In situ monitoring of collagen fibers in human skin using a photonic-crystal-fiber-coupled, hand-held, second-harmonic-generation microscope

Second-harmonic-generation (SHG) microscopy is a powerful tool for in situ monitoring of collagen fibers in human skin. However, its practical use is still limited in the dermatological field due to the bulky and complicated setup. In this paper, we constructed a photonic-crystal-fiber-coupled, hand-held SHG microscope for in situ monitoring of collagen fibers in human skin. Fiber delivery of femtosecond pulse light was achieved by a large-mode-area photonic-crystal-fiber whereas the compact SHG microscopy setup was enclosed into a lens tube system. The combination of PCF with the lens tube system largely enhances the flexibility of measurement sites in the human skin.