NirSFE: an ultrathin, flexible, near-infrared endoscope (Conference Presentation)

Abstract

We present a scanning fiber endoscope (SFE) designed for near-infrared (nir) imaging. The SFE piezo actuator drives a single mode fiber in spiral patterns; meanwhile return fibers collect the reflective light; then signals from detector are mapped onto an image according to the fiber scan trajectory. Many SFE prototypes have been developed based on red/green/blue reflectance, enhanced spectral, fluorescence, optical coherence, and multimodal imaging. These forward-view SFE prototypes have the advantage of miniature size (1-3mm), flexible shaft, video-speed frame rate (10-30Hz), wide field of view (60-100 degree) and good resolution quality. A new SFE prototype is being developed that operates entirely in near-infrared wavelength range, which is expected to have great potential in imaging dental lesions and monitoring therapy. The first nirSFE probe has a diameter of around 3mm, frame rate of 17Hz, 53 degree FOV and spatial resolution of 40um. Although the specific optical fibers made for nir makes the probe stiffer than previous prototypes, the flexible 2m shaft allows for easy orientation. Using this prototype we can achieve reflectance mode imaging and also switch between different wavelengths (1310nm, 1460nm, 1550nm) and light sources (SLD or laser). In the development of this prototype, we encounter several issues: 1) the speckle noise caused by interference of laser beams, 2) uneven illumination and reduced visual field caused by collection fiber distribution and numerical aperture, and 3) specular reflection patterns which can obscure important enamel target detail. We explore solutions to these issues by using multiple detector channels, light sources, and filtering.