N231-016 TITLE: Emissive Image Display for Flight Simulators Wide-angle Collimated Displays

OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): General Warfighting Requirements (GWR)

OBJECTIVE: Develop an emissive image surface (EIS) for flight simulator wide-angle collimated display applications that significantly increases the American National Standards Institute (ANSI) contrast performance without degrading other performance.

DESCRIPTION: Collimated cross-cockpit displays are common in fixed- and rotary-wing aircraft flight simulators and/or flight training devices (FTD). This type of wide-angle collimated display provides two pilots, seated side by side, the same out-the-window (OTW) imagery (i.e., cross cockpit) without angular errors or distortions. A large spherical mirror is used that subtends the OTW field of view (FOV), and has a center of curvature located near the center-point between the eye boxes of the two pilots [Ref 1]. Current wide-angle collimated display technology uses multiple display projectors to illuminate a smaller toroidal-like screen called the back-projection screen (BPS), which is typically located above the cockpit and approximately half the radius of the large spherical mirror. While not as common, wide-angle collimated displays may also use front-projected screens (FPS). In the FPS configuration the projectors are in front of the toroidal screen. Together, the large spherical mirror and BPS/FPS create a virtual or collimated image, which appears to be at a fixed distance away from the eye point. For example, a collimated display with an 11 ft (3.35 m) radius is used to make a virtual image that appears to be 10 m away when, in reality, the pilot is sitting only 3 m away.

A display with a low contrast ratio makes an image look washed out. Although collimated cross-cockpit display projectors typically have a sequential contrast ratio (e.g., full on/full off) on the order of 2,000:1, the effective ANSI contrast ratio can be on the average 10:1. The ANSI contrast ratio is a more representative metric of contrast because it considers realistic operating conditions. It has been documented that ANSI contrast exhibits a better correlation with the perceived contrast by a pilot in an FTD.

Attempts to increase ANSI contrast in the FTD industry have only generated marginal increases in contrast from 8:1 to 15:1, with an average of 10:1 over the last 20 years. The low ANSI contrast is due to scattering from transmission through the BPS, back-reflection from the lower portions of the main collimated mirror, reflections from the cockpit windshield, secondary scattering off the BPS, cross reflections inside the BPS, and other unwanted reflection. Scattering not only affects luminance and contrast but the perceived resolution as well.

High-density, emissive display technology has greatly advanced over the past several decades and is approaching a point where it may be able to replace the BPS/FPS and projectors in modern flight simulators. However, challenges remain in the construction of such EIS, integration of the collimated display optical components, and integration with existing image generators (IG). This SBIR topic seeks to develop next-generation EIS for use in FTD/FTD -wide-angle FOV collimated display systems.

Requirements for collimated cross-cockpit displays with EIS performance:

* Support dual pilot cross-cockpit views for flight simulation applications separated at least 48 in. (1.22 m) apart.

* Viewing volume sphere 12 in. (30 cm) in diameter at pilot view point.

* Threshold horizontal FOV no less than 180� with an objective of 220�.

* Threshold vertical FOV no less than 60� with an objective of 80�.

* Threshold ANSI contrast greater than 15:1 with an objective of 25:1.

* Threshold static spatial resolution less than 5 arc min/OLP with objective 2 arc min/OLP.

* Threshold display average luminance of 10 ft (3.05 m) lamberts (fL) with objective of 20 fL.

* Threshold display average black level 0.001 fL with objective of 0.0001 fL.

* Support the use of multiple image generator rendering channels.

* Objective is to support night vision goggles (NVG) stimulation.

* Threshold 100% of the sRGB color space with objective of Rec. 2020 (UHDTV) color space.

* Support for auto-alignment.

 

The main challenges include development of a emissive image surface, high-contrast and high-luminance display, limited vertical FOV, NVG stimulation, calibration, maintenance, and use in motion platforms. These challenges must be addressed in the proposal.

Development of an emissive toroidal-like curved surface presents a significant challenge. If tiled subpanels are used, discontinuities and distortions at the boundaries need to be carefully considered.

