MEASUREMENT OF SMALL ANGLES BETWEEN ELECTROMAGNETIC-WAVES FOR REFRACTION STUDIES

In the measurement system under investigation two light beams of different colour and small difference angles (deltabeta almost-equal-to 0.1'') are focused within a telescope onto two displaced spots, which are then chopped by a piezoelectric transducer and directed to red- and blue-sensitive detector elements. The distance of the focal points is proportional to the angle between the two light beams, which can be calculated with the phase difference of the photodiode signals and the speed function of the chopper. The accuracy and sensitivity of this principle are demonstrated by various experiments under reproducible conditions.