The lensless in-line holographic microscope offers a compact, low-cost, and wide-field solution for microscopic imaging. Instead of using lenses, lensless microscopy relies on diffraction patterns to reconstruct images of the sample. Therefore, coherent light sources such as lasers are typically used to illuminate the sample for reconstruction images. However, lasers will introduce speckle and multiple reflection interference noise, while also being high in cost. As a result, LED illumination sources have been employed in lensless microscopy systems. However, the temporal coherence of LEDs affects the imaging resolution, which results in poor quality of the reconstructed images. In this paper, we propose an iterative twin image removal method based on a single diffraction pattern based on a lensless on-chip microscopy with a partially coherent illumination source. This method combines the wavelength demultiplexing method with positive absorption constraint and phase flipping. It can not only reduce the temporal coherence limitation of broadband light sources but also improve the convergence speed during iteration and provide better support estimation for complexshaped samples, thus improving the quality of reconstructed images. We provide numerical simulations and optical experiments to illustrate the effectiveness of our method. This work helps extend the application of lensless in-line holographic microscopy based on partially coherent light sources in biomedical detection, offering a more convenient and cost-effective option for microscopic imaging.
We propose a single-frame lensfree phase retrieval(SFLFPR) method based on coherence-limited light-emitting diode (LED) illumination. Combining multi-wavelength scanning iteration for broad-spectrum illumination with phase support constraint, SFLFPR corrects resolution loss caused by the temporal coherence of LED, obtaining quantitative phase imaging results. Using only one hologram, our method can retrieve the high signal-to noise(SNR) phase of the sample and achieve a half-width resolution of 977 nm across a large field-of-view (FOV) of 19.53 mm2 , surpassing 1.41 times the resolution achieved by the conventional single-frame method. We confirmed the effectiveness of this method in quantitative phase imaging (QPI) by measuring various label-free samples including polystyrene microspheres, phase resolution target (PRT) and HeLa cell slices. Considering its fast real-time single-frame imaging capability, our method has a wide range of biological and medical applications.
We report a novel wide-field lens-free 3D microscopy, which is based on Fourier ptychography diffraction tomography (FPDT) technique. This method uses only one illumination angle to obtain a large enough number of diffractograms by scanning a wide range of wavelengths, applying an iterative method to fill the 3D spectrum, and finally recovering the refractive index (RI) distribution of the sample. And the effectiveness of the method in the 3D RI distribution reconstruction of a tilted phase target is experimentally verified.
In traditional lensless in-line holographic microscopy, phase recovery based on multi-defocus distance is a common pixel-super-resolution technique. This method usually requires accurate displacement as a predictive condition, and the introduction of a precision mechanical displacement platform can bring about accurate displacement, but makes a simple lensless system complicated and expensive. In this paper, the samples are illuminated by a nearly coherent illumination system, and holograms at different heights are captured by the sensor driven by a low-cost servo motor without feedback system. Inaccurate displacement interval results in poor phase recovery. We propose a multi-height phase recovery algorithm based on z-axis correction to recover the phase information of the sample, which can improve the result by 1.58 times compared with that before correction. The reconstruction USAF target demonstrates a half-pitch lateral resolution of 775 nm across a large field-ofview of ∼29.84 mm2 , surpassing 2.15 times that of the theoretical Nyquist–Shannon sampling resolution limit imposed by the pixel size of the imaging sensor (1.67 μm).
We report a multi-wavelength multiplexed setup and associated super-resolution reconstruction method in lensless microscopy, which can generate high-resolution reconstructions from undersampled raw measurements captured at multiple wavelengths. The reconstruction result of the Benchmark Quantitative Phase Microscopy Target (QPTTM) demonstrates the resolution enhancement quantitatively, which achieves a half-pitch lateral resolution of 691 nm across a large field of view (~29.85 mm2), surpassing 2.41 times of the theoretical NyquistShannon sampling resolution limit imposed by the pixel-size of the sensor (1.67 µm). Compared with other superresolution methods such as lateral or axial shift-based device and illumination source rotation design, wavelength multiplexed avoids the need for shifting/rotating mechanical components. This multi-wavelength multiplexed super-resolution method would benet the research and development of a more stable lensless microscopy system.
In this paper, we present a multi-wavelength multiplexed setup and associated super-resolution reconstruction method in lensfree microscopy that generates high-resolution reconstructions from undersampled raw measurements captured at multiple wavelengths. The reconstruction result of the standard 1951 USAF achieves a half-pitch lateral resolution of 775 nm, corresponding to a numerical aperture of 1.0, across a large field of view (∼ 29.85 mm2). Compared with other super-resolution methods such as lateral or axial shift-based device and illumination source rotation design, wavelength multiplexed avoids the need for shifting/rotating mechanical components. This multi-wavelength multiplexed super-resolution method would benefit the research and development of a more stable lensfree microscopy system.
We present a wavelength-scanning-based lensfree microscopy that generates high-resolution reconstructions from undersampled raw measurements captured at multiple wavelengths.The reconstruction result of the standard 1951 USAF achieves a half-pitch lateral resolution of 775 nm, corresponding to a numerical aperture of ∼ 1.0, across a large field of view (∼ 29.85 mm2). Compared with other super-resolution methods such as lateral or axial shift-based device and illumination source rotation design, wavelength scanning avoids the need for shifting/rotating mechanical components. This wavelength-scanning super-resolution method would benefit the research and development of more stable lensfree microscopy system.
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