Compact low-cost lensless digital holographic microscope for topographic measurements of microstructures in reflection geometry

Abstract

Digital holography is capable of providing surface profiles of samples with axial resolution in the nanometer range. Lensless digital holography is a well-established microscopic method providing diffraction limited resolution of the order of the wavelength of the used light source. It is based on inline holography and usually allows imaging only in transmission geometry. In this contribution we propose a compact low cost lensless digital holographic microscope capable of performing measurements on reflective microstructures. The novelty of the system consists on a direct use of a laser diode without any need of coupling optics as light source. This simplifies the setup and provides sufficient magnification to measure microstructures. We evaluate our setup by imaging reflective microstructures. We have achieved ̴ 6 mm2 field of view amplitude images with ̴ 2.5μm lateral resolution and phase images with axial resolution in nanometer range. The phase image provides a full-field profile measurement of the sample in nanometer range.