研究目的
To implement a common path quantitative phase imaging setup using a partially spatially coherent multi-spectral light source to achieve speckle-free imaging with high temporal phase stability, overcoming the limitations of coherent noise in traditional digital holographic microscopy.
研究成果
The implemented common path QPI setup with a partially spatially coherent light source and Fresnel biprism interferometer provides speckle-free imaging, high temporal phase stability, and easy alignment. It eliminates the need for spatial filtering and offers advantages such as no optical power loss, uniform illumination, and suitability for multi-wavelength studies. Experiments on industrial and biological samples confirm reduced noise and improved phase measurement accuracy, making it valuable for applications requiring quantitative phase imaging.
研究不足
The setup may have limitations in handling highly dense samples or in environments with extreme vibrations, though the common path design reduces sensitivity to ambient noise. The use of specific wavelengths (532 nm and 632.8 nm) might not cover all spectral needs, and the rotating diffuser could introduce mechanical wear over time.
1：Experimental Design and Method Selection:
The study employs a common path digital holographic microscopy setup using a Fresnel biprism interferometer in self-referencing mode. A partially spatially coherent light source is created by combining lasers at 532 nm and 632.8 nm wavelengths with a rotating diffuser to reduce spatial coherence. The method includes Fourier fringe analysis for phase reconstruction.
2：8 nm wavelengths with a rotating diffuser to reduce spatial coherence. The method includes Fourier fringe analysis for phase reconstruction. Sample Selection and Data Sources:
2. Sample Selection and Data Sources: Industrial samples (e.g., 1951 USAF resolution chart) and biological samples (e.g., human erythrocytes) are used. Samples are selected to demonstrate the effectiveness of the setup in reducing speckle and improving image quality.
3：List of Experimental Equipment and Materials:
Lasers (532 nm and 632.8 nm), beam splitter, rotating diffuser, lenses (L1-L4 with focal lengths 150 mm, 100 mm, 100 mm, 150 mm), microscopic objective lens (20x), Fresnel biprism, 3-chip color CCD camera.
4：8 nm), beam splitter, rotating diffuser, lenses (L1-L4 with focal lengths 150 mm, 100 mm, 100 mm, 150 mm), microscopic objective lens (20x), Fresnel biprism, 3-chip color CCD camera. Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: Lasers are combined and passed through a rotating diffuser to create a partially coherent source. The light illuminates the sample, and the scattered light is collected by the objective lens. The Fresnel biprism splits the beam into reference and object beams, which interfere on the image plane. Holograms are recorded with the CCD camera and processed using Fourier transform and filtering techniques.
5：Data Analysis Methods:
Fourier fringe analysis is used to extract phase information from holograms. Phase difference is calculated using the formula Δφ = 2π(no - ns)d/λ, where no and ns are refractive indices, d is thickness, and λ is wavelength. Temporal stability is assessed by measuring standard deviation of phase differences over time.
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laser
532 nm
Provides coherent light source at specified wavelength for illumination in the experimental setup.
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laser
632.8 nm
Provides coherent light source at specified wavelength for illumination in the experimental setup.
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beam splitter
Combines light from multiple lasers into a single beam.
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rotating diffuser
Reduces spatial coherence of the laser light to create a partially spatially coherent source, minimizing speckle artifacts.
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lens
L1
Collimates the light after it passes through the rotating diffuser.
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lens
L2
Part of the imaging system to focus and magnify the light.
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lens
L3
Part of the imaging system to focus and magnify the light.
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lens
L4
Part of the imaging system to focus and magnify the light.
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microscopic objective lens
20x
Collects and magnifies the scattered light from the sample.
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Fresnel biprism
Splits the beam into reference and object beams for interference in the common path interferometer.
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CCD camera
3-chip color
Records the interference patterns (holograms) for further processing and analysis.
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