Single-shot Phase Imaging Research Articles

Single-Shot Super-Resolution Phase Imaging Method Using Band-Limited Image and Its Fourier Transform Constraints via Analytic Extrapolation

Single-Shot Super-Resolution Phase Imaging Method Using Band-Limited Image and Its Fourier Transform Constraints via Analytic Extrapolation

Meta Shack–Hartmann wavefront sensor with large sampling density and large angular field of view: phase imaging of complex objects

Shack–Hartmann wavefront sensors measure the local slopes of an incoming wavefront based on the displacement of focal spots created by a lenslet array, serving as key components for adaptive optics for astronomical and biomedical imaging. Traditionally, the challenges in increasing the density and the curvature of the lenslet have limited the use of such wavefront sensors in characterizing slowly varying wavefront structures. Here, we develop a metasurface-enhanced Shack–Hartmann wavefront sensor (meta SHWFS) to break this limit, considering the interplay between the lenslet parameters and the performance of SHWFS. We experimentally validate the meta SHWFS with a sampling density of 5963 per mm2 and a maximum acceptance angle of 8° which outperforms the traditional SFWFS by an order of magnitude. Furthermore, to the best of our knowledge, we demonstrate the first use of a wavefront sensing scheme in single-shot phase imaging of highly complex patterns, including biological tissue patterns. The proposed approach opens up new opportunities in incorporating exceptional light manipulation capabilities of the metasurface platform in complex wavefront characterization.

Single-shot differential phase contrast microscopy using ring-shaped polarisation multiplexing illumination.

We propose a differential phase contrast microscopy that enables single-shot phase imaging for unstained biological samples. The proposed approach employs a ring-shaped LED array for polarisation multiplexing illumination and a polarisation camera for image acquisition. As such, multiple images of different polarisation angles can be simultaneously captured with a single shot. Through polarisation demultiplexing, the sample phase can therefore be recovered from the single-shot measurement. Both simulations and experiments demonstrate the effectiveness of the approach. We also demonstrate that ring-shaped illumination enables higher contrast and lower-distortion imaging results than disk-shaped illumination does. The proposed single-shot approach potentially enables phase contrast imaging for live cell samples in vitro. Lay Description: We propose a microscopy that enables imaging of transparent samples, unstained cells, etc. We demonstrate that the proposed method enables higher contrast and lower-distortion imaging results than conventional methods, and significantly improves imaging efficiency. The proposed method potentially enables dynamic imaging for live cell samples in vitro.

Accessible low-cost, open-source, single-shot phase imaging implemented on an openFrame-based microscope

Accessible low-cost, open-source, single-shot phase imaging implemented on an openFrame-based microscope

Hard X-ray stereographic microscopy for single-shot differential phase imaging.

The characterisation of fast phenomena at the microscopic scale is required for the understanding of catastrophic responses of materials to loads and shocks, the processing of materials by optical or mechanical means, the processes involved in many key technologies such as additive manufacturing and microfluidics, and the mixing of fuels in combustion. Such processes are usually stochastic in nature and occur within the opaque interior volumes of materials or samples, with complex dynamics that evolve in all three dimensions at speeds exceeding many meters per second. There is therefore a need for the ability to record three-dimensional X-ray movies of irreversible processes with resolutions of micrometers and frame rates of microseconds. Here we demonstrate a method to achieve this by recording a stereo phase-contrast image pair in a single exposure. The two images are combined computationally to reconstruct a 3D model of the object. The method is extendable to more than two simultaneous views. When combined with megahertz pulse trains of X-ray free-electron lasers (XFELs) it will be possible to create movies able to resolve 3D trajectories with velocities of kilometers per second.

Single-Shot High-Throughput Phase Imaging with Multibeam Array Interferometric Microscopy

