Adaptive Optics

the adaptive optics revolution in astronomy

Transcript

2. collecting area
4. Diffraction limited telescope: angular resolution=λ/D Strehl ratio: measure of contrast = ratio of peak intensity to perfect optical system Point Spread Function: image of a point source
5. Atmospheric Turbulence Fried's coherence length r 0 is level of turbulence: 5-20 cm usually Kolmogorov model: kinetic energy air > dissipated as heat Greenwood frequency: how quickly atmospheric turbulence changes Coherence time τ 0 = coherence length/wind velocity ~ milliseconds atmospheric structure constant C n 2 is measure of strength of turbulence
6. Phase Conjugation of Light amplitude A, phase Φ light wave: Ae(-iΦ) cancel with: Ae(+iΦ) e(+iΦ -iΦ) = e(0) = 1 think of it like noise cancelling headphones, but with light instead of sound!
10. Power-Series Zernike Polynomials Represent Phase: n=radial, m=azimuthal
14. The Math for Closed Loop Control Φ k+1 = Φ k + Bu k + d k y k = Φ k + v k and u k = -Ry k Φ: wavefront aberrations vector B: mirror's influence matrix u: actuator commands vector d: wavefront turbulence vector v: measurement noise vector WANT reconstructor R = B-1 Inverse for non-square matrix calculated using least-squares by SVD or Moore-Penrose
17. cost comparison
21. The Future