Gabriel Jeffers was born in Scotland and has lived in the
United Kingdom, Chile and different parts of the United States
of America. He lived on Maui full time from 2015 until moving
to the University of Colorado at Denver for college. He is
pursuing a Bachelor of Science degree in physics with a minor
in math and honors and leadership. He is currently
considering going to graduate school or entering industry.
Outside of classes he is in multiple physics clubs, volunteers at
punk shows, likes skating, snowboarding, climbing, cooking,
dungeons and dragons, anime and playing video games with
friends.
Home Island: Maui
High School:
Institution when accepted: University of Colorado Denver
Site: University of California Observatories (UCO). Santa Cruz, CA
Mentors: Renate Kupke
Project title: Modeling Diffraction in Shack-Hartmann Wavefront Sensors with Varying Lenslet Pitch and Focal Ratio
Project Abstract:
The atmosphere acts like a large number of lenses, changing the path of light traveling through it
and deforming the light’s wavefront, producing a blurry image. Wavefront sensors calculate this
wavefront and correct for the aberration. Shack-Hartmann wavefront sensors use lenslet arrays to
find the slope of wavefronts by focusing the light in each subaperture and measuring the centroid
location. The University of California Observatories (UCO) is swapping from charge-coupled devices
(CCD) to complementary metal-oxide semiconductor (CMOS) sensors for their Shack-Hartmann
wavefront sensors. This change reduces the pixel size and must be accompanied by a smaller lenslet
pitch, as we wish to keep signal-to-noise high. As the size of subapertures approaches the
wavelength, the effects of diffraction increase. Diffraction effects are also dependent on the focal
ratio of the lenslet array. We theorize that crosstalk between lenslets can become significant with
greater diffraction effects. Modeling these effects will allow UCO to design systems to minimize the
impact of diffraction on wavefront sensor performance. To achieve this goal, we modeled several
optical systems using both High Contrast Imaging in Python (HCIPy) and Physical Optical
Propagation in Python (POPPy). In this process, we created specialized lenslets and aberrations to
allow for proper optical interference between the modeled lenslets. Following this, we created a
centroiding function that, when applied to both a lenslet array system and an isolated lenslet model,
could quantify the effects of interference between lenslets. The final results of the models will be
presented in detail to highlight the interplay of diffraction effects and lenslet crosstalk on wavefront
accuracy.