WESTPSFMINUTES Compute Westheimer estimate of human PSF
psf = WestPSFMinutes(radius)
Compute Westheimer’s PSF function as a function
of passed radius. Radius passed in minutes of arc.
Formula from Westheimer G. 1986. The eye as an optical instrument. In
Handbook of perception and human performance, KR Boff, L Kaufman,
JP Thomas (eds). New York: Wiley. Equation 7.
This is only approximately consistent with Westheimer’s LSF estimate.
This comes back normalized to a maximum of 1.