Optical method to measure the surface of objects by using only one photo.

What we believe is a novel method to measure the dimension of an object with one defocused photo of an object is presented in this paper. To do this, a photo of the object is taken by a camera. The focal plane is chosen as a reference plane. The coordinates of the object surface are obtained by using the camera's parameters and corresponding defocused distance. The depth from the reference plane is obtained by evaluating the confusion degree of the photo around an edge. The relationship between the confusion degree and the distance from the reference plane has been given theoretically and experimentally. Several objects have been measured with the method, and it is shown that the results obtained are reliable. For nontextured surfaces, the edges of objects can be used to make the measurement.