Wavefront Sensing with the Differential Optical Transfer Function (dOTF)

Dr. Johanan L. Codona
University of Arizona, Steward Observatory

The difference between the Fourier transforms of two point source
images with a small pupil change introduced between them is all that
is required to find the complex field in the pupil. We will discuss
this surprisingly simple result, the theory behind it, and its
experimental validation. Because dOTF is inherently not as photon
efficient as other wavefront sensing techniques, it is not a candidate
for high-speed adaptive optics applications. However, there are many
places where it is a very simple and uniquely-powerful method. We will
talk about applications ranging from optical shop testing to
ophthalmological applications to a new technique for phasing the JWST
segments with no additional required hardware. The dOTF can give
interferometer-quality results with nothing more sophisticated than a
laser pointer and an uncalibrated fingertip. With a bit more
sophistication it is possible to perform the equivalent of image
processing on the complex pupil field, enabling visualization and
measurement of small and subtle wavefront features. By using dOTF with
more than one point source simultaneously in a system with a
shift-dependent PSF, the 3-dimensional structure of the aberrations
and vignetting can be revealed from two images.