Multimodal Biomedical Imaging Systems - Biomedical Optical Imaging Technologies: Design and Applications - page 339

Fig. 9.16 OCT scan lens. ( a ) Lens layout, ( b ) MTF of the lens, and ( c ) chief ray angles when the
first scan mirror and second scan mirror scan separately
fiber is collimated and reflected by a mirror which is movable to match the optical
path lengths between the sample arm and reference arm. In the sample arm, the
light is collimated and is directed by the XY galvo scan mirrors toward the sample
for transverse scans (B-scans). The axial scans (A-scans) are performed at 16 kHz,
same as the frequency-swept speed of the laser. An aiming laser with the wavelength
of 632 nm is coupled into the reference and sample arms to indicate the focused
spot position. The interference signal between the light from the reference arm and
from the sample arm is detected by a balanced detector (Thorlabs PDB120C, 75
MHz) and is sampled by a 14-bit high-speed digitizer capable of 100 MS/s. The
depth-dependent reflectivity profiles of the sample are generated through the Fourier
transform of the OCT interference signals. The configuration of area imaging system
is same as Fig. 9.7 b. The dichroic mirror shown in Fig. 9.14 b combines OCT path
and area imaging path.