A small-angle self-mixing measurement system with improved detection resolution based on a rotatable pentagonal prism

A modified small-angle measurement system is proposed to improve the angle measurement resolution by selecting a rotatable pentagonal prism to replace the right-angle prism based on the original small-angle measurement system. In our measurement system, the right-angle side length of pentagonal prism is crucial to the measurement resolution. For the pentagonal prism with 2 cm side length, the resolution can reach 64.68 urad, while the resolution is up to 30.48 urad for the pentagonal prism with 4 cm side length. Therefore, it is possible to obtain higher measurement resolution by choosing the pentagonal prism with a larger side length within a proper range as the key optical element in the modified small-angle measurement system, so as to achieve the purpose of system optimization. In addition, the small-angle measurement system with a rotatable pentagonal prism we have designed can be helpful and referential to the future study of self-mixing interference technology with high-resolution requirements on the basis of different prisms.