You are here

Innovative Methods for Limited Dynamic Range Optical Detectors to More Effectively Operate in High Dynamic Range Environments

Description:

 
 

TECHNOLOGY AREA(S): Battlespace, Electronics, Sensors

ACQUISITION PROGRAM: PMS 495, Mine Warfare Office, Airborne Laser Mine Detection System (ALMDS)

OBJECTIVE: Develop an innovative technique to allow current state-of-the-art electro-optic systems to extend their dynamic range beyond their fixed capability.

DESCRIPTION: Organic mine countermeasures (MCM) give naval and marine units the ability to detect, characterize, and neutralize mines using their own assets. The US Navy and Marines fill gaps in MCM capabilities with electro-optic sensor systems. Airborne and underwater MCM sensors are vital to enabling operational maneuverability from the ship to the objective. To meet Naval MCM requirements, a “system-of-systems” approach has been adopted which consists of mine-hunting, minesweeping, and mine neutralization systems. These weapon systems are primarily deployed and operated from MH-60S helicopter platforms equipped with Airborne Mine Countermeasures (AMCM).

Mine-hunting is the preferred method of locating and neutralizing sea mines. One such system, which helps to fill a significant capability gap in complete coverage of the upper water volume and complements other MCM systems, is the Navy’s Airborne Laser Mine Detection System (ALMDS).

The ALMDS provides a capability for the rapid detection, laser image classification, and localization of near surface moored mine threats. Moreover, ALMDS uses pulsed laser light and streak tube receivers (Ref. 3) in a push broom mode for high coverage rate. The transmitted laser light passes through the atmosphere, ruffled air-water interface, and seawater then returns along the similar path to the airborne receivers. This imposes an environmentally induced high dynamic range requirement over the area of interest, which is beyond that of the receiver, limiting system performance.

As with all airborne laser interrogation systems flying over water, the optical return from the surface of the air-water interface is relatively large and the return from within the water column decreases exponentially with depth as the optical scattering blurs the image (Ref. 1). The obvious objective is to clearly image from the surface to as deep as possible. Intuitively, increasing the dynamic range of the optical receiver would be the most logical approach; however, receiver technology limits the dynamic range. Setting the receiver gain too high saturates the surface return and setting the gain lower limits depth penetration. Note that laser safety and natural in-water phenomena limit the system’s practical laser power.

The ALMDS program is currently experimenting with modifications to the pod receiver cameras to increase dynamic range (i.e. dual slope) and improve the quality of images at the surface (bright area) while maintaining depth performance. Additional concepts and techniques, which may be considered, are located within references #1-5.

This topic is seeking novel and innovative technological techniques and/or new software algorithms that will effectively increase the technology’s dynamic range capability for its intended operational mission by extending the range (water depth) for target detection classification and location. Conceptual proposals should include discussions on any developmental history, technical risks, maturity levels, challenges, and applicable mitigation alternatives.

The intended product for Phase I is a technical report describing innovative technologies and novel techniques that will enhance the future naval system’s limited dynamic range detector capabilities. These novel concepts must support operations in high dynamic range environments. Emphasis should be upon the technological feasibility to meet the Navy’s needs that include but are not limited to an enhanced airborne active electro-optic system capable of detecting and identifying in-water objects, reduced false alarm rate, increased depth penetration, and sustained area coverage rate capability. The desired threshold improvement is an effective increase in dynamic range of 10% (for example, increasing a 10 bit dynamic range receiver to an effective 11 bit dynamic range).

This topic’s intent is to provide significant increase in the ability to find mines in an expanded water column using innovative techniques utilizing current technology to modify MCM systems. Implementing these newly SBIR developed techniques with demonstrated feasibility of a capability increase into the ALMDS system is a cost effective way to improve capability with a shortened developmental time for the acquisition program to support resulting in significant development costs. The ability to locate mines in depth regimes legacy systems have difficulty operating in has the real potential to save ship and life losses when hostile actions require ship presence.

PHASE I: The Phase I effort will articulate the feasibility of the concept to meet Navy needs and will establish if the concepts can be practicably developed into a useful product for the Navy as outlined in the description. The company will identify a methodology for integrating the high dynamic range environmental problem of active airborne Light Detection and Ranging (LIDAR) imaging through the air-water interface with current technology. Generating experimental data to predict performance, mathematical calculations, and modeling are in order to demonstrate proof of concept. The intended product for Phase I is a technical report describing innovative technologies and novel techniques that will enhance the future naval system’s limited dynamic range detector capabilities. The Phase I Option, if awarded, should include the initial description and capabilities to build the unit in Phase II.

PHASE II: Based on the results of Phase I and the Phase II Statement of Work (SOW), the small business will develop a Phase II prototype for integrating the high dynamic range environmental problem of active airborne LIDAR imaging through the air-water interface with current technology. Metrics for increased performance for Phase II efforts will be defined to quantify the increased depth performance of an active airborne imaging system through the air-water interface based on the effective dynamic range increase. The company will provide the experimental test bed(s) (configuration of technologies and test equipment necessary to collect pertinent data) and/or prototype hardware/software configured for testing, evaluation, and data collection for the accompanying algorithm and model development. The company will demonstrate an increased performance (extending the sensor’s native dynamic range) in terms of depth performance. The company will perform detailed analysis to ensure materials are appropriate for Navy applications. The company will deliver a final report documenting all findings to include recommendations for transition to Phase III for Navy use, along with all hardware and software prototypes developed under this effort.

PHASE III DUAL USE APPLICATIONS: The small business will apply the knowledge gained in Phase II to build finalize the design of hardware/software prototypes. Moreover, the company will demonstrate and characterize the performance in an operationally relevant environment as defined by Navy requirements and support the Navy in transitioning the technology for Navy use. Private Sector Commercial Potential: The technology and techniques developed will have direct applicability to other Government and private airborne LIDAR ocean sensing systems as well as laser interrogations systems operating through the air.

REFERENCES:

  • Josset, et al, LIDAR equation for ocean surface and subsurface, Optics Express, Vol. 18, Issue 20, pp. 20862-20875 (2010), http://dx.doi.org/10.1364/OE.18.020862
  • Mullen, Alley, Cochenouv, Investigation of the effect of scattering agent and scattering albedo on modulated light propagation in water. Applied Optics, Vol. 50, No. 10, 1 April 2011.
  • H. Yang, et. al., Signal-to-noise performance analysis of streak tube imaging lidar systems: Part 1: Cascaded model, Part 2: Theoretical analysis and discussion. Applied Optics, Vol. 51, No. 36, 20 December 2012.
  • Arnaud Darmont, High Dynamic Range Imaging: Sensors and Architectures (First ed.). SPIE press, 2012. ISBN 978-0-81948-830-5.
  • Banterle, Francesco; Artusi, Alessandro; Debattista, Kurt; Chalmers, Alan (2011). Advanced High dynamic Range Imaging: theory and practice. AK Peters/CRC Press. ISBN 978-156881-719-4.

KEYWORDS: Airborne LIDAR (Light Detection and Ranging); imaging in high dynamic range environments; extending optical sensor’s dynamic range; dynamic range compression; LIDAR signal processing; frequency modulated laser imaging

US Flag An Official Website of the United States Government