Michael J. DeWeert

Lensless coded-aperture imaging with separable Doubly-Toeplitz masks

Abstract. In certain imaging applications, conventional lens technology is constrained by the lack of materials which can effectively focus the radiation within a reasonable weight and volume. One solution is to use coded apertures—opaque plates perforated with multiple pinhole-like openings. If the openings are arranged in an appropriate pattern, then the images can be decoded and a clear image computed. Recently, computational imaging and the search for a means of producing programmable software-defined optics have revived interest in coded apertures. The former state-of-the-art masks, modified uniformly redundant arrays (MURAs), are effective for compact objects against uniform backgrounds, but have substantial drawbacks for extended scenes: (1) MURAs present an inherently ill-posed inversion problem that is unmanageable for large images, and (2) they are susceptible to diffraction: a diffracted MURA is no longer a MURA. We present a new class of coded apertures, separable Doubly-Toeplitz masks, which are efficiently decodable even for very large images—orders of magnitude faster than MURAs, and which remain decodable when diffracted. We implemented the masks using programmable spatial-light-modulators. Imaging experiments confirmed the effectiveness of separable Doubly-Toeplitz masks—images collected in natural light of extended outdoor scenes are rendered clearly.

Photon transfer methods and results for electron multiplication CCDs

Optical systems designed for some defense, environmental, and commercial remote-sensing applications must simultaneously have a high dynamic range, high sensitivity, and low noise-equivalent contrast. We have adapted James Janesick’s photon transfer technique for characterizing the noise performance of an electron multiplication CCD (EMCCD), and we have developed methods for characterizing performance parameters in a lab environment. We have defined a new figure of merit to complement the traditionally used dynamic range that quantifies the usefulness of EMCCD imagers. We use the results for EMCCDs to predict their performance with hyperspectral and multispectral imaging systems.

Findings of the NATO workshop on data fusion technologies for harbour protection

The NATO Security Through Science Program and the Defence Investment Division requested and sponsored the organization of a NATO Advanced Research Workshop (ARW) on the topic of Data Fusion Technologies for Harbour Protection, which was held June 27-July 1, 2005 in Tallinn, Estonia. The goal of the workshop was to help knowledge exchange between the technology experts and the security policy makers for a better understanding of goals, functions and information requirements of the decision makers as well as the way the data fusion technology can help enhancing security of harbours. In addition to presentations by experts from the research community on detection and fusion technologies as well as in practice and policy the workshop program included daily breakout sessions, in which the participants were given an opportunity to brainstorm on the topics of the workshop in interdisciplinary smaller teams. The working groups: (i) chose a scenario, including threat stages, threat types, threat methods and ranges, and response constraints due to the particular harbour environment; then (ii) identified: (a) requirements (objectives, functions and essential elements of information); (b) technologies (available and future); (c) information available and necessary through sensors and other sources, as agencies and jurisdiction; (d) methods: detection, identification, situation assessment, prediction. This paper describes the main issues and proposed approaches that were identified by the working groups.

Performance of an EO/IR sensor system in marine search and rescue

This investigation centered on the most challenging search and rescue requirements: finding small targets in high seas. Our course of action was to investigate the capabilities of known hyperspectral and LWIR sensors in realistic conditions of target and environment to drive the design of a sensor system capable of substantially improving search efficiency and efficacy for these conditions. The relevant results from this study include demonstration of significant power in clutter rejection (e.g., whitewater and wave complexity) by the LWIR sensor. In addition, several factors combine to indicate that a modest implementation of HSI and IR sensors would provide significant improvement in search efficiency and efficacy for small targets in high seas. These factors include high PD, low PFA, and the untiring nature of the sensors when combined with the potential of real-time automatic target/background discrimination. This modest implementation would translate directly into faster, more complete coverage, at lower overall costs to the USCG, and a more likely probability of a successful search mission.

In-flight MTF characterization for high-resolution aerial reconnaissance

The demands of the unmanned airborne multispectral surf-zone mine counter-measures (MCM) mission require high spatial resolution. Weight, volume and power constraints preclude stabilized operation of the cameras for this application. Further, the system is to be flown on a rotary-winged platform, with its attendant vibration characteristics. Thus, the MTF needs to be measured in flight to insure it meets the resolution requirements. We apply the slanted-edge MTF method to the in-flight characterization of airborne high-resolution cameras, analyzing images of orthogonal slanted edges to estimate the motion and vibration contributions to the MTF, and show that the system meets its requirements. We also apply a methodology for scaling to other altitudes and speeds to show that the system will have excellent imaging performance throughout its operational envelope. For our application, the slanted-edge method is more accurate and reproducible than the alternative of placing MTF bar targets under the aircraft flight path. Further, the slanted-edge targets are much easier to deploy and recover, and ease the navigation tolerances.

