We have developed a coherent anti-Stokes Raman scattering (CARS) rigid endoscope for label-free nerve imaging during an operation. The CARS rigid endoscope consists of a single-mode fiber which delivers two color lasers, a galvano scanning system, and homemade ϕ12 mm lens tubes which include two relay lenses and an objective lens. The label-free imaging of rat sciatic nerve is demonstrated. To attain CARS image with high- speed, correcting chromatic aberration is focused on. The split between the focal spots of two lasers passed through the lens tubes is 21 μm and a numerical simulation shows that the intensity of CARS signal by correcting the chromatic aberration is 2.3 times as strong as non-correcting. The rigid endoscope has been modified to suppress the chromatic aberration by using two single-mode fibers which deliver the two lasers individually. The experimental result shows the increase of CARS intensity at least 1.5 times.
