研究目的
To improve the imaging quality of digital holographic microscopy (DHM) by reducing phase noise through the application of bidimensional empirical mode decomposition (BEMD) on digital holograms.
研究成果
The proposed BEMD method effectively reduces phase noise in DHM by enhancing interference fringes in the hologram, leading to improved measurement accuracy and reduced noise levels, as validated by experimental results on a nano-step.
研究不足
The method may be sensitive to the quality of initial hologram recording and environmental factors. Optimization of BEMD parameters could be further explored for different sample types.
1：Experimental Design and Method Selection:
The study employs a digital holographic microscopy setup to record holograms of a nano-step sample. BEMD is applied to decompose the hologram and enhance interference fringes for noise reduction.
2：Sample Selection and Data Sources:
A standard nano-step (VLSI, SHS-440-QC) is used as the sample. Holograms are recorded using a CCD camera.
3：List of Experimental Equipment and Materials:
Includes a diode laser (λ=690nm, Nanobase, Xperay-TL-STD), neutral filters, beam splitters, microscope objective (Mitutoyo M Plan Apo SL, NA=
4：42, 50X), beam expanders, lenses, mirrors, and a CCD detector (Imperx, 33 fps). Experimental Procedures and Operational Workflow:
The optical setup splits laser beams into object and reference beams, which interfere at the sample plane. Holograms are recorded, processed using BEMD to obtain IMF1, and reconstructed to extract phase and amplitude images.
5：Data Analysis Methods:
Phase images are analyzed for noise reduction, with height measurements compared to stylus profilometer data using statistical averaging.
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