Angular deflection sensing apparatus for load, force, and other types of measurements

A displacement transducer for converting displacement into an electrical signal comprising

• mechanical means whereby a linear displacement applied to a certain part will result in an angular displacement in another part;
• means for attaching a first light polarizer to said mechanical means so that said angular displacement will cause the polarization axis of the first polarizer to rotate by an angle equivalent to said angular displacement whereas this angle will be referred to as .theta.;
• a second light polarizer in such a configuration that it is parallel to said first polarizer, that the polarization axis of said first and second polarizers are inclined with respect to each other at an angle referred to as .phi., prior to application of aforementioned linear displacement, and that said linear displacement will cause .phi. to change by an amount .theta.;
• a first photodetector that receives light from
• a light source transmitted through said first and second polarizers so that the intensity of transmitted light through said first and second polarizers varies as the angle between said polarization axes varies, resulting in a variation of the output of said first photodetector;
• a second photodetector that receives light directly from said light source in a fixed geometrical configuration such that light received by said second photodetector is not affected by said linear displacement;
• means of configuring aforementioned first and second polarizers such that the angle .phi. is in the general neighbourhood of 45.degree., that when .phi. takes this value, the range of linearity of the variations of the intensity of light that is transmitted through the combination of said first and second polarizers, as a function of the variation of the angle between said polarization axes of said first and second polarizers, is maximally extended;
• associated circuitry that enables the intensity of said light source to be rigorously controlled by comparing the output of said second photodetector with a reference, and
• circuitry that enables the intensity of light received by said first photodetector to be converted into an electric signal.