MEMS parallel plate rotation for real-time stereoscopic endoscopic imaging

Abstract

This work reports a miniaturized optical device with an electrothermal actuator for real-time stereoscopic endoscopic imaging. The microelectromechanical system (MEMS) parallel plate rotation allows single camera based stereoscopic imaging with both high resolution and wide field of view (FOV). Medical endoscopes serve as efficient tools for in vivo optical diagnosis or clinical surgery to investigate internal organs and stereoscopic endoscopes are more efficient than conventional 2D endoscopes by providing precise depth information. Stereoscopic systems include two cameras like left and right sight of human eyes. When images are captured in two cameras, object has different positions centering on optical axis in images and distance between the positions, called binocular disparity that inversely proportional to depth, is used for depth estimation. Conventional stereoscopic systems with two cameras are bulky system to applied in endoscope therefore single camera based stereoscopic systems have researched. The parallel plate rotation, the novel single camera based stereoscopic methods, deflects path of light by Snell’s law and enable to capture images at different viewpoints maintaining high resolution and wide FOV. The physical volume of MEMS PPR is well fit within 3.4mm $\times$ 3.3mm $\times$ 1mm. The electrothermal actuation under low operational voltages, 6VAC, precisely rotates the plate by $26.4^\circ$ in front of an endoscopic camera and creates binocular disparities, comparable to those from binocular cameras with a baseline distance of 84μm. The disparity map was successfully reconstructed by extracting local binocular disparities from optical images captured at the maximum relative angle in actuation in dynamic mode. This method provides a new direction for realizing a single camera based real-time stereoscopic imaging inside a medical endoscope.