Patent ID: 8049158

Claim:
A photonic proximity sensor, comprising: a first light source operable to emit first light of a first wavelength and at a first duty cycle; a second light source operable to emit second light of a second wavelength and at a second duty cycle and 180-degrees out of phase with the first light; an input polarizer coupled to receive the first light and the second light and configured to polarize the first light and the second light; a magneto-optic element coupled to the input polarizer to receive the polarized first light and the polarized second light, the magneto-optic element having greater sensitivity to the first wavelength than the second wavelength, and thereby being responsive to variations of a magnetic field to rotate the polarized first light more than the polarized second light; an output polarizer coupled to the magneto-optic element to receive the rotated and polarized first light and the polarized second light and configured to further polarize the first light and further polarize the second light; a target movable relative to the magneto-optic element to cause the variations of the magnetic field; and a first photodetector coupled to receive at least the further polarized first light and operable, in response thereto, to supply a first signal of a first amplitude magnitude that varies at least with the rotation of the further polarized first light.