1 Characterization of a Bimorph Deformable Mirror in a Closed Loop Adaptive Optics System for Vision Science Purposes Zachary Graham 1 Sophie Laut 2, David Horsley 3, John Werner 2 1 Hartnell Community College, Salinas, CA 2 Department of Ophthalmology and Psychophysics, UC Davis 3 Department of Mechanical and Aeronautical Engineering, UC Davis

2 AO in vision science  Removes aberrations in the eye  Increases resolving power  Allows for more thorough and advanced study of the eye and brain (psychophysics)

3 My Project  To help characterize a mirror for use in a next generation Adaptive Optics imaging system  Helped with the setup of the system  Wrote a program in MATLAB to generate Zernike mode aberrations  Took data on the mirror

4 Next Gen. AO System  Will operate in 2 modes  Scanning Laser Ophthalmoscope (SLO)  Optical Coherence Tomography (OCT)  2 Deformable Mirrors  MEMS and Bimorph will be cascaded in one system  Bimorph will replacethe role trial lenses  Will remove more aberrations  Computer automated  Much more flexible

5 Slide Courtesy of Sophie Laut, UC Davis Medical Center

6 Slide Courtesy of Sophie Laut, UC Davis Medical Center

7 Imaging Setup Bimorph DM Hartmann – Shack Wave front sensor Pupil Plane Laser Diode Telescope 2  = 1 Telescope 1  = 1 System Information total  = 1.00 flatness = /13

8 Characterization Process

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10 Aberrations  Lower order aberrations  were introduced using trial lenses.  Cylinder and Sphere  Higher ordered aberrations  Trial lenses cannot be used  Generated in MATLAB

11 Solution Vector (Slope) Matrix of partial derivatives for all used zernike modes Vector of normalized zernike coefficients Centroid Displacement Algorithm Starts with a file of reference positions Reads the value of each reference Centro id from a matrix of partial derivatives for the particular Fernike mode. and calculates the slope in x and y The slope is direcly proportional to the displacement The displacement is added to the reference position and logged

12 Preparing Simulated Aberrations 1. A specific Zernike mode is picked 2. Maximum detectable amplitude is determined 3. Aberrations are generated 4. Aberrations introduced to the system

13 Characterization Process Control Loop closes and mirror corrects wave front Before/After data analyzed Place aberration into system

14 AO in Action

15 Problems with trial lenses The lenslet array could not resolve more than 1.8 diopters of error (defocus)  If aberration too strong the WFS spots will be displaced outside their sub-aperture  Occurs on physically introduced aberrations only  Limits testing to resolution of lenslet and not stroke of mirror.

16 Dealing With Loss of WFS Spots Some aberrations are so strong that the computer cannot find all of the WFS spots Using MATLAB we can correct for this by using an extrapolation algorithm

17 Characterization Process Control Loop closes and mirror corrects wave front Before/After data analyzed Place aberration into system

18 Results  The group are continuing to work on data analysis algorithms and are implementing them in MATLAB  Will be presented at Optics East 2005 SPIE Conference in Boston 1  The OCT / SLO set-up is under construction 1 Bimorph deformable mirror; an appropriate wavefront corrector for retinal imaging? –Sophie Laut, Steve Jones, Hyunkyu Park, David Horsley, Scot Olivier, John Werner

19 Talk about the SLO system Slide Courtesy of Sophie Laut, UC Davis Medical Center Bimorph DM MEMS DM OCT / SLO Schematic

20 Acknowledgements  This project is supported by the National Science Foundation Science and Technology Center for Adaptive Optics, managed by the University of California at Santa Cruz under cooperative agreement No. AST  Dr. Scot Olivier and Dr. Steven Jones at LLNL  Dr. Sophie Laut and Prof. John Werner at UCDMC  Prof. David Horsley at UCD  Everyone at the CfAO, LLNL, and UCD for a great internship experience