Microparticle characterization using digital holography

Abstract

a b s t r a c tDigital holography is an effective 3D imaging technique, with the potential to be used for particle size measurements. A digital hologram can provide reconstructions of volume samples focused at different depths, overcoming the focusing problems encountered by other imaging based techniques. Several particle analysis methods discussed in the literature consider spherical particles only. With the object sphericity assumption in place, analysis of the holographic data can be significantly simplified. However, there are applications, such as particle analysis and crystallization monitoring, where non-spherical particles are often encountered. This paper discusses the processing of digital holograms for particle size and shape measurement for both spherical and arbitrarily shaped particles. An automated algorithm for identification of particles from recorded hologram and subsequent size and shape measurement is described. Experimental results using holograms of spherical and non-spherical particles demonstrate the performance of the proposed measuring algorithm.

Measurement, modelling, and closed-loop control of crystal shape distribution: Literature review and future perspectives

“…However, for on-line monitoring, optimisation and control of shape and size distributions in a crystalliser, it is essential to accurately and efficiently obtain 3D crystal information of the whole crystal population and the associated properties. Of the many techniques [1,[41][42][43][44][45][46][47][48][49][50][51] for the imaging and reconstruction of 3D objects, optical imaging and image analysis techniques proved to be the most promising ones for 2D shape measurements [1,17,19,23,24,26,29,30,32,34,37,39,[52][53][54], and the techniques that are likely the most suitable ones for obtaining 3D crystal shape, hence growth rate of each crystal face, have made some advances in recent years [1, 45-50, 55, 56]. This is a very active research area with huge challenges and opportunities to innovatively develop process instrument and/or process probes and the associated image processing and shape reconstruction software for the real-time monitoring, optimisation and control of particulate processes.…”

“…Zhang et al [51] used non-invasive stereovision imaging technique to to perform on-line measurements for the accurate determination of real size and shape of crystals grown in a stirred tank crystalliser. Darakis et al [42] presented the application of digital holography, an effective 3D imaging technique, for the measurement of size, orientation and location of opaque micro fibres. The method can provide 3D volume information from a single hologram acquisition with the actual location of the particle being determined subsequently by reconstructing the recorded hologram at different depths, hence avoiding the problem of out-of-focus particles from classical imaging techniques.…”

Construction of a portable parallel phase-shifting digital holography system

“…The technique is capable of an instantaneous 3D measurement and is researched in many fields: microscopy, 4, 5 shape measurement, 6, 7 particle measurement, 8,9 object recognition, 10, 11 polarization analysis, 12,13 and so on. However, it is impossible for image sensors to record fine interference fringes.…”

Single-shot 3-D sensing of micro-meter height by multi-wavelength parallel phase-shifting digital holography

“…Digital holography [1]- [5] is a technique being capable of 3-D measurement of a moving object and is applied to a variety of fields, such as, particle and flow measurement [6], [7], microscopy [8], [9], quantitative phase measurement [10], [11], object recognition [12], [13] and so on. In digital holography, a hologram is recorded by image sensor and the image of an object is reconstructed by computer.…”