Incremental shape integration with inter-frame shape consistency using neural SDF for a 3D endoscopic system.

3D measurement for endoscopic systems has been largely demanded. One promising approach is to utilize active-stereo systems using a micro-sized pattern-projector attached to the head of an endoscope. Furthermore, a multi-frame integration is also desired to enlarge the reconstructed area. This paper proposes an incremental optimization technique of both the shape-field parameters and the positional parameters of the cameras and projectors. The method assumes that the input data is temporarily sequential images, that is, endoscopic videos, and the relative positions between the camera and the projector may vary continuously. As solution, a differential volume rendering algorithm in conjunction with neural signed distance field (NeuralSDF) representation is proposed to simultaneously optimize the 3D scene and the camera/projector poses. Also, an incremental optimization strategy where the optimized frames are gradually increased is proposed. In the experiment, the proposed method is evaluated by performing 3D reconstruction using both synthetic and real images, proving the effectiveness of our method.