Depth recovery using active focus in robotics [vision]

In practice focusing can be obtained by displacing the sensor plate with respect to the image plane, by moving the lens or by moving the object with respect to the optical system. Moving the lens or sensor plate with respect to each other, causes changes of the magnification and corresponding changes on the object coordinates. In order to overcome these problems, the authors propose a technique to vary the degree of focusing by moving the camera with respect to the object position. The camera is attached to the tool of a manipulator in a hand-eye configuration with the position of the camera always known. This approach ensures that the focused areas of the image are always subjected to the same magnification. To measure the focus quality operators are used to evaluate the quantity of high-frequency components on the image. Different types of these operators was tested and the results compared