Abstract:

Future fully digital surgical visualization systems enable a wide range of new options. Caused by optomechanical limitations a main disadvantage of todays surgical microscopes is their incapability of providing arbitrary perspectives to more than two observers. In a fully digital microscopic system, multiple arbitrary views can be generated from a 3D reconstruction. Modern surgical microscopes allow replacing the eyepieces by cameras in order to record stereoscopic videos. A reconstruction from these videos can only contain the amount of detail the recording camera system gathers from the scene. Therefore, covered surfaces can result in a faulty reconstruction for deviating stereoscopic perspectives. By adding cameras recording the object from different angles, additional information of the scene is acquired, allowing to improve the reconstruction. Our approach is to use a fixed four-camera setup as a front-end system to capture enhanced 3D topography of a pseudo-surgical scene. This experimental setup would provide images for the reconstruction algorithms and generation of multiple observing stereo perspectives. The concept of the designed setup is based on the common main objective (CMO) principle of current surgical microscopes. These systems are well established and optically mature. Furthermore, the CMO principle allows a more compact design and a lowered effort in calibration than cameras with separate optics. Behind the CMO four pupils separate the four channels which are recorded by one camera each. The designed system captures an area of approximately 28mm × 28mm with four cameras. Thus, allowing to process images of 6 different stereo perspectives. In order to verify the setup, it is modelled in silico. It can be used in further studies to test algorithms for 3D reconstruction from up to four perspectives and provide information about the impact of additionally recorded perspectives on the enhancement of a reconstruction.

Abstract:

Current surgical microscopic systems are limited in providing a stereoscopic view to multiple users. When trying to provide higher degree of freedom in the perspective of additional observers, the optomechanical effort increases rapidly. This is limiting current systems to two or three observers. An approach to offer free choice of view is to digitalize the microscopic system and generate multiple arbitrary views from a 3D reconstruction. Modern commercial surgical microscopes allow for recording stereoscopic videos. However, filming is only possible through the two channels used for the eyes. A reconstruction can only contain the amount of detail the recording camera system gathers from the scene. For deviating stereoscopic perspectives, the reconstruction can become defective through masking and occlusion. By adding cameras recording the object from different angles, additional informa- tion of the scene is acquired, allowing to improve the reconstruction. Current research at IBT tries to optimize the effort in hardware and software to give a sufficient reconstruction of a surgical scene to allow a change of view. Yet multicamera systems for application in microsurgery are not commercially available. Therefore, a four-camera setup was designed, allowing verification of the reconstruction from multiple observing perspectives. Its concept is based on current surgical microscopes as these systems are well established and optically mature. As in a surgical microscope we used a setup with common main objective (CMO). Behind the CMO four pupils separate the channels which are filmed by one camera each. The designed system is able to image an area of approximately 28 mm × 28 mm with four cameras. Thus, allowing to process stereo images of 6 different stereo bases. The setup can be used in further studies to test algorithms for 3D reconstruction from up to four cameras and angles. In order to verify the setup, it was modelled in Zemax OpticStudio. To improve the feasibility of the setup, simulations of tolerance affected parts were conducted. This way relations of performance and tolerances can be denoted, and alternative setups with reduced susceptibility are suggested.