Ultraminiature video-rate forward-view spectrally encoded endoscopy with straight axis configuration

As one of the smallest endoscopes that have been demonstrated, the spectrally encoded endoscope (SEE) shows potential for the use in minimally invasive surgeries. While the original SEE is designed for side-view applications, the forwardview (FV) scope is more desired by physicians for many clinical applications because it provides a more natural navigation. Several FV SEEs have been designed in the past, which involve either multiple optical elements or one optical element with multiple optically active surfaces. Here we report a complete FV SEE which comprises a rotating illumination probe within a drive cable, a sheath and a window to cover the optics, a customized spectrometer, hardware controllers for both motor control and synchronization, and a software suite to capture, process and store images and videos. In this solution, the optical axis is straight and the dispersion element, i.e. the grating, is designed such that the slightly focused light after the focusing element will be dispersed by the grating, covering forward view angles with high diffraction efficiencies. As such, the illumination probe is fabricated with a diameter of only 275 μm. The twodimensional video-rate image acquisition is realized by rotating the illumination optics at 30 Hz. In one finished design, the scope diameter including the window assembly is 1.2 mm.