Compact digital holographic microscopes and application Anand Asundi, Vijay Raj Singh, Qu Weijuan, Taslima Khanam

School of Mechanical and Aerospace Engineering Nanyang Technological University

Singapore

Digital Holographic Microscopy (DHM) has shown increased interest over the recent years with applications ranging from MEMS inspection and testing, to Microscopy of cells and also for particle sizing and characterization. Various set-ups have been exploited for these applications. In this paper we describe three of such compact set-ups suitable for each of the above mentioned areas.

1. LRDHM – MEMS Characterization and Inspection DHM The optical system for this compact system is shown in fig. 1(a) with the aim to develop it into a commercial hand-held system. Working on a proof of concept fund from the National Research Foundation, this system is capable of inspection and characterization MEMS and Micro devices and system. Figure 1 shows application for MEMS inspection, MEMS deformation characterization for both static and dynamic situations

Figure 1 showing schematic of the LRDHM and application for MEMS inspection and Characterization

2. COMPACT – Particle Sizing and Characterization DHMA lens-less digital in-line holography based system as shown in Fig. 1 is the basis for this COMPACT particle sizing and characterization system. A novel processing algorithm allows for particles from a 3D volume to be identified both in terms of size and position as shown in the example below.

(a) (b) (c)

Figure 2 (a) Schematic of COMPACT System (b) Particle imaging (c) Fiber imaging

3. PCDHM for Bioimaging In bio-imaging applications, quantitative phase contrast images are required and these should not be influenced by phase introduced by other optical components in the system. While these can be eliminated numerically, this becomes a cumbersome and time consuming approach. In the PCDHM shown in Fig. 3, the phase is physically compensated by the set-up and hence computational processing is minimized.

Figure 3 Schematic of PCDHM and reconstructed intensity and phase images of a dicot root cell