Field Of Imaging System Research Articles

Design of a Novel Microlens Array and Imaging System for Light Fields.

Light field cameras are unsuitable for further acquisition of high-quality images due to their small depth of field, insufficient spatial resolution, and poor imaging quality. To address these issues, we proposed a novel four-focal-square microlens and light field system. A square aspheric microlens array with four orthogonal focal lengths was designed, in which the aperture of a single lens was 100 μm. The square arrangement improves pixel utilization, the four focal lengths increase the depth of field, and the aspheric improves image quality. The simulations demonstrate pixel utilization rates exceeding 90%, depth-of-field ranges 6.57 times that of a single focal length, and image quality is significantly improved. We have provided a potential solution for improving the depth of field and image quality of the light field imaging system.

A High-Resolution Magnetic Field Imaging System Based on the Unpackaged Hall Element Array

We have designed a high-resolution magnetic field imaging system using 256 unpackaged Hall elements. These unpackaged Hall elements are arranged in a Hall linear array, and the distance between adjacent elements reaches 255 µm. The sensitivity of the unpackaged Hall element array can be adjusted using a computer to measure magnetic environments with different magnetic field strengths. High-resolution magnetic field images of 256 × 256 pixels can be generated by moving the array using the X–Y axis motorized rail. This spatial resolution can reach 99.61 pixels per inch (ppi). This rail allows for the spatial resolution of the system to be further increased to 199.22 ppi by using a special movement route. In the experiments, we employ this system to image magnetized metal scissors, and the result displays the structural features of the scissor surface. We also detected the magnetic suction wireless charging coil inside an Apple phone. The image obtained shows the shape of the coil and the gap between the magnets. The high-resolution magnetic imaging system displays the magnetic characteristics of the sample very well and easily obtains information about small-shaped structures and defects on the sample surface. This provides the system with potential in several fields such as quality inspection, security, biomedicine, and detection imaging.

Millimeter-Wave Band Electro-Optical Imaging System Using Polarization CMOS Image Sensor and Amplified Optical Local Oscillator Source.

In this study, we developed and demonstrated a millimeter-wave electric field imaging system using an electro-optic crystal and a highly sensitive polarization measurement technique using a polarization image sensor, which was fabricated using a 0.35-µm standard CMOS process. The polarization image sensor was equipped with differential amplifiers that amplified the difference between the 0° and 90° pixels. With the amplifier, the signal-to-noise ratio at low incident light levels was improved. Also, an optical modulator and a semiconductor optical amplifier were used to generate an optical local oscillator (LO) signal with a high modulation accuracy and sufficient optical intensity. By combining the amplified LO signal and a highly sensitive polarization imaging system, we successfully performed millimeter-wave electric field imaging with a spatial resolution of 30×60 µm at a rate of 1 FPS, corresponding to 2400 pixels/s.

Accurate nanoparticle size measurement by combining photometry and tracking analysis

Accurate determination of nanoparticle size is paramount in various fields, including molecular imaging, food safety, drug delivery, and nanobiotechnology. Conventional methods face limitations in accurately resolving different size distributions. Here, we introduce an approach to measure size distribution by combining photometry and tracking analysis of single particles. Our approach is based on a plasmonic dark field imaging system to image and track individual nanoparticles. Scattering intensity, spot size, and diffusion coefficient are quantified and fed into the machine learning model to establish the relationship with particle sizes. Compared with conventional methods, our approach shows improved accuracy in size measurement. To verify the universality of our method, we further demonstrate the sizing capability at diverse and complex conditions, enabling us to discriminate particle size differences within 20 nm in polydisperse systems.

Full-resolution image restoration for light field images via a spatial shift-variant degradation network.

The light field (LF) imaging systems face a trade-off between the spatial and angular resolution in a limited sensor resolution. Various networks have been proposed to enhance the spatial resolution of the sub-aperture image (SAI). However, the spatial shift-variant characteristics of the LF are not considered, and few efforts have been made to recover a full-resolution (FR) image. In this paper, we propose an FR image restoration method by embedding LF degradation kernels into the network. An explicit convolution model based on the scalar diffraction theory is first derived to calculate the system response and imaging matrix. Based on the analysis of LF image formation, we establish the mapping from an FR image to the SAI through the SAI kernel, which is a spatial shift-variant degradation (SSVD) kernel. Then, the SSVD kernels are embedded into the proposed network as prior knowledge. An SSVD convolution layer is specially designed to handle the view-wise degradation feature and speed up the training process. A refinement block is designed to preserve the entire image details. Moreover, our network is evaluated on extensive simulated and real-world LF images to demonstrate its superior performance compared with other methods. Experiments on a multi-focus scene further prove that our network is suitable for any in-focus or defocused conditions.

