ROBUST OPTICAL-SYSTEMS FOR NONDESTRUCTIVE TESTING BASED ON LASER-DIODES AND DIFFRACTIVE OPTICAL-ELEMENTS

Two robust systems for vibration measurements are presented. Both syst ems are based on low-cost laser diodes. The stability of the optical s ystems is achieved by implementing the optical system as a holographic optical element (HOE) while using a common-path interferometer concep t for the measurement scheme. The former system facilitates real-time simultaneous tracking of vibrations about two axes perpendicular to th e optical axis. The latter system is an electronic speckle interferome ter working in a differential mode providing whole-field information o n the angular deformation about one axis between two states of the obj ect. It will be argued that these concepts will provide compact, self- aligning systems for industrial use due to the inherent possibility of mass fabrication. (C) 1998 Elsevier Science Ltd. All rights reserved.