Focus optimization for long-range OCT and short-range LiDAR

In focused Gaussian beam imaging systems, the low-numerical aperture (NA) of the beam inherently degrades signal and resolution. We demonstrate and experimentally validate a theory for optimally focusing a Gaussian beam source with a low-NA lens to maximize imaging quality. Specifically, reflectance signal and lateral resolution were optimized over two system parameters: (1) the axial working distance to the sample, and (2) the geometric focal length of the lens. In the former, we find that placing the sample at the waist of the beam is optimal, as expected. More interestingly, in the latter, we find that a higher reflectance signal and better lateral resolution are obtained at a fixed working distance by choosing the lens focal length to be equal to the working distance, even though this does not place the beam waist on the sample due to the focal shift effect.

Duke Scholars

Author Al-Hafeez Z Dhalla Biomedical Engineering