An improved phase retrieval method based on Hilbert transform in interferometric microscopy (original) (raw)
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Three-Dimensional Measurements Using Hilbert Phase Microscopy
New Physics: Sae Mulli, 2017
In this study, we used Hilbert phase microscopy to obtain quantitative, high spatial resolution phase images of sample objects with a large depth of field (DOF) based on interferometric methods. The Hilbert microscope is suitable for investigating fast-occurring phenomena because it requires only one image. The pitch of the interference pattern can be controlled by changing the angle between the two interference beams, and the DOF can be controlled by varying the overlapping width of the beam. The Hilbert transform was used to retrieve the phase of the sample in computer simulations, as well as in experiments, that measure the phase by using the fringe method.
Applied Optics, 1980
Observations of phase objects with a microscope generally involve interferometric methods. However, visual or photometric analysis of the interferogram interprets in the same way the information corresponding to the advance and retardation of the wave front transmitted or reflected by an object. Hence, no information about the direction of relief of the object is obtained. An experimental process is described here that is capable of restoring both sign and magnitude of the phase throughout the field. This method, based on modulation interferometry using a microscope and a scanning device, provides the user with different information about the object, such as a display of an intensity image of the interference pattern and its photometric analysis as well as the equal phase contours inside the scanned area, a display of the complex amplitude components and-extending the use of the instrument to the phase measurement technique to complete the data-measurement of the phase for an array of points in the object area.
Quantitative cell imaging using single beam phase retrieval method
Journal of Biomedical Optics, 2011
Quantitative three-dimensional imaging of cells can provide important information about their morphology as well as their dynamics, which will be useful in studying their behavior under various conditions. There are several microscopic techniques to image unstained, semitransparent specimens, by converting the phase information into intensity information. But most of the quantitative phase contrast imaging techniques is realized either by using interference of the object wavefront with a known reference beam or using phase shifting interferometry. A two-beam interferometric method is challenging to implement especially with low coherent sources and it also requires a fine adjustment of beams to achieve high contrast fringes. In this letter, the development of a single beam phase retrieval microscopy technique for quantitative phase contrast imaging of cells using multiple intensity samplings of a volume speckle field in the axial direction is described. Single beam illumination with multiple intensity samplings provides fast convergence and a unique solution of the object wavefront. Three-dimensional thickness profiles of different cells such as red blood cells and onion skin cells were reconstructed using this technique with an axial resolution of the order of several nanometers. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).
Derivative method for phase retrieval in off-axis quantitative phase imaging
2012
We present a method for phase retrieval in off-axis interferometric systems. By numerically calculating the transverse 1st and 2nd order derivatives of the interferogram, we show that one can directly retrieve the quantitative phase image, without the need for Fourier or Hilbert transformations. Because of this, the method is significantly faster than the current approaches. We illustrate our method using biological specimen data from three different off-axis quantitative phase imaging techniques.
Quantitative Phase Microscopy: how to make phase data meaningful
Proceedings - Society of Photo-Optical Instrumentation Engineers, 2014
The continued development of hardware and associated image processing techniques for quantitative phase microscopy has allowed superior phase data to be acquired that readily shows dynamic optical volume changes and enables particle tracking. Recent efforts have focused on tying phase data and associated metrics to cell morphology. One challenge in measuring biological objects using interferometrically obtained phase information is achieving consistent phase unwrapping and -dimensions and correct for temporal discrepanices using a temporal unwrapping procedure. The residual background shape due to mean value fluctuations and residual tilts can be removed automatically using a simple object characterization algorithm. Once the phase data are processed consistently, it is then possible to characterize biological samples such as myocytes and myoblasts in terms of their size, texture and optical volume and track those features dynamically. By observing optical volume dynamically it is p...
Fast pixel shifting phase unwrapping algorithm in quantitative interferometric microscopy
SPIE Proceedings, 2014
Quantitative interferometric microscopy is an important method for observing biological samples such as cells and tissues. As a key step in phase recovery, a fast phase unwrapping algorithm is proposed. By shifting mod 2π wrapped phase map for one pixel, then multiplying the original phase map and the shifted one, the phase discontinuities could be easily determined with high speed and efficiency. The method aims at enhancing phase retrieving efficiency without any background knowledge. We test our algorithm with both numerical simulation and experiments, by focusing our attentions on wrapped quantitative phase maps of cells. The results indicate that this algorithm features fast, precise and reliable.
Fast phase reconstruction in white light diffraction phase microscopy
Applied Optics, 2012
In off-axis interferometry, we usually have to deal with the unwrapping process, which is very computationally intensive and prevents us from real time phase reconstruction. The wrapping problem usually occurs when imaging thick objects, which introduce phase shifts of more than 2π radians. However, in off-axis interferometry, the nonzero angle of interference of the two beams creates a ramp in the phase across the image that can produce phase wrapping errors. In this paper, we propose a simple technique that avoids the need for the unwrapping step in reconstructing quantitative phase images in white light diffraction phase microscopy of thin samples. We show that this approach can improve significantly the phase reconstruction speed and allow high impact applications, such as real-time blood testing.
Precise phase retrieval under harsh conditions by constructing new connected interferograms
Scientific reports, 2016
To date, no phase-shifting method can accurately retrieve the phase map from a small set of noisy interferograms with low phase-shifts. In this Letter, we develop a novel approach to resolve this limitation under such harsh conditions. The proposed new method is based on constructing a set of connected interferograms by means of simple subtraction and addition operations, in which all the subset of interferograms have the same phase-shift interval of π/2. According to this characteristic, this set of connected interferograms can be processed with conventional phase retrieval methods as PCA or AIA obtaining accurate results. The reduction in the RMS errors after using our method reaches as high as 93.7% and 89.3% respectively comparing with conventional PCA and AIA methods under harsh conditions. Both simulation and experiment results demonstrate that the new proposed method provides an effective way, with high precision and robustness against noise, for phase retrieval.
WHITE LIGHT DIFFRACTION PHASE MICROSCOPY
Quantitative phase imaging (QPI) techniques are very advantageous compared to the qualitative phase imaging techniques like bright field microscopy, phase contrast microscopy, differential interference contrast microscopy due to measurement of phase information quantitatively. In QPI techniques, there is no need of exogenous contrast agents to stain or tag the specimen. White light diffraction phase microscopy (wDPM) is one of the QPI techniques which is used to quantify the phase information from the samples. The phase information retrieved is dependent on the local refractive index and thickness of the biological cells. So, by measuring the phase one can find the refractive index and/or thickness of the specimen in nanometer scales. In this technique, the acquisition speed is only limited by the sensing device due to its single shot feature, it is better compared to other quantitative phase imaging techniques as its common path geometry provides better temporal phase sensitivity by cancelling out the most mechanisms responsible for noise and with the use of white light source the images are speckle-free. So we achieve better spatial phase sensitivity compared to other techniques. This method has attractive applications in biomedicine. We have developed wDPM set up for extracting phase information from the live yeast cells and sperm cells. The phase is reconstructed from the recorded interferograms by using a fast phase reconstruction algorithm. This algorithm avoids the unwrapping step which is needed in conventional phase reconstruction by Hilbert's transform method. We have calculated the thickness of the yeast cells and sperm cells and demonstrate a video for visualizing the dynamics of yeast cells.