Refractometry of microscopic objects using digital holography

Digital holography has some desirable properties for refractometry of microscopic objects since it gives phase and amplitude information of an object in all depths of focus from one set of exposures. The refractive index of the object can be determined by observation of the movements of the Becke lines between different focus depths. It is also shown that one single phase image provides an independent technique to determine sign of the relief between an object and the surrounding medium

Object characterization with refractometric digital holography

We demonstrate a Digital Holographic method where two different substances in a blend can be discerned. The method requires only one set of exposures and one reconstruction in the plane of focus. The large scale phase variation of the phase image is unwrapped by Flynn’s discontinuity algorithm to reveal which regions in the sample the phase has decreased or increased upon transmission of the illuminating wave. Objects with higher or lower index of refraction than the mounting liquid can be detected as regions where the phase has been shifted. We also present a method to calculate the volume distribution of substrates in a sample. Experimental results of both methods are demonstrated with crystals of NaCl and KCl

Object characterization with refractometric digital Fourier holography

We demonstrate a digital holographic method in which two different substances in a blend are discerned. The method requires only one set of exposures and one reconstruction in the plane of focus. The phase is unwrapped by Flynn's discontinuity algorithm to produce an image of the variation of the optical distance of the illuminating wave. Objects with indices of refraction that are higher and lower than the mounting liquid are detected as regions in which the phase is increased and decreased, respectively. We also present a method for calculating the volume distribution of substrates in a sample. The method is experimentally demonstrated with crystals of NaCl and KCl

Refractometry of microscopic objects with digital holography

Digital holography has some desirable properties for refractometry of microscopic objects since it gives phase and amplitude information of an object in all depths of focus from one set of exposures. We show that the amplitude part of the image can be used to observe how the Becke lines move between different depths of focus and hence determine whether an object has a higher or a lower index of refraction than its surrounding medium, i.e., the sign of the relief. It is also shown that one single-phase image provides an independent technique to determine the sign of relief between an object and the surrounding medium

Det digitala holografiska mikroskopet : innovativ teknik för analys av levande celler

Bakgrund: Digital holografi är en ny teknik som de senaste fem åren använts för att studera levande celler. Tekniken utgör en innovativ, icke-förstörande metod som möjliggör studier av levande celler över tid. Material och metoder: Litteraturen har valts ut genom att söka på redan kända forskargrupper och företag som arbetar både med digital holografi och cellstudier samt PubMed-sökningar. Resultat och sammanfattning: Digital holografi ger kunskap om cellernas brytningsindex, som kan ändras under olika förhållanden. De parametrar som kan mätas ger unik information om cellantal, cellernas area, tjocklek och volym, vilket kan omvandlas till proliferation, viabilitet och celldöd. Tekniken är relativt billig, snabb och enkel att använda.Background: Digital holography is a novel technique that has been used for about five years to study living cells. The technique is an innovative, non-destructive method with possibilities to study living cells over time. Materials and methods: The literature in this paper was selected on the basis of already known research groups and companies in the field working with both digital holography and cell studies, as well as PubMed search. Results and conclusions: Digital holography is a method that gives us information about the refractive index of cells, which can change under different circumstances. The unique measurable parameters are the cell number, cell area, thickness and volume, which can be transformed to proliferation, viability and cell death. The technique is cheap, fast and simple to use

Accelerating signal processing algorithms in digital holography using an FPGA platform

This paper describes the implementation of a custom DSP system to accelerate image processing algorithms used in the field of digital holography. The system, implemented on an FPGA platform, is intended for real-time reconstruction of images captured on a large image sensor. Due to the large amount of processing information, it is not possible to perform a HDL simulation of a complete image reconstruction in reasonable time. Instead, a reconfigurable solution is being used for full scale image reconstruction, exhaustive testing of the functionality and for connecting the accelerator to external components, i.e. the image sensor, monitor output device and high-speed memory bank

Non-invasive, label.free cell counting and quantitative analysis of adherent cells using digital holography

Manual cell counting is time consuming and requires a high degree of skill on behalf of the person performing the count. Here we use a technique that combines digital holography and phase contrast microscopy allowing label-free and completely non-invasive cell counting directly in cell culture vessels with adherent viable cells. Digital holography can provide both quantitative and qualitative phase information from a single hologram. The recently constructed microscope HolomonitorTM M2 combines digital holography with the benefits of the commonly used phase contrast microscope, allowing us to combine the advantages of light imaging with the possibility of achieving quantitative information on cellular shape, area, confluence and optical thickness. This project aimed at determining the accuracy and repeatability of cell counting measurements using digital holography compared to the conventional manual cell counting method using a haemocytometer. The collected data were also used to determine cell size and cellular optical thickness. The results show that digital holography can be used for non-invasive cell counting as precisely and much faster than conventional manual cell counting

High-resolution digital transmission microscopy: a Fourier holography approach

A spherical reference field is used to construct a digital holographic system with a demonstrated resolution up to 228 line pairs per mm. The reference field originates from a GRIN lens placed 1 mm from the illuminated object. This allows the use of a standard sensor to record the hologram with the required numerical aperture. The image is determined by evaluation of the Rayleigh–Sommerfeld diffraction integral that relates the object field in the image plane to the object field in the sensor plane. Experimental results are given for two charge coupled device sensors and one complementary metal-oxide-semiconductor active pixel sensor