DET_OVERSAMP header keyword does not return detector oversampling

[douglase]

When the MFT detector sampling is not equal to the wavefront oversampling the correct value is not passed to the output FITS file header.

Example code:

osys = poppy.OpticalSystem(oversample=18)
osys.add_pupil(poppy.CircularAperture())
osys.add_detector(0.1, fov_pixels=30,oversample=10)
psf=osys.calc_psf()
psf[0].header["OVERSAMP"], psf[0].header["DET_SAMP"]

returns:
(18,18)

rather than (18,10) as expected.

[mperrin]

Argh, good catch. I have to admit, the multiple types of oversampling available is sort of a confused and tricky area of the code, for various historical reasons.

The wavefront oversampling is set when instantiating a Wavefront object, and stored as an object attribute which persists throughout the calculation. The detector oversampling isn't; it's read from the Detector object inside Wavefront._propagate_mft. The cleanest fix here is probably to modify that function to record the detector oversampling as another attribute, and update Wavefront.as_fits correspondingly.