Color lens-free imaging using multi-wavelength illumination based phase retrieval (original) (raw)

Lensless Three-Dimensional Quantitative Phase Imaging Using Phase Retrieval Algorithm

Journal of Imaging, 2020

Quantitative phase imaging (QPI) techniques are widely used for the label-free examining of transparent biological samples. QPI techniques can be broadly classified into interference-based and interferenceless methods. The interferometric methods which record the complex amplitude are usually bulky with many optical components and use coherent illumination. The interferenceless approaches which need only the intensity distribution and works using phase retrieval algorithms have gained attention as they require lesser resources, cost, space and can work with incoherent illumination. With rapid developments in computational optical techniques and deep learning, QPI has reached new levels of applications. In this tutorial, we discuss one of the basic optical configurations of a lensless QPI technique based on the phase-retrieval algorithm. Simulative studies on QPI of thin, thick, and greyscale phase objects with assistive pseudo-codes and computational codes in Octave is provided. Bin...

Lensless phase microscopy using phase retrieval with multiple illumination wavelengths

2012

A phase retrieval method for microscopy using multiple illumination wavelengths is proposed. A fast algorithm suitable for calculations with high numerical aperture is used for the iterative retrieval of the object wavefront. The advantages and limitations of the technique are systematically analyzed and demonstrated by both simulation and experimental results.

Phase retrieval with resolution enhancement by using structured illumination

Optics Letters, 2013

In this Letter, we present referenceless phase retrieval methods with resolution enhancement. Structured illuminations with different orientations and phase shifts are generated by a spatial light modulator and are used to illuminate the specimen. The generated diffraction patterns are recorded by a CCD camera, and the phase of the wavefront is reconstructed from these patterns.

Lensless coherent imaging by phase retrieval with an illumination pattern constraint

Optics Express, 2006

It is often possible to reduce the requirements on an imaging system by placing greater demands either on an illumination system or on post-detection processing of the data collected by the system. An extreme example of this is a system with no receiver optics whatsoever. By illuminating an object or scene with coherent light having a shaped illumination pattern, the receiver can be a simple detector array with no imaging optics, detecting the speckle intensity pattern reflected from the object; an image of the object can be reconstructed by a phase retrieval algorithm.

Phase retrieval for undersampled broadband images

Journal of the Optical Society of America A, 1999

Phase-retrieval algorithms have been used for wave-front sensing to determine the aberrations of an optical system from system point-spread functions (blurred images of point sources). Previously, computationally efficient algorithms were developed and applied to data from the Hubble Space Telescope [Appl. Opt. 32, 1737 (1993); Appl. Opt. 32, 1747 (1993)], but those algorithms, which employ analytic expressions for the gradient of an error metric, required narrow-band light and adequately sampled images. Generalizations of those phaseretrieval algorithms, which accommodate broadband light, allow for undersampled images, permit fitting of multiple images simultaneously, and have a flexible description of the aberrations, are described in this study.

Phase retrieval using spatially modulated illumination

Optics letters, 2014

In this Letter, we propose a method for retrieving the phase of a wavefront from the diffraction patterns recorded when the object is sequentially illuminated by spatially modulated light. For wavefronts having a smooth phase, the retrieval is achieved by using a deterministic method. When the phase has discontinuities, an iterative process is used for the retrieval and enhancement of the spatial resolution. Both the deterministic and iterative phase reconstructions are demonstrated by experiments.

An adaptive algorithm for phase retrieval from high intensity images

2010

In this paper, we present an adaptive Gerchberg-Saxton algorithm for phase retrieval. One of the drawbacks of the original Gerchberg-Saxton algorithm is the poor results it yields for very bright images. In this paper we demonstrate how a dynamic phase retrieval approach can improve the correlation between the required image and the reconstructed image by up to 10 percent. The paper gives explicit explanations to the principle behind the algorithm and shows experimental results to support the dynamic approach.

Phase retrieval using coherent imaging systems with linear transfer functions

Optics Communications, 2004

We consider the problem of quantitative phase retrieval from images obtained using a coherent shift-invariant linear imaging system whose associated transfer function (i.e., the Fourier transform of the complex point-spread function) is well approximated by a linear function of spatial frequency. This linear approximation to the transfer function is applicable when the spread of spatial frequencies, in a two-dimensional complex wavefield, is sufficiently narrow when compared to the characteristic length of variation of the transfer function for an imaging system taking such a wavefield as input. We give several algorithms for reconstructing both the phase and amplitude of a given two-dimensional coherent wavefield, given as input data one or more images of such a wavefield which may be formed by different states of the imaging system. When an object to be imaged consists of a single material, or of a single material embedded in a substrate of constant thickness, the phase-amplitude reconstruction can be performed using a single image. As a first application of these ideas, we write down an algorithm for using a single diffraction-enhanced image (DEI) to obtain a quantitative reconstruction of the projected thickness of a single-material sample which is embedded within a substrate of approximately constant thickness. This algorithm is used to quantitatively map inclusions in a breast phantom, from a single synchrotron DEI image of the same. In particular, the reconstructed images quantitatively represent the projected thickness in the bulk of the sample, in contrast to raw DEI images which greatly emphasise sharp edges (high spatial frequencies). Lastly, we point out that the methods presented here are also applicable to the quantitative analysis of differential interference contrast (DIC) images, obtained using both visible-light and X-ray microscopy.

Quantitative phase retrieval with arbitrary pupil and illumination

Optics Express, 2015

We present a general algorithm for combining measurements taken under various illumination and imaging conditions to quantitatively extract the amplitude and phase of an object wave. The algorithm uses the weak object transfer function, which incorporates arbitrary pupil functions and partially coherent illumination. The approach is extended beyond the weak object regime using an iterative algorithm. We demonstrate the method on measurements of Extreme Ultraviolet Lithography (EUV) multilayer mask defects taken in an EUV zone plate microscope with both a standard zone plate lens and a zone plate implementing Zernike phase contrast.

A variable-wavelength-based approach of phase retrieval for contrast transfer function based methods

Journal of Synchrotron Radiation, 2010

X-ray phase-contrast imaging has emerged as an important method for improving contrast and sensitivity in the field of X-ray imaging. This increase in the sensitivity is attributed to the fact that, in the hard X-ray regime, the phase shift is more prominent as compared with the attenuation for materials having a low X-ray absorption coefficient. Among all the methods using the X-ray phasecontrast technique, in-line phase-contrast imaging scores over the other methods in terms of ease of implementation and efficient use of available X-ray flux. In order to retrieve the projected phase map of the object from the recorded intensity pattern, a large number of algorithms have been proposed. These algorithms generally use either the transport of intensity or contrast transfer function based approach for phase retrieval. In this paper it is proposed to use multiple wavelengths for phase retrieval using the contrast transfer function based formalism.