Comparative appraisal of global and local thresholding methods for binarisation of off-axis digital holograms.

Highlights • Holograms binarization for displays, media characterization, optical encryption. • 12 local and 18 global thresholding techniques were analyzed. • Optically recorded off-axis digital holograms were binarized. • The highest quality was achieved using clustering-based thresholding methods. Abstract Binary digital and computer-generated holograms are used in a number of digital micromirror device (DMD) applications, including holographic displays, media characterisation, optical encryption, and others. Binarisation is one of the most simple and efficient methods of hologram compression. In this paper, 12 local and 18 global thresholding techniques of different groups were analysed and compared based on attribute similarity, clustering, entropy, histogram shape, and local adaptive factors. Optically recorded off-axis digital holograms of different objects were binarised using these methods. The amplitude quality of the obtained reconstructed images was compared using PSNR and SSIM values. The clustering-based methods achieved the highest quality. The results of binarisation by global and local methods were comparable on average. [ABSTRACT FROM AUTHOR]