Structure measurement of phase grating on post-magnification digital micro-holography

It develops a digital micro-holographic optical system to record the magnified hologram (named post-magnification digital micro-holography in this paper), which can suppress the quadratic phase aberration introduced by micro-objective (MO) and the wave-front difference between the object wave and reference wave. In order to show its remarkable trait, post-magnification micro-holography is compared with the traditional digital micro-holography (DMH) (named pre-magnification DMH) from the view of digital processing and aberration eliminating. Their differences are also analyzed by the measurement results of a phase grating with period 30lines/mm and depth 0.3 μm. Fresnel approximation algorithm is used to reconstruct the phase-contrast one of this phase grating. The results show that the presented system is greatly helpful to restrain the quadratic phase error.