Optical design concepts using wavelength-selective diffractive optics to enable miniaturized multimodal endoscopic...

We present optical design concepts for a miniaturized multimodal endoscopic imaging system capable of targeting the same sample plane across widely separated wavelength ranges. The system uses a scanning-fiber approach and exploits the wavelength-selective imaging properties of diffractive optical elements (DOEs), allowing different diffraction orders to form images for distinct spectral bands and partially decoupling the optical design for each range. The system is designed to achieve high first-order diffraction efficiency in the UV/short visible region while simultaneously operating in the zeroth order for 1300-1700 nm. Angular emission variations of the scanning fiber are compensated, enabling a compact layout and low-loss beam delivery. Both three- and two-element designs with strongly aspheric surfaces are analyzed. Backward light propagation to the scanning fiber is evaluated theoretically, highlighting efficient collection via the fiber cladding and its potential enhancement by introducing ring-shaped lenses and reflective surfaces.