Vertical FOV in wide-angle collimated display today is limited to 60�. The limitation in vertical FOV is a limitation of the current optical design. Increasing the vertical FOV is possible by increasing the diameter of the display but that increases the FTD footprint. Larger vertical FOV is a desirable feature for helicopter FTD.

Traditional RGB emissive displays may not provide enough energy in the near-infrared to stimulate NVG. The ability to provide a simultaneous near infrared light source component to the emissive display, which can be driven by a separate image generation channel, is desirable objective.

Distortions at display boundaries must be adjusted or calibrated and maintained over time. Furthermore, the use of wide-angle collimated displays in motion platforms is also a desired feature. Replacement of the complete display due to subcomponent failure is not economically or functionally practical. The display should allow for the replacement of sub display components (e.g., emissive tiles) and the fast calibration to achieve a seamless display. Motion platforms generate stress and forces that require a ruggedized design and therefore need to be accounted for in the design.

In addition to addressing emissive displays for wide-angle collimated displays, the proposal should include an assessment of how the proposed collimated concepts and technology can be extended to being used in real image dome type display training devices.

PHASE I: Design, demonstrate, and prototype a collimated display that includes novel EIS technology to meet or exceed the required collimated display performance thresholds. Determine technical feasibility through analysis, prototyping, and testing. The Phase I effort will include a scale down prototype, metrics and measured of performance. Demonstrate that the scaled down prototype performance will scale to meet or exceed the required performance thresholds on a full-scale collimated display. Determine if the novel EIS can be used as a replacement for current BPS/FPS. Identify, address, and document benefits (e.g., cost and performance), deficiencies, main challenges, and areas for improvement. The Phase I effort will include prototype plans to be developed under Phase II.

Address how this EIS technology can be modified to be used in real image dome type display systems. Identify, address, and document benefits (e.g. cost and performance), deficiencies, main challenges and areas for improvement.

PHASE II: Develop, prototype, and demonstrate that a full-scale functional prototype of the novel EIS display will meet or exceed the required performance thresholds and capabilities for a collimated display system. The Phase II effort will include a large-scale prototype based on Phase I prototype, and measured performance. Demonstrate that this large-scale prototype performance will scale to meet or exceed the required performance thresholds/objectives. Determine if the novel EIS can be used as a replacement for current BPS/FPS systems. Identify, address, and document benefits (e.g. cost and performance), deficiencies, main challenges and areas for improvement.

Determine how the EIS technology/design can be used in real image dome type display systems. Identify, address, and document benefits (e.g. cost and performance), deficiencies, main challenges and areas for improvement.

PHASE III DUAL USE APPLICATIONS: Develop full-scale collimated display that uses the EIS technology or integrate the full-scale EIS technology into an existing flight training device collimated display that meets or exceeds the required performance thresholds. Measure performance and document lessons learned. Perform pilot evaluations of the display�s performance and capabilities. Compare the new display�s performance to current collimated display systems. Determine if the novel EIS can be used as a replacement for current BPS/FPS. Identify, address, and document benefits (e.g., cost and performance), deficiencies, main challenges, and areas for improvement.

Federal Aviation Administration (FAA) uses collimated displays for flight training devices at level D [Ref 3]. Advances in EIS and collimated displays can be applicable to the commercial pilot training industry.

REFERENCES:

1.       Long, J. L., Lloyd, C. J., and Beane, D. A. (2010). Practical geometry alignment challenges in flight simulation display systems [Paper presentation]. IMAGE 2010 Conference, Scottsdale, AZ, United States. http://www.charleslloyd.us.com/PDF/Practical_Geometry_Alignment_Challenges_in_Flight_Simulation_Display_Systems.pdf

2.       National Simulator Program (NSP) (2016), 14 CFR part 60, Federal Aviation Administration (FAA). https://www.faa.gov/about/initiatives/nsp

3.       Joseph, D., Burch T., & Connolly, R. (2002). Comparison of Display System Options for Helicopter Aircrew Tactical Training Systems. Proceedings of the I/ITSEC Conference, Orlando, FL, United States. http://www.iitsecdocs.com/

 

KEYWORDS: flight training devices; FTD;; collimated displays; back projection screens; emissive displays; emissive image surface; EIS

---