Data Structures
struct	locfft_t

Functions
locfft_t *	locfft_init (loc_t loc, const dmat amp, const dmat wvl, const lmat fftsize, real oversize, real fieldstop)

void	locfft_free (locfft_t *locfft)

void	locfft_psf (ccell *psfs, const locfft_t locfft, const dmat opd, const lmat psfsize, int sum2one)

void	locfft_fieldstop (const locfft_t locfft, dmat opd, const dmat *wvlwts)

void	fresnel_prop (cmat *out, real dxout, const cmat *in, real dxin, real wvl, real z, real scale, int method)

Detailed Description

Routines used to embed OPDs defined on loc_t to square array with embeding factor and compute PSF using FFT.

Data Structure Documentation

◆ locfft_t

struct locfft_t

Collaboration diagram for locfft_t:

Data Fields
loc_t *	loc
const dmat *	amp
dmat *	wvl
lmat *	nembed	size of embedding array (square)
lcell *	embed	embedding index
real	ampsum	sum(amp)
real	ampnorm	sum(amp.*amp)
dcell *	fieldmask	Masking the PSF in fourier domain
real	fieldstop

Function Documentation

◆ locfft_init()

locfft_t* locfft_init	(	loc_t *	loc,
		const dmat *	amp,
		const dmat *	wvl,
		const lmat *	fftsize,
		const real	oversize,
		real	fieldstop
	)

For routines that embed OPDs defined on loc to square(rectangular) array and do fft on it.

Parameters

[in]	loc	The loc
[in]	amp	The amplitude
[in]	wvl	The wavelength
[in]	fftsize	The suggested size for FFT, nwvl values
[in]	oversize	Factor of oversize. 2 fot FFT
[in]	fieldstop	Size of field stop (radian) if used

◆ locfft_free()

void locfft_free ( locfft_t * locfft )

Frees the struct

◆ locfft_psf()

void locfft_psf	(	ccell **	psf2sp,
		const locfft_t *	locfft,
		const dmat *	opd,
		const lmat *	psfsize,
		int	sum2one
	)

Computes PSF from OPD by FFT. The PSF is computed as

\(\textrm{PSF}=\mathcal{F}[A\times exp[\frac{2\pi i}{\lambda}*\textrm{OPD}]]\)

The peak value (center) in the computed PSF is normalized by the peak value in the differaction limited PSF. In other words, the peak value in the computed PSF is the Strehl. Keep this in mind when you compute enclosed energy.

Extract center part of psfsize.

◆ locfft_fieldstop()

void locfft_fieldstop	(	const locfft_t *	locfft,
		dmat *	opd,
		const dmat *	wvlwts
	)

Apply a field stop to the OPD.

◆ fresnel_prop()

void fresnel_prop	(	cmat **	pout,
		real *	pdxout,
		const cmat *	in,
		real	dxin,
		real	wvl,
		real	z,
		real	scale,
		int	method
	)

Fresnel propagation using either FFT or angular spectrum method.

For FFT method, the output sampling is z*wvl/(dxin*nxin). For angular spectrum method, the output sampling equals to the input sampling. When the output sampling equals, the two methods agree. Notice that at near field when dp is smaller than dx, the output of angular spectrum method is periodic.

The output is normalized so that its squared sum equals to nx*ny*sum(abs(in)^2). Input argument scale should be supplied to cancel this scaling.

The brutal force method (method=0) has the exact solution without using fresnel approximation. It is however very slow. The results agrees with method=1 or 2 when the sampling agrees and the approximation holds.