Point Source Illumination Stereo for Objects with Uniform Reflectance

In an earlier report, a point source stereo method was proposed which determines the distance from the viewpoint to the surface element as well as the inclination of the element surface for the completely diffusive surface based on five density images obtained by a point source illumination. The present paper proposes a new method along the line which can determine accurately the distance distribution for the measurement in the general environment from the illumination equation with the intensity resolution of some 8 bits. A diffusive surface is considered which may contain any inclination but has a uniform reflectance over the entire surface. The distance distribution is determined by the following two procedures. In procedure 1, the common reflectance is determined by selecting the surface element with the maximum luminance in each image and combining the data. In procedure 2, the uniform reflectance is used as the constraint, and the distance distribution is determined for each surface element. The proposed method is called the solution by combined maximum luminance surface elements. An algorithm (three-source stereo method) was developed for the case of the continuous surface, where t h e distance distribution can be determined using only three images. An experiment was made for the proposed method using an 8-bit quantized image for a diffusive object. As a result, it is shown that both five-source and three-source methods can determine accurately the distance distribution with accuracy within 1 percent from the quantized intensity image data, for the measurement in the general environment.