Multi-angle Illumination Research Articles

Single-shot ultrafast phase retrieval photography.

Single-shot ultrafast photography is a powerful tool for science research and industry applications. In this Letter, a novel strategy for ultrafast imaging of two-dimensional complex (amplitude and phase) objects, which is termed single-shot ultrafast phase retrieval photography (SUP), is proposed and demonstrated. The key component of SUP is a silicon photonic integrated chip, which not only has the function of multi-angle illumination, but also provides ultra-short delays for each illumination source. Combined with an ultra-short pulse source and coherent diffraction imaging, SUP can realize ultrafast single-shot imaging. As a proof of concept, the self-developed multiplexed time delay illumination chip was used for experiments, and we demonstrated the reconstructing of a static complex-valued object with a frame sequence depth of 16 frames from single-shot ptychographic data.

Isotropic-resolution photoacoustic microscopy with multi-angle illumination.

We have developed photoacoustic microscopy (PAM) with three-dimensional (3D) micron-level spatial resolution. With multi-angle illumination, PAM images from different view angles can be simultaneously acquired for multi-view deconvolution, without the rotation of imaging targets. A side-by-side comparison of this multi-angle-illumination PAM (MAI-PAM) and conventional PAM, which share the same ultrasonic detector, was performed in phantoms and live mice. The phantom study showed that MAI-PAM achieved a high axial resolution of 3.7μm, which was 10-fold higher than that of conventional PAM and approached the lateral resolution of 2.7μm. Furthermore, the in vivo study demonstrated that MAI-PAM was able to image the 3D microvasculature with isotropic spatial resolution.

Invited Article: Mask-modulated lensless imaging with multi-angle illuminations

The use of multiple diverse measurements can make lensless phase retrieval more robust. Conventional diversity functions include aperture diversity, wavelength diversity, translational diversity, and defocus diversity. Here we discuss a lensless imaging scheme that employs multiple spherical-wave illuminations from a light-emitting diode array as diversity functions. In this scheme, we place a binary mask between the sample and the detector for imposing support constraints for the phase retrieval process. This support constraint enforces the light field to be zero at certain locations and is similar to the aperture constraint in Fourier ptychographic microscopy. We use a self-calibration algorithm to correct the misalignment of the binary mask. The efficacy of the proposed scheme is first demonstrated by simulations where we evaluate the reconstruction quality using mean square error and structural similarity index. The scheme is then experimentally tested by recovering images of a resolution target and biological samples. The proposed scheme may provide new insights for developing compact and large field-of-view lensless imaging platforms. The use of the binary mask can also be combined with other diversity functions for better constraining the phase retrieval solution space. We provide the open-source implementation code for the broad research community.

On-chip Microscopy Using Random Phase Mask Scheme

In this study, a simple and novel phase-retrieval scheme is implemented using multi-angle illumination to enhance the resolution of lensless microscopy. A random-phase mask (from 0 to 2π) precedes the sample to encode the information at the sensor plane. The sample is illuminated with multiple angles that are symmetrical along the optical axis of the system. The system is initially calibrated while recording the images without any sample at the corresponding multi angles. The two types of image are mutually subtracted, and the resultant images are summed at the sensor plane and backpropagated to the sample plane. The final image is free of the twin-image effect, and has a high signal-to-noise ratio owing to the multi angles of the illumination scheme. This scheme gives a resolution of ~4 micron for a large field-of-view (~15 mm2). The scheme is useful for robust imaging owing to the fast phase-retrieval method, and it enables a straightforward analytical reconstruction instead of using complicated iterative algorithms in a lensless microscopic setup.

Toward whole-body quantitative photoacoustic tomography of small-animals with multi-angle light-sheet illuminations.

Several attempts to achieve the quantitative photoacoustic tomography (q-PAT) have been investigated using point sources or a single-angle wide-field illumination. However, these schemes normally suffer from low signal-to-noise ratio (SNR) or poor quantification in imaging applications on large-size domains, due to the limitation of ANSI-safety incidence and incompleteness in the data acquisition. We herein present a q-PAT implementation that uses multi-angle light-sheet illuminations and calibrated recovering-and-averaging iterations. The scheme can obtain more complete information on the intrinsic absorption from the multi-angle illumination mode, and collect SNR-boosted photoacoustic signals in the selected planes from the wide-field light-sheet excitation. Therefore, the sliced absorption maps over whole body of small-animals can be recovered in a measurement-flexible, noise-robust and computation-economic way. The proposed approach is validated by phantom, ex vivo and in vivo experiments, exhibiting promising performances in image fidelity and quantitative accuracy for practical applications.

Lensless phase microscopy and diffraction tomography with multi-angle and multi-wavelength illuminations using a LED matrix.

We demonstrate lensless quantitative phase microscopy and diffraction tomography based on a compact on-chip platform, using only a CMOS image sensor and a programmable color LED matrix. Based on the multi-wavelength phase retrieval and multi-angle illumination diffraction tomography, this platform offers high quality, depth resolved images with a lateral resolution of 3.72μm and an axial resolution of 5μm, across a wide field-of-view of 24mm2. We experimentally demonstrate the success of our method by imaging cheek cells, micro-beads, and fertilized eggs of Parascaris equorum. Such high-throughput and miniaturized imaging device can provide a cost-effective tool for telemedicine applications and point-of-care diagnostics in resource-limited environments.

