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Abstract

An integrated-photocircuit interferometer (20) comprises a substrate (21) in which coherent light for measurement emitted from a light source (23) is directed through an exit waveguide (22) toward a corner cube prism (34) which can be movable with an object to be measured. The light reflected back from the prism (34) can enter an inlet waveguide (33) having branch waveguides (35, 36) which split the incident measurement light. Part of the light transmitted through the exit waveguide (22) is transferred to reference waveguides (26, 27) which provide different optical path lengths for the light propagated therethrough. The 'reference beams of light' which has been transmitted through the different lengths of optical paths provided by the reference waveguides (26, 27) are introduced into the branch waveguides (35, 36) where interference occurs between the reference beams and the split beams of incident light from the corner cube prism (34). The interference will cause changes in brightness detected by photodetectors (37, 38) as the prism (34) is shifted toward or away from the interferometer (20). Since there is an optical path length difference between the reference waveguides (26, 27), a great number of changes can be detected by the photodetectors for a shift of the prism. Thus, the amount of the shift can be determined to a high resolution. In addition, the relationship in phase between the detected brightnesses will change depending on the direction of movement of the corner cube prism (34). The direction of the prism's movement can thus be detected.

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First Claim