Alternate Faceplate Materials for Improving Image Intensifier Tube Performance

ABSTRACT: The military is constantly looking to improve night vision goggle performance. There are many components to optimize but one that is often overlooked is faceplate. The faceplate serves both as a substrate for the photocathode as well as a method for sealing the tube for high vacuum. It is usually made from Corning 7056 glass, of a thickness great enough to reduce halo due to reflected photons from the photocathode. We have verified that by increasing the index of refraction on the faceplate and by allowing it to be curved, significant performance gain is possible. In addition to a desire to improve performance of these tubes also comes a desire to help protect them from laser damage on the battlefield. An optical limiter that could be incorporated into the faceplate of the tube (to take advantage of the high flux densities near the image plane) would be very beneficial. A variety of new glass types have become available that may prove to have advantages when used in image intensifier tube (IIT) faceplates. High index glasses and chalcogenide glasses have promise to improve performance and we have also evaluated using glass with a curved front surface. BENEFIT: There are multiple benefits to the military in improving image intensifier tube performance via alternate faceplate materials. These benefits include: Protection against battlefield laser damage. By using alternative glass types and leveraging AFRL research, we can provide an optical limiter capability to night vision goggles to prevent them from being damaged by battlefield lasers. Improved resolution and MTF via higher index optical glasses and a redesign of the objective lens assembly. This will allow users to see smaller targets with higher contrast. Improved (reduced) f/#, which increases the amount of signal and the SNR. This will reduce the noise in the image and allow users to see targets under lower levels of illumination. Better filtering of off-axis light to reduce veiling glare in NVGs due to cockpit displays.