Focal length and target range estimation for focused, apertured Gaussian laser beams

In some laser transmitting applications where system performance requires maximum intensity at the receiver plane, it is necessary to expand and focus the laser wavefront. Maximum intensity occurs when the wavefront focal length and the range to the receiver plane are the same. This paper considers the use of an extended Kalman filter and an iterated extended Kalman filter to estimate the range to the receiver plane, the focal length of the laser system, and the scale factor uncertainty in target reflectivity characteristics. The information can be then used to set the focal length of the laser to obtain maximum intensity. The laser is a truncated Gaussian, focused and apertured beam.