Optical fiber coupled displacement probe with a new compensation method for surface measurement

Abstract

Displacement sensing has been the most basic and important measuring techniques due to it`s much relation to the other measurements and standards. And the surface characterization, the nature of surfaces and the measurement of surfaces are key factors for precision industries. The intensity modulated type (reflective method) optical fiber displacement sensor is a well-known method and widely applied to displacement measurement and other industrial purposes. Though this type displacement sensor has lots of advantages (relatively cheap cost, small sensor size and easiness of operation), the sensitivity of the sensor is very dependent on several sources of error (the variation in the intensity of the light source, the changes in the surface reflectivity of the object). A optical fiber coupled displacement probe with a new compensation method is presented in this paper. A newly designed optical fiber coupled displacement probe is developed to measure the different surfaces independent of those different surface characteristics. In general every surface has the different surface characteristics. Surface reflectivity, surface processed grade and surface stuff can affect the result of the light intensity measuring techniques. So, each measurement should be compensated according to its surface characteristics. In order to eliminate those surface characteristics effect on the light intensity modulated measuring technique we need some compensation skills. In this paper, we aimed to develop the compact and cheap fast light intensity modulated type displacement measuring technique using optical fiber bundle probe. This probe is composed of 5-main parts. Light source, sensor probe, detector system, scanning stage. We use the two laser sources (one for 633nm He-Ne laser, the other for 780nm laser diode) and adopt two band pass filters to segregate the two different output signals. And we set the offset length (d) for two source fiber, which is 300μm longer than 780nm source ...