Fiber optic displacement sensor for thickness measurement based on transmission and reflection of transparent plate

A comparison in measuring thickness of transparent plate between transmission and reflection based fiber optic displacement sensor is reported. A series of standard glass slide each with thickness of 150 pm is utilized as specimens. The performance both of the sensor is characterized based on the estimation of the peak voltage, sensing displacement, and slope's variation. The thickness sensor based beam through technique is found to be more pronounces in all aspects compared to reflection one. It is realized to be three times better in sensitivity. Even more prominently in slope variation whereby 65 times compare to front slope and 657 times to back slope. Inherently the transmission based also shown higher resolution. Hence transmission based FODS is more precision system for measuring the thickness of transparent plate in comparison to reflection. Directionality, lack of beam losses during insertion, no scattering, diffusions and absorption involve attribute to such high accuracy of beam through thickness sensor. Furthermore it is more reliable and user friendly sensor since its simplicity in setting, low cost and nondestructive testing and yet enables to provide precision measurement.