Large depth range DH-PSF with high peak confinement invariance

In recent years, DH-PSF designs have gradually been improved regarding achievable precision, but are still somewhat limited in the applicable range. Based on the Fresnel zone design, DH-PSF can achieve large-range depth localization. However, it suffers from low precision because the side lobes increase and the main lobes weaken. This paper concludes that the rotating PSF range depends on the diffracted-free beam's superposition field range. By substituting the constraint of the Fresnel zone with that of the superposition field range, we can first determine the measurement range (i.e., the range of the superimposed field) and then adjust the position of the radial regions to make the largest width of the radial region, thus generating a double-helix PSF with high peak confinement invariance (compact main lobes). Theoretical and experimental results demonstrate that the applicable range of DH-PSF with high peak confinement invariance can be flexibly adjusted by radial region width. The experiment shows that the appropriate measurement range has improved under specific design parameters from 30 mm to 100 mm. The localization performance of the presented approach in industrial applications is tested experimentally by particle imaging at different positions.