Wide-Field Lensless 3D Imaging and Visualization of Micro-objects

Three dimensional (3D) imaging of objects requires the retrieval of both phase and amplitude of the object wavefront. Two beam techniques such as digital holography can reconstruct the whole field from the interference pattern, resulting from the superposition of the object wavefront and a known reference wavefront using light sources with sufficient coherence length. The diffraction field originating from the interaction of the probe wavefront with the object contains the spatial frequency information about the object. By studying the variation in the diffraction field with axial position, the phase of the object wavefront can be determined by iterative use of the scalar diffraction integral. Based on this approach, the development of a lensless whole field imaging technique using a low temporally coherent source (LED) in combination with axially arranged sensors is presented. Since the developed technique uses a single beam approach, less complex instrumentation compared to interferometric (two-beam) techniques is required. The technique was tested on technical as well as biological specimen to reconstruct and display their intensity and phase distributions. Since the developed microscope is lensless in nature with unit magnification, larger field of views become possible.