Fig. 1. OCT longitudinal resolution enhancement based on measured point spread function^[18]. (a) Measured longitudinal point spread function of OCT system; (b) measured sample signal of OCT longitudinal line scan; (c) sample signal after deconvolution

Fig. 2. OCT measurements (The vertical dotted lines in the figure indicate the relevant distinct spectral features)^[19]. (a) Typical spectrum of crystal fiber emission before spectral shaping; (b) interference signal obtained by scanning a sample with a reflector, in which the half-height full width of the envelope is 0.64 μm; (c) (d) spectrum and phase mismatch curve of the actual detection response obtained from the Fourier transform of the interference signal in Fig.2 (b)

Fig. 3. Subcellular imaging of mice in vivo^[20]. (a) 2D image of a two-cell stage embryo with conventional 2D microscope, in the observation plane of which the first cleavage plane (2PB) and Blastomere 2 (BM2) are blocked by Blastomere 1 (BM1); (b) 3D reconstruction of the same embryo after rotational operation to the 3D dataset of FF-OCT, from which we can see that major structures are all clearly revealed; (c) 3D reconstruction of a four-cell stage embryo, in the plane 1 of which BM1 and BM2 contact with each other; (d) at the opposite angle of view, in the plane 2 perpendicular to plane 1, we can see that BM3 and BM4 contact with each other; (e) 3D reconstruction of a blastocyst; (f) cross-section view of the same blastocyst, in which blastocoele, trophoblast, and inner cell mass (ICM) are clearly visible; (g) 3D reconstruction of the segmented nuclei of this blastocyst, in which point O is the geometry center of the whole blastocyst and point O'is that of the ICM, and Em-Ab axis is defined by the line which contains the two points O and O'

Fig. 4. Imaging of the zygotes^[22]. (a) Zygotes image at metaphase; (b) zygotes image at telophase; (c)--(e) other zygotes with mitotic spindles (arrow)

Fig. 5. Schematic of the k-linear swept laser^[27]

Fig. 6. Schematic of the buffered optical time-stretch-based 40 MHz swept-source^[29]

Fig. 7. Schematic of the experimental setup of OC2T^[30]

Fig. 8. Experimental results^[30]. (a) A single period of the cos(at²) waveform data used in AWG; (b) a single period of the waveform measured by AC-coupled balanced amplified photodetector; (c) en-face OCT image of a variable-frequency resolution target; (d) image of a variable-frequency resolution target; (e) image of a cover glass; (f) image of onion layer

Fig. 9. Schematic of the stationary-fiber rotary scanning optical coherence tomography (OCT) probe driven by a hollow ultrasonic motor^[32]

Fig. 10. OCT images of a grape^[33]. The focal position is in the (a) shallow layer, (b) middle layer, and (c) deep layer; (d) fused image of Fig. 10(a)--(c) (C-mode scanning image); (e)--(h) 4× zoomed-in images of the boxed regions in Fig. 10 (a)--(d), respectively, in which the white dashed lines divide the images into three layers from bottom to top: the shallow layer, the middle layer, and the deep layer