| 摘要 |
PURPOSE:To measure the thickness of each layer on an in-process basis by providing a light source, a collimator lens, and an optical separating element. CONSTITUTION:When the light source 5 emits light beams which differ in wavelength alternately, those light beams are formed into pieces of parallel luminous flux by passing through a collimator lens 6 to illuminate a magnetic tape 1. At this time, the light emitted by the light source 5 is branched by separating elements 8 and 9 and sent to filters 10 and 11. The filter 10 transmits only light with one wavelength and sends its transmitted light to a detection part 13 through a condenser lens 12. The filter 11, on the other hand, transmits only the light with the other wavelength and sends its transmitted light to a detection part 15 through a condenser lens 14. Respective detection parts 13, 15, 20, and 23 when receiving light beams send out electric signals corresponding to the quantities of the incident light beams and they are amplified 24-27 and sent to a thickness calculation part 28. This calculation part 28 receives those electric signals to calculate the film thickness of the magnetic layer of the magnetic tape 1. |
