Spectral LADAR: Active Range-Resolved Imaging Spectroscopy

Imaging spectroscopy using ambient or thermally generated optical sources is a well developed technique for capturing two dimensional images with high per-pixel spectral resolution. The per-pixel spectral data is often a sufficient sampling of a material's backscatter spectrum to infer chemical properties of the constituent material to aid in substance identification. Separately, conventional LADAR sensors use quasi-monochromatic laser radiation to create three dimensional images of objects at high angular resolution, compared to RADAR. Advances in dispersion engineered photonic crystal fibers in recent years have made high spectral radiance optical supercontinuum sources practical, enabling this study of Spectral LADAR, a continuous polychromatic spectrum augmentation of conventional LADAR. This imaging concept, which combines multi-spectral and 3D sensing at a physical level, is demonstrated with 25 independent and parallel LADAR channels and generates point cloud images with three spatial dimensions and one spectral dimension. The independence of spectral bands is a key characteristic of Spectral LADAR. Each spectral band maintains a separate time waveform record, from which target parameters are estimated. Accordingly, the spectrum computed for each backscatter reflection is independently and unambiguously range unmixed from multiple target reflections that may arise from transmission of a single panchromatic pulse. This dissertation presents the theoretical background of Spectral LADAR, a shortwave infrared laboratory demonstrator system constructed as a proof-of-concept prototype, and the experimental results obtained by the prototype when imaging scenes at stand off ranges of 45 meters. The resultant point cloud voxels are spectrally classified into a number of material categories which enhances object and feature recognition. Experimental results demonstrate the physical level combination of active backscatter spectroscopy and range resolved sensing to produce images with a level of complexity, detail, and accuracy that is not obtainable with data-level registration and fusion of conventional imaging spectroscopy and LADAR. The capabilities of Spectral LADAR are expected to be useful in a range of applications, such as biomedical imaging and agriculture, but particularly when applied as a sensor in unmanned ground vehicle navigation. Applications to autonomous mobile robotics are the principal motivators of this study, and are specifically addressed

Non contact surface metrology in a hazardous environment

The EFDA-JET tokamak is an experimental fusion device researching fusion as a means of energy production. Inside the toroidal vessel, plasma with temperature in excess of 100 million degrees Celsius is generated and constrained by high power magnetic fields. Additional protection is provided by tiles which clad the inside of the machine. As part of a major upgrade existing heat protective tiles are to be replaced with an advanced design, and renewed interest has been shown in dimensional measurement of the surface. Measurement must occur during shutdown periods where temperature and pressure are at ambient levels. Manned entry is not permissible and all work should be performed remotely. To avoid contamination which could affect the fusion reaction and experimental results, contact with the measurement surface is not permitted. This work assesses non-contact surface measurement technologies, along with standards and guidelines for dimensional surface measurement. Existing measurement test artefacts do not offer the required surface finish and features, so specific test artefacts have been designed and produced. These artefacts are traceable to the national length standard, as traceability is a pre-requisite to evaluate accuracy. Exploratory tests highlighted two technologies for further investigation, laser triangulation and white light fringe projection. Two commercially available, state-ofthe- art examples of each technology have been evaluated using a processing method developed to highlight performance in key areas relevant to EFDA-JET. These areas include quantitative assessments of the effect of surface angle on measurement quality, the effect of depth of field for fringe projection systems and the ability of technologies to record gap and flush from tens of micrometres to millimetres. Tests enable a user to begin to assess the impact the measurement system has on the measurement result, how different technologies and systems used alone or in combination may resolve or compound erroneous results, clarifying or disrupting the meaning of results