Strehl Ratio

The Strehl ratio is one commonly used measure of optical image quality for very high quality imaging systems. The Strehl ratio is defined as the peak intensity of the diffraction point spread function (PSF) divided by the peak intensity of the diffraction point spread function (PSF) in the absence of aberrations. OpticStudio computes the Strehl ratio by computing the PSF with and without considering aberrations, and taking the ratio of the peak intensity. The Strehl ratio is not useful when the aberrations are large enough to make the peak of the PSF ambiguous, or for Strehl ratios smaller than about 0.1.