LED板状肋片散热器性能的方向效应

The plate-fin heat sink is widely used in LED lamp for application of multi-angle illumination. According to the key structures of a LED projection lamp,the orientation effects on heat dissipation performance of plate-fin heat sink with natural convection cooling were researched under 3driving currents and 7 inclination angles between illumination direction and gravity direction. Based on the validity and accuracy of numerical simulation verified by experimental results,the thermal mechanisms with respect to maximum excess temperature and temperature uniformity were investigated through analyzing temperature and flow data derived from numerical simulation. The obvious differences of air velocity distribution in the flow channel of fins are found among inclination angles,these differences are the main reason of sensitive orientation effect about maximum excess temperature and temperature uniformity. In addition,air velocity difference between upstream and downstream around the measuring point with maximum temperature can be used to quantitatively interpret the variation trend of temperature uniformity in different inclination angles. Furthermore,the effects of inclination angle and fin spacing on the maximum excess temperature were analyzed. The results showthat the heat dissipation performance of plate-fin heat sink with optimal fin spacing has high orientation sensitivity,so the study of orientation effects on the air flow and heat transfer of plate-fin heat sinks is an indispensable task in the thermal design of LED with multi-angle illumination function.

Lensfree On-chip Tomographic Microscopy Employing Multi-angle Illumination and Pixel Super-resolution

Tomographic imaging has been a widely used tool in medicine as it can provide three-dimensional (3D) structural information regarding objects of different size scales. In micrometer and millimeter scales, optical microscopy modalities find increasing use owing to the non-ionizing nature of visible light, and the availability of a rich set of illumination sources (such as lasers and light-emitting-diodes) and detection elements (such as large format CCD and CMOS detector-arrays). Among the recently developed optical tomographic microscopy modalities, one can include optical coherence tomography, optical diffraction tomography, optical projection tomography and light-sheet microscopy. 1-6 These platforms provide sectional imaging of cells, microorganisms and model animals such as C. elegans, zebrafish and mouse embryos. Existing 3D optical imagers generally have relatively bulky and complex architectures, limiting the availability of these equipments to advanced laboratories, and impeding their integration with lab-on-a-chip platforms and microfluidic chips. To provide an alternative tomographic microscope, we recently developed lensfree optical tomography (LOT) as a high-throughput, compact and cost-effective optical tomography modality. 7 LOT discards the use of lenses and bulky optical components, and instead relies on multi-angle illumination and digital computation to achieve depth-resolved imaging of micro-objects over a large imaging volume. LOT can image biological specimen at a spatial resolution of <1 μm x <1 μm x <3 μm in the x, y and z dimensions, respectively, over a large imaging volume of 15-100 mm3, and can be particularly useful for lab-on-a-chip platforms.

Lensfree On-chip Tomographic Microscopy Employing Multi-angle Illumination and Pixel Super-resolution

Tomographic imaging has been a widely used tool in medicine as it can provide three-dimensional (3D) structural information regarding objects of different size scales. In micrometer and millimeter scales, optical microscopy modalities find increasing use owing to the non-ionizing nature of visible light, and the availability of a rich set of illumination sources (such as lasers and light-emitting-diodes) and detection elements (such as large format CCD and CMOS detector-arrays). Among the recently developed optical tomographic microscopy modalities, one can include optical coherence tomography, optical diffraction tomography, optical projection tomography and light-sheet microscopy. These platforms provide sectional imaging of cells, microorganisms and model animals such as C. elegans, zebrafish and mouse embryos. Existing 3D optical imagers generally have relatively bulky and complex architectures, limiting the availability of these equipments to advanced laboratories, and impeding their integration with lab-on-a-chip platforms and microfluidic chips. To provide an alternative tomographic microscope, we recently developed lensfree optical tomography (LOT) as a high-throughput, compact and cost-effective optical tomography modality. LOT discards the use of lenses and bulky optical components, and instead relies on multi-angle illumination and digital computation to achieve depth-resolved imaging of micro-objects over a large imaging volume. LOT can image biological specimen at a spatial resolution of <1 μm x <1 μm x <3 μm in the x, y and z dimensions, respectively, over a large imaging volume of 15-100 mm(3), and can be particularly useful for lab-on-a-chip platforms.

Multi-angle illumination with pixel super-resolution enables lensfree on-chip tomography

Multi-angle illumination with pixel super-resolution enables lensfree on-chip tomography

Tensor-based subspace learning and its applications in multi-pose face synthesis

Facial pose synthesis is applied to generate much required information for several applications, such as public security, facial cosmetology, etc. How to synthesize facial pose images from one image accurately without spatial information is still a challenging problem. In this paper we propose a tensor-based subspace learning method (TSL) for synthesizing human multi-pose facial images from a single two-dimensional image. In the proposed TSL method, two-dimensional multi-pose images in the database are previously organized into a tensor form and a tensor decomposition technique is applied to build projection subspaces. In synthesis processing, the input two-dimensional image is first projected into its corresponding projection subspace to get an identity vector and then the identity vector is used to generate other novel pose images. Our technique is applied on KAO-Ritsumeikan Multi-angle View, Illumination and Cosmetic Facial Database (MaVIC) and experiment results show the effectiveness of our proposed method for facial pose synthesis.

Interference artifact reduction by multiangle illumination in millimeter wave images: Model and experimental validation

AbstractSuccessful interference artifact reduction in mm‐wave images by multiangle illumination is presented. Imaging simulations were performed in a Fourier‐domain coherent optics framework. Both the model and experimental results show that interference patterns highly depend on the illumination angles and can be reduced by simply processing the multiangle images. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1845–1848, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24498