Application Of Imaging System Research Articles

Liquid crystal lens with four driving voltages and its applications in imaging system with rectangular aperture

Liquid crystal (LC) lens has the characteristic of variable focal length. Many studies have demonstrated that electronically controlled focusing without mechanical movements can be realized by using LC lenses in imaging system. In this paper, a four-electrodes LC lens with a rectangular aperture is applied to focus. The aperture’s aspect ratio of the LC lens can be designed arbitrarily so that installing it with the periscope lens in phones becomes possible.

Nighttime Chlorophyll Fluorescence Imaging of Dark-Adapted Plants Using a Robotic Field Phenotyping Platform.

Photosynthetic efficiency is increasingly recognized as an integration of plant responses to dynamic environments, establishing the need for data sets from both field trials and controlled environments. A robotic field scanner phenotyping platform at the University of Arizona is equipped with a high-throughput chlorophyll fluorescence imaging system capable of collecting data on field trials for genetic studies of a photosynthetic trait (Fv/Fm). A description of the fluorescence imaging system is provided in addition to methods for measurements across experimental field plots and a test to determine the impact of variable plant heights. The overall focus is on aspects of field applications of a chlorophyll fluorescence imaging system that differ from analogous systems in controlled environments.

Toward Unaligned Guided Thermal Super-Resolution.

Thermography is a useful imaging technique as it works well in poor visibility conditions. High-resolution thermal imaging sensors are usually expensive and this limits the general applicability of such imaging systems. Many thermal cameras are accompanied by a high-resolution visible-range camera, which can be used as a guide to super-resolve the low-resolution thermal images. However, the thermal and visible images form a stereo pair and the difference in their spectral range makes it very challenging to pixel-wise align the two images. The existing guided super-resolution (GSR) methods are based on aligned image pairs and hence are not appropriate for this task. In this paper, we attempt to remove the necessity of pixel-to-pixel alignment for GSR by proposing two models: the first one employs a correlation-based feature-alignment loss to reduce the misalignment in the feature-space itself and the second model includes a misalignment-map estimation block as a part of an end-to-end framework that adequately aligns the input images for performing guided super-resolution. We conduct multiple experiments to compare our methods with existing state-of-the-art single and guided super-resolution techniques and show that our models are better suited for the task of unaligned guided super-resolution from very low-resolution thermal images.

Hyperspectral Snapshot Compressive Imaging With Dense Back-Projection Joint Attention Network

Hyperspectral Snapshot Compressive Imaging (SCI) system encodes three-dimensional hyperspectral images into a single two-dimensional snapshot measurement and then decodes the underlying 3D hyperspectral images by solving the compressive sensing reconstruction problem. Practical applications of SCI imaging systems require fast and high-quality reconstruction. To meet this requirement, we propose a novel encoder and decoder network with dense back-projection joint attention for hyperspectral SCI. The main contributions of our network lie in two aspects. First, we propose a dense back-projection module and deploy it in an encoder with five scales. It computes the back-projection between each scale and all its preceding scales, thereby fusing complementary information between different scales for efficient reconstruction. Second, we design a spatial-spectral attention module and deploy it in the decoder to boost reconstruction quality. By exploiting a cascade of spatial-spectral attention, it can efficiently capture spatial and spectral correlations in hyperspectral images with a low volume of parameters. In addition, a compound loss, including the reconstruction loss and the spatial-spectral total variation loss, is designed to guide network learning in an end-to-end manner. Intensive experiments on simulation and real data show that our method has obvious advantages over multiple state-of-the-art methods, achieving a significant improvement in reconstruction quality and a substantial reduction in running time.

Electrically Tunable Lens (ETL)-Based Variable Focus Imaging System for Parametric Surface Texture Analysis of Materials.

Electrically tunable lenses (ETLs) are those with the ability to alter their optical power in response to an electric signal. This feature allows such systems to not only image the areas of interest but also obtain spatial depth perception (depth of field, DOF). The aim of the present study was to develop an ETL-based imaging system for quantitative surface analysis. Firstly, the system was calibrated to achieve high depth resolution, warranting the accurate measurement of the depth and to account for and correct any influences from external factors on the ETL. This was completed using the Tenengrad operator which effectively identified the plane of best focus as demonstrated by the linear relationship between the control current applied to the ETL and the height at which the optical system focuses. The system was then employed to measure amplitude, spatial, hybrid, and volume surface texture parameters of a model material (pharmaceutical dosage form) which were validated against the parameters obtained using a previously validated surface texture analysis technique, optical profilometry. There were no statistically significant differences between the surface texture parameters measured by the techniques, highlighting the potential application of ETL-based imaging systems as an easily adaptable and low-cost alternative surface texture analysis technique to conventional microscopy techniques.

