Study of Three-Dimensional Sensing by Using Inverse Square Law

Because a sense of reality of a stereopicture used to display a real scene is better than that of a two-dimensional image, the former has been widely paid much attention in application. Recently, there are several methods used on three-dimensional sensing. In this study, our system to construct a stereopicture is composed of a single co-axial point-light source associated with a video camera. Different images of a scene could be taken by the camera when the light source was moving away relative to the scene from a point to another one. Based on the inverse square law for light intensity, the depth information of a scene can be obtained by using the pixel ratio obtained from two consecutive frames. Because the gray-level of each pixel in an image taken by the camera is related to an angle made by the line of sight of the pixel with the optical axis, the image plane is bent. Comparison the distance measured from the camera to the object with theoretical data obtained by the inverse square law, we found that their error corresponding to different pixels located at the margin of the image plane is higher than that at the center of the image plane. However, this problem can be improved by making an angular correction. Consequently, a low-pass filter was used to smooth the raw data of the range to reduce the distance error.