According to the phase gradient transfer function (PGTF) derived from the phase space theory, the phase recovery algorithm based on the transport of intensity equation (TIE) has the problem that the high-frequency phase is underestimated due to the coherence effect of the limited aperture system under partially coherent illumination. Therefore, based on the theory of PGTF and phase transfer function (PTF), a phase reconstruction algorithm named high-resolution synthetic spectrum (HSS) method combining the TIE and the PTF-based deconvolution is proposed. This technique broadens the application range and provides high contrast, high accuracy, and highresolution quantitative phase results with high robustness. The performances of this technology are demonstrated by simulation and experiments, showing efficient for phase retrieval in the near-Fresnel region. Such a highresolution method can offer a flexible and cost-effective alternative for biomedical research and cell analysis, providing new avenues to design powerful computational imaging systems
Phase unwrapping is an essential procedure in digital holographic microscopy (DHM). There are many algorithms have been proposed to unwrap the phase such as the reliability-guided phase unwrapping algorithm that intro- duced in this paper. It is necessary to do a comparison of these algorithms in order to determine which method has better performance in the actual experiment. For higher quality and fewer error points, we also introduce an improved phase unwrapping path base on path-following method such as the reliability-guided phase unwrapping algorithm, and the experimental images demonstrate the validity of our algorithms. In addition, we propose a method to accelerate the phase unwrapping process for biomedical dynamic imaging. The experimental results suggest that this method can significantly improve the dynamic measurement speed while ensuring the accuracy of phase unwrapping.
We demonstrate a method for increasing the effective resolution of phase retrieval based on the transport of intensity equation (TIE) named speckle high-resolution synthetic spectrum (speckle-HSS), as the upgraded version of the speckle-TIE approach we proposed before based on the quantitative phase imaging camera with a weak diffuser (QPICWD). Benefit from the phase gradient transfer function (PGTF) and phase transfer function (PTF), the phase blurring caused by the underestimation of phase gradient can be compensated correctly via combining TIE and PTF-based deconvolution. This method broadens the application range, alleviating the artifacts and enhancing the contrast and resolution in more accurate value. The experimental results of live HeLa cells have been presented, showing the effectiveness of the proposed method.
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.
In this paper, a holographic lensless quantitative phase imaging (QPI) microscope is presented, which is composed of a CMOS detector image sensor with a programmable color LED matrix, without any lens and mechanical displacement device. Such a miniaturized system can provide a field-portable cost-effective platform for highthroughput quantification of multiple samples. Coordinating the self-developed software operating system, the bright-field imaging, the quantitative phase imaging as well as cell counting, profile analysis, three-dimensional (3D) imaging and differential interference contrast (DIC) imaging can be realized. With its high-resolution based computational microscopy interface, this system can be also adaptively used for telemedicine applications and point-of-care testing (POCT) in resource-limited environments.
Lensless imaging technique, as a newly developed microscopic imaging method, combined with its corresponding image restoration algorithm, and it can obtain large-field, high-resolution three-dimensional images without labeling. Therefore, the lensless imaging system has the advantages of low cost, good portability, large field of view and high resolution. However, due to the limitation of pixel size, hardware implementation and post data processing, the imaging resolution of lensless microscopy is far away from theoretical performance. In order to solve above problems, this paper proposes a method to improve the capability registration and information coupling based on multi-wavelength illumination. Moreover, this work combines a stack of captured low-resolution images into a high-resolution result image, and the pixel super-resolution can be realized throught the reconstruction algorithm based on the exist illumination light source, Finally, experimental results utilizing USAF target demonstrate the success of proposed lensless imaging method.
We present a new quantitative phase imaging method on the basis of the novel camera named quantitative phase imaging camera with a weak diffuser (QPICWD). It measures object under low-coherence quasi-monochromatic illumination via examining the deformation of the speckle intensity pattern. The speckle deformation can be analyzed by means of ensemble average of geometric flow method, realizing high resolution distortion field by using the transport of intensity equation (TIE). There are some applications for the proposed new design including nondestructive optical testing of microlens array with nanometric thickness. Since the proposed QPICWD needs no modification of the common bright-field microscope, it may promote QPI as a useful tool for subcellular level biological analysis.
We present a novel approach to compensate coherence effect via combining the transport of intensity equation (TIE) with look-up table phase compensation (LUT-PC) method. It is the better version of the Speckle-TIE method we demonstrated before on the basis of the quantitative phase imaging camera with a weak diffuser (QPICWD). With the phase gradient ratio theory and the look-up table method, the phase blurring caused by underestimation of phase gradient will be compensated correctly by reasonable rescaling. The LUT-PC SpeckleTIE method has the evident predominance of speediness since it only needs one slightly defocused speckle image in one time owing to that the reference speckle image can be captured beforehand. The deblurring achieved by this method improves the imaging resolution to the theoretical partial coherence limit with good robustness, reducing artifacts and improving the accuracy and contrast. The experimental results show the effectiveness of the technique.
We present an efficient quantitative phase imaging camera with a weak diffuser (QPICWD) based on the transport of intensity equation (TIE). The compact QPICWD measures object induced phase delay under low-coherence quasi-monochromatic illumination via examining the deformation of the speckle intensity pattern. Analysing the speckle deformation with an ensemble average of the geometric ow, we can achieve the high-resolution distortion field by the TIE. We present some applications for the proposed design involving nondestructive optical testing of microlens array with nanometric thickness and imaging of fixed and live unstained HeLa cells. Since the designed QPICWD needs no modification of the common bright-field microscope or additional accessories, it may advance QPI as a widely useful tool for biological analysis at subcellular levels.
In this paper, we employ coded aperture imaging (CAI), an emerging computational technology that captures 4D light-field information to realize pixel super-resolution imaging via post-processing. Our CAI experimental setup is built based on 4f delay system with reflective optical path structure, where a programmable LCOS spatial light modulator is integrated at the Fourier plane to implement high-resolution high-contrast aperture coding, without requiring specialized hardware or any moving parts. In addition, we propose an iterative super-solution reconstruction algorithm based on aperture coding, optical fields manipulation and compressed sensing. First, we establish an accurate mathematical model for the OTF of coded aperture system and pixel binning process. Then, based on a series of low-resolution intensity image, we computationally reconstruct the high-resolution image with the convex projection iterative algorithm. The effectiveness of this algorithm is demonstrated with both simulation and experimental results. Due to its flexibility and simplicity, this technology can break physical limitations of the detectors’ resolution to one that is solvable through computation, rendering it a promising tool in public security, military survey, medical science and many other fields.