Perspective Projection Geometry Research Articles

Wigner inverse transform based computer generated hologram for large object at far field from its perspective light field

Wigner inverse transform based light field computer generated hologram (WignerLFH) synthesizes complex optical field of three-dimensional objects from its view array without a depth map. Higher resolution than the traditional hogel-based methods, complete control on the carrier wave, and no need for the depth map are its major advantages. However, the WignerLFH method requires the view array in orthographic projection geometry which prohibits its application to real scene and limits the depth range only around the hologram plane. In this paper, we propose a novel WignerLFH technique using perspective projection geometry. The proposed technique synthesizes a hologram of large three-dimensional objects at a far distance from its perspective views. Numerical simulations and optical experiments verify the feasibility of the proposed technique.

Vehicle localisation and deep model for automatic calibration of monocular camera in expressway scenes

The authors present a fully automatic method for camera calibration in expressway scenes and vehicle localisation on curved roads. Our approach does not depend on specific targets or a priori information and adapts to a wide range of variations in road appearances and camera views. We make three main contributions to automatic camera calibration. Firstly, we propose a Deep Calibration Network to estimate the vanishing point and camera extrinsic parameters from an RGB image in an end-to-end manner. The vanishing point and camera rotation angles are then used to calculate the camera focal length according to the perspective projection geometry, thus constructing the complete camera matrix. Secondly, we introduce a Multi-View Camera Calibration Dataset, which contains a total of 32,712 images for 17 expressway scenes. The dataset covers a wide range of camera views and expressway types, which is challenging. Thirdly, we present a novel Curved Reference Line System adapted to the expressway shape to locate vehicles on curved roads accurately. This coordinate system can effectively transform the vehicle coordinates from a Cartesian system to the vehicle's mileage and horizontal distance relative to the lane line. A comprehensive evaluation on Multi-View Camera Calibration Dataset shows that our technique can automatically calibrate a single camera at about 40fps on an NVIDIA GTX1060 processor and accurately locate vehicles on curved roads, making it suitable for deployment in expressway surveillance systems.

Vision-Based Calibration of Dual RCM-Based Robot Arms in Human-Robot Collaborative Minimally Invasive Surgery

This letter reports the development of a vision-based calibration method for dual remote center-of-motion (RCM) based robot arms in a human-robot collaborative minimally invasive surgery (MIS) scenario. The method does not require any external tracking sensors and directly uses images captured by the endoscopic camera and the robot encoder readings as calibration data, which leads to a minimal and practical system in the operating room. By taking advantage of the motion constraints imposed by the RCM-based kinematics of the robotic surgical tools and cameras, we can find unique relationships between the endoscope and the surgical tool using camera perspective projection geometry without the geometric information of the tool. A customized vision-based centerline detection algorithm is also proposed, which provides robust estimation of centerline positions for a variety of settings. We validate the method through simulations and an experimental study in a simulated MIS scenario, in which the first generation da Vinci surgical system controlled by the open source da Vinci research kit electronics and cisst/SAW software environment is used.

An enhanced obstacle avoidance method for the visually impaired using deformable grid

Various obstacle avoidance (OA) methods with the monocular vision have been studied to assist visually impaired people. Recently, a method that effectively locates obstacles at a risk of collision using the shape variation of a grid, called deformable grid (DG), was introduced [11]. To further improve the detection performance of the previous work, a vertex deformation function representing the displacement of each vertex in the DG is firstly defined employing the perspective projection geometry. Then, the collision risk is accurately estimated based on the shape variation of the DG that is measured using the vertex deformation function. Experimental results show that the proposed method outperforms other conventional methods as well as the previous work in terms of both the accuracy and processing time, and clearly detects obstacles that present a risk of collision in a variety of scenarios. This method is suitable for application to electronic travel aid (ETA) systems using consumer devices, such as smart-phones, tablets, and wearable devices.

Self-calibration of vision parameters via genetic algorithms with simulated binary crossover and laser line projection

A self-calibration technique based on genetic algorithms (GAs) with simulated binary crossover (SBX) and laser line imaging is presented. In this technique, the GA determines the vision parameters based on perspective projection geometry. The GA is constructed by means of an objective function, which is deduced from the equations of the laser line projection. To minimize the objective function, the GA performs a recombination of chromosomes through the SBX. This procedure provides the vision parameters, which are represented as chromosomes. The approach of the proposed GA is to achieve calibration and recalibration without external references and physical measurements. Thus, limitations caused by the missing of references are overcome to make self-calibration and three-dimensional (3-D) vision. Therefore, the proposed technique improves the self-calibration obtained by GAs with references. Additionally, 3-D vision is carried out via laser line position and vision parameters. The contribution of the proposed method is elucidated based on the accuracy of the self-calibration, which is performed with GAs.

50.3: Arbitrary View Generation in Perspective and Orthographic Projection Geometry using Lens Array

AbstractA novel view image generation algorithm using lens array is proposed. Arbitrary view image in perspective projection geometry is generated through the central pixel disparity estimation and elemental image mapping with wide field of view and high resolution. View image in orthographic projection geometry is also synthesized with high resolution from the elemental images using directional pixel disparity estimation and elemental image mapping.

Camera location determination based on the perspective projection geometry of three points

An approach to camera location determination based on the perspective projection geometry of three points is proposed, which is simple and straightforward. No rigid restrictions are placed on the original positional and orientational relationships between the camera and the mark. Experimental results verify the feasibility of the proposed approach.