Digital holographic systems for particulate processes

• Main Author: Mohammad Nurur Rahman
• Other Authors: Lee Kijoon
• Format: Theses and Dissertations
• Language: English
• Published: 2014
• Subjects: DRNTU::Engineering::Chemical engineering; DRNTU::Science::Physics::Optics and light
• Online Access: https://hdl.handle.net/10356/61802
• Institution: Nanyang Technological University

Digital holography (DH) is an established three dimensional (3-D) imaging tool to measure particle size and shape. In this thesis, the effect of particle concentration and turbidity is studied on the efficiency of digital inline holography (DIH) used for particle characterization. This study is important to assess the performance of the technique under practical situations where a wide range of particle concentrations may be employed, and very often the solution in which the particles are present is turbid. A theoretical relationship is also deduced here between the particle size and the digital image sensor resolution, both for collimated and diverging illumination, considering DIH system. This relationship provides information about how small particle size can be measured with a given optical and digital system before using any magnifying optics. From the algorithm development side, two computer programs are also developed for more complicated particulate systems unlike spherical, such as needles and mixed morphologies. Single crystal study and it’s results are also described in this thesis. To check the effect of particle concentration on DH for particle characterization, two sample depths are analyzed. It is demonstrated that measurement performance can be significantly improved by reducing the sample depth. The results are analyzed based on the two metrics, i.e., detection efficiency and mean size of the particle population. Considering 50% detection efficiency as a threshold, it is concluded that DH works well up to 0.1 v/v% and 0.2 v/v% particle concentrations for 10 mm and 5 mm sample depths, respectively. From the turbidity tests, it is found that DH works well up to 150 nephelometric turbidity units (NTU) turbidity level for 10 mm sample depth. From the theoretical derivation, the required digital image sensor resolution (pixel dimension) can be recommended for resolving particular particle size. Finally, the two developed algorithms have been applied in the real particulate systems and the results quite match well with the known values measured with another independent technology. Single crystal study’s results will direct this tool in the pharmaceutical industries.