3DLASE-M: three-dimensional lidar airborne system emulator, maritime

Imaging flash LIDAR (LIght Detection and Ranging) is an effective method for airborne searches of the ocean surface and subsurface volume. The performance of ocean LIDAR depends strongly on the sea surface (e.g., waves, whitecaps, and flotsam), water turbidity, and the characteristics of the objects of interest. Cost-effective design of the LIDAR system and processing algorithms requires a modeling capability that can deal with the physics of light propagation through the air-water interface, into the ocean, and back to the LIDAR receiver. 3DLASE-M is a physics-based LIDAR simulator that yields high-fidelity images for three-dimensional algorithm development and performance predictions.

Lensless coded aperture imaging with separable doubly Toeplitz masks

In certain imaging applications, conventional lens technology is constrained by the lack of materials which can effectively focus the radiation within reasonable weight and volume. One solution is to use coded apertures –opaque plates perforated with multiple pinhole-like openings. If the openings are arranged in an appropriate pattern, the images can be decoded, and a clear image computed. Recently, computational imaging and the search for means of producing programmable software-defined optics have revived interest in coded apertures. The former state-of-the-art masks, MURAs (Modified Uniformly Redundant Arrays) are effective for compact objects against uniform backgrounds, but have substantial drawbacks for extended scenes: 1) MURAs present an inherently ill-posed inversion problem that is unmanageable for large images, and 2) they are susceptible to diffraction: a diffracted MURA is no longer a MURA. This paper presents a new class of coded apertures, Separable Doubly-Toeplitz masks, which are efficiently decodable, even for very large images –orders of magnitude faster than MURAs, and which remain decodable when diffracted. We implemented the masks using programmable spatial-lightmodulators. Imaging experiments confirmed the effectiveness of Separable Doubly-Toeplitz masks - images collected in natural light of extended outdoor scenes are rendered clearly.

3DLASE-M: three-dimensional-LIDAR airborne system emulator -maritime

Imaging flash LIDAR (LIght Detection and Ranging) is an effective method for airborne searches of the ocean surface and subsurface volume. The performance of ocean LIDAR depends strongly on the sea surface (e.g., waves, whitecaps, and flotsam), water turbidity, and the characteristics of the objects of interest. Cost-effective design of the LIDAR system and processing algorithms requires a modeling capability that can deal with the physics of light propagation through the air-water interface, into the ocean, and back to the LIDAR receiver. 3DLASE-M is a physics-based LIDAR simulator that yields high-fidelity images for three-dimensional algorithm development and performance predictions.Imaging flash LIDAR (LIght Detection and Ranging) is an effective method for airborne searches of the ocean surface and subsurface volume. The performance of ocean LIDAR depends strongly on the sea surface (e.g., waves, whitecaps, and flotsam), water turbidity, and the characteristics of the objects of interest. Cost-effective design of the LIDAR system and processing algorithms requires a modeling capability that can deal with the physics of light propagation through the air-water interface, into the ocean, and back to the LIDAR receiver. 3DLASE-M is a physics-based LIDAR simulator that yields high-fidelity images for three-dimensional algorithm development and performance predictions.

Fusion of Information from Disparate Electro-Optical Imagers for Maritime Surveillance

This work presents an overview of a portion of the sensor-fusion work being done at BAE Spectral Solutions LLC. The emphasis is on imaging technologies with near-term applications for maritime homeland security. General categories of sensor fusion are outlined, followed by a more in-depth discussion of work being done at two BAE North America facilities on systems for maritime security.

TACMSI : A novel multi-look multispectral imager for maritime mine detection

Airborne EO imagery, including wideband, hyperspectral, and multispectral modalities, has greatly enhanced the ability of the ISR community to detect and classify various targets of interest from long standoff distances and with large area coverage rates. The surf zone is a dynamic environment that presents physical and operational challenges to effective remote sensing with optical systems. In response to these challenges, BAE Systems has developed the Tactical Multi-spectral (TACMSI) system. The system includes a VNIR six-band multispectral sensor and all other hardware that is used to acquire, store and process imagery, navigation, and supporting metadata on the airborne platform. In conjunction with the hardware, BAE Systems has innovative data processing methods that exploit the inherent capabilities of multi-look framing imagery to essentially remove the overlying clutter or obscuration to enable EO visualization of the objects of interest.