Optical measurements with stereoscopic shadows

The phenomenon of colored shadows were first published by Goethe in 1810. These colored shadows can be displayed stereoscopically through a pair of colored glasses. Furthermore, the stereoscopic shadow images can also be used to perform optical measurements. We present the principles of the measurements, particularly for measuring the threedimensional position of an object. The limits of the measurement method, in terms of its sensitivity, resolution, and sources of errors, are described. When the size of the measured object becomes comparable with the light wavelength, and when the light intensity becomes smaller and the photon nature of the light needs to be taken into account, the geometrical analysis of the measurement method needs to be replaced first with the wave analysis and then with the photon analysis. Our measurement of position can be extended into measurements of displacement, velocity, acceleration, shape, and orientation. Copyright © 2020 SPIE.