Optoelectronic apparatus for the remote measuring of a physical magnitude

An optoelectronic apparatus for the remote measuring of a physical magnitude, the apparatus comprising two light sources emitting luminous fluxes centered on two different wavelengths, means for controlling the alternate operation of these light sources, a sensor receiving the luminous flux emitted by one of the said light sources and then the luminous flux emitted by the other of said light sources, the sensor being subjected to the physical magnitude to be measured and causing a periodic spectral modulation of the luminous flux at a frequency depending on the value of the physical magnitude, and analysis means for analyzing the luminous flux transmitted by the sensor, said analysis means being of the static type and comprising a birefringent element which is tuned to the sensor and produces an optical path difference close to that produced by the sensor, the analysis means further comprising a set of polarization separating cubes which form four parallel analyzing channels, and a quarter wave-plate placed on two of the analyzing channels, the light signals at the outputs of the analyzing channels being of the form 1+cos.phi., 1-cos.phi., 1+sin.phi. and 1-sin .phi. respectively, .phi. being the phase of the light signal transmitted by the birefringent element, the analysis means further comprising photodetectors at the outputs of the four analyzing channels and data processing means connected to the photodetectors for computing the modulo 2.pi. value of the said phase .phi., the difference of the central wavelengths of the luminous fluxes emitted by the light sources being such that the absolute value of the difference of the phase .phi.1 and .phi.2 of the signals transmitted successively by the birefringent element when the light sources are alternatively on and off remains less than .pi. for a given range of values of the physical magnitude to be measured.