Browsing by Author "Selvagumar, Senthurran"
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Item Open Access 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, DavidNovel 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 conditionsItem Open Access Design of a tunable snapshot multispectral imaging system through ray tracing simulation(MDPI, 2019-01-05) Ding, Mengjia; Yuen, Peter W. T.; Piper, Jonathan; Godfree, Peter; Chatterjee, Ayan; Zahidi, Usman; Selvagumar, Senthurran; James, David; Richardson, Mark A.Research on snapshot multispectral imaging has been popular in the remote sensing community due to the high demands of video-rate remote sensing system for various applications. Existing snapshot multispectral imaging techniques are mainly of a fixed wavelength type, which limits their practical usefulness. This paper describes a tunable multispectral snapshot system by using a dual prism assembly as the dispersion element of the coded aperture snapshot spectral imagers (CASSI). Spectral tuning is achieved by adjusting the air gap displacement of the dual prism assembly. Typical spectral shifts of about 1 nm at 400 nm and 12 nm at 700 nm wavelength have been achieved in the present design when the air-gap of the dual prism is changed from 4.24 mm to 5.04 mm. The paper outlines the optical designs, the performance, and the pros and cons of the dual-prism CASSI (DP-CASSI) system. The performance of the system is illustrated by TraceProTM ray tracing, to allow researchers in the field to repeat or to validate the results presented in this paper.Item Open Access 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.