High-resolution angular measurement arithmetic based on pixel interpolations

Abstract

Image angular displacement measurement devices are equipped with image sensors which identify calibration grating to digitalize angular displacement outputs. It is easier to realize high-resolution angular displacement measurement than the traditional optical moiré fringe measurement method in a miniaturized device. This paper proposes a high-resolution angular displacement measurement algorithm based on pixel interpolation which was designed to resolve the measurement output error caused by low pixel resolution in the image sensor. An optical path for angular displacement measurement using a linear image sensor close to the calibration grating is proposed. We find that the effects of insufficient pixel quantity in the range of the grating marking line can be ameliorated using a high-resolution measurement algorithm based on pixel interpolation. The proposed algorithm is applied to simulated and experimental image angular displacement measurements to verify its performance. The results show that the proposed algorithm markedly improves the measurement resolution when the number of pixels in the range of marking lines detected by the image sensor is insufficient. We achieve a resolution of 0.15″ and accuracy of 12.93″ with circular grating diameter of 38 mm. The results presented here may enhance the theoretical basis of high-resolution angular displacement measurement.