Engineering topics

Poyneer, Lisa A.

Publications and source records attributed to Poyneer, Lisa A..

3 records

DOE OSTI2023

Laboratory demonstration of the prediction of wind-blown turbulence by adaptive optics at 8 kHz with use of LQG control

The low-latency adaptive optical mirror system (LLAMAS) is designed to push the limits on achievable latencies and frame rates. It has 21 subapertures across its pupil. Here, a reformulated version of the linear quadratic Gaussian (LQG) method predictive Fourier control is implemented in LLAMAS; for all modes, it takes just 30 µs to compute. In the testbed, a turbulator mixes hot and ambient air to produce wind-blown turbulence. Wind prediction clearly improves correction when compared to an integral controller. Closed-loop telemetry shows that wind-predictive LQG removes the characteristic “butterfly” and reduces temporal error power by up to a factor of three for mid-spatial frequency modes. Strehl changes seen in focal plane images are consistent with telemetry and the system error budget.

47 OTHER INSTRUMENTATION↗

DOE OSTI2022

Wavefront shaping with a Hadamard basis for scattering soil imaging

Here, soil is a scattering medium that inhibits imaging of plant-microbial-mineral interactions that are essential to plant health and soil carbon sequestration. However, optical imaging in the complex medium of soil has been stymied by the seemingly intractable problems of scattering and contrast. Here, we develop a wavefront shaping method based on adaptive stochastic parallel gradient descent optimization with a Hadamard basis to focus light through soil mineral samples. Our approach allows a sparse representation of the wavefront with reduced dimensionality for the optimization. We further divide the used Hadamard basis set into subsets and optimize a certain subset at once. Simulation and experimental optimization results demonstrate our method has an approximately seven times higher convergence rate and overall better performance compared to that with optimizing all pixels at once. The proposed method can benefit other high-dimensional optimization problems in adaptive optics and wavefront shaping.

47 OTHER INSTRUMENTATION↗

DOE OSTI2021

Icy Moon Project (Final Report)

For this Icy Moon project, we designed, procured, built, tested and used a compact ICI instrument. This instrument has several technical advances, including a compact form factor that uses fiber arrays to relay light to six APDs. This enables a single data acquisition to measure eleven unique baselines simultaneously. The DAQ is well-synchronized and provides a path forward to even more channels. The combination of a bright LED, a sinusoidal target and cylindrical optics enables high-SNR measurements based on a known formula: a 25-ms measurement should have an SNR of 188 on the baseline zero signal. This rapid measurement time should enable two-dimensional operation and obviate the impact of temperature drifts. However, the experiment did not detect a coherence signal on any baseline (see Section Single-shot measurement results).

47 OTHER INSTRUMENTATION↗