Expanding the realm of fiber optic confocal sensing for probing position, displacement, and velocity

We describe a fiber optic confocal sensor (FOCOS) system that uses an optical fiber and a lens to accurately detect the position of an object at, or close to, the image plane of the fiber tip. The fiber characteristics (diameter and numerical aperture) and optics (lens F/# and magnification) define the span and precision of the sensor and may be chosen to fit a desired application of position and displacement sensing. Multiple measurement points (i.e., fiber-tip images) may be achieved by use of multiple wavelengths in the fiber, so that each wavelength images the fiber at a different plane due to the chromatic dispersion of the optics. Further multiplexing may be achieved by adding fibers on the optical axis. A FOCOS with multiplexed fibers and wavelengths may also be used for velocity measurements.