High-Performance Chip Design With Parallel Architecture for Magnetic Field Imaging System

High-Performance Chip Design With Parallel Architecture for Magnetic Field Imaging System

Experimental validation and mathematical simulation for laser protection performance of light field imaging

Photoelectric imaging systems typically employ a focal plane detector structure, rendering them vulnerable to laser damage. Laser damage can severely impair or even completely deprive the information acquisition capability of photoelectric imaging systems. A laser damage protection method based on a microlens array light field imaging system is proposed to prevent photoelectric imaging systems from laser damage. The technique utilizes the light field modulation effect of the microlens array to homogenize the spot energy, thereby reducing the maximum single-pixel receiving power at the image sensor. The method’s effectiveness has been verified through numerical simulations and experimental validation. First, the laser transmission theoretical model of light field imaging is proposed. Then an experimental setup is established, and measurements are conducted to capture the spot profiles and intensity distributions on the imaging plane across various defocus distances. Finally, the impact of the propagation distance on the maximum single-pixel receiving power and suppression ratio of the light field imaging system is experimentally measured. The simulation and experimental results indicate that, with the proposed method, the energy suppression ratio can easily reach two orders of magnitude, significantly reducing the probability of laser damage in photoelectric imaging systems.

Embedded Processing for Extended Depth of Field Imaging Systems: From Infinite Impulse Response Wiener Filter to Learned Deconvolution.

Many works in the state of the art are interested in the increase of the camera depth of field (DoF) via the joint optimization of an optical component (typically a phase mask) and a digital processing step with an infinite deconvolution support or a neural network. This can be used either to see sharp objects from a greater distance or to reduce manufacturing costs due to tolerance regarding the sensor position. Here, we study the case of an embedded processing with only one convolution with a finite kernel size. The finite impulse response (FIR) filter coefficients are learned or computed based on a Wiener filter paradigm. It involves an optical model typical of codesigned systems for DoF extension and a scene power spectral density, which is either learned or modeled. We compare different FIR filters and present a method for dimensioning their sizes prior to a joint optimization. We also show that, among the filters compared, the learning approach enables an easy adaptation to a database, but the other approaches are equally robust.

Comparison of three fundus inspection methods during phacoemulsification in diabetic white cataract.

To investigate whether Wild Field Imaging System (WFIS SW-8000), 25G endoilluminator, and intraoperative optical coherence tomography (iOCT) can perform real-time screening and diagnosing in patients with suspicious diabetic retinopathy (DR) during phacoemulsification, especially in cases of white cataract. A cross-sectional study was carried out. A total of 204 dense diabetic cataractous eyes of 204 patients with suspected DR treated from April 2020 to March 2021 were included. Phacoemulsification combined with intraocular lens implantation was performed. Following the removal of the lens opacity, the 25G endo-illuminator, fundus photography, and iOCT were performed successively. Optical coherence tomography (OCT) and/or fundus fluorescein angiography (FFA) were used to verify the fundus findings postoperatively. Intraoperative and postoperative results were compared to verify the accuracy of intraoperative diagnosis in each group. Intraoperative and postoperative examinations revealed 58 and 62 eyes with DR, respectively (positive rate, 28.43% and 30.39%, respectively). During the phacoemulsification, WFIS SW-8000 detected 44 eyes with DR (the detection rate, 70.97%); 25G endo-illuminator found 56 eyes with DR (the detection rate, 90.32%); iOCT found 46 eyes with DR (the detection rate, 74.19%); and 58 eyes with DR were found by combining the three methods (the detection rate, 93.55%). There were statistically significant differences in the diagnostic sensitivity for DR among the methods (χ2=16.36, P=0.001). WFIS SW-8000, 25G endo-illuminator, iOCT, and especially their combination can be used to inspect the fundus and detect DR intraoperatively; they are helpful for the timely diagnosis and treatment of DR in patients with dense cataract.