High‐Efficiency Full‐Space Complex‐Amplitude Metasurfaces Enabled by a Bi‐Spectral Single‐Substrate‐Layer Meta‐Atom

AbstractFull‐space metasurfaces have attracted significant interest due to their unprecedented abilities to tailor the electromagnetic wavefronts in both transmission and reflection half‐spaces. However, it remains difficult and challenging to achieve high‐efficiency complex‐amplitude modulation within a single‐substrate‐layer structure for circularly polarized (CP) waves, which can enhance the power distribution regulation. Herein, a universal design strategy for the frequency‐multiplexed full‐space meta‐device is proposed by employing a single‐substrate‐layer meta‐atom with complex‐amplitude modulations. The full‐space metasurface is composed of a subwavelength‐thickness substrate and two discrepant metallic layers, where a modified complementary split‐ring resonator and an electric field coupled resonator are selected to refract and reflect the CP incidences to the cross‐ and co‐polarized components at two distinct frequencies. Based on this emerging meta‐atom, a multifunctional bi‐spectral metasurface is designed and verified by both full‐wave simulations and experiments, which generates the quad‐vortex beam and the hologram in transmission and reflection modes, respectively. The proposed method employs a single‐substrate layer to maintain high efficiency, while incorporating the complex‐amplitude modulation, which has potential applications in imaging and communication systems.

Multi-curved variable-focus liquid lens

We demonstrate a multi-curved liquid lens with movable liquid–liquid(L–L)​ interface, which has a wide range of focal length. Due to movable L–L interface, the proposed lens can also be used as a single lens to achieve zoom function. The movement of the L–L interface can be achieved by controlling the flow of the liquid, which in turn changes the object distance and image distance to achieve the desired magnification. We fabricated a prototype based on this concept. The experimental result shows that when the movement distance of the L–L interface is ∼10 mm, the shortest positive and negative focal lengths of the lens are 9.3 mm and −8 mm, respectively, and the zoom ratio is 1.3×. The proposed multi-curved variable-focus lens simplifies the zoom imaging system, and its widespread applications in imaging systems are predictable.

Robust Single-Probe Quantitative Ultrasonic Imaging System With a Target-Aware Deep Neural Network.

The speed of sound (SoS) has great potential as a quantitative imaging biomarker since it is sensitive to pathological changes in tissues. In this paper, a target-aware deep neural (TAD) network reconstructing an SoS image quantitatively from pulse-echo phase-shift maps gathered from a single conventional ultrasound probe is presented. In the proposed TAD network, the reconstruction process is guided by feature maps created from segmented target images for accuracy and contrast. In addition, the feature extraction process utilizes phase difference information instead of direct pulse-echo radio frequency (RF) data for robust image reconstruction against noise in the pulse-echo data. The TAD network outperforms the fully convolutional network in root mean square error (RMSE), contrast-to-noise ratio (CNR), and structural similarity index (SSIM) in the presence of nearby reflectors. The measured RMSE and CNR are 5.4 m/s and 22 dB, respectively with the tissue attenuation coefficient of 2 dB/cm/MHz, which are 72% and 13 dB improvement over the state of the art design in RMSE and CNR, respectively. In the in-vivo test, the proposed method classifies the tissues in the neck area using SoS with a p-value below 0.025. The proposed TAD network is the most accurate and robust single-probe SoS image reconstruction method reported to date. The accuracy and robustness demonstrated by the proposed SoS imaging method open up the possibilities of wide-spread clinical application of the single-probe SoS imaging system.

Vanadium dioxide-assisted switchable broadband terahertz metasurface for polarization conversion and phase modulation

Switchable metasurfaces with diversified functionalities have become an emerging research area owing to its potential for realizing integrated and miniature meta-devices. Although great efforts have been devoted in this area, switchable metasurfaces with diversified functionalities still require dealing with formidable challenges. In this paper, a switchable broadband terahertz (THz) metasurface with multiple functionalities is proposed utilizing the phase transition property of vanadium dioxide (VO2), and it can switch functionalities by changing the state of VO2 from metal to insulator thermally. The simulation results demonstrate that when VO2 is in metallic state at the temperature of 400 K, the designed metasurface works as a half wave plane with polarization conversion ratio more than 90% at THz frequency band ranging from 0.66 to 1.44 THz. When VO2 is in insulating state at the temperature of 300 K, the metasurface can flexibly control the phase of the THz wave. As a proof of concept, several devices with high performance for realizing anomalous reflection, diffuse scattering, vortex beam and beam-focusing are numerically investigated. The proposed metasurface has potential applications in THz imaging, sensing and other intellectual systems for photonics integration.

