Biomedical Engineering Reference
In-Depth Information
Fig. 8.9 Fundus camera
Fig. 8.10 Time domain OCT
Axial
Scanning
Mirror
Short
Coherence
Laser
To/From
Fundus
Camera
Detector
With TD-OCT scanning speeds are generally slow. State-of-the-art systems can
achieve scan rates up to 8,000 depth scans/s but the reduced sensitivity at these
scanning speeds makes retinal imaging impracticable [ 18 ]. The need for mechani-
cal scanning is obviated in frequency domain OCT (FD-OCT) and consequently the
time necessary to perform a depth scan can be reduced dramatically.
FD-OCT can be implemented using either a tunable source or a white light
source together with a spectrometer array as shown in Fig. 8.11 . In either case
the interference between object and reference paths is recorded as a function of
the source frequency (or wave number). In contrast with TD-OCT, the interference
signal acquired by FD-OCT has greater modulation and a significantly greater
signal to noise ratio (SNR). For this reason FD-OCT is preferred in high speed,
high resolution systems.
 
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