Research on a portable shielding-free ultra-low field magnetic resonance imaging system

The portable light-weight magnetic resonance imaging system can be deployed in special occasions such as Intensive Care Unit (ICU) and ambulances, making it possible to implement bedside monitoring imaging systems, mobile stroke units and magnetic resonance platforms in remote areas. Compared with medium and high field imaging systems, ultra-low-field magnetic resonance imaging equipment utilizes light-weight permanent magnets, which are compact and easy to move. However, the image quality is highly susceptible to external electromagnetic interference without a shielded room and there are still many key technical problems in hardware design to be solved. In this paper, the system hardware design and environmental electromagnetic interference elimination algorithm were studied. Consequently, some research results were obtained and a prototype of portable shielding-free 50 mT magnetic resonance imaging system was built. The light-weight magnet and its uniformity, coil system and noise elimination algorithm and human brain imaging were verified. Finally, high-quality images of the healthy human brain were obtained. The results of this study would provide reference for the development and application of ultra-low-field magnetic resonance imaging technology.

Snapshot Multispectral Light‐Field Imaging Based on Nematic Liquid‐Crystal Microlens Array via Deep Learning

In this study, a multispectral light‐field imaging system is developed using nematic liquid‐crystal microlens arrays (LC‐MLAs). The system solves the spectral under‐sampling and complex system issues in existing light‐field and spectral cameras. The LC‐MLA is the core optical element of the snapshot imaging system. No dispersion or customized scanning machinery is required to obtain multispectral light fields. Deep learning technology is utilized to reconstruct spectral information from raw data. In the experiments, it is demonstrated that the proposed method efficiently reconstructs multispectral data with 10 nm accuracy in the visible wavelength range of 400–700 nm. The system offers high precision, simple equipment, and relatively low cost without additional dispersion and filtering devices.

Analysis of modern atmospheric electrostatic field measuring instruments and methods

The object of research is the process of measuring the strength of the atmospheric electrostatic field. This paper is devoted to an analytical review and comparative analysis of modern methods and instruments for measuring atmospheric electrostatic field strength. The results of scientific research and modern practical technologies, which are used to develop technical means and increase the accuracy of measuring the strength of electrostatic fields, are considered. In the work, the general functional requirements for the hardware of systems for measuring the atmospheric electrostatic field strength are formed and the main directions of research and practical tasks for its creation are defined. The design features and characteristics of existing measuring instruments are considered in detail. The advantages and disadvantages of electrometers, electrostatic field mills, microelectromechanical electrostatic field mills, and electric field imaging systems are determined given their portability, sensitivity, measuring frequency, accuracy, measurement range, linearity, and cost. The analysis of the state of modern methods and measuring instruments for the strength of the electrostatic field showed that one of the best solutions for measuring the electrostatic field strength of the atmosphere today is the use of an improved electrostatic field mill. It was determined that one of the important problems for ensuring the development of methods and means of atmospheric electrostatic field strength measuring is the need to generalize the structure of the measuring instruments and calculate its metrological characteristics. It has been established that solving the problem of increasing the accuracy of atmospheric electrostatic field strength measurement requires a comprehensive approach based on improving the design of the sensor structure of the meter, increasing the accuracy of navigation and positioning, increasing the autonomy of work, improving communication and data transmission systems, as well as ensuring high stability and reliability of work under the influence of external factors. Improving the structure and improving the characteristics of electrostatic field mills in the future will ensure the necessary accuracy, compactness, and availability for measurement and its inclusion in the automated system of atmospheric electrostatic field monitoring and forecasting.

One-shot colored reflectance direction field imaging system for optical inspection.

Detecting microscale defects on the surface of an object is often difficult with conventional cameras. Microscale defects are known to greatly affect the bidirectional reflectance distribution function (BRDF) of light rays reflected from the surface. Therefore, an imaging system for capturing the reflectance direction field by color mapping using a multicolor filter placed in front of an imaging lens is proposed, which can have a simple structure. From the color variations of light rays passing through several different color regions of the multicolor filter, this imaging system can detect the extent of broadening of the BRDF. The effectiveness of the imaging system for optical inspection is experimentally validated by testing it on a plastic surface that has a shallow scratch with a depth of a few micrometers.

