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Variable Attenuator for See-Through Day/Night Displays


TECHNOLOGY AREA(S): Electronics 

OBJECTIVE: Develop and demonstrate a variable attenuator for head-worn see-through day/night displays suitable for military aviation and untethered infantry use. Attenuator will capable of changing from high optical transmission for an unobscured view of the environment to low transmission to enhance the contrast of the display versus the ambient. 

DESCRIPTION: See-through displays, which are used for situational awareness and targeting for Soldier Lethality and Future Vertical Lift, can be overwhelmed by high level ambient light such that the content of the display is not readable. A contrast of 1.2:1 of the display to the background is the general rule for see-through readability, with the worst case ambient conditions being 2,000-fL for a white cloud or snow bank on a clear day. Reducing the transmission of the see-through optic, such as a visor, can aid with display contrast and readability, but the transmission needs to be high in some operations, especially at night, to allow the user to see details in the real environment through the optic. Arbitrarily driving the brightness of the display source brighter would enable readability, but it may increase power and thermal management demands beyond allowable limits, especially for untethered infantry. It also limits the display and optical technologies available for augmented reality solutions. See-through displays are also subject to external hazards and threats that occluded systems are not. A continuously variable attenuator can allow full daylight readability in bright ambient conditions, a clear view of the real world in night operations, and can have built in protections against hazards and threats. One potential form of the variable attenuator will be to provide the ability to transition bi-directionally between a broad-band, visually neutral, low transmission state of not more than 20% and a broadband, optically neutral, high transmission state of at least 80% in under 1 second. Other potential variable attenuator implementations for consideration include video rate attenuation switching speeds, localized and/or tailorable spectral attenuation/switching, and integrated eye/display hazard and threat protection. This effort will include the development of the 80%/20% ambient transmission attenuator and will also include its integration into a headworn system. An automatic adjustment of the transmission is optional, but a manual adjustment override is essential. Hazard and threat protection is also optional. 

PHASE I: Complete a notional design and model performance for a variable attenuator for day/night readability. Address spectrum, level of attenuation, switching speeds, localized attenuation, and potential hazard and threat protection. Provide sample demonstrators of attenuator technology (TRL 4). Phase I demonstrators may utilize planar substrates. 

PHASE II: Refine system design and build lab demonstrator capable of a minimum of 80%/20% continuous variability (spectrally flat) and will include other design concepts Offeror intends to include, such as localized attenuation (TRL 5). Develop a fully functional demonstrator that is integrated with a see-through head worn display (TRL 6). This demonstrator will examine the commercial practicality and cost related to implementing the variable attenuator on curved and/or plastic substrates. 

PHASE III: Integrate with a military AR HMD, possibly partnering with an HMD manufacturer for this effort (TRL 7). Apply technology to larger HUDs in aircraft and to vehicle windows. Implement hazard and threat protection if not already included. 


1: Clarence E. Rash et al., Helmet-Mounted Displays: Sensation, Perception and Cognition Issues, ed. Clarence E. Rash, U.S. Army Aeromedical Research Laboratory (2009)

2:  Russell S. Draper et al., "Electrochromic Variable Transmission Optical Combiner", SPIE Proceedings Volume 5801, Cockpit and Future Displays for Defense and Security (2005)

3:  Thomas H. Harding, Clarence E. Rash, "Daylight luminance requirements for full-color, see-through helmet-mounted display systems", SPIE Optical Engineering Vol. 56 Issue 5 (2017)

4:  Thomas H. Harding et al., "HMD daylight symbology: color choice and luminance considerations", SPIE Proceedings 10197, Degraded Environments: Sensing, Processing, and Display (2017)

KEYWORDS: Attenuator, Optical Attenuator, Variable Attenuator, See-through Display, Augmented Reality, HMD, HUD 

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