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Calibration Results - April 10th, 2009
Experiments were performed at a near 90 degree angle using reflected light to improve contrast. A schematic of the setup is below.
Optigrid Warm-up Routine
Before calibration took place, the grid voltage on the Optigrid was varied in order to condition the piezo for repeatable phase shifts. The voltage was cycled 13 times (approximately 5 minutes) in order from 0 V, 20 V, 68 V, and 100 V.
Coarse Calibration
27 Images from 0-130 V were taken and the phase was calculated. The phase versus voltage curve can be seen below.
From this graph, voltages of 47.2 V and 72 V were selected for midpoints for fine calibration.
Original Nikon Images
The current setup utilizes a Nikon camera which has a native file format of .NEF. A MATLAB script was written to convert these images to .TIF format.
Files required to Convert NEF to .TIF
TIF Images to be Processed
Fine Calibration
147 images were taken in 1 V increments around the voltages selected during coarse calibration. An Excel spreadsheet was used a Calibration Key to record the grid voltage at which each image was taken. The images were processed using the Merit Map script provided by Qioptiq, edited to support our images.
Merit Map Script Used for Processing
Our Merit Maps resulted in Merit Scores ranging for in the teens to near 200. One Merit figure can be seen below. All MATLAB figures can be downloaded below.