A comparison of the Long Working Distance of the GRIN Lens- and C-Lens-Based OCT Probe

The standard technical scheme for imaging with an endoscopic optical coherence tomography (OCT) probe is to use a GRIN lens to focus the beam. However, when a long working distance is required of the OCT probe, various factors will affect the imaging quality. Here, we conduct a theoretical calculation to analyze the sensitivity of the GRIN lens and the C-lens of an OCT probe. The sensitivity of ω
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L of the GRIN lens is ten times higher than that of the C-lens. The sensitivity of Z
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L of the GRIN lens is 24 times higher than that of the C-lens. In addition, the sensitivity of the radius of curvature of the C-lens is compared with the sensitivity of the length of the GRIN lens, and the sensitivity for the GRIN lens is about five times higher than the sensitivity of the radius of curvature for the C-lens. Furthermore, fabricating a C-lens-based OCT probe is much cheaper than a GRIN-lens-based one. Hence, our calculations suggest that the C-lens is a better choice for a long-working-distance OCT probe.