公开(公告)号：US4075555A

公开(公告)日：1978-02-21

申请号：US781506

申请日：1977-03-25

申请人： James S. Wight ,  Walter J. Chudobiak ,  Vassilios Makios

发明人： James S. Wight ,  Walter J. Chudobiak ,  Vassilios Makios

IPC分类号： G01B7/06 ,  G01R25/02 ,  G01R27/04

CPC分类号： G01R25/02 ,  G01B7/06

摘要： A continuous wave, phase measurement system which provides at least an order of magnitude improvement in accuracy over modulated carrier systems is disclosed for the determination of the thicknesses of layered targets consisting of a known number of dielectric layers, each of a known maximum thickness. This system uses related frequencies such as the fundamental and its harmonics to establish a multi-harmonic coherence relationship whereby a homodyne phase reference between harmonics can be conserved and information extracted from just the received and not the transmitted signals. Consequently doppler effects due to motion between the target and the apparatus, as well as severe local oscillator stability and drift limitations are avoided, and thus this system can measure remote target parameters by interferometric techniques without the distance being a constraint.