Single-shot wavelength-multiplexed phase microscopy under Gabor regime in a regular microscope embodiment

Abstract

Phase imaging microscopy under Gabor regime has been recently reported as an extremely simple, low cost and compact way to update a standard bright-field microscope with coherent sensing capabilities. By inserting coherent illumination in the microscope embodiment and producing a small defocus distance of the sample at the input plane, the digital sensor records an in-line Gabor hologram of the target sample, which is then numerically post-processed to finally achieve the sample’s quantitative phase information. However, the retrieved phase distribution is affected by the two well-known drawbacks when dealing with Gabor’s regime, that is, coherent noise and twin image disturbances. Here, we present a single-shot technique based on wavelength multiplexing for mitigating these two effects. A multi-illumination laser source (including 3 diode lasers) illuminates the sample and a color digital sensor (conventional RGB color camera) is used to record the wavelength-multiplexed Gabor hologram in a single exposure. The technique is completed by presenting a novel algorithm based on a modified Gerchberg–Saxton kernel to finally retrieve an enhanced quantitative phase image of the sample, enhanced in terms of coherent noise removal and twin image minimization. Experimental validations are performed in a regular Olympus BX-60 upright microscope using a 20X 0.46NA objective lens and considering static (resolution test targets) and dynamic (living spermatozoa) phase samples.

Quantitative study of phase sensitivity in immersion-based lensless digital holographic microscopy

“…Remarkable space-bandwidth product, resulting from the combination of high resolution and a large field of view (FOV) in LDHM setups, encourages investigation of large area biological cell cultures and tissue slices. These structures are typically immersed in specific nourishing or curative medium [4], allowing prolonged observation, such as monitoring disease recovery over a significant period of time [5].…”

Soft Contact Lens Engraving Characterization by Wavefront Holoscopy

“…Nevertheless, as a direct consequence of in-line configuration, an additional symmetrical image plane (the twin image one) will appear at the same distance from the sensor but at the opposite side. Therefore, the defocussed distribution provided by one of the images will overlap with the in-focus plane of the other image, causing a priori deterioration of the optical quality of the reconstructed image, a problem that can be solved by different image processing techniques [ 44 , 45 , 46 , 47 , 48 ].…”