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Hypertensive retinopathy is a retinal vascular damage caused by high blood pressure which results in loss of vision. In the present work, effort has been devoted to enhance and segment the retinal vasculature which is required to calculate its anatomical characteristics such as width, length for the quantitative measurement of arterio-venous ratio (AVR). Enhancement of the retinal fundus images is done using tophat transform and segmentation of the vessels using iterative thresholding. The performance of the proposed method is tested on 50 digital fundus images of publicly available MESSIDOR dataset. The hypertensive retinopathy can be measured quantitatively by detecting the decrement in the ratio of width of retinal artery-vein to that of the normal images. The arterio-venous ratio obtained by applying the proposed methodology was found to be 0.62-0.735 in normal cases and 0.203-0.495 in case of patients suffering from hypertensive retinopathy on MESSIDOR dataset which was not performed earlier. This measurement of arterio-venous ratio will be further helpful to identify the stages of hypertensive retinopathy.

Active infrared imaging is one of the promising remote and whole field characterisation techniques for non‐destructive testing and evaluation of various solids irrespective of their electrical and magnetic prosperities. This technique relies on a mapping of thermal response for a predefined incident heat flux over the test object to detect the presence of surface and subsurface anomalies. Due to its fast, non‐contact, safe and quantitative testing capabilities, infrared thermography has gained significant importance in the testing of fibre reinforced polymers. This Letter highlights testing and evaluation of glass fibre‐reinforced polymer (GFRP) specimen for detection of subsurface hidden defects using pulse compression favourable thermal wave imaging techniques (for an imposed digitised chirp as well as a 7‐bit Barker coded modulated heat fluxes over the test specimen). Further depth scanning capabilities of the proposed schemes have been compared using a time‐domain pulse compression based approach. Proposed analytical, as well as simulation studies, have been validated with the experimental results on GFRP material having flat bottom holes as defects.

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We study correlations in the speckle patterns generated by the scattering of perfect optical vortex (POV) beams and use them to produce a new class of coherence functions, namely Bessel coherence functions. Higher (zeroth) order Bessel coherence functions have been realized in cross (auto)-correlation between the speckle patterns generated by the scattering of perfect vortex beams of different orders. We have also studied the propagation of produced Bessel coherence functions and characterized their divergence with respect to the radius of their first ring for different orders m = 0–4. We observe that the divergence varies linearly with the order of the coherence function. We provide the exact analytical expression for the auto-correlation, as well as cross-correlation functions for speckle patterns. Our experimental results are in good agreement with the analytical results.