Single exposure lensless subpixel phase imaging (original) (raw)
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Optics Express, 2020
Design and optimization of lensless phase-retrieval optical system with phase modulation of free-space propagation wavefront is proposed for subpixel imaging to achieve super-resolution reconstruction. Contrary to the traditional super-resolution phase-retrieval, the method in this paper requires a single observation only and uses the advanced Super-Resolution Sparse Phase Amplitude Retrieval (SR-SPAR) iterative technique which contains optimized sparsity based filters and multi-scale filters. The successful object imaging relies on modulation of the object wavefront with a random phase-mask, which generates coded diffracted intensity pattern, allowing us to extract subpixel information. The system’s noise-robustness was investigated and verified. The super-resolution phase-imaging is demonstrated by simulations and physical experiments. The simulations included high quality reconstructions with super-resolution factor of 5, and acceptable at factor up to 9. By physical experiments ...
SSR-PR: Single-shot Super-Resolution Phase Retrieval based two prior calibration tests
2021
We propose a novel approach and algorithm based on two preliminary tests of the optical system elements to enhance the super-resolved complex-valued imaging. The approach is developed for inverse phase imaging in a single-shot lensless optical setup. Imaging is based on wavefront modulation by a single binary phase mask. The preliminary tests compensate errors in the optical system and correct a carrying wavefront, reducing the gap between real-life experiments and computational modeling, which improve imaging significantly both qualitatively and quantitatively. These two tests are performed for observation of the laser beam and phase mask along, and might be considered as a preliminary system calibration. The corrected carrying wavefront is embedded into the proposed iterative Single-shot Super-Resolution Phase Retrieval (SSR-PR) algorithm. Improved initial diffraction pattern upsampling, and a combination of sparse and deep learning based filters achieves the super-resolved recons...
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.
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 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.
Lensless imaging through multiple phase patterns illumination
Journal of biomedical optics, 2017
A stable optical system is required to acquire a high-quality image. A motionless lensless setup is designated to obtain high-resolution and large field of view images. The sample is sequentially illuminated with multiple random phase patterns, and the recorded images are subtracted from the system calibration images correspondingly. The resultant images are propagated to the sample plane. The summation of all images yields a final image with resolution of ∼4 μm, field of view of ∼15 mm2, and better signal-to-noise ratio. This technique provides a compact, stable, and cost-effective optical system.
Enhanced wavefront reconstruction by random phase modulation with a phase diffuser
Optics and Lasers in Engineering, 2011
A phase retrieval technique for enhanced wavefront reconstruction using random phase modulation and a phase diffuser is proposed. The speckle field generated is sampled at multiple axially displaced planes and the speckle patterns are used in an iterative algorithm based on the optical wave propagation in free space. The presentation of this technique is carried out using two setups. In the first setup, a diffuser plate is placed at the image plane of a metallic test object. The benefit of randomizing the phase of the object wave is the enhanced intensity recording due to high dynamic range of the diffusely scattered beam. The use of demagnification optics will also allow the investigations of relatively large objects. In the second setup, a transparent object is illuminated using a wavefront with random phase and constant amplitude by positioning the phase diffuser close to the object. The benefit of phase-only modulation is the increased resolution of the phase structures of the transparent test objects.
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.
Color lens-free imaging using multi-wavelength illumination based phase retrieval
Optics Express, 2020
Accurate image reconstruction in color lens-free imaging has proven challenging. The color image reconstruction of a sample is impacted not only by how strongly the illumination intensity is absorbed at a given spectral range, but also by the lack of phase information recorded on the image sensor. We present a compact and cost-effective approach of addressing the need for phase retrieval to enable robust color image reconstruction in lens-free imaging. The amplitude images obtained at transparent wavelength bands are used to estimate the phase in highly absorbed wavelength bands. The accurate phase information, obtained through our iterative algorithm, removes the color artefacts due to twin-image noise in the reconstructed image and improves image reconstruction quality to allow accurate color reconstruction. This could enable the technique to be applied for imaging of stained pathology slides, an important tool in medical diagnostics.
Non-iterative coherent diffractive imaging using a phase-shifting reference frame
New Journal of …, 2009
Lensless imaging is a high potential and currently intensely targeted research goal, in view of those fields of applications for which aberrationfree high-resolution lenses are not available, for example for x-ray imaging. A recently proposed (direct inversion) variant of lensless imaging combines the advantages of two classical routes toward lensless imaging, the high-resolution characteristics of iterative object reconstruction, and the direct and deterministic nature of holographic reconstruction. Here, we use a simple standard optical setup using visible wavelength, a lithographic test object and a phase-shifting reference object to demonstrate the approach. Importantly, we show that a phaseshifting reference object, instead of the absorption mask proposed earlier, is sufficient for object reconstruction. This is relevant in view of the much easier implementation in future x-ray applications.