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Alternate Faceplate Materials for Improving Image Intensifier Tube Performance


OBJECTIVE: Develop Improved Performance Image Intensifier Tubes by Utilizing Alternate Faceplate Materials DESCRIPTION: An Image Intensifier Tube is an electro-optical device which converts photons to electrons, amplifies them, and then converts them back to photons so the user can see at light levels that are normally too low. These Image Intensifier Tubes are commonly used in night vision goggles and night scopes to allow vision in low-light level conditions. The main components of modern Image Intensifier Tubes are a faceplate, photocathode, multichannel plate, and phosphor screen. This purpose of this effort is to develop Image Intensifier Tubes with alternate faceplate materials for improved performance and compatibility with USAF systems. Historically, the faceplate has been 5.537mm thick Corning 7056 glass, or equivalent (MIL-L-49426). There are several potential advantages to using faceplate materials other than Corning 7056 glass. These include higher quality Modulation Transfer Function (MTF) performance, spectral filtering, and ease of processing. The Image Intensifier Tube faceplate is an integral component of the objective lens assembly in Night Vision Goggles. Replacing the current faceplate with an alternate one having higher refractive index opens the possibility of new optical designs with reduced aberrations. In addition, alternate materials such as chalcogenide glasses can be patterned in ways that may increase light collection, including the implementation of microlens structures on the faceplate. Alternate faceplate materials may also offer advantages for compatibility with cockpit display standards. The performance figure of merit (FOM) for night vision goggles is derived from the number of line pairs per millimeter multiplied by the tube's signal-to-noise ratio. PHASE I: Demonstrate the feasibility of incorporating alternate, high refractive index, faceplate materials into Image Intensifier Tubes. Investigate methods for improving sensitivity and lowering signal to noise ratio; These Image Intensifier Tubes must retain similar performance (FOM should be equal to or greater than 1400) to standard tubes including size and weight. PHASE II: Optimize selection of alternate faceplate materials for enhanced MTF performance. Analyze impact of Image Intensifier Tubes incorporating alternate faceplate materials on objective lens design and performance. Validate FOM performance equal to or greater than 1400. Deliver prototype Image Intensifier Tubes with alternate faceplate materials to the government for additional testing and comparative demonstration with current image intensifier tubes. PHASE III: Perform Manufacturing Readiness Level Assessment. Optimize manufacturability of Image Intensifier Tubes made with alternate faceplate materials. REFERENCES: 1. Image Intensifier Tube Performance is What Matters; Leon A. Bosch, SPIE Proceedings Vol. 4128, Image Intensifiers and Applications II, 2000, pp.65-78. 2. Night Vision Devices and Image Intensifier Tubes; Nikolay F. Koshchavtsev, SPIE Proceedings Vol. 4369, Infrared Technology and Applications XXVII, 2001, pp. 81-85.
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