Fiber optic sensor for angular displacement and surface slope measurement

Abstract

ABSTRACT This paper introduces opticalfiber based a novel high speed sensing technique to measure angular displacement as well asslope of a smooth object. The scheme is based on the analysis of the directional intensity distribution of the reflected andscattered electromagnetic wave from the object. Theoretical predictions supported by the experimentally verfled results arepresented. A fairly good accuracy in the angular displacement and slope measurement in the range of 1 0' radians to 1 06radians can be achieved by this proposed technique.Key Words: Fiber optic sensors, Optical sensors, Precision measurement, Precision surface metrology, Optical metrology,Optical testing. 1. INTRODUCTION The automation in manufacturing and quality assurance in industries require non-destructive measurement of angular displacement of different parts of an instrument as well as surface characterization of a product with great precision.The increasing higher standards of on-line and in-process quality tests necessitate novel, fast and flexible sensors, whichshould as far as possible, be non-interacting to record quality characteristics directly in the production environment. Severalauthors have proposed optical fiber based sensors for surface topology and slope measurement [1-7]. Optical sensors withopto-electronic converters and with matching signal processing algorithm are indispensable in systems that form integral partof the measurement and characterization scheme. They provide a good basis for the implementation in on-line and in-processquality control environment. The precision of measurement and its resolution depends on the type of the optical sensor and itsdimension. This paper presents a fiber optic sensor which finds its use in angular displacement and slope measurement incases, where the probed target is of the order of few microns, it becomes necessary to use fiber optic probe whose dimensionsare at most of the same order.