Which OCT technology employs a moving reference mirror to obtain depth information?

Which OCT technology employs a moving reference mirror to obtain depth information?

• A. Time Domain
• B. Polarization-Sensitive OCT
• C. Swept-Source OCT
• D. Spectral Domain

Answer: (A)

In time-domain OCT, depth information comes from coherence gating achieved by physically moving the reference mirror. By scanning the mirror along the reference arm, the optical path length is varied, so interference occurs only with tissue reflections at a specific depth. As the mirror moves, different depths come into coherence, producing an axial scan (A-scan) one depth at a time. This mechanical path-length sweep directly converts depth into the time domain signal you detect. In contrast, spectral-domain and swept-source OCT keep the reference mirror stationary and extract depth information from the interference spectrum. A Fourier transform of the spectral interference lets you reconstruct the depth profile without moving the mirror, enabling faster imaging. Polarization-sensitive OCT adds information about polarization changes in the sample, not the mechanism for depth scanning, which is why the moving mirror in time-domain OCT is the defining feature for obtaining depth information.

In time-domain OCT, depth information comes from coherence gating achieved by physically moving the reference mirror. By scanning the mirror along the reference arm, the optical path length is varied, so interference occurs only with tissue reflections at a specific depth. As the mirror moves, different depths come into coherence, producing an axial scan (A-scan) one depth at a time. This mechanical path-length sweep directly converts depth into the time domain signal you detect.

In contrast, spectral-domain and swept-source OCT keep the reference mirror stationary and extract depth information from the interference spectrum. A Fourier transform of the spectral interference lets you reconstruct the depth profile without moving the mirror, enabling faster imaging. Polarization-sensitive OCT adds information about polarization changes in the sample, not the mechanism for depth scanning, which is why the moving mirror in time-domain OCT is the defining feature for obtaining depth information.