To observe targets in expanded depths of view in light field imaging, we design an open-source light field parallel refocusing code-free GUI tool named OpenRefocus, which is based on classical spatial projection integration. OpenRefocus has been successfully used for refocusing light field images selected from open-source datasets as well as captured using commercial light field cameras faster than other released light field refocusing programs. Considering its fast processing speed and user-friendly operations, OpenRefocus can be a useful tool for light field refocusing in many light field imaging applications.
Transport of intensity phase microscopy (TIPM) can obtain sample phase images with commercial microscope and simple procedures; however, it requires multi-focal images limiting its real-time detection capability. In order to achieve dynamics of the live cells, we adopted dual-view TIPM which simultaneously captures under- and over-focus images for phase retrieval. In dual-view TIPM, two identify CMOS cameras were first set on the binocular tube of the microscope with different focal position of 3 mm difference to simultaneously capture both the under- and over-focus images. Afterwards, scaling, rotation and shifting are all corrected to maintain the same fields of view of under- and over-focus images. Next, the cellular phase can be extracted by solving the Poisson equation. The dual-view TIPM was finally adopted in live cell imaging, proving the dual-view TIPM can obtain real-time quantitative cellular phase imaging.
In order to obtain high contrast and resolution images, in-focus [14] image should be collected by microscope. Though, traditional autofocusing method can determine the in-focus position, it is time consuming and requires difficult manual operations. In our previous works, we have proposed wavefront sensing based autofocusing method. Three multi-focal images are captured and the wavefront in the central position is calculated. Then, with wavefront propagation, multiple intensities at different focal planes can be computed, and the in-focus position can be determined according to the infocus criterion as Tamura coefficient. This method only needs few image recordings and is rapid, it still requires heavy computational load in wavefront propagation, limiting its application in fast conditions. In this conference paper, we improve the our previously proposed wavefront sensing based autofocusing method [15] using graphics processing unit [13], field of view reduction and down-sampling, which can efficiently accelerate the wavefront sensing based autofocusing speed. According to the advantages as fast speed, high accuracy and easy operation, the wavefront sensing based autofocusing method can be future applied in microscopy.
Single molecule fluorescence detecting technique often has extremely high accuracy and sensitivity, thus it is often adopted in biomedicine detection, pollutant monitoring and chemical analysis. However, traditional single molecule fluorescence detecting devices often suffer from huge sizes and expensive costs, inevitably limiting their applications especially in on-site detections. In order to extend its application scope, we design a single molecule fluorescence imaging device (smFID), in which a laser is tilted illuminated on the sample chip, and a micro-objective is used for fluorescence signal collection, moreover, a smartphone with a filter is adopted to record the fluorescence images. According to the system design, smFID can reach a wide field of view of 1.5mm2, a high resolution of 2.2 μm and signal to noise ratio of ~22dB. Additionally, smFID is implemented in single molecule detection combining with the magnetic bead system, and its sensitivity can reach 1 nM and its detection range is wide from 1 nM to 1 μM, which are much better than traditional chemical and optical methods. Considering smFID can be used for single molecule testing with compact configuration, fast speed, high sensitivity and accuracy, it is a favorable device potentially used in on-site single molecule sensing and imaging fields.
Cell observations and analysis are often required in biological and medical fields for cell condition evaluations and disease diagnostics. Compared to classical methods such as bright/dark field microscopy and fluorescent microscopy, quantitative interferometric microscopy as one of the quantitative phase microscopic techniques is able to provide high contrast image of label free samples thus can be potentially using in live cell imaging. While it often suffers from the low processing speed often due to the heavy computational load in phase unwrapping. In order to accelerate the imaging speed, we design a rapid cell phase imaging technique relying on the fast shearing phase unwrapping method. It can extract the sample information from a single-shot interferogram showing that it can capture live cell images. Moreover, the phase unwrapping process is significantly reduced with accelerated speed. Considering the system can provide quantitative and high-contrast live cell imaging in label free mode with high accuracy, fast speed and large field of view, it can be a potential tool for cell observations and measurements in biological and medical applications.
Though laser repairing can smooth the surfaces of laser damaged optical elements, it is difficult to compensate all the stress in them. Therefore, residual stress detection and compensation are significant as surface smoothing during laser repairing. In order to quantitatively detect the residual stress especially in laser damage detection and laser repairing quality evaluation, we plan to use polarized digital holography to measure and analyze the residual stress distribution inside the target; and we also propose the numerical model of quantitative stress detection using the polarized digital holography. Since the polarized digital holography can reconstruct the residual stress in high resolution, fast speed and high accuracy, the proposed method can be a potential tool in laser damage detection and laser repairing quality evaluation in high power laser fields.
A computational method is proposed to measure the aberration of a lens using an extended ptychographic iterative engine. By reconstructing the entering wavefront φin and exiting wavefront φex of the lens under detection from two sets of diffraction patterns iteratively, the lens aberration can be easily extracted by subtracting the phase of φin and theoretical lens phase from the phase of φex. Since it needs no extra reference beam and high quality optics, this suggested method has advantages of simplicity in structure, high accuracy, and low requirement on working environment, and it is free of the aberration of other optical elements in the experimental system, indicating it can find lots of applications in lens evaluation.
