ShackHartmann SH Sensors Wavefront Sensing Applications Astronomical Telescope

Shack-Hartmann (S-H) Sensors Wavefront Sensing Applications Astronomical Telescope System W/O Adaptive Optics Ophthalmic Analysis System With Adaptive Optics Human Eye (Neptune Observed at = 1. 65 m*) S-H Sensor *http: //cfao. ucolick. org/pgallery/ © 2005 University of California Prepublication Data Spring 2005 1

Conventional Shack-Hartmann Sensors Microlens Array CCD Camera Gap CCD Imager © 2005 University of California Prepublication Data Spring 2005 2

S-H Sensor Operating Principle Light travels in a direction perpendicular to the wavefront! Lens 3 Optical Axis Focal Point Wavefront Slope Optical Axis © 2005 University of California Prepublication Data Spring 2005

Incoming Wavefront S-H Sensor Operating Principle (Cont. ) * Side view 1 3 Front view (CCD) CCD 1 1 3 3 2 1 3 *J. M Geary, Wavefront Sensors, 1995 © 2005 University of California Prepublication Data Spring 2005 2 4 4 4

Dynamic Range and Sensitivity 5 Sub-aperture MAX Dynamic Range: MAX Sensitivity: MIN f MIN CCD f , MAX (worse), MIN (better) f , MAX (better), MIN (worse) © 2005 University of California Prepublication Data Spring 2005

Incoming Wavefront Shack-Hartmann Sensor Limitations Side view Largely Aberrate d Wavefro nt 1 3 Error! 1 Front view (CCD) 1 2 1 3 3 6 3 2 4 4 Focal point #3 is misplaced into subaperture 1! © 2005 University of California Prepublication Data Spring 2005

7 Incoming Wavefront Vibrating Microlens Side view 1 f. R 3 3 Front view (CCD) 1 1 f. R 3 3 2 1 3 3 2 4 4 Identify the microlens and its associated focal point by resonating the lens: focal point scanning line. © 2005 University of California Prepublication Data Spring 2005

MEMS Addressable Array: Concept Unit 2 f. R 1 f. R 2 f. R 3 f. R(N-1) f. RN GND Unit 1 VDC+VAC exp(j t) Unit 3 Unit(N-1) Unit. N VDC+VAC exp(j t+j /4) Make the mechanical unit (of interest) resonate by setting the frequency of the driving voltage equal to the unit’s resonant frequency. Pair of electrical interconnects per row/array © 2005 University of California Prepublication Data Spring 2005 8

SEM of MEMS Lens-Carriage Array Lens Carriage Comb Sets Flexures Nitride Membrane Flexures Drive Lines © 2005 University of California Prepublication Data Spring 2005 9

Microlens Fabrication Process Using Polymer-Jet Printing 10 Stroboscopic View of Micro. Jet-Dispenser Droplet Formatio 1 2 3 4 Stroboscopic View of Microlens Formation 1 2 © 2005 University of California 3 Prepublication Data Spring 2005 4

Addressable MEMS-Microlens Array 1500 m 800 m © 2005 University of California Prepublication Data Spring 2005 11

Individual Resonant Motions 12 • Expect improvements by a factor of 20 -40 over the ynamic range and sensitivity of conventional SH senso © 2005 University of California Prepublication Data Spring 2005