The central framework for signal recovery in compressive sensing is l_1 norm minimization. In recent years, tremendous progress has been made on algorithms, typically based on some kind of gradient descent or Newton iterations, for performing l_1 norm minimization. These algorithms, however, are for the most part “static”: they focus on finding the solution for a fixed set of measurements. In this paper, we will present a method for quickly updating the solution to some l_1 norm minimization problems as new measurements are added. The result is an “l_1 filter” and can be implemented using standard techniques from numerical linear algebra. Our proposed scheme is homotopy based where we add new measurements in the system and instead of solving updated problem directly, we solve a series of simple (easy to solve) intermediate problems which lead to the desired solution.
SB091-010 TITLE: Panoramic Helmet-Mounted Display and Processing
TECHNOLOGY AREAS: Sensors, Electronics
OBJECTIVE: Develop a prototype of a panoramic, wide field of view helmet-mounted display, which presents the user with information from a minimum 90 degree horizontal field of view (FOV) with a goal of 120 degree horizontal and 40 to 50 degree vertical field of view, including signal processing adaptable to scene content.
DESCRIPTION: Significant advances have taken place in the development of large format imaging sensors, with mega-pixel sensors available in several spectral bands. These large sensors, which cover a wide field of view, fulfill the requirements for many applications, but are especially important in helmet-mounted systems for both ground and pilotage applications. However, the display technology essential to presenting the large amount of information generated by the sensor lags considerably behind the sensor technology. Currently, display technology is limited in field of view, and does not have the integral signal processing to match the capability of large format sensors and to adapt the information to meet user needs.
The need to efficiently display a large amount of information to the user is crucial to mission success. Information must be available to detect threats at the periphery of vision, to discern details as needed by the situation, and to perform intricate tasks. Meeting all of these requirements simultaneously requires a significant leap-forward in display and signal processing technology. The display must meld the requirement for full panoramic field of view with the need for an adaptable, high resolution instantaneous field of view.
The display must provide high image quality in a light weight package, with the ergonomics required for user acceptance, such as the center of mass optimized for head-mounted applications. The display format must be extended beyond the current state of the art, leading to innovative concepts in Mega-pixel displays with a high visual acuity in the central region and lower resolution in the periphery of the display. Novel signal processing and image reconstruction techniques must be applied to present the user with the essential scene content. The goal is to develop innovative sampling techniques that require only a small percentage of the data to reconstruct high quality scene information. These techniques have been demonstrated in radar and acoustic signal processing, but not implemented in helmet mounted displays. Although signal processing techniques have been demonstrated, there is considerable risk in the implementation of these techniques in display systems. However, the pay-off is large, enabling the user to grasp the large amount of information generated in a panoramic scene.
Emerging technologies in compressive sampling, where the information rate may be much smaller than the bandwidth, enables the presentation of only the essential information without loss of scene content. These new techniques can be integrated with wide field of view display components to present information from a wide field of view at minimum power, essential to helmet-mounted systems. The integrated display/processor not only presents information to the user, but also integrates functions to reduce workload, increase the situational awareness and enhance the ability to perform essential tasks.
In military display applications, a wide field of view combined with the flexibility to perform multiple functions, and elimination of display artifacts that detract from image quality, are essential to user acceptance of the technology. The display technology must have a fast response time so that the image is free of artifacts due to target movement or head-movement. Frame update rate of at least 60 Hz minimizes image artifacts and blurring. An innovative feature of the display technology should be the flexibility to integrate inputs from external sources as well as the ability to export selected areas to other sensor systems.
The physical configuration of the display must conform to the user with an unobtrusive format, conformal with the helmet, fitting similar to a visor, and with the display configured with optimum binocular overlap to provide high resolution and a contiguous view of displayed information. The brightness should be sufficient to present high contrast information, even in high light ambient environments. Also, the physical configuration must be such that illumination from the display is visible only to the user and keeps the system convert.
Applications include aviation and ground applications. The signal processing functions should be adaptable, allowing the display processing system to be used in multiple environments.
PHASE I: Define issues associated with the development of a novel concept in wide field of view display technology for helmet mounted applications; design the micro-system concept for panoramic helmet mounted display that includes adaptable compressive sampling to present essential scene content to the user. Perform simulations to demonstrate significant features of the display and advantages in military ground and airborne applications. Plans for Phase II will be proposed, including display component requirements and signal processing design.
PHASE II: Demonstrate the wide field of view display concept demonstrator with panoramic field of view, showing central region visual acuity approaching 20/20, with a minimum of 8 bits per pixel with a goal of 16 bits per pixel; show viability of the signal processing approach, display component technology, and the integration of signal processing with the display.
PHASE III: DUAL USE APPLICATIONS: Multiple applications for wide field of view display technology are in aircraft simulators and training systems. The display will present information from a wide field of view and provide a realistic view of the scene, while the integral signal processing will maintain and enhance the details in the scene necessary to perform intricate tasks.
1. Patterson R., Pierce B.J., Winterbottom M. C., “Perceptual Issues in the use of Head-Mounted Visual Displays” Journal of the Human Factors and Ergonomics Society, Vol 48 No. 3, 2006. pp 555-573.
2. Brickner M.S., “Helicopter Flights with Night-Vision Goggles-Human Factors Aspect” NASA Technical Memorandum 101039, March 1989.
3. E. J. Candès and M. Wakin. An introduction to compressive sampling. IEEE Signal Processing Magazine, March 2008 21-30. (pdf)
4. E. J. Candès. Compressive sampling. Proceedings of the International Congress of Mathematicians, Madrid, Spain, 2006. (pdf)
5. Compressive Optical MONTAGE Photography David J. Bradya, Michael Feldmanb, Nikos Pitsianisa, J. P. Guoa, Andrew Portnoya, Michael Fiddyc aFitzpatrick Center, Box 90291, Pratt School of Engineering, Duke University, Durham, NC 27708.
Digital Optics Corporation, 9815 David Taylor Drive, Charlotte, NC 28262.
Center for Optoelectronics and Optical Communications, University of North Carolina Charlotte, 9201 University City Blvd. Charlotte, NC 28223.
Proc. of SPIE Vol. 5907 590708-7.
KEYWORDS: Helmet-mounted displays; wide field of view; visual perception.
TPOC: Dr. Stuart Horn
Phone: (571) 218-4271
Fax: (703) 741-0086
Photo: Igor Carron, Greenland from 30000 feet.