研究目的
To present two-step phase-shifting off-axis digital holography with maximum space-bandwidth product for three-dimensional (3D) digital holography, removing the autocorrelation term to significantly increase the available bandwidth for off-axis interferometry.
研究成果
The two-step phase-shifting technique removes the AC frequencies that are the main source of restricted bandwidth in off-axis holography. The optimized diagonal scheme has a bandwidth that is eight times that of previously reported techniques and four times that of single-shot off-axis interferometry with a square scheme. The experimental results demonstrate the capability of scan-free imaging, even for critical sampling.
研究不足
The system is very sensitive to dust and requires accurate alignment to appropriately remove the effect of the DC. The technique requires two frames to be taken, which may limit its application in high-speed scenarios.
1：Experimental Design and Method Selection:
The study employs a two-step phase-shifting technique and an optimizing super-diagonal two-dimensional (2D) spatial frequency sampling scheme at the sub-Nyquist frequency for off-axis interferometry.
2：Sample Selection and Data Sources:
Polystyrene microspheres with 15, 20, and 30 μm diameters were used as samples.
3：List of Experimental Equipment and Materials:
A 405-nm laser beam, beam splitter, half-waveplates, mirrors, objective lens, tube lens, lens, CCD camera, and a 4f optical system.
4：Experimental Procedures and Operational Workflow:
The setup involves Mach–Zehnder type interferometry, with phase shifts induced by half-waveplate rotation at the reference arm, and images captured by a CCD camera.
5：Data Analysis Methods:
The Fourier method was employed for phase retrieval, and an unwrapping algorithm was used to resolve any phase ambiguity.
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