Research On Several Key Technologies Of Image Processing For Virtual Reality

Flight simulators are essential pilot training-and-checking equipments in aviation industry. Compared with traditional flight simulators, Virtual reality based light flight simulators, i.e. VR simulators, have great potentialities in the applications for compact structure and relatively low price. Along with the project of"Prototype of Light Flight Simulator System", several key technologies of image processing for virtual reality, especially for virtual scene generation and human-machine interaction of the light flight simulator, are studied to meet the high-end demands. The contributions of this dissertation are mainly summarized as follows:Firstly, the light Flight Simulator is equipped with Head Mount Display (HMD) to display virtural scene. The pilot with HMD does not see the real environment inside the cockpit,which needs to be generated in VR scene. Moreover, it is difficult to interact between human and machine. According to the specialties of virtual scene and the demand for interaction in light flight simulator, the structure of light flight simulator's virtual environment is constructed. GBMR and IBR are respectively used to generate the inside and outside scenes of the cockpit. The concept of semi-virtual reality cockpit is proposed to achieve a natural human-machine interaction.Secondly, the pre-processing method of extracting feature from image is the basis image processing included in VR. In order to improve the real-time and robustness and reduce redundancy for image processing, this dissertation extracts edge feature for image pre-processing. For avoiding being sensitive to noise as traditional edge detectors, a direction-based edge detection method is put forward. Experiments prove that it has the superiority in removing noise and detecting edge accurately. Furthermore, considering Hough transform line detection only can locate in the range of pixel, an improved method of line detection based on Hough transform is proposed to enhance the precision of line detection. Experiments show that it improves the detection accuracy while maintaining efficient capability of anti-noise. It is also the base and prerequisite for some key problems,e.g. camera calibration and image registration.Thirdly, camera calibration plays an important role in image registration and finger-tracking. Two new camera calibrations are provided in this disseration. One is vanishing point (VP)-based calibration, the other is rectangle-based calibration. VP-based calibration directly obtains all camera parameters only by two vanishing points. Compared with classical VP-based calibration, it enhances the practical application of VP-based calibration. In rectangle-based calibration, linear constrains on camera intrinsic parameters are set up via the absolute conic imageωand the images of rectangle vertexes. Compared with existing methods, the two proposed avoid complex image matching, which simplifies the calibration process and decreases the computational complexity. What is more important, the two calibrations get all camera extrinsic parameters without computing homography of planes between image and space. Extensive tests with real and synthetic images show that two proposed approaches are both accurate and robust.Fourthly, image stitching is one of the important techniques to the study on cylindrical panoramic image mosaic. The main problem of imagestitching is correspondence, that is image matching. Considering the low computational complexity and high fault tolerance of Hausdorff distance, a new image matching method using direction-based robust hausdorff distance (DRHD) is presented. DRHD constructs a similarity measure based on the proposed improved Hausdorff distance. The experimental results show that the proposed algorithm speeds up the matching process and it improves the resistance to noise. In addition, this method matches the image occlusions correctly and overcomes the mismatching problems that induced by noise, spurious edge segments and outlier points, which demonstrate that the proposed method is feasible and effective.Finally, existing interaction equipments are expensive and do not provide realistic and rich sense, such as touch and force. To satisfy natural interaction in VR system, semi-virtual reality cockpit is put forward. In addition, two finger-tracking techniques are provided. One is the ring type video measure base on camera calibration; the other is finger tracking based on computer vision. For the demand of real-time in finger-tracking system, a gradient direction based detection algorithm is provided to detect moving object (hand) from a video image sequence,. Experimental results show that the proposed algorithm overcomes the shortcoming of not correctly detecting moving object of traditional frame difference algorithms and can effectively and accurately extract moving object contour from indoor and outdoor environments...