2π double-helix point spread function based on ring segmentation method for nanoparticle tracking technique

A well-established method for 3D nanoparticle tracking is the double-helix point spread function (DH-PSF) engineering, which uses additional optical elements to make the PSF exhibit different rotation angles with varying depths of nanoparticles. Splicing the symmetric spiral phases together using the phase splicing method can generate the modulated phase mask of 2π-DH-PSF. The 2π-DH-PSF has a linear rotation rate at each axial position and has a larger rotation angle, showing a more accurate rotation angle and depth translation. Experiments with a phase-only spatial light modulator demonstrate the potential of the 2π-DH-PSF. Finally, we successfully conducted 3D nanoparticle tracking experiments at 8-μm depth with a numerical aperture of 1.4, showing its great potential.