Fig. 1. Diagram of TD-OCM system and axial PSF^[23]. (a) Schematic of TD-OCM system; (b) comparison of axial PSF under confocal and coherence-gated configuration of OCM system

Fig. 2. Schematic of FD-OCM system and comparison of sensitivity between TD-OCM and FD-OCM. (a) Schematic of FD-OCM system; (b) comparison of sensitivity between TD-OCM and FD-OCM with Gaussian source at 1300 nm^[27]

Fig. 3. Overview of FF-OCM system

Fig. 4. Principle of data acquisition in FF-OCM system

Fig. 5. Illustrations of scanning imaging modes of PS-OCM and FF-OCM. (a) Scanning imaging mode of PS-OCM; (b) scanning imaging mode of FF-OCM

Fig. 6. Simulation of resolution varying with source central wavelength, bandwidth, and numerical aperture of objective in OCM. (a) Relation among axial resolution, source central wavelength, and bandwidth; (b) relation among lateral resolution, source central wavelength, and numerical aperture

Fig. 7. Ultrahigh resolution images of industrial sandpaper^[38]. (a) Industrial sandpaper with particle size about 125 μm; (b) sandpaper longitudinal section image of general system; (c) sandpaper cross section image of ultra-high resolution system

Fig. 8. High-resolution images of onion epithelium obtained by FF-OCM system^[29]

Fig. 9. Images of scattering samples without and with random phase^[49].(a) Without random phase; (b) with random phase

Fig. 10. Axial resolution of OCM system versus detection depth and source bandwidth^[13]. (a) Axial resolution versus FWHM of the Gaussian spectrum at different depths of human epidermis; (b) reachable minimum axial resolution versus depth of epidermis

Fig. 11. Diagram of dark-field OCM with extended depth of focus in sample arm

Fig. 12. En face images of murine pancreas at different depths obtained by extended-focus OCM system^[68]. Scale bar: 200 μm. (a) 11 μm; (b) 54 μm; (c) 97 μm; (d) 110 μm

Fig. 13. Example of imaging process of human fingertip by GD-OCM^[71]

Fig. 14. Cross-section images of African frog tadpole^[70]. (a) Image acquired by GD-OCM system; (b) image acquired by OCM system at fixed focal plane

Fig. 15. Images of posterior layers of human corneas of healthy and FED corneas^[91]. (a)(c)(d) Images of healthy cornea in the posterior elastic layer, endothelial cell layer, and posterior stromal layer; (b)(e)(f) images of FED cornea in the posterior elastic layer, endothelial cell layer, and posterior stromal layer

Fig. 16. Ex vivo images of cortical and subcortical structures in mouse brain slice^[39]. (a) Transmission image showing imaging area; (b) result of Vis-OCM imaging; (c)(d) Vis-OCM images, fluorescence images of labeled amyloid plaques, and overlays of cortical and subcortical structures

Fig. 17. En face images of fibroblast obtained by dynamic detection^[110]. Scale bar: 50 μm.(a) En face image; (b) fiber stretch detection; (c) cell migration detection

Fig. 18. Diagram of focus-extended OCM and angiograms of mouse cortex^[109]. (a) Illustration of focus-extended system; (b)(c) interpolation process for angiogram; (d) angiogram of mouse cortex; (e)(f) quantitative distributions of total flow rate and axial flow rate

Table 1. Typical performance parameters of different imaging systems^[88-90]