The focal length of camera is estimated efficiently by using the algorithm of equidistant matching, images are warped to the surface of sphere whose radius equals to the focal length of camera.
使用等距离匹配算法计算相机的焦距，以相机焦距作为球体半径，将照片图像投影至球面上。
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The results of computer simulation show that both the radius of disk and the depth of focal length decrease as increasing incidence wavelength, meanwhile, the intensity of disk is enhanced.
The analysis that the size of the focal shift is related to the factors such as Fresnel number, separating degree of lens-diaphragm and curvature radius of incident wave wavefront, etc.