Improved Field of Regard for Strap Down Semi Active Laser Seekers

While strap down seekers offer improved reliability, reduced weight, and lower cost over traditional gimbaled seekers, one past disadvantage of the strap down seeker has been its limited field of regard (FOR).  As part of a Phase I SBIR project for the Aviation and Missile Research Development and Engineering Center (AMRDEC), AOS has demonstrated a multi-faceted ball lens approach to strap-down semi-active seeker technology that is capable of detecting a laser designator spot within a 60 degree field of regard using no moving parts.  It is optimized for background-rejecting narrow band filters, and is easily fabricated using inexpensive, durable parts.

In our Phase I work we have:

• Implemented a rigorous model of lens and detector performance

Figure 1 - Integrated Five Facet Lens Model The AOS model accurately predicts detector transfer functions based on lens size, facet location and angle, and detector size and location

Figure 2 - Four Facet Lens Model As with the five facet design, this model accurately predicts detector transfer functions based on lens size, facet location and angle, and detector size and location.

• Fabricated, tested, and selected the best of several variations on the design
• Integrated our custom optics with discrete detectors and quad cells to demonstrate agreement with our model predictions

With these efforts we were able to:

• Demonstrate greater than 60 degree full field of regard with proportional signal
• Demonstrate up to 80 degree field of regard for non-proportional signal with no filtering
• Establish quantitative bounds on spectral filtering bandwidth to ensure
  • Ambient interference stays within acceptable limits
  • Facet angles and position are optimized to maximize signal while preventing internal reflections