Fig. 1. Schematic of the spiral PC idler imaging system.

Fig. 2. Theoretical simulations: (a) the spiral PC idler image of a phase-only object, (b) the traditional spiral PC image (without OPA), the idler images (c) with a Gaussian laser pump and (d) with a vortex laser pump of a quasi-phase object.

Fig. 3. Setup of the spiral PC idler imaging. VOA, variable optical attenuator; M, mirror; TA, target; MS, microscope; L1–L5, optical lenses; DM, dichroic mirror; TDL, time delay line; SPP, spiral phase plate; NC, OPA crystal; CCD, CCD camera.

Fig. 4. Idler images: (a1) and (b1) with Gaussian pump, (a2) and (b2) with vortex pump, and (c1) and (c2) for the local 1D intensity profile of Group 4.4 marked with the white arrow in (a1) and (a2), respectively. Meanwhile, (a1) and (a2) for an intensity object (a USAF 1951 resolution testing pattern) and (b1) and (b2) for a phase object (a pattern formed by a piece of flat glass coated with UV curing adhesive).

Fig. 5. Idler images of the USAF 1951 resolution testing pattern with a 40× MS: (a) Gaussian laser pump and (b) vortex laser pump.

Fig. 6. Microscopic images of frog egg cells and onion epidermis by (a1) and (b1) conventional MS imaging, (a2) and (b2) bright-field idler imaging, and (a3) and (b3) spiral PC idler imaging.