Fig. 1. (a) Schematic of the HISTR-SAPM setup. DMD1 and DMD2, digital micromirror devices; M1 and M2, mirrors; OL1 and OL2, objective lenses; and BS, beam splitter. (b) (i)–(iii) are the raw interferograms under three different illumination angles, and (iv)–(vi) are their corresponding spatial spectra.

Fig. 2. (a) The spatial spectrum synthesis process in HISTR-SAPM. The dotted circles correspond to the frequency passband in Fig. 1(b). (b), (c) High-resolution amplitude and phase reconstruction, respectively.

Fig. 3. Imaging of a custom-made subwavelength grating structure: (a) the original design of the structure; (b) a portion of the structure imaged under SEM; (c) the height map retrieved using conventional QPM; (d) the height map reconstructed using HISTR-SAPM; and (e) the line profiles along the white lines in (b) and (d).

Fig. 4. RBC membrane height fluctuation over a time period of 1 s (Video S1): (A) cell center region; (B) cell outer region; and (C) background region. Time-lapse video of RBC membrane fluctuation (Video S1, MP4, 5.87 MB [URL: https://doi.org/10.1117/1.AP.2.6.065002.1]).

Fig. 5. Observation of subcellular structures in unlabeled living cells: (a), (d) the phase maps of a COS-7 and a HeLa cell under normal illumination; (b), (e) the phase maps reconstructed with HISTR-SAPM for the cells in (a), (d); and (c), (f) the phase gradient maps obtained from (b), (e).

Fig. 6. Observation of living 3T3 cell dynamics after exposure to acetic acid (Video S2). (a)–(c) The representative phase map frames reconstructed with HISTR-SAPM for the 3T3 cell during exposure to acetic acid. (d) The time-lapse curves showing phase evolution in the nucleus, cytoplasm, and background over time. Time-lapse video of 3T3 cell dynamics after exposure to acetic acid (Video S2, MP4, 6.19 MB [URL: https://doi.org/10.1117/1.AP.2.6.065002.2]).