High-throughput microscopic imaging is highly desirable in biomedical applications. Advances in computational microscopy have achieved high space-bandwidth products and even permitted gigapixel imaging in a stepwise fashion, yet temporal resolution remains challenging for investigating live-sample dynamics. Here, we report multibeam array interferometric microscopy (MAIM) for a single-shot high space-bandwidth product. The MAIM method overcomes the limitations of conventional digital holographic microscopy, providing complex field reconstruction with a maximum 5-fold field of view (FOV) increase in a single camera acquisition, while maintaining sub-nanometer optical path-length stability. This is achieved by integrating common-path holographic microscopy, multibeam interference technology, and holographic multiplexing technology. The temporal resolving power of MAIM is significantly higher than that of computational illumination microscopy. MAIM has major advantages over previous holographic multiplexing techniques in that it integrates more wavefronts and offers high temporal stability. The fundamentals of MAIM are analyzed theoretically. As a demonstration, we build MAIM prototypes to increase the FOV by factors of 5, 4, and 3, respectively. We present proof-of-concept MAIM imaging results of both natural and artificial samples and show biomedical applications such as monitoring sub-cellular dynamical phenomena in flowing live erythrocytes in vitro and label-free microrefractometry imaging of unstained cancer tissue slices. MAIM gives rise to (ultra)fast or long-term (time-lapse) imaging of nanoscale dynamics of unstained live samples in vitro with a high throughput.

Second Harmonic Imaging Enhanced by Deep Learning Decipher

Wavefront sensing and reconstruction are widely used for adaptive optics, aberration correction, and high-resolution optical phase imaging. Traditionally, interference and/or microlens arrays are used to convert the optical phase into intensity variation. Direct imaging of distorted wavefront usually results in complicated phase retrieval with low contrast and low sensitivity. Here, a novel approach has been developed and experimentally demonstrated based on the phase-sensitive information encoded into second harmonic signals, which are intrinsically sensitive to wavefront modulations. By designing and implementing a deep neural network, we demonstrate the second harmonic imaging enhanced by deep learning decipher (SHIELD) for efficient and resilient phase retrieval. Inheriting the advantages of two-photon microscopy, SHIELD demonstrates single-shot, reference-free, and video-rate phase imaging with sensitivity better than {\lambda}/100 and high robustness against noises, facilitating numerous applications from biological imaging to wavefront sensing.

Single-shot phase imaging based on transport of intensity equation

In this paper, we demonstrate a cost effective set-up for transport of intensity equation (TIE)-based single-shot phase imaging. A Michelson interferometer like set-up has been utilized for optical implementation with light emitting diode as a light source. The mirrors used in the set-up are slightly tilted to obtain the two laterally separated defocused images as single-shot to the intensity-recording sensor. The experimental set-up does not require any costly optical instrument/module such as spatial light modulator. The experimental demonstration has been carried out with a micro-lens array. The adopted TIE algorithm has been verified with the simulation results of quadrature phase function.

Phase retrieval with extended field of view based on continuous phase modulation

In order to address two main obstacles that affect the practical application of coherent modulation imaging (CMI)i.e., the low signal-to-noise ratio (SNR) and limited field of view (FOV), a new algorithm providing extended FOV based on CMI is proposed. A weak scattering modulator was used instead of a binary random phase modulator with strong scattering ability, to improve the final resolution of CMI combined with probe scanning. An unlimited FOV was achieved in a noniterative manner, resulting in a superior SNR compared with ptychography. Compared with the original CMI with a binary random phase modulator, the errors decreased obviously when continuous phase plate was utilized based on simulation and experimental results. Moreover, the random speckles that are associated with coherent diffractive imaging could be effectively eliminated. The proposed algorithm facilitates single-shot or extended FOV phase imaging with a high SNR and high resolution.

Endoscopic diffraction phase microscopy.

In this Letter, we present, to our knowledge, the first endoscopic diffraction phase microscopy (eDPM) system. This instrument consists of a gradient-index-lens-based endoscope probe followed by a DPM module, which enables single-shot phase imaging at a single-cell-level resolution. Using the phase information provided by eDPM, we show that the geometric aberrations associated with the endoscope can be reduced by digitally applying a spectral phase filter to the raw data. The filter function is a linear combination of polynomials with weighting optimized to improve resolution. We validate the principle of the proposed method using reflective semiconductor samples and blood cells. This research extends the current scope of quantitative phase imaging applications, and proves its potential for future in vivo studies.

Subpixel reconstruction for single-shot phase imaging with coded diffraction.

We present an algorithm for reconstructing an object complex field with resolution below that of an image sensor (subpixel resolution) in single-shot diffractive imaging with coded diffraction. The algorithm employs subpixel phase retrieval and sparse regularization based on compressive sensing. This is useful for high-speed or high-sensitivity imaging using an image sensor with a low pixel count and/or a large pixel size. We experimentally demonstrated the proposed method with two types of moving objects.

