Fig. 1. Diagram of 4pi focusing configuration. The lateral and axial directions are denoted by the r axis and z axis, respectively.

Fig. 2. Calculated PSF profiles (a) in the transverse direction and (b) in the axial direction for the RP‐LG1,1 beam, RP beam, circularly polarized beam, and x-axis linearly polarized beam, respectively. The peak intensities have been normalized to one.

Fig. 3. 2D intensity distributions of the (a) PSFbright and (b) PSFdark in the xz plane (y=0). Axial profiles of the PSFdark for different values of (c) NA and (d) β0, respectively. (e) Axial profiles of the PSFbright (red dashed line), PSFdark (green dotted line), and PSFsub (blue solid line) in the z axis. (f) Intensity distribution of the PSFsub in the xz plane (y=0).

Fig. 4. Corresponding axial OTFs calculated for the PSFbright (blue solid line) and PSFsub (red dashed line) when the value of γ is 0.3.

Fig. 5. Transverse intensity distributions in the focal plane when illuminated by (a) RP‐LG1,1 beams and (b) circularly polarized beams, respectively. (c) Intensity distributions of the PSFsub in the xy plane (z=0). (d) The corresponding lateral profiles of intensity distributions along the x axis.

Fig. 6. (a) 3D point array sample. (b) Cross section of the 3D sample in the xz plane.

Fig. 7. (a) 3D image reconstruction of the point array sample with the PSFbright. (b) xz slice and (c) xy slice of the image in (a). (d) 3D image reconstruction of the point array sample with the PSFsub. (e) xz slice and (f) xy slice of the subtracted image in (d).