Simultaneous dual-wavelength digital holographic microscopy with compensation of chromatic aberration for accurate surface characterization.
In this paper, a simultaneous dual-wavelength digital holographic microscope with compensation of chromatic aberration is presented. The microscope has been used to calibrate two standard step heights of 1340 and 1000 nm. The extracted results have been compared with those extracted by the single-shot, dual-wavelength digital holographic microscope, and the comparison has shown that measurements by the proposed microscope are more accurate by around 40 nm. We claim that the high accuracy in measurement is due to the fact that the proposed system works in real time with very low chromatic aberration. Judging the performance of the measurement process over time is explained by the control charts. Evidence from the control measurements sets a probable limit on precision for this process at about 3σ=3.5  nm.