西安交通大学机械工程学院机械制造系统国家重点实验室, 陕西 西安 710049
球体由于其旋转对称性和成像不变性,在双目视觉系统中作为球型靶标具有独特优势。然而球体在像面的成像一般是椭圆,而不是标准圆,其椭圆中心与球心成像点并不是同一个点,这就会对球心的空间定位带来误差。为了找到真实的球心成像点坐标以提高球心的定位精度,建立并分析了空间球的成像模型。基于针孔成像模型和透视成像原理,提出了一种球心成像点的高精度定位方法。该方法结合相机焦距,对边缘点进行畸变校正后可直接拟合出球心成像点坐标。仿真分析了边缘噪声以及边缘提取不完整对所提方法的影响。最后通过实验验证了所提方法可以显著提高球心坐标的定位精度,适用于双目视觉中球靶标的定位以及其他需要对球心进行定位的应用中。
测量 双目立体视觉 球心定位 球型靶标 透视成像误差 激光与光电子学进展
2019, 56(2): 021501
Author Affiliations
Abstract
1 State Key Laboratory for Manufacturing Systems Engineering, School of Mechanical Engineering, Xi’an Jiaotong University, Xi’an 710049, China
2 Institute of Systems Engineering, China Academy of Engineering Physics, Mianyang 621000, China
The phase modulation characteristics of a reflective liquid crystal (LC) spatial light modulator (SLM) under oblique incidence are studied by using our proposed self-interference method. The experimental setup of the method is very simple and has good robustness to mechanical vibrations. By changing the gray value of the combined grayscale loaded on the LC-SLM, different sheared fringe patterns, generated by the interference between the constant phase-modulated beam and the +1-order diffracted beam of the blazed grating, can be obtained. The amount of phase modulation of the LC-SLM is obtained by subtracting the phase of the two side lobes in the frequency domain. By turning the turntable where the SLM is mounted, the phase modulation characteristics at different incident angles can be measured. The experimental results show that the phase modulation curves do not change significantly with the small angle. When the angle is large (i.e. larger than 10°), the phase modulation curves become different, especially for the high gray levels. With the increase of the incident angle, the phase modulation depth is reduced. The results indicate that the incident angle plays an important role in the performance of the phase modulation of an LC-SLM.
070.6120 Spatial light modulators 120.5060 Phase modulation 120.5050 Phase measurement Chinese Optics Letters
2018, 16(9): 090701
