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F35 Panoramic Projection Display Calibration Process and Fixturing

This 8” x 20” display was comprised of 2 8x10 3 channel color LCoS projection units placed side by side.

The requirements for no mullion between the displays and that the units must be plug and play interchangeable resulted in very stringent geometric and color balance criteria.  My assignment was as leader of a team to develop the alignment process and implement the necessary fixturing for manufacture of the projectors.

The human eye is an excellent null detector for most visual criteria, so the lack of a mullion between the displays made all alignments hypercritical.  The primary geometrical metrics for the projected images included scale (overall magnification), distortion, convergence, and focus.  The traditional manual method of using a loop to compare the projected image to a reference reticule placed against the projection screen was labor intensive and could not reliably support the required resolution and precision of measurement.  We implemented a camera system to observe projected geometry at high magnification and interpret those images using machine vision algorithms to extract the necessary metrics including MTF.  This approach was novel and somewhat controversial when proposed but achieved very good results.  Combined with mechanical actuators to drive the physical adjustments in the projector we achieved a stable and efficient implementation for geometrical co-calibration of the 3 color channels of the projector.

The color calibration of the projectors represented another challenge.  Gamma calibration software provided by the LC imager manufacturer did not sufficiently control gray scale across the 3 channels.  We found it necessary to explicitly evaluate drive signal for all 256 gray levels of each channel in order to insure color congruence between arbitrarily selected projectors.  This repetitive trial and error method for picking driver values was first modeled manually and then implemented in an automated fixture resulting in another efficient implementation.

My team for this project included 2 optical engineers, a LabView specialist, systems engineer, mechanical design, and a manufacturing engineer.

I wish I could provide system diagrams and pictorial documentation of the assembly and calibration fixtures but this was a defense project and restricted. 

Top is a published illustration of the two projection units side by side.

Middle is the display in context of the cockpit.

Bottom is a picture of the F35.  We didn't design the airplane, but a benefit of working on fighter aircraft is you get to plaster pictures of them all over your stuff.

© 2019 Donna Kelley

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