1. array of red LEDs at 660 nm filter holders (commercial) film polarizer in frame (0 o, 90 o, 10 o ) + circular polarized commercial optical bench, circa 10 cm x 50 cm existing mounting flange (connection to bench … TBD) adjustable leg MSE turret Remotely controllable Rotating filter mount. Linear/circular polarizers Original MSE In-Vessel Calibtion Jig (9/22/03)

2. MSE In-Vessel Calibration Jig (9/22/03) LED array Diffuser Polarizer 11 22 33 MSE optics

3.    observed = tan -1 ( tan(  ) / cos  )   observed -  0 0.00 90 0.00 10 0 0.00 10 10 0.15 10 20 0.63 Orientation of Polarized Light Differs from Polarizer Transmission Axis Unless Polarizer Surface is Normal to Viewing Direction - Same is true for rotation about horizontal axis

4. New Calibration Apparatus: Keep Polarizer Perpendicular to each MSE sightline LED array Diffuser Polarizer (on rotating stage) MSE optics

5. Illuminate polarizer with backlight through fibers – then adjust orientation of polarizer until the reflected light hits lens L1 – this ensures that polarizer is perpendicular to sightline. Stability of apparatus is important – over a 30 cm arm, a vibration of 50 microns = change in angle of 0.1 degrees. Studies with circularly polarized light will be interesting.