detected by the light receivers 20A, 20C. Analogue signal representing the intensities of the transmitted lights are amplified by AMPs 23A, 23C, converted into digital data by A/DCs 24A, 24C and input to a computer 30. In accordance with the intensities of the lights transmitted through the base film and the intensities of the lights transmitted through the magnetic recording medium 1, a film thickness t1 of a first layer and the film thickness t2 of a second layer can be calculated by the computer 30.
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