Embedded Structured Light-based Multi-projection Display System

With rapid development of projection display technology, multi-projector display wall system, which provides immersive, high-resolution and large-scale display, is more and more widely used in fields like large-scale scientific visualization, military simulation, engineering design, exhibition industry, digital cinema and so on. Projector movement is not allowed in most existed multi-projector display wall system, which can not be used in real-time working environment. How to build a multi-projector display system with real-time autonomic calibration capability becomes an important problem.This thesis presents a multi-projector display system with real-time autonomic calibration capability, which is based on embedded structured light. Our system consists of one master node and multiple rendering nodes. The master node employs multiple cameras capturing projection images. Each rendering node embeds structured light image into projection image by modifying the intensity of projection image on a per-pixel basis, and computes the corresponding compensating image. Each rendering node display the embedded image and its compensating image alternatively with a 120Hz projector. All rendering nodes and cameras are connected to a single signal generator, to synchronize the refresh action of projectors and capturing action of cameras.After the initial installment of our system, meshes are projected onto display surface with multiple projectors, to assign the global texture coordinate system on display surface. To achieve a regular global mesh, the projected meshes are interactively edited using free-form mesh deformation. In the runtime of system, the master node captures two sequential frames of projection image, which are the embedded image and its compensating image; extracts the structured light image embedded respectively for each camera, and stitches extraction results of all cameras; finally detects movement events of projectors using the stitched results. If movement of any projectors is detected, each rendering node embeds a structured light image of vertices of a regular mesh into the projection image. With the method described above, the master node computes global texture coordinates of all vertices of the regular mesh. Global texture coordinates of the internal vertices of the mesh is computed by interpolation. Using global texture coordinates of all pixels of the projection image, the master node computes projection calibration parameters, and sends these parameters to all rendering nodes. Then each rendering node warps its projection image using the calibration parameters, achieving a seamless and uniform projection display.Experimental results show that our system achieves real-time autonomic projection calibration. Compared to existed multi-projector display systems with real-time autonomic calibration capability, our system does not impose a large reduction of dynamic range of projection image, or any requirements on the number of feature points in the projection image. Also, no interruption of normal projection display is required during the projection calibration process.