Perspective (geometry)

About: Perspective (geometry) is a research topic. Over the lifetime, 277 publications have been published within this topic receiving 5795 citations. The topic is also known as: perspective (geometry).

Ground-image plane mapping for lane marks detection

Abstract: Autonomous vehicles are equipped with optical sensors and micro-processing units to perform intelligent visual analysis of its surroundings. Due to the high speed of moving vehicle, the captured information has to be processed in a short duration to avoid possible collision. In this paper, a ground-image plane mapping technique is proposed to quickly locate detected object if the object's position is known in the real world. A three dimensional (3D) world coordinate is mathematically derived to an image plane using pinhole camera model. Several 3D perspective parameters such as vehicle's steering angle and its velocity, sensor's height and tilting angle are encompassed in the ground plane measurement. The optical sensor's intrinsic parameters such as focal length, principal point, pixel's height and width are also inserted for the mathematical model derivation. The importance of this ground to image plane mapping enables a rapid search of an object in a moving scene to achieve fast object identification during sensor acquisition. Experimental results have been carried on the application of lane marks detection with 93.82% correct mapping, using approximately 20% less processing time.

Anti-perspective plane transformation-based ultrasonic plane wave imaging method

Abstract: The invention discloses an anti-perspective plane transformation-based ultrasonic plane wave imaging method. The method comprises the following steps of (1) collecting data; (2) preprocessing the data: converting imaging points on an original imaging plane into imaging points on a new plane by utilizing plane conversion, calculating delay time according to the imaging points on the new plane to obtain corrected delay time, then receiving and focusing the imaging points on the original imaging plane by utilizing a synthetic aperture focusing technology according to the corrected delay time, and obtaining a value of each imaging point on the original imaging plane; and (3) post-processing the data: performing envelope detection, logarithmic compression and grayscale mapping in sequence, and finally obtaining an ultrasonic plane wave imaging image. According to the method, a key delay time calculation mode is improved and matched with the synthetic aperture focusing technology, so that compared with the prior art, the problem of low plane wave imaging quality can be effectively solved and the ultrasonic plane wave imaging resolution is effectively increased.

Video measurement of linear displacement along an oblique line using the cross-ratio

Abstract: The purpose of this study was to rediscover the cross-ratio and assess its effectiveness for measuring linear displacement when the image plane is not parallel to the object plane. In the laboratory a fixed, 4m object length was reconstructed with a mean absolute error of 2.6mm (s.d. = 1.6mm, maximum = 4.9mm). In the field, two cameras filmed a fixed, 8m object length with a mean absolute error of 13mm (s.d. = 5mm, maximum = 20mm). The method is very accessible to non-specialists in projective geometry and the results are both valid and reliable.

A rectification algorithm for distorted images from the inclination plane paper

Abstract: In this paper, we deal with the problem of image rectification with the images captured by digital cameras at an angle. The procedure of forensic photography requires that the film plane should be paralleled to a taken image. Another procedure must be followed when the print is located on reflexible surfaces such as vehicles, or faint marks on porous surfaces. Examinations were made of the evidential value of mark images which were received from the scene or taken deliberately at an angle out of proper perspective (i.e., the lens axis is not perpendicular to the target plane). Based on geometry of differential and projection as well as the theory of imaging optics, a robust and fast inclination rectification algorithm is proposed using perspective transform of camera lens, and validated using MATLAB.

A fast 3D reconstruction method based on curve segment of binocular vision

Abstract: Aiming at the problem of low efficiency of the 3D reconstruction, a fast method based on piecewise quadratic curve is proposed. Firstly, a multi-line structured light binocular vision measurement system is used to obtain the two-dimensional image. Through the two-dimensional image, the center line and feature points of the laser strip are quickly acquired. Then, the acquired feature points are used as the given data points of curve interpolation, and NURBS curves are used to interpolate the feature lines of the image. According to the perspective invariance principle of plane curve, the zero curvature point and cusp point on the curve are detected and used as segmentation points. Using the segmentation results, a number of points on each NURBS curve segment are taken to fit as the quadratic curve. Finally, by constructing the right and left space straight taper surfaces, the three-dimensional reconstruction of the feature lines is completed by the method of surface intersection. Taking the black shoe sole as the experimental object, the results show that the method proposed in this paper can quickly complete the three-dimensional reconstruction of the inner and outer feature lines of the shoe sole, which can provide the basis and guarantee for the follow-up shoe sole process monitoring and quality inspection.