The device null which decides three dimensional position of the interest dot in the body

摘要

A set of two-dimensional views of a body are provided from successive azimuthal angles with respect to a given axis. The set of views of the body are successively displayed on a display screen which shows the body as rotating about an axis. A point of interest in the body also appears to rotate about the axis. That view at which the point of interest is maximally displaced from the apparent axis of rotation is used to determine the angular position of the point of interest. The true displacement of the point of interest from the axis of rotation and its true displacement along the axis of rotation are available from that view. Thus, the cylindrical coordinates of the point of interest are known. To check the accuracy with which the coordinates of the point of interest have been determined, a cursor is established in the stopped view, and the projection of the cursor in the other views is calculated in a conventional manner. While sequential display of the views continues, the cursor appears to move with but not relative to the point of interest if the cursor actually overlies the point of interest. If the cursor appears to move relative to the point of interest, the cursor is modified until no relative motion appears.