The Application of the Big Data Medical Imaging System in Improving the Medical and Health Examination.

To explore the application effect of the big data medical imaging tertiary diagnostic system in improving the medical and health examination, cases in township health centers were collected by the medical imaging tertiary diagnosis system. Clinical cases examined by the tertiary diagnostic system of big data medical imaging will be set as the observation group. Clinical cases not involved in the tertiary diagnostic system of big data medical imaging were set as the control group. The qualified rate, film positive rate, and film diagnosis accuracy between the two groups are compared, and X-ray perspective, X-ray examination, and CT multiple medical imaging examinations are used in two groups. The experimental results showed that the pass rate was 86.57%, positive rate was 72.32%, and diagnosis rate was 80.17%. Pass rate, positive rate, and diagnostic accuracy were higher than the control group (P < 0.05). X-line film is the most cost effective. CT examination has a high diagnostic sensitivity and can achieve a clear diagnosis of the benign and malignant diseases. The three-level diagnosis system of medical imaging has significantly improved and improved the technical level in the medical and health examination, which has good practical value.

Spatial Frequency Domain Imaging System Calibration, Correction and Application for Pear Surface Damage Detection.

Spatial frequency domain imaging (SFDI) is a non-contact wide-field optical imaging technique for optical property detection. This study aimed to establish an SFDI system and investigate the effects of system calibration, error analysis and correction on the measurement of optical properties. Optical parameter characteristic measurements of normal pears with three different damage types were performed using the calibrated system. The obtained absorption coefficient μa and the reduced scattering coefficient μ’s were used for discriminating pears with different surface damage using a linear discriminant analysis model. The results showed that at 527 nm and 675 nm, the pears’ quadruple classification (normal, bruised, scratched and abraded) accuracy using the SFDI technique was 92.5% and 83.8%, respectively, which has an advantage compared with the conventional planar light classification results of 82.5% and 77.5%. The three-way classification (normal, minor damage and serious damage) SFDI technique was as high as 100% and 98.8% at 527 nm and 675 nm, respectively, while the classification accuracy of conventional planar light was 93.8% and 93.8%, respectively. The results of this study indicated that SFDI has the potential to detect different damage types in fruit and that the SFDI technique has a promising future in agricultural product quality inspection in further research.

Application of an indocyanine green surgical fluorescence imaging system in sentinel lymph node biopsy of acral malignant melanoma.

BackgroundRegional lymph node status is an independent influencing factor for the prognosis of acral malignant melanoma, and the accuracy of sentinel lymph node biopsy (SLNB) is directly related to the judgment of regional lymph node status. This study aimed to explore the application value of indocyanine green (ICG) surgical fluorescence imaging system in the SLNB of acral malignant melanoma.MethodsA total of 34 patients with acral malignant melanoma were admitted to the Department of Burn and Plastic Surgery in Jiangsu Provincial People’s Hospital from January 2020 to March 2020. Among these patients, 22 required SLNB. ICG and methylene blue (MB) were combined to intraoperatively trace the sentinel lymph nodes (SLNs). The total number of SLNs detected during the operation was counted. We compared the number, detection rate, as well as the detection rate and false negative rate of positive SLNs of SLNs detected by ICG, MB, and ICG combined with MB.ResultsA total of 56 SLNs were detected in the 22 patients, among which 55 were detected by ICG (98%), 41 were detected by MB (71%), and 56 (100%) were detected by ICG combined with MB, and the average number of SLNs were 2.5, 1.64, and 2.55, respectively. A total of nine SLNs were detected, of which nine were detected by ICG (100%), seven by MB (78%), and nine by ICG combined with MB (100%). Patients with negative SLNs had no recurrence at the 6-month follow-up.ConclusionsCompared with MB, the ICG fluorescent imaging system can improve the detection rate of SLNs in patients with acral malignant melanoma. Also, ICG combined with MB was superior to ICG alone.

Active Modulating the Intensity of Bifocal Metalens with Electrically Tunable Barium Titanate (BTO) Nanofins.

