Nanoscale surface profile measurement using state space approach in digital holographic microscopy

Abstract

Abstract Surface profile measurement at the nanoscale level has important applications in non-destructive testing and evaluation. The paper proposes a robust method for surface profilometry using digital holographic microscopy setup. The proposed method relies on extracting the phase map encoded in the hologram signal, which directly corresponds to the surface profile, using state space approach. The main advantage of the proposed method is high robustness against noise, which is demonstrated using numerical simulations. For designing the experimental system, a combination of Raspberry-Pi computer and camera module is used for hologram acquisition and processing, which is a step towards low cost imaging. For surface profile measurement, the experimental system has both temporal and spatial sensitivity parameters within 5 nanometers, which indicates robust design. In addition, experimental results show that the proposed method shows superior performance compared to the existing methods for measuring 100 nanometers surface profile features corresponding to different micro-structure regions of a standard calibration test target. Overall, the proposed method allows for single shot, non-contact and full-field measurement of nanoscale surface profile with additional benefits of noise robustness and low cost imaging design.