1. Characterizing Lenslet Arrays for the Keck Adaptive Optics System Laboratory for Adaptive optics (LAO) UC Santa Cruz Name: Abubakarr Bah Home Institution: Santa Rosa Junior College Advisor: Dr. Don Gavel Mentor: Dr. Renate Kupke

2. 2 What are Lenslets? Small lenses (50 um- 1 mm) Part of an array. Found in Shack-Hartmann wave front sensors. Image taken from http://www.ctio.noao.edu Lenslet on a Shack-Hartmann wavefront sensor

3. 3 My Project Information Characterizing Lenslets arrays for the Keck adaptive optics system: Focal Length Pitch Measurement Transmission Lenslet Optical Figure

4. 4 Focal length setup CCD Pinhole (5 µ).633 um f Microscope Objective (10x) Microscope Objective (50x) Diode laser Aperture Collimated light Lenslet Computer Hartmann Spots

5. 5 Focal length at a single wavelength (.633 um) Array Focal length spec. (mm) Focal length Meas. (mm) Depth of focus (uncertainty) A4.9 ± 0.54.95± 0.39 B3.1 ± 0.33.11±0.17 C2.4 ± 0.22.39±0.11

6. 6 Focal length set up for different Wavelength. White light Source CCD Lenslet Microscope Objective (10x) Computer Microscope Objective (50x) Filter

7. 7 Wavelength Focal length A Focal Length B Focal length C 4004.422.902.23 5004.813.002.42 6004.923.142.35 8004.863.022.23 7004.603.022.46 Focal length at diff. wavelength

8. 8 Pitch Measurements: Spot Pitch Measurements: - Same as Focal Length Setup - Distance b/w Spots Pitch Measurements: - LAO's Olympus microscope - 20 Lenslet at a time

9. 9 Focal Spot Pitch Lenslet Focal Spot Pitch Spec (mm) Focal Spot Pitch Meas. (mm) RMS Error A0.2000.1996± 0.00134 B0.2000.1995± 0.00088 C0.2000.1997± 0.00091

10. 10 up= towards lenslet III Right= towards markings. Pitch Measurements Using the LAO's Olympus microscope Measurements were taking 20 lenslet at time lenslet Up (mm) Down (mm) Right (mm) Left (mm)RMS Error A4.00003.99804.0000 ± 0.0010 B4.0000 ± 0.0000 C4.0000 3.9660± 0.0170

11. 11 Transmission of the Lenslets: Keck Specification: >97 % EXPERIMENTS: Used The UCO Lick Optical Shop's spectrophotometer. Made a simple optical setup

12. 12 Throughput. White light Source FilterLenslet Photometer Pin Hole

13. 13 Min 0.84 Max 1.00 Transmission of Lenslet:

14. 14 Lenslets optical Figure:

15. 15 Conclusions:. Focal length and Pitch meet specifications.Transmission meets the specifications within 500-950 nm. Lenslet has a parabolic shape and steps patterns (surprising observation !)

16. 16 Acknowledgments Dr. Don Gavel Dr. Renate Kupke Sandrine Thomas Daren Dillon Marco Reinig Members of the LAO lab Center for Adaptive Optics (CFAO) This work has been 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 - 9876783."