Research on Digital Testing Technology for Full Surface Defects of Cross scale Heteromorphic Metal Devices

There are many types of cross scale special-shaped metal components in various fields, and the surface quality (defects) of some key components will affect the device performance and even cause the long-term stability and reliability of the system to decline. The existing manual inspection methods are difficult to accurately quantify and establish a digital traceability database, so it is urgent to study the automatic digital inspection technology of full surface defects. However, most of the devices are curved surfaces with different shapes, large size spans, various types of surface defects and diffuse reflection imaging, and the background of machine vision images is complex, which greatly increases the difficulty of defect detection. Based on the principle of machine vision imaging, this paper designs a long depth of field and low distortion imaging system for curved surfaces. Combined with a flexible scanning motion mechanism with multiple degrees of freedom, this paper studies the technology of complex background defect extraction to realize the full surface defect detection of cross scale special-shaped metal devices.

High responsivity of VIS-NIR photodetector based on Ag2S/P3HT heterojunction

Ag2S quantum dot (QD) photodetectors (PDs) have attracted a lot of attention in the field of imaging system and optical communication. However, the current Ag2S PDs mainly works in the near-infrared band, and its detection ability in the visible band remains to be strengthened. In this paper, we used poly(3-hexylthiophene) (P3HT) with high carrier mobility and Ag2S QDs to construct heterojunction PD. Stronger absorption in blends with polymer P3HT compared to single Ag2S QDs. The optical absorption spectra show that the Ag2S/P3HT has strong light absorption peak at 394 and 598 nm. The results show that P3HT significantly enhances the absorption of Ag2S QDs from the visible to near-infrared band. The output characteristics, transfer characteristics and fast switching capability of the device at 405 nm, 532 nm and 808 nm were tested. The device has the responsivity of 6.05 A W−1, 83.72 A W−1 and 37.31 A W−1 under 405 nm, 532 nm and 808 nm laser irradiation. This work plays an important role in improving the detection performance of Ag2S QDs and broadening its applications in photoelectric devices for weak light and wide spectrum detection.

High-resolution light field imaging based on liquid crytal microlens arrays with ZnO microstructure orientation

We proposed a liquid crystal (LC) microlens array (MLA) based on zinc oxide (ZnO) microstructure orientation and used it in a light field imaging system. The system uses convex optimization theory to jointly optimize the multi-voltage light field information and obtain a high-resolution imaging method. The core element in this system is an LCMLA, which induces the horizontal orientation of LC molecules by ZnO microstructure to effectively overcome the physical defects caused by orientation, such as mechanical friction. Combined with the proposed joint optimization high-resolution algorithm based on convex optimization theory, high-resolution imaging can be achieved using the redundant characteristics of light field images. The experiments show that the proposed method's PSNR of the reconstructed image is about 32 dB compared with the conventional method. The designed imaging system is flexible, simple, and suitable for high-resolution reconstruction.

Ultra‐wide field fluorescein angiography in intermediate and posterior uveitis: A retrospective study

AbstractPurpose: To review the diagnostic value of the Ultra‐wide field imaging system Optomap Panoramic 200A (Optos, PLC, Scotland) in patients with intermediate, posterior uveitis or panuveitis of our department and the presence of findings in the periphery of the retina compared to the conventional 7 standard field fluorescein (7SF) angiography, as well as the contribution of the findings to the change of the therapeutic approach.Methods: This is a retrospective study. A medical records electronic search using Medisoft (Medisoft Limited, UK) conducted and included 69 patients and 121 eyes with intermediate, posterior uveitis or panuveitis that underwent Ultra‐wide field fluorescein angiography imaging. Subsequently, imaging was observed for detection of vasculitis, ischemia, neovascularisation and/or choroidal lesions in areas beyond 75° that was detected by conventional fluorescein angiography. The therapeutic approach based on the presence/absence of relevant findings was also reviewed.Results: Out of 121 eyes in total, 67 were classified as intermediate uveitis, 44 as posterior uveitis and 5 as panuveitis. The presence of at least one form of peripheral angiographic finding was noted in 52 eyes, peripheral vasculitis was observed in 40 eyes and peripheral ischemia in 31 eyes. Decision to change the therapeutic approach was decided in 42 eyes overall, 31 of which presented peripheral findings and 11 lacked any. 21 eyes were noted with peripheral findings, but no change of treatment was decided. There was a statistically significant correlation between presence and absence of findings and change of treatment (p < 0.00001). No other statistically significant correlation between treatment alteration and score or specific uveitis type was found.Conclusions: Compared with conventional 7SF imaging, the Ultra‐wide field fluorescein angiography is an extremely useful diagnostic test for the detection of active disease and can significantly change the therapeutic approach in patients with intermediate, posterior uveitis or panuveitis.

