Compact lensless off-axis transmission digital holographic microscope

Abstract

Current compact lensless holographic microscopes are based on either multiple angle in-line holograms, multiple wavelength illumination or a combination thereof. Complex computational algorithms are necessary to retrieve the phase image which slows down the visualization of the image. Here we propose a simple compact lensless transmission holographic microscope with an off-axis configuration which simplifies considerably the computational processing to visualize the phase images and opens the possibility of real time phase imaging using off the shelf smart phone processors and less than $3 worth of optics and detectors, suitable for broad educational dissemination. This is achieved using a side illumination and analog hologram gratings to shape the reference and signal illumination beams from one light source. We demonstrate experimentally imaging of cells with a field of view (FOV) of ~12mm, and a resolution of ~3.9μm.

Compact in-line lensfree digital holographic microscope

“…The real image, virtual image and zero order are then separated in the spectrum, which allows retrieving a twin-image free image and a correct phase with simple spectrum filtering and backpropagation algorithm. Compact off-axis DHM have already been presented, either as a device to be inserted in a classical microscope [27] , or as a portable device that uses a grating to redirect part of the incident light to create a reference beam with a specific angle [28] , [29] , [30] . This technique still limits the compactness and/or the FOV due to the necessary angle between the two beams to have interference fringes resolved by a camera with specific pixel size and the fact that the reference beam should not go through the sample part.…”

Single-shot dual-wavelength lensless digital holography using a dichroic mirror

“…To solve this issue, common-path and compact configuration is used to improve the temporal stability of LDH [4]. The common-path and compact LDH can be constructed using cyclic lateral shearing interferometer [5], specific K9 prism [6], Fresnel biprism [7], two spherical waves [8], and beam splitter [9], etc. In addition, dual-wavelength illumination is introduced into digital holography which can avoid the 2π discontinuities and expand the measurement range greatly [10].…”

3D-printable portable open-source platform for low-cost lens-less holographic cellular imaging

“…Electron holography today is a mature research field and widely in use, allowing for molecular imaging [9,10]. Digital holography within the visible wavelength regime has attracted considerable attention where a broad spectrum of light sources has been employed, ranging from gas [11,12], solid state [13] and semiconductor [1,14,15,16] lasers over light emitting diodes (LEDs) [17,18,19,20] to halogen lamps [21]. Recently, ultra-broadband digital holography with sunlight illumination has been demonstrated, employing a new reconstruction algorithm [22].…”