Browsing by Author "Soori, Umair"

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    Comparative noise performance of a coded aperture spectral imager
    (SPIE, 2016-10) Piper, James; Yuen, Peter W. T.; Godfree, Peter; Ding, Mengjia; Soori, Umair; Selvagumar, Senthurran; James, David
    Novel types of spectral sensors using coded apertures may offer various advantages over conventional designs, especially the possibility of compressive measurements that could exceed the expected spatial, temporal or spectral resolution of the system. However, the nature of the measurement process imposes certain limitations, especially on the noise performance of the sensor. This paper considers a particular type of coded-aperture spectral imager and uses analytical and numerical modelling to compare its expected noise performance with conventional hyperspectral sensors. It is shown that conventional sensors may have an advantage in conditions where signal levels are high, such as bright light or slow scanning, but that coded-aperture sensors may be advantageous in low-signal conditions
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    HySim: a tool for space-to-space hyperspectral resolved imagery
    (International Astronautical Federation (IAF), 2023-10-06) Felicetti, Leonard; Hobbs, Stephen; Leslie, Cameron; Rowling, Samuel; Dhesi, Mekhi; Harris, Toby; Brydon, George; Chermak, Lounis; Soori, Umair; Allworth, James; Balson, David
    This paper introduces HySim, a novel tool addressing the need for hyperspectral space-to-space imaging simulations, vital for in-orbit spacecraft inspection missions. This tool fills the gap by enabling the generation of hyperspectral space-to-space images across various scenarios, including fly-bys, inspections, rendezvous, and proximity operations. HySim combines open-source tools to handle complex scenarios, providing versatile configuration options for imaging scenarios, camera specifications, and material properties. It accurately simulates hyperspectral images of the target scene. This paper outlines HySim's features, validation against real space-borne images, and discusses its potential applications in space missions, emphasising its role in advancing space-to-space inspection and in-orbit servicing planning.
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    Modelling of a new X-ray backscatter imaging system: simulation investigation
    (IS&T Society for Imaging Science and Technology, 2022-04-04) Selvagumar, Senthurran; Yuen, Peter W. T.; Soori, Umair; Piper, Johnathan; James, David; Andre, David; Richardson, Mark A.
    X-ray backscatter imaging is a powerful technique for medical, aerospace, and security applications. Conventionally, a pinhole is commonly used for focusing x-ray, but there is always a desire to enhance the signal-to-noise-ratio (SNR) and optical throughput compared to a single pinhole. The main aim of this paper is to present a new x-ray backscatter imaging system which was inspired by a Twisted Slit collimator system called the Vortex Collimator and compare the optical throughput and the imaging performance with that of the Twisted Slit' collimator1,2 and the Pinhole imaging systems for axial point sources, where the pinhole system was used purely for comparison purposes. All the comparisons were performed through Ray tracing (Trace-Pro) simulation software. This work shows that the Vortex design yields ~4% higher SNR/optical throughput than that of the Twisted Slit collimator, and ~42.5% higher transmittance. Furthermore, the opening of the Vortex Collimator was increased and reduced to observe the performance, resulting in about ~1% transmittance increment when the opening was increased. Also, thicknesses of the Vortex Collimator and Twisted Slit collimator were increased and reduced and found that reducing the thickness seems to increase the system's throughput marginally.
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    Progress towards recalibration of spectrographs
    (IEEE, 2019-03-07) Kallepalli, Akhil; Soori, Umair; James, David; Richardson, Mark A.
    The spectral resolution of a spectrograph depends on the input slit width, the diffraction grating grooves and the number of imaging sensor/detector pixels. Due to the proprietary nature of spectrograph designs, recalibration by end-users can be challenging. Most calibration procedures currently published are applicable to in-house instruments or spectrographs with access to the internal specifications. Narrowing the input slit improves the resolution but also reduces the throughput of the imaging system. We attempted to recalibrate an Offner-based spectrograph by using a larger detector plane (an imaging system with a larger sensor), to vary the distance along the focal plane; and by utilising lens optics. Basic experiments were conducted by varying the distance from the exit window and inserting a lens to magnify the spectrograph output onto the larger detector plane. We concluded that the calibration could not be achieved using simple optics within the scope of our experiments. This article addresses a gap in literature that does not present the research community with the unsuccessful steps that are not applicable to similar problem statements. The alternative would be to rely on reflective optics, but this approach may reduce portability.
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    Target recognitions in multiple camera CCTV using colour constancy
    (Spie -- the Int Soc for Optical Engineering, 2013-06-28T00:00:00Z) Soori, Umair; Yuen, Peter W. T.; Ibrahim, Izzati; Han, Ji Wen; Hong, Kan; Chen, Wentao; Merfort, Christian; James, David B.; Richardson, Mark A.
    People tracking using colour feature in crowded scene through CCTV network have been a popular and at the same time a very difficult topic in computer vision. It is mainly because of the difficulty for the acquisition of intrinsic signatures of targets from a single view of the scene. Many factors, such as variable illumination conditions and viewing angles, will induce illusive modification of intrinsic signatures of targets. The objective of this paper is to verify if colour constancy (CC) approach really helps people tracking in CCTV network system. We have testified a number of CC algorithms together with various colour descriptors, to assess the efficiencies of people recognitions from real multi-camera i-LIDS data set via Receiver Operating Characteristics (ROC). It is found that when CC is applied together with some form of colour restoration mechanisms such as colour transfer, the recognition performance can be improved by at least a factor of two. An elementary luminance based CC coupled with a pixel based colour transfer algorithm, together with experimental results are reported in the present paper.
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    Towards in-orbit hyperspectral imaging of space debris
    (2023-01-26) Hobbs, Stephen E.; Felicetti, Leonard; Leslie, Cameron; Rowling, Samuel; Brydon, George; Dhesi, Mekhi; Harris, Toby; Chermak, Lounis; Soori, Umair
    Satellites are vulnerable to space debris larger than ~1 cm, but much of this debris cannot be tracked from the ground. In-orbit detection and tracking of debris is one solution to this problem. We present some steps towards achieving this, and in particular to use hyperspectral imaging to maximise the information obtained. We present current work related to hyperspectral in-orbit imaging of space debris in three areas: scenario evaluation, a reflectance database, and an image simulator. Example results are presented. Hyperspectral imaging has the potential to provide valuable additional information, such as assessments of spacecraft or debris condition and even spectral “finger-printing” of material types or use (e.g. propellant contamination). These project components are being merged to assess mission opportunities and to develop enhanced data processing methods to improve knowledge and understanding of the orbital environment.