fraunhofer: Star test simulator

In matwey/Rfringe: Rfringe

Description

A simple star test simulator, with optional MTF or wavefront plot.

Usage

fraunhofer(zcoef, zlist = zlist.qf, obstruct = 0, lambda = 1, defocus = 5, 
    pupilsize = 255, npad=1024, gamma=2, psfmag = 2, 
    displaymtf = TRUE, displaywf = FALSE, fileout = FALSE)

Arguments

zcoef	Vector of Zernike coefficients
zlist	A list with named components n, m, t describing the contents of zcoef
obstruct	central obstruction fraction
lambda	Wavelength. Defaults to 1 for a wavefront in waves.
defocus	Amount of defocus for side panes, in waves P-V.
pupilsize	Size of matrix representing pupil
npad	Size of the 0 padded matrix for fft calculations
gamma	gamma value for image display
psfmag	Magnification factor for in focus PSF display
displaymtf	Boolean: display MTF?
displaywf	Boolean: display Wavefront?
fileout	Boolean: Is the intended output a file?

Details

Computes the intensity distribution from a monochromatic point source in the approximation of Fraunhofer diffraction theory. See Suiter (1994) for a full discussion of the application of the theory to practical star testing of small telescopes.

Note

The ratio of npad to pupilsize determines the size of the Airy disk in the “in focus” image. The default choices will produce an Airy disk with a diameter of approximately 10 pixels, and the amount of zero padding is sufficient to prevent significant aliasing for defocus values up to about 20 waves.

If memory limitations cause errors satisfactory images can still be obtained with, say, npad=512 and pupilsize=127.

Author(s)

M.L. Peck [e-mail]

References

Born, M. and Wolf, E. 1999, Principles of Optics, 7th Edition, Cambridge University Press.

Suiter, H. R., 1994, Star Testing Astronomical Telescopes, Willman-Bell, Inc.

See Also

Zernike, pupil.

Examples

# a random, but probably almost diffraction limited, wavefront

fraunhofer(rnorm(length(zlist.qf$n), mean=0, sd=0.01), displaywf=TRUE)

matwey/Rfringe documentation built on May 12, 2019, 8:43 a.m.