Design of low-order Hartmann-Shack wavefront sensor for annular laser beam

Based on the fact that there were a large percentage of low-order aberrations which had large PV values in high-energy laser beam, a Hartmann-Shack wavefront sensor for measuring first five-order Zernike aberrations was presented and designed. The lens part of the sensor adopted a method with combination of a 6-units micro-lens array and a convex lens, and the micro-lens array was distributed in annular. Since the lens material of this sensor was GaF₂, the designed sensor could be applied to the low-order aberrations measurement of visible and infrared laser beam. This method had the advantages of low cost, simple structure and large detection range, which was suitable for the measurement of large PV-value low-order aberrations of the annular laser beam. Afterwards, a measurement system for the low-order Hartmann-Shack wavefront sensor had been set up, and the results show that the measuring range was ±8λ (λ=3.39 μm) and the accuracy was less than λ/10 (λ=3.39 μm).