/public/

Calibration Results - April 10th, 2009

Table of Contents 1 Calibration Results - April 10th, 2009 2 Optigrid Warm-up Routine 3 Coarse Calibration 4 Original Nikon Images 5 TIF Images to be Processed 6 Fine Calibration

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.

Coarse NEF Images

Files required to Convert NEF to .TIF

TIF Images to be Processed

Coarse TIF Images

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.

Calibration Key

Fine NEF Images

Fine TIF 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.

MATLAB Figures