Simon Roy

Chemical detection with hyperspectral lidar using dual frequency combs

High-resolution spectral lidar measurements using dual frequency combs as a source is presented. The technique enables the range-resolved measurement of fine spectral features, such as gas absorption lines, provided that a suitable scatterer is present in the scene. Measurements of HCN absorption lines at 20 meters are presented, with a water droplet cloud and a diffusely reflective surface as scatterers.

Concept of operation and preliminary experimental results of the DRDC through-wall SAR system

Mapping the interior of buildings is of great interest to military forces operating in an urban battlefield. Throughwall radars have the potential of mapping interior room layout, including the location of walls, doors and furniture. They could provide information on the in-wall structure, and detect objects of interest concealed in buildings, such as persons and arms caches. We are proposing to provide further context to the end user by fusing the radar data with LIDAR (Light Detection and Ranging) images of the building exterior. In this paper, we present our system concept of operation, which involves a vehicle driven along a path in front of a building of interest. The vehicle is equipped with both radar and LIDAR systems, as well as a motion compensation unit. We describe our ultra wideband through-wall L-band radar system which uses stretch processing techniques to obtain high range resolution, and synthetic aperture radar (SAR) techniques to achieve good azimuth resolution. We demonstrate its current 2-D capabilities with experimental data, and discuss the current progress in using array processing in elevation to provide a 3-D image. Finally, we show preliminary data fusion of SAR and LIDAR data.

Baseline processing pipeline for fast automatic target detection and recognition in airborne 3D ladar imagery

It has been proven that 3D ladar imagery has a strong potential for automatic target detection (ATD) and automatic target recognition (ATR); ladars enhance target information, which may then be exploited to yield higher recognition rates and lower false alarms. Although numerous techniques have been proposed for both 3D ATD and 3D ATR, no single approach has proven capable of systematically outperforming all other techniques for every possible scenario. In this context, this paper describes a set of fast 3D ATD/ATR algorithms designed to process cooperative targets in airborne 3D ladar imagery. This algorithmic chain consists of four modules: detection, segmentation, classification and recognition. In each module, fast algorithms were implemented, some of which stem from open literature while others were designed in-house. The purpose of this algorithmic chain is to provide a baseline approach for efficient processing of simple scenarios. The ultimate goal of this work is to characterize and compare algorithms with respect to increasingly complex scenarios, in hopes of progressing towards an adaptive processing pipeline for context-driven 3D ATD/ATR. In this paper, the four modules of the baseline processing pipeline are first described. Preliminary test results obtained with real airborne ladar imagery are then presented, in which fast and accurate 3D ATD/ATR is performed with a library of 20 scanned vehicles. Finally, a demonstration is presented to illustrate how this baseline approach may be expanded to tackle more complex scenarios, such as non-cooperative targets concealed under vegetation.

Enhanced scanning agility using a double pair of Risley prisms.

Scanners with one pair of Risley prisms are robust and precise and they can be operated continuously. In this paper, we present a new scanner based on the use of two pairs of Risley prisms. The concept was driven by the need to add flexibility to Risley prism scanners used for lidar 3D mapping applications, while maintaining compactness and robustness. The first pair covers a FOV narrower than the second pair. The second pair is used to position the first Risley pair scan pattern anywhere within its own, larger, FOV. Doing so, it becomes possible, without additional scanner components, to increase the sampling point density at a specific location, to increase the sampling uniformity of the scanned area, and, while in motion, to maintain the sampling of a specific area of interest.

