Optical Coherence Tomography (OCT) Depth-Slicing Simulator (2D)

Optical coherence tomography images tissue the way ultrasound images it with sound, but with light: a low-coherence beam is split into a reference path and a sample path, and because the light source's coherence length is extremely short, only reflections that traveled the exact same round-trip distance as the reference mirror produce a detectable interference signal. Sweeping the reference-arm mirror therefore traces a depth-resolved reflectivity profile — an A-scan — with a peak at every real interface inside the tissue. Repeating that sweep at many lateral positions builds a full cross-sectional image (a B-scan) showing internal layers that a surface photograph, which only ever sees the outermost surface, could never reveal. This 2D companion renders the same interferometer math and layered-retina model as a flat schematic and depth cross-section: switch to the surface-photo mode to see how little a camera actually captures, then switch to OCT and sweep the reference mirror to watch the internal layer boundaries emerge one by one.