KEYWORDS: Digital imaging, Live cell imaging, Numerical simulations, Microscopy, Real time imaging, Phase retrieval, Microscopes, Image retrieval, Phase imaging, Digital image correlation
As an ideal way for quantitative live cell imaging, dual view transport of intensity equation (TIE) method can provide both real time imaging, multi-mode observations, simple setup and large field of view (FoV). However, the image recorder installation error reduces the accuracy in both amplitude and phase retrievals, because of the inevitable FoV mismatch between the captured under- and over-focus intensities. In order to obtain higher accuracy amplitude and phase retrievals, the phase correlation based digital FoV correction is introduced into our method, rotation, scale and translation between the under- and over-focus images are compensated by the phase correlation based digital FoV correction. Measurements are implemented using standard sample detection and quantitative live cell imaging, proving that the proposed method can improve the accurate of the amplitude and phase computations.
Autofocusing is widely used in microscopy since it provides sample details with high resolution and contrast. However, massive image recording along optical axis is often indispensable in classical autofocusing tactics, obviously decreasing autofocusing speed. To increase processing efficiency, we propose numerical wavefront propagation based autofocusing with high speed and large effective range. Firstly, quantitative sample phase is retrieved from multi-focal images according to transport of intensity equation with Gerchberg-Saxton algorithm. Then, various intensities along optical axis are numerically computed via wavefront propagation, thus focal position can be determined according to in-focus criterion. Finally, in-focus image is recorded via sample stage shifting. Since the proposed autofocusing approach can be easily integrated into commercial microscopes, additionally, it considerably reduces image captures as well as time consuming, we believe it can be adopted for rapid autofocusing in microscope.
As an important marker in disease diagnosis, red blood cell morphology measurement is necessary in biological and medical fields. However, traditional setups as microscopes and cytometers cannot provide enough quantitative information in morphology detections. In order to capture tiny variations of red blood cells affected by metal ions in external environment, quantitative interferometric microscopy is applied: combining with phase retrieval and cell recognition, cellular phases as well as additional quantitative cellular parameters can be acquired automatically and accurately. The research proves that quantitative interferometric microscopy can be potentially applied in cellular observations and measurements for both biological and medical applications.
KEYWORDS: Digital imaging, Live cell imaging, Digital image correlation, Numerical simulations, Real time imaging, Phase retrieval, Optical engineering, Image processing, Microscopy, Blood
Dual-view transport of intensity equation (TIE) method is an ideal way for quantitative live cell imaging as it has advantages such as real-time imaging, multimode observations, compact setup, and large field of view (FoV). However, due to the image recorder installation error, the inevitable FoV mismatch between the captured under- and over-focus intensities reduces the accuracy in both amplitude and phase retrievals. Here, to eliminate this undesired FoV mismatch, the phase correlation-based digital FoV correction is adopted to recognize and compensate the rotation, scale, and translation between the under- and over-focus images. Both the numerical simulations as well as the experiments in standard sample detection and quantitative live cell imaging prove that the digital FoV correction combined dual-view TIE method can maintain the consistence of the dual FoVs, thus guaranteeing the high-accurate amplitude and phase computations, proving the proposed method is a promising quantitative live cell imaging tool in various applications such as biological observations and medical diagnostics.
A variable aperture-based ptychographical iterative engine (vaPIE) is demonstrated both numerically and experimentally to reconstruct the sample phase and amplitude rapidly. By adjusting the size of a tiny aperture under the illumination of a parallel light beam to change the illumination on the sample step by step and recording the corresponding diffraction patterns sequentially, both the sample phase and amplitude can be faithfully reconstructed with a modified ptychographical iterative engine (PIE) algorithm. Since many fewer diffraction patterns are required than in common PIE and the shape, the size, and the position of the aperture need not to be known exactly, this proposed vaPIE method remarkably reduces the data acquisition time and makes PIE less dependent on the mechanical accuracy of the translation stage; therefore, the proposed technique can be potentially applied for various scientific researches.
To realize portable device with high contrast imaging capability, we designed a quantitative phase microscope using transport of intensity equation method based on a smartphone. The whole system employs an objective and an eyepiece as imaging system and a cost-effective LED as illumination source. A 3-D printed cradle is used to align these components. Images of different focal planes are captured by manual focusing, followed by calculation of sample phase via a self-developed Android application. To validate its accuracy, we first tested the device by measuring a random phase plate with known phases, and then red blood cell smear, Pap smear, broad bean epidermis sections and monocot root were also measured to show its performance. Owing to its advantages as accuracy, high-contrast, cost-effective and portability, the portable smartphone based quantitative phase microscope is a promising tool which can be future adopted in remote healthcare and medical diagnosis.
As a lensfree imaging technique, ptychographic iterative engine (PIE) method can provide both quantitative sample amplitude and phase distributions avoiding aberration. However, it requires field of view (FoV) scanning often relying on mechanical translation, which not only slows down measuring speed, but also introduces mechanical errors decreasing both resolution and accuracy in retrieved information. In order to achieve high-accurate quantitative imaging with fast speed, digital micromirror device (DMD) is adopted in PIE for large FoV scanning controlled by on/off state coding by DMD. Measurements were implemented using biological samples as well as USAF resolution target, proving high resolution in quantitative imaging using the proposed system. Considering its fast and accurate imaging capability, it is believed the DMD based PIE technique provides a potential solution for medical observation and measurements.
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