The multifocal metalens with an adjustable intensity has great potential in many applications such as the multi-imaging system, but it is less studied. In this paper, by combining the electro-optic material barium titanate (BTO) with the Pancharatnam-Berry phase, an electrically modulated bifocal metalens in a visible light band is innovatively proposed. Due to the electro-optic effect, we can control the refractive index of the BTO nanofins to vary between 2.4 and 3.07 by applying different voltages (0–60 V). Thus, the method of modulating the intensity ratio of the two focal points is applying an electric field. It is different from using phase change materials or changing the ellipticity of incident light, the strategies proposed in previous studies. Moreover, when the applied voltage is 0 V or 60 V, the bifocal metalens becomes a single focal metalens with different focal lengths, and the full width at half maximum of each focal point is close to the diffraction limit. It has great potential in applications of optical storage, communication and imaging systems.

Detection and 2D Imaging of Dopamine Distribution Using a Closed Bipolar Electrode System by Applying a Cathodic Luminophore

AbstractA 2D imaging system using closed bipolar electrodes (cBPEs) and electrochemiluminescence (ECL) is expected to realize high spatio‐temporal resolution imaging. However, imaging of the distributions of molecules that cause an oxidation reaction on the electrode surface was not achieved by the cBPE/ECL system because the conventionally used luminophore can generate ECL only by an oxidation reaction. In this paper, we propose to implement a cathodic luminophore, [Ru(bpy)3]Cl2/glutathione disulfide (GSSG) producing ECL by reduction reaction into the cBPE/ECL system to enable detection and 2D imaging of dopamine, which is an oxidizable redox species and an important neurotransmitter. The applicability of [Ru(bpy)3]Cl2/GSSG for dopamine detection using a single cBPE was shown and its electrochemical properties were discussed. In addition, the demonstration of the 2D imaging of dopamine was performed using a cBPE array. These results show the potential to greatly expand the applicability of detection and imaging systems using cBPE/ECL.

Rotationally tunable varifocal 3D metalens.

Varifocal optics have a variety of applications in imaging systems. Metasurfaces offer control of the phase, transmission, and polarization of light using subwavelength engineered structures. However, conventional metasurface designs lack dynamic wavefront shaping which limits their application. In this work, we design and fabricate 3D doublet metalenses with a tunable focal length. The phase control of light is obtained through the mutual rotation of the singlet structures. Inspired by Moiré lenses, the proposed structure consists of two all-dielectric metasurfaces. The singlets have reverse-phase profiles resulting in the cancellation of the phase shift in the nominal position. In this design, we show that the mutual rotation of the elements produces different wavefronts with quadratic radial dependence. Thus, an input plane wave is converted to spherical wavefronts whose focal length depends on the rotation. We use a combination of a nanopillar and a phase plate as the unit cell structure working at a wavelength of 1500 nm. Our design holds promise for a range of applications such as zoom lenses, microscopy, and augmented reality.

Development and application of a tender X-ray ptychographic coherent diffraction imaging system on BL27SU at SPring-8.

Ptychographic coherent diffraction imaging (CDI) allows the visualization of both the structure and chemical state of materials on the nanoscale, and has been developed for use in the soft and hard X-ray regions. In this study, a ptychographic CDI system with pinhole or Fresnel zone-plate optics for use in the tender X-ray region (2-5 keV) was developed on beamline BL27SU at SPring-8, in which high-precision pinholes optimized for the tender energy range were used to obtain diffraction intensity patterns with a low background, and a temperature stabilization system was developed to reduce the drift of the sample position. A ptychography measurement of a 200 nm thick tantalum test chart was performed at an incident X-ray energy of 2.500 keV, and the phase image of the test chart was successfully reconstructed with approximately 50 nm resolution. As an application to practical materials, a sulfur polymer material was measured in the range of 2.465 to 2.500 keV including the sulfur K absorption edge, and the phase and absorption images were successfully reconstructed and the nanoscale absorption/phase spectra were derived from images at multiple energies. In 3 GeV synchrotron radiation facilities with a low-emittance storage ring, the use of the present system will allow the visualization on the nanoscale of the chemical states of various light elements that play important roles in materials science, biology and environmental science.

