Miniaturized optical-fiber endoscope without inertial scan for simultaneous imaging and laser microsurgery

摘要

Minimally invasive surgery benefits from small-sized, multi-purpose endoscopic devices. To this end, a single-fiber-based optical concept performing simultaneous, spectrally encoded, inertial-free, confocal microscopy and high-precision laser microsurgery (SECOMM) was recently demonstrated. SECOMM achieves a 2D spatial dispersion by the use of a virtually imaged phased array (VIPA) spectral disperser, in conjunction with a reflective diffraction grating, creating a one-to-one mapping between spatial coordinates and optical wavelength. In this contribution we review a highly miniaturized, axial, 2D spatial disperser design, also based on a VIPA, but together with a perpendicularly aligned volume holographic grating embedded between two prisms (GRISM). This combination produces a 2D-angular dispersion often referred to as spectral shower. We specifically consider a tissue-ablation-friendly 800 nm center wavelength, with a 20 nm pulse bandwidth representing a Ti:sapphire pulsed laser light source. Our endoscope design can, however, also operate at other wavelengths such as visible and infrared. We first theoretically investigate the spectral shower in angular units and provide a parameter analysis for the proposed axial design. Second, we concentrate on the crucial part of light coupling into the spectral disperser. With respect to the underlying center wavelength and bandwidth, and to our theoretical findings, we exemplarily show an optimized device that supports a 50 × 50 pixel resolution at a device diameter as small as 3.6 mm.