Application of Vernier Principle to Photoelectric Autocollimator for Improvement of Accuracy, Angular Range and Speed

An improvement of photoelectric autocollimator is proposed. Periodical structures of light source grating and photodetector array form an additional combination signal of Vernier type. The solution promises to exceed the limits of accuracy, angular range and speed imposed by finite number of photodetector elements. Calculation of a lens for trial version of the device with specified characteristics necessary to ensure measurement accuracy shows attainability of F-theta distortion within 10–
⁶
% - tenths of nanometres, without taking manufacturing tolerances into consideration. It is significantly less than value of light spot within diffraction limit (3 microns) and typical pixel pitch of the linear or matrix sensor. The transverse aberrations also seem hard attainable lower than the diffraction limit. The processing speed of designed trial version of autocollimator is about 30 measurements per second and if needed it can be increased in case of using digital camera with higher frame rate in the device construction.