A new instrument design allows the M<sup>2</sup> beam propagation ratio to be measured in real time at the update
rate of a standard CCD camera. This allows lasers from single shot to CW to be measured while the laser
cavities are being adjusted. This drastically reduces the test time required for this operation. In this paper
we will discuss the theory behind this innovative approach to the M<sup>2</sup> measurement and the methods for the
selection of the proper optical components for use of the system with various laser types and beam shapes.
The authors will show results of numerous measurements of different lasers and laser types, including solid
state diode and traditional gas lasers with M<sup>2</sup> values from near 1 to considerably higher values, and show
comparisons these results with other measurement methods.
The instrument design is based on a method of simultaneous capture of the waist and several Rayleigh
ranges, allowing the instantaneous fit of the ISO M<sup>2</sup> propagation curve. The authors will discuss the
important considerations necessary to generate accurate results for different laser configurations.