Low-voltage driving high-resistance liquid crystal micro-lens with electrically tunable depth of field for the light field imaging system

Light field imaging (LFI) based on Liquid crystal microlens array (LC MLAs) are emerging as a significant area for 3D imaging technology in the field of upcoming Internet of things and artificial intelligence era. However, in scenes of LFI through conventional MLAs, such as biological imaging and medicine imaging, the quality of imaging reconstruction will be severely reduced due to the limited depth of field. Here, we are proposed a low-voltage driving LC MLAs with electrically tunable depth of field (DOF) for the LFI system. An aluminum-doped zinc oxide (AZO) film was deposited on the top of the hole-patterned driven-electrode arrays and used as a high resistance (Hi-R) layer, a uniform gradient electric field was obtained across the sandwiched LC cell. Experimental results confirm that the proposed LC MLAs possess high-quality interference rings and tunable focal length at a lower working voltage. In addition, the focal lengths are tunable from 3.93 to 2.62 mm and the DOF are adjustable from 15.60 to 1.23 mm. The experiments demonstrated that the LFI system based on the proposed structure can clearly capture 3D information of the insets with enlarged depths by changing the working voltage and driving frequency, which indicates that the tunable DOF LC MLAs have a potential application prospects for the biological and medical imaging.

Non-contact widefield neonatal retinal imaging for retinopathy of prematurity using the Clarus 700 high resolution true colour reflectance imaging.

To illustrate the role of non-contact widefield retinal imaging (NC-WFI) of retinopathy of prematurity (ROP) using the Clarus 700 high resolution true colour reflectance imaging. All babies were examined by the vitreoretinal faculty in a tertiary eye care centre from a period of March 2021 to November 2021 using the indirect ophthalmoscope after pupillary dilatation. ROP grading was done according to the revised ICROP (2005) classification. NC-WFI was then performed using the Clarus 700 high resolution true colour reflectance imaging (Carl Zeiss Meditec, Dublin, CA) in the retina diagnostic set up of a tertiary eye care centre. A total of 22 babies (44 eyes) underwent NC-WFI from March 2021 to November 2021. 13 unique cases of retinopathy of prematurity with images captured on Clarus 700 and the clinical summary is described. Clarus is a non-contact wide field imaging (NC-WFI) system that can capture high resolution and true colour images (images of the fundus appear similar colour to direct observation by ophthalmoscopy) helping in more accurate diagnosis and grading of the severity of ROP.

Novel light field imaging device with enhanced light collection for cold atom clouds

We present a light field imaging system that captures multiple views of an object with a single shot. The system is designed to maximize the total light collection by accepting a larger solid angle of light than a conventional lens with equivalent depth of field. This is achieved by populating a plane of virtual objects using mirrors and fully utilizing the available field of view and depth of field. Simulation results demonstrate that this design is capable of single-shot tomography of objects of size \U0001d4aa(1 mm3), reconstructing the 3-dimensional (3D) distribution and features not accessible from any single view angle in isolation. In particular, for atom clouds used in atom interferometry experiments, the system can reconstruct 3D fringe patterns with size \U0001d4aa(100 μm). We also demonstrate this system with a 3D-printed prototype. The prototype is used to take images of \U0001d4aa(1 mm3) sized objects, and 3D reconstruction algorithms running on a single-shot image successfully reconstruct \U0001d4aa(100 μm) internal features. The prototype also shows that the system can be built with 3D printing technology and hence can be deployed quickly and cost-effectively in experiments with needs for enhanced light collection or 3D reconstruction. Imaging of cold atom clouds in atom interferometry is a key application of this new type of imaging device where enhanced light collection, high depth of field, and 3D tomographic reconstruction can provide new handles to characterize the atom clouds.