OCT Depth-Slicing Simulator

View mode

Reference-arm path length

Depth position 0.00 mm

Interference signal

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Boundary detected

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A-scan (depth profile)

0 mmdrag the slider above5.9 mm

B-scan (cross-section)

lateral →not built yetdepth ↓

How it works

OCT is "optical ultrasound": a low-coherence near-infrared source is split into a reference beam (bounced off a movable mirror) and a sample beam (sent into the tissue). Because the source's coherence length is tiny, the two beams only interfere when their round-trip path lengths match almost exactly — so as the reference mirror sweeps, the detector lights up only when it is scanning a real reflective interface inside the tissue.

I(z) ∝ Σ Rᵢ · exp( −(z − dᵢ)² / 2ℓc² )
z = reference-arm depth,  dᵢ = true boundary depth
ℓc = coherence length (interference gate width)

Reference-arm depth — mirror position; scanning it traces one A-scan (depth profile) at a single lateral point.
Auto A-scan sweep — sweeps the mirror through the whole sample so every layer interface produces its own interference peak.
Build cross-section — repeats the A-scan at many lateral positions and stitches the results into a 2D B-scan image, revealing the tissue's layered structure.
Surface photo — a normal camera only catches light reflected from the outer surface; it cannot see anything below it, however many layers are underneath.

Real-world relevance: this exact technique is how ophthalmologists image the living retina non-invasively, resolving individual cell layers a few microns thick without ever touching the eye.

Surface photo — only the outer tissue surface is visible. No internal structure can be seen.

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Optical Coherence Tomography (OCT) Depth-Slicing Simulator