Abstract: The present application discloses a method and apparatus for compensation of focal errors in laser beam measurement instruments that characterize beam parameters by analyzing images of Rayleigh scatter taken at multiple angles around the beam axis. If the laser beam is not precisely positioned, these images may not be in focus, and the instrument will not report accurate results. This method and apparatus finds the longitudinal axis of the beam by analyzing the beam location in at least two images. All images are subdivided into slices and distances from the beam axis to the focal plane for each slice are calculated and used to find an out-of-focus transfer function for each slice, which is used in combination with the modulation transfer function of the system to deconvolve the slice. Images formed by reassembling the deconvolved slices can then be analyzed to obtain the correct beam parameters.

Abstract: The present application discloses a method and apparatus for compensation of focal errors in laser beam measurement instruments that characterize beam parameters by analyzing images of Rayleigh scatter taken at multiple angles around the beam axis. If the laser beam is not precisely positioned, these images may not be in focus, and the instrument will not report accurate results. This method and apparatus finds the longitudinal axis of the beam by analyzing the beam location in at least two images. All images are subdivided into slices and distances from the beam axis to the focal plane for each slice are calculated and used to find an out-of-focus transfer function for each slice, which is used in combination with the modulation transfer function of the system to deconvolve the slice. Images formed by reassembling the deconvolved slices can then be analyzed to obtain the correct beam parameters.