Spectral domain OCT introduces the use of a(n):

• A. Interferometer
• B. Spectrometer
• C. Light source
• D. Detector array

Answer: (B)

In spectral-domain OCT, the defining feature is using a spectrometer to resolve the interference signal across wavelengths. The spectrometer disperses the light from the interferometer into its constituent wavelengths, and a detector array records the spectrum all at once. This spectral data is then transformed (via Fourier transform) to produce depth-resolved reflectivity, letting you obtain A-scans without moving a reference mirror and at much faster speeds with greater sensitivity over depth.

The other components—an interferometer and a light source—are still essential in OCT, so they aren’t the new element being introduced. A detector array is involved, but the key difference that makes this modality “spectral-domain” is the spectrometer that provides the spectral information used to reconstruct depth.