Monolithic fabrication of microprism arrays for stereoscopic endoscope

Abstract

Three-dimensional (3D) endoscopes can provide depth information of the real physical world to the surgeons during the surgeries and help them to perceive and understand the patient’s anatomy more accu-rately compared to the traditional two-dimensional endoscope. However, conventional 3D endoscope tech-niques to acquire stereo image pairs with two cameras, additional actuator for temporal division stereo imag-ing, or other bulky optical components for spatial division stereo imaging has limitations on image acquisition stability and miniaturization of endoscopic systems. This work presents fabrication of symmetric microprism arrays for stereo endoscopic imaging with simple method using two-step lithography and geometric guided resist reflow in a wafer scale, and optically characterized to form stereo image pair with single image sensor chip. Microprism arrays has advantages over other techniques, such as capability of shooting image pairs simultaneously with great stability, less issues on aligning the optical component, and favorable size for compact packaging of endoscopic system. Microfab-rication of the microprism arrays utilizes thermoset photoresist SU-8, thermoplastic photoresist AZ9260, and thermal reflow of thermoplastic photoresist to form 3D inclined microstructure. After making microprism ar-ray structures above the silicon substrate through microfabrication, microstructures were transferred onto the desired substrate with soft lithography using PDMS mold and UV curable resin. Transferred microprism ar-rays with UV curable resin were placed in front of a single endoscopic camera and compactly packed for stereo endoscopic imaging. Imaging with the stereo endoscope using microprism arrays, disparity map be-tween the corresponding left and right images of the distanced object were calculated after calibration of the system. Furthermore, the internal organs of the live mice and swine were imaged with microprism arrays based stereo endoscope.