High-precision phase compensation in digital holographic microscopy using a Shack-Hartmann wavefront sensor and a telecentric configuration

Abstract

Digital holographic microscopy (DHM) enables the reconstruction of threedimensional surface profiles with nanometre-scale axial resolution. However, measurement accuracy may be compromised by phase distortions arising from the spherical aberration of the microscope objective lens and by imperfections in other optical components. In this study, we propose a method that combines a ShackHartmann wavefront sensor (SH-WFS) with a reference-mirror arrangement, integrated within a telecentric optical system for phase compensation. This hybrid approach-melding physical calibration with digital correction-simultaneously reduces both global and local system errors. Consequently, it achieves precise phase correction without complex manual adjustments and maintains high stability when switching between samples. Experiments were conducted on surface-roughness standards with arithmetic roughness values (Sa) of 20.3 and 11.6 nm, measured using a ZeGage™ Pro surface-scanning device. The results exhibited excellent agreement with the reference values provided by the ZeGage™ Pro, thereby confirming the effectiveness of the proposed method. Overall, this technique markedly improves measurement accuracy in DHM and underpins the development of highly automated measurement systems, offering promising applications in precision optics.