Optical measuring device with means for suppressing reflections

Claim 1

An optical measuring device for measuring a physical quantity, comprising: a light source means adapted to generate incident light, a measuring transducer exposed to the quantity to be measured and responsive to the incident light and able to modify the latter in response to changes in the quantity to be measured, photo-detector means to respond to light coming from said measuring transducer and to produce electrical signals therefrom, electronic means to process said signals and produce an output indicative of the quantity to be measured, a light-transmitting system comprising a single optical fiber, the means for coupling incident light into said single fiber and modified light out of said single fiber consisting of a fiber optical Y-branch, said light-transmitting system feeding incident light from said light source means to said measuring transducer and feeding modified light from said measuring transducer to said photo-detector means, a first element for polarizing the incident light entering said light-transmitting system from said light source means, and a second element for polarizing the light fed to the photo-detector means, the difference in the direction of polarization between the two polarizing elements being chosen so that a direct path for light from said light source means to said photo-detector means via reflections in said light-transmitting system in and adjacent to the photo-detector means are substantially blocked from said photo-detector means by said second polarizing element, thus preventing said reflected signal from interfering with the measurement result, thus light polarized in one direction, and being reflected, being blocked in a polarizing device for polarization in another direction.