Development of an underwater fiber-optic lidar for the characterization of sea water and ice properties

DRDC Valcartier has developed a unique underwater lidar for the measurement of different sea water and ice properties. The lidar head is designed for underwater operation and consists of four telescopes that are connected to the detection and emission unit via five 42 m fused silica optical fibers. Three telescopes are used for data collection, while the fourth is used for laser emission. The laser source and the detection unit are located on a surface vessel. The laser beam is injected into a 100 μm diameter optical fiber. The collimation of the laser beam is done in the lidar head via a lens with 25 mm diameter and 45 mm focal length; the laser beam is linearly polarized using a polarization beamsplitter. A 50 mm receiving telescope co-aligned with the laser beam is used for linear depolarization measurements. A second 50 mm telescope is used to collect off-axis scattered light while a third 50 mm telescope is used to collect inelastic scattered radiation (Raman and induced fluorescence signal). The laser source and detection units are mounted on a small optical table for easy access/modification. Various laser sources and lidar detection techniques (Q-switched pulses or frequency modulated) could be easily implemented. The lidar head can be deployed underwater or mounted on an airborne platform. In this work, the lidar system will be described in detail and preliminary results obtained with a Q-Switch, 532 nm, 1 ns pulse laser source will be presented and compared with the anticipated performance for different water bodies.

Remote range resolved chemical detection using dual comb interferometry

We demonstrate detection and ranging of various targets, including aerosols, gas spectral signatures and translucent sample thickness using dual comb interferometry. Highresolution hyperspectral traces are obtained from targets at a distance of 175 m.

Workbench for 3D target detection and recognition from airborne motion stereo and ladar imagery

3D imagery has a well-known potential for improving situational awareness and battlespace visualization by providing enhanced knowledge of uncooperative targets. This potential arises from the numerous advantages that 3D imagery has to offer over traditional 2D imagery, thereby increasing the accuracy of automatic target detection (ATD) and recognition (ATR). Despite advancements in both 3D sensing and 3D data exploitation, 3D imagery has yet to demonstrate a true operational gain, partly due to the processing burden of the massive dataloads generated by modern sensors. In this context, this paper describes the current status of a workbench designed for the study of 3D ATD/ATR. Among the project goals is the comparative assessment of algorithms and 3D sensing technologies given various scenarios. The workbench is comprised of three components: a database, a toolbox, and a simulation environment. The database stores, manages, and edits input data of various types such as point clouds, video, still imagery frames, CAD models and metadata. The toolbox features data processing modules, including range data manipulation, surface mesh generation, texture mapping, and a shape-from-motion module to extract a 3D target representation from video frames or from a sequence of still imagery. The simulation environment includes synthetic point cloud generation, 3D ATD/ATR algorithm prototyping environment and performance metrics for comparative assessment. In this paper, the workbench components are described and preliminary results are presented. Ladar, video and still imagery datasets collected during airborne trials are also detailed.

State-of-the-art imaging Fourier-transform spectrometer with CCD camera

Imaging Fourier-transform spectrometers can quickly produce massive amounts of raw data, especially when paired with large focal plane arrays. As the spatial resolution is increased, overwhelming amounts of data must be managed properly. A suitable design of the data processing chain is thus required to minimize the dataload and deliver processed information in real-time. This paper reviews the work being done to tailor data processing pipelines for Fourier-transform spectrometers (FTS) coupled with externally triggered CCD cameras. Various sampling techniques as well as spectral calibration and line shape correction approaches will be reviewed. Since traditional sampling techniques are not well suited for an FTS operating with a CCD camera, a hybrid time-position sampling approach is presented to reduce the number of samples per pixel. Furthermore, the approach enables a sampling jitter correction algorithm that can account for velocity fluctuations and channel delays, such as the CCD integration time. A fast spectral calibration approach is also demonstrated, based on a rapid line shape integration scheme. The calibration algorithm brings all pixel spectra on the same spectral grid and allows the user to directly compare spectral features between pixels. Moreover, the correction method offers software field-widening capabilities by binning pixels after spectral calibration. A large single-pixel detector can thus be emulated from the CCD array, allowing the user to broaden the field of view and to increase the SNR.

New Sampling Approach Suitable for Imaging Fourier Transform Spectrometers with Integrating Detector

A new approach to interferogram sampling is presented. The method reduces data load and processing overhead while allowing post-correction of sampling errors. It is particularly well suited for continuous-scan spectrometers equipped with a CCD camera.

New Spectral Calibration Approach Suitable for Imaging Fourier Transform Spectrometers

A new approach to line shape correction is presented. The method uses line shape integration to calibrate the spectral grids of pixels and is thus convenient for spectrometers equipped a CCD camera.