Relaxation of mask design for single-shot phase imaging with a coded aperture.

We present a method of relaxing the conditions of mask design in single-shot phase imaging with a coded aperture (SPICA), for extending the applications of SPICA. SPICA, based on compressive sensing, enables the acquisition of wide, high-resolution optical complex fields in a single exposure without the need for reference light. In our previous work on SPICA, a coded aperture (CA) was implemented with only amplitude modulation, resulting in a low transmission factor and low light efficiency because of the need for an independent phase retrieval process in the reconstruction. We attempt to alleviate these limitations by adapting a reconstruction algorithm to directly associate the phase-retrieval process with a sparsity-based reconstruction. With this approach, it is possible to realize SPICA with an amplitude-modulation-based CA having a high transmission factor, a phase-modulation-based CA, and a complex-amplitude (amplitude and phase)-modulation-based CA. We verified the effectiveness of these relaxed CA designs numerically and experimentally.

Single-shot phase imaging with randomized light (SPIRaL).

We present a method for single-shot phase imaging with randomized light (SPIRaL). In SPIRaL, the complex (amplitude and phase) field of an object illuminated with a randomized coherent beam is captured with an image sensor, without the need for any reference light. The object field is retrieved from the single captured intensity image by a compressive sensing-based algorithm with a sparsity constraint. SPIRaL has higher observation speed, light efficiency, and flexibility of the implementation compared with previous methods. We demonstrate SPIRaL numerically and experimentally.

Experimental demonstration of single-shot phase imaging with a coded aperture.

We experimentally demonstrated single-shot phase imaging with a coded aperture (SPICA), which connects digital holography and coherent diffractive imaging based on compressive sensing to realize the advantages of both methods simultaneously. SPICA allows the observation of a complex field with a simple, single-shot optical setup that does not need reference light and does not suffer from losses associated with the field-of-view and spatial resolution. Experiments showed the promising capabilities of SPICA for single-shot holographic imaging.

Multidimensional object acquisition by single-shot phase imaging with a coded aperture.

We propose a generalized framework for quantitatively acquiring multidimensional complex objects based on single-shot phase imaging with a coded aperture (SPICA). In multidimensional SPICA, a propagating field from a multidimensional complex object is sieved by a coded aperture, the sieved field is modulated by an optical element, which is called coding optics, and then the resultant field is captured by a monochrome image sensor. The original complex field is reconstructed from the single captured intensity image by a phase retrieval algorithm with a support constraint of the coded aperture and a sparsity-based reconstruction algorithm based on compressive sensing. We also present theoretical conditions for the proposed method. As a demonstration, we numerically verified an application of this generalized framework for single-shot acquisition of depth-variant multispectral objects.

Single-shot phase imaging with a coded aperture.

We present a method of quantitatively acquiring a large complex field, containing not only amplitude information but also phase information, based on single-shot phase imaging with a coded aperture (SPICA). In SPICA, the propagating field from an object illuminated by partially coherent visible light is sieved by a coded mask, and the sieved field propagates to an image sensor, where it is captured. The sieved field is recovered from the single captured intensity image via a phase retrieval algorithm with an amplitude support constraint using the mask pattern, and then the object's complex field is reconstructed from the recovered sieved field by an algorithm employing a sparsity constraint based on compressive sensing. The system model and the theoretical bounds of SPICA are derived. We also verified the concept with numerical demonstrations.

Single-shot x-ray phase imaging with grating interferometry and photon-counting detectors

In this Letter, we present a single-shot approach to quantitatively retrieve x-ray absorption and phase shift in grating interferometry. The proposed approach makes use of the energy-resolving capability of x-ray photon-counting detectors. The retrieval method is derived and presented and is tested based on numerical simulations, including photon shot noise. The good agreement between retrieval results and theoretical values confirms the feasibility of the presented approach.

Diffraction phase microscopy for quantifying cell structure and dynamics

We have developed diffraction phase microscopy as a new technique for quantitative phase imaging of biological structures. The method combines the principles of common path interferometry and single-shot phase imaging and is characterized by subnanometer path-length stability and millisecond-scale acquisition time. The potential of the technique for quantifying nanoscale motions in live cells is demonstrated by experiments on red blood cells.