3D endoscope system of monoscopic endoscope with external stereo lens

Yenyu Wang¹, Tien-Shou Yeh², Atul Kumar, PhD¹, Wan Chi Hung¹, Wei-Chia Su, PhD², Kai-Che Liu¹, Hurng-Sheng Wu, MD¹. ¹Chang Bing Show Chwan Memorial Hospital, ²National Changhua University of Education

Objective of the technology or device: Endoscope is a critical component of the minimally invasive surgery. Majority of the current endoscope systems are monoscopic (single camera system). A stereo endoscope (dual camera system) can provide the depth information of a scene. Previous studies have reported that the use of stereo endoscope shortens the surgical time and reduces the risk of error during the surgery. However, the current monoscopic system cannot be upgraded to a stereo system which enforces surgeons to replace the entire monoscopic endoscope system with the stereo endoscope system if they want stereoscopic vision during the surgery. In this study, we develop a system which can produce stereo image with the monoscopic system. The system would comprise of an external stereo lens which can be mounted on the monoscopic endoscope, and software based on stereo visualization technology which would synthesize stereo image to be displayed on a 3D monitor.

Description of the technology and method of its use or application: The external lens system would be designed based on optical design of the monoscopic endoscope lens system. Since the endoscope’s lens parameters were unknown, we started to analyze the endoscope camera internal parameters. Furthermore, we simulated the dual-camera light path which accurately projects on a diffuser. The diffuser receives images of the same scene from two different view angles and those images are further captured by endoscope.

To achieve a practically applicable prototype, the system must be high-precision package that makes two lens focus on the diffuser and also focus on CMOS(Complementary Metal-Oxide Semiconductor) image sensor. However, the image can’t be used directly to synthesize a stereo image as the images from different views need to be separated and rectified. The software part must include stereo visualization control and a program for stereo display.

Preliminary results if available: The external lens system creates images from two different view angles with the monoscopic endoscope, and the views are captured on the single CMOS image sensor. When we use high-precision package and smaller particle size of the diffuser, the image resolution is high. After image segmentation for two different views and changing the disparity of two lens projection image, the image was visualized as 3D interlaced format on a 3D polarizer monitor.

Conclusions / future directions: This study presents a method that can generate stereo visualization with a monoscopic endoscope. An external stereo lens system allowed us to use conventional endoscope system without replacing it with a new stereo endoscope system.  When the stereo display is not required the mounted lens can be easily removed and help in avoiding problems related to human factors. In future we will apply methods to improve the image quality and involve a light guide that can transfer light from endoscope to the external lens system.