Gamma-corrected, SNR-enhanced and sharpness-projection-based reconstruction approach for particle holography

ABSTRACT We report a Gamma-corrected, SNR-enhanced and sharpness-projection-based reconstruction approach for digital particle holography. In this approach, we mitigate the artefacts from off-focal planes by capturing three holograms with various illumination angles, and extract particle information by applying image processing to a high-quality maximum – sharpness-projection (MSP) image. This approach reinforces weak edges using a Gamma correction procedure, and segments particles from the MSP image by using a new hybrid threshold, which comprises both local and global features. Experimental results for nonspherical particles show that the reported approach can provide a high-quality MSP image, being less likely than the conventional method to be fooled by noise and more likely to retain particle features. The hybrid threshold helps in retaining fine features, separating neighbouring particles and differentiating particles from the background. For the large particles (>20 pixels), the diameter error is generally less than 10% while using the proposed automatic hybrid thresholding technique.