Apparatus for measuring thickness of film

Abstract

Abstract PURPOSE:To make it possible to measure the thickness of a film to be measured even if the position of said film changes, by transmitting light with a predetermined wavelength through the film to be measured to detect the signal proportional to the thickness of said film. CONSTITUTION:A light source 2 is driven on the basis of the order of a digital processing circuit 10 by a drive apparatus 13 to emit light which is, in turn, condensed by a condensing lens 3 to be transmitted through a magnetic tape 1. This light is branched into two lights by a spectroscope 4 and both lights respectively pass through first and second filters 5, 6 to form lights with different wavelengths. These lights are respectively photoelectrically converted to first and second signals by light receivers 7, 8. These signals are converted to a digital value by an A/D converter 9 and said value is processed by the digital processing circuit 10. At this time, because the light source 2 is subjected to pulse driving by the order of the circuit 10 and two signals are converted so as to shift a time in synchronous relation to timing performing the A/D conversion of both signals, two signals are converted to a digital signals by the single converter 9. The circuit 10 calculates the inclination of light transmissivity of a film 1b to be measured from both values obtained when lights enter the light receivers 7, 8 and when said lights do not enter said receivers 7, 8 an the output proportional to the thickness of the film can be obtained without receiving the effect of a dark current.

Inventors

• 👤 Yoshiaki Ida
• 👤 井田　芳明

Bibliographic Details