Photonic Generation of Wideband Chirped Microwave Waveforms

A chirped microwave waveform with a large time-bandwidth product (TBWP) can find important applications in modern radar systems and microwave imaging systems. Microwave photonics, a field that studies the generation and processing of microwave signals in the optical domain to take advantage of the ultra-wide bandwidth offered by photonics, has been considered an effective solution for high-frequency and large-bandwidth microwave waveform generation. In this paper, an overview on photonic generation of wideband chirped microwave waveforms is provided. Three major methods are discussed including chirped microwave waveform generation based on spectral shaping and frequency-to-time (SS-FTT) mapping, frequency and bandwidth multiplication, and Fourier-domain mode-locking of an optoelectronic oscillator (OEO). The performance of the techniques for chirped microwave waveform generation is studied. Techniques to generate chirped microwave waveforms based on photonic integrated circuits (PICs) are also discussed.

Study on the characteristics of microcirculation in the site of pressure ulcer in patients with spinal cord injury.

To investigate the characteristics of pressure ulcer microcirculation in SCI patients with pressure ulcer, and to provide evidence for the treatment of pressure ulcer in patients with SCI. Group 1 (n = 12) SCI patients with pressure ulcer, 23 pressure ulcers were included. Group 2 (n = 15) SCI patients without pressure ulcer and the control group (n = 16) healthy adults. The application of laser Doppler perfusion imaging system (Moor FLPI) detector to the microcirculation perfusion of the sacrum area of the control group, the observation group 2 and the pressure ulcer site of the observation group 1, record the microcirculation perfusion (PU), The data of microcirculation perfusion (PU) were compared and analyzed. The correlation between microcirculation perfusion and healing time of pressure ulcer was analyzed. (1) The microcirculation perfusion was highest in the pressure ulcer center. (2) SCI patients and healthy adults had no significant difference of microcirculation perfusion at sacrococcygeal skin. (3) The lower the microcirculation perfusion of the pressure ulcer center, the longer the healing time of pressure ulcer. The healing time and the microcirculation perfusion of pressure ulcer center was negatively correlated. Microcirculation perfusion detection is a noninvasive and effective method for the determination of the scope of pressure ulcer, detection and direction judgment of pressure ulcer sinus tract, monitoring and guidance of pressure ulcer treatment, and prediction of the healing time of pressure ulcer.

Vector-apodizing phase plate coronagraph: design, current performance, and future development [Invited

Over the last decade, the vector-apodizing phase plate (vAPP) coronagraph has been developed from concept to on-sky application in many high-contrast imaging systems on 8 m class telescopes. The vAPP is a geometric-phase patterned coronagraph that is inherently broadband, and its manufacturing is enabled only by direct-write technology for liquid-crystal patterns. The vAPP generates two coronagraphic point spread functions (PSFs) that cancel starlight on opposite sides of the PSF and have opposite circular polarization states. The efficiency, that is, the amount of light in these PSFs, depends on the retardance offset from a half-wave of the liquid-crystal retarder. Using different liquid-crystal recipes to tune the retardance, different vAPPs operate with high efficiencies (${\gt}96\%$) in the visible and thermal infrared (0.55 µm to 5 µm). Since 2015, seven vAPPs have been installed in a total of six different instruments, including Magellan/MagAO, Magellan/MagAO-X, Subaru/SCExAO, and LBT/LMIRcam. Using two integral field spectrographs installed on the latter two instruments, these vAPPs can provide low-resolution spectra (${\rm{R}} \sim 30$) between 1 µm and 5 µm. We review the design process, development, commissioning, on-sky performance, and first scientific results of all commissioned vAPPs. We report on the lessons learned and conclude with perspectives for future developments and applications.

Programmable Amplitude‐Coding Metasurface with Multifrequency Modulations

Recently, programmable metasurfaces have aroused great attention for various applications such as beam manipulation, wireless communication, and holograms by modulating the spatial phase or amplitude. However, programmable amplitude‐coding modulations have rarely been investigated due to the difficulty in realizing dynamic control of amplitude. Herein, a real‐time programmable amplitude‐coding metasurface with multifrequency modulation is proposed by integrating PIN diodes and chip attenuators to the metaelement. The element is encoded as “11,” “10,” and “00,” corresponding to the ON/OFF states of two diodes. By switching the two states of the PIN diode, the metaelement exhibits distinctly reflected amplitude responses in three frequencies (2.98, 4.11, and 5.73 GHz). For the whole metasurface, the magnitude of the reflected beam can be modulated with some specific coding patterns. To verify the performance, six coding patterns with 10 × 10 metaelements are designed, and four of them are measured. Experimental results are fundamentally consistent with theoretical designs and simulations. Further a wireless communication demonstration is designed and implemented to perform direct modulation of digital signals without using mixers required in the conventional wireless communication systems. It is envisioned that this work will find applications in new architecture encrypted communication and imaging systems.