Fiberoptic displacement sensor using interferometric techniques

摘要

Displacement of an object from a sensor is detected using a fiber optic a discharge end of which is arranged adjacent to the space from the object. Light passing along the fiber optic is reflected at the discharge end and is also reflected by the object at a position spaced from the discharge end. These two reflected parts of the light interfere causing an interference pattern. The light path from the discharge end to the object is cyclically varied using a sinusoidal dither obtained either by physical movement or by electro-optical means. This allows the output from the photo diode detecting the return reflected light to be analyzed as an alternating signal varying over time rather than as a simple comparison of absolute values as is used in the conventional techniques.