Fixed-mount Imager Integration Guide

Getting Started 2 - 5
Chemically Tempered Float Glass
Glass is a hard material which provides excellent scratch and abrasion resistance. However, unannealed glass is
brittle. Increasing flexibility strength with minimal optical distortion requires chemical tempering. Glass cannot be
ultrasonically welded and is difficult to cut into odd shapes.
Window Coatings
Table 2-2 lists some exit window manufacturers and anti-reflection coaters.
Anti-Reflection Coatings
Apply an anti-reflection coating to the inside and/or outside of the window to significantly reduce the amount of light
reflected off the window, back into the imager engine. The coating can also improve the range of acceptable window
positions and minimize performance degradation due to signal loss as the light passes through the window. Using
anti-reflection coatings on both the inside and outside of the window is highly recommended.
Table 2-1 Suggested Window Properties
Property Description
Material Clear cell-cast acrylic.
Spectral Transmission 85% minimum from 640 to 690 nanometers.
Thickness 0.059 ± 0.005
Wavefront Distortion (transmission) 0.2 wavelengths peak-to-valley maximum over any
0.08 in. diameter within the clear aperture.
Clear Aperture To extend to within 0.04 in. of the edges all around.
Surface Quality 60-20 scratch/dig
Coating Both sides to be anti-reflection coated to provide
0.5% max reflectivity (each side) from 640 to 690
nanometers at nominal window tilt angle. Coatings
must comply with the hardness adherence
requirements of MIL-M-13508.