Abstract: Measurement of object depth information in an image is an important task in the stereo vision domain. An automatic method of the depth measurement from two images captured by an ordinary monocular camera is proposed. While keeping the parameters of camera constant, two images are captured at the distance between object and the lens definted as u and u+d, respectively. Objects in the images are acquired by the image segment method using the LBF model. The objects are matched automatically using the combined the relative difference ratios of entropy from the object image and the weighted HU invariant moment. The object depth can be calculated by a formula presented in this paper.. Experimental results show that the method is effective.