In Time Domain OCT, what is the typical axial resolution?

• A. 8-10 microns
• B. 1-2 microns
• C. 15-20 microns
• D. 0.5-1 micron

Answer: (A)

In Time Domain OCT, the detail along the depth (axial resolution) comes from the coherence length of the light source. This coherence length depends on how broad the light’s spectrum is: a wider bandwidth gives a shorter coherence length and finer axial resolution. For typical Time Domain OCT setups using near-infrared light around 1,300 nm, the bandwidth isn’t extreme, so the axial resolution in tissue tends to be around 8–10 micrometers. That’s why 8–10 μm is the best fit.

Widths like 1–2 μm would require a much broader spectral bandwidth than is typical for Time Domain systems, 0.5–1 μm corresponds to ultra-high-resolution sources often seen in more advanced or different OCT configurations, and 15–20 μm is coarser than what standard TD-OCT yields.