An edge-lit volume holographic optical element for an objective turret in a lensless digital holographic microscope

In this paper, we propose and demonstrate the use of an edge-lit volume holographic optical element (EL-VHOE) as a reference waveguide to reduce the volume of a lensless digital holographic microscope. Additionally, a hybrid lensless Fourier transform digital holography is applied to make the EL-VHOE function as an objective turret. It used a spherical wave in the object beam of the EL-VHOE, which served as the reference beam of the microscope. Another sheared spherical wave was used to illuminate the sample. The longitudinal position of the spherical reference beam is changeable. It was shown that the tradeoff between resolution and field of view can be adjusted by changing the longitudinal position of the spherical reference beam. The corresponding experimental results matched the simulational and theoretical predictions. A resolution of approximately 3.11 μm was achieved when the object distance was 6 mm and the longitudinal distance of the spherical reference was 10 mm.