Speckle structured illumination endoscopy with enhanced resolution at wide field of view and depth of field

Structured illumination microscopy(SIM)is one of the most widely applied wide field super resolution imaging techniques with high temporal resolution and low phototoxicity.The spatial resolution of SIM is typically limited to two times of the diffraction limit and the depth of field is small.In this work,we propose and experimentally demonstrate a low cost,easy to implement,novel technique called speckle structured illumination endoscopy(SSIE)to enhance the resolution of a wide field endoscope with large depth of field.Here,speckle patterns are used to excite objects on the sample which is then followed by a blind-SIM algorithm for super resolution image reconstruction.Our approach is insensitive to the 3D morphology of the specimen,or the deformation of illuminations used.It greatly simplifies the experimental setup as there are no calibration protocols and no stringent control of illumination patterns nor focusing optics.We demonstrate that the SSIE can enhance the resolution 2–4.5 times that of a standard white light endoscopic(WLE)system.The SSIE presents a unique route to super resolution in endoscopic imaging at wide field of view and depth of field,which might be beneficial to the practice of clinical endoscopy.

Impact of random and scattered coincidences from outside of field of view on positron emission tomography/computed tomography imaging with different reconstruction protocols

Image quality in positron emission tomography(PET)is affected by random and scattered coincidences and reconstruction protocols.In this study,we investigated the effects of scattered and random coincidences from outside the field of view(FOV)on PET image quality for different reconstruction protocols.Imaging was performed on the Discovery 690 PET/CT scanner,using experimental configurations including the NEMA phantom(a body phantom,with six spheres of different sizes)with a signal background ratio of 4:1.The NEMA phantom(phantom I)was scanned separately in a one-bed position.To simulate the effect of random and scatter coincidences from outside the FOV,six cylindrical phantoms with various diameters were added to the NEMA phantom(phantom II).The 18 emission datasets with mean intervals of 15 min were acquired(3 min/scan).The emission data were reconstructed using different techniques.The image quality parameters were evaluated by both phantoms.Variations in the signal-to-noise ratio(SNR)in a 28-mm(10-mm)sphere of phantom II were 37.9%(86.5%)for ordered-subset expectation maximization(OSEM-only),36.8%(81.5%)for point spread function(PSF),32.7%(80.7%)for time of flight(TOF),and 31.5%(77.8%)for OSEM+PSF+TOF,respectively,indicating that OSEM+PSF+TOF reconstruction had the lowest noise levels and lowest coefficient of variation(COV)values.Random and scatter coincidences from outside the FOV induced lower SNR,lower contrast,and higher COV values,indicating image deterioration and significantly impacting smaller sphere sizes.Amongst reconstruction protocols,OSEM+PSF+TOF and OSEM+PSF showed higher contrast values for sphere sizes of 22,28,and 37 mm and higher contrast recovery coefficient values for smaller sphere sizes of 10 and 13 mm.

Design of three-dimensional imaging lidar optical system for large field of view scanning

Three-dimensional(3D)lidar has been widely used in various fields.The MEMS scanning system is one of its most important components,while the limitation of scanning angle is the main obstacle to improve the demerit for its application in various fields.In this paper,a folded large field of view scanning optical system is proposed.The structure and parameters of the system are determined by theoretical derivation of ray tracing.The optical design software Zemax is used to design the system.After optimization,the final structure performs well in collimation and beam expansion.The results show that the scan angle can be expanded from±5°to±26.5°,and finally the parallel light scanning is realized.The spot diagram at a distance of 100 mm from the exit surface shows that the maximum radius of the spot is 0.506 mm with a uniformly distributed spot.The maximum radius of the spot at 100 m is 19 cm,and the diffusion angle is less than 2 mrad.The energy concentration in the spot range is greater than 90%with a high system energy concentration,and the parallelism is good.This design overcomes the shortcoming of the small mechanical scanning angle of the MEMS lidar,and has good performance in collimation and beam expansion.It provides a design method for large-scale application of MEMS lidar.

Structured scene modeling using micro stereo vision system with large field of view

This paper presents a method for structured scene modeling using micro stereo vision system with large field of view. The proposed algorithm includes edge detection with Canny detector, line fitting with principle axis based approach, finding corresponding lines using feature based matching method, and 3D line depth computation.

Performance of the Large Field of View Airborne Infrared Scanner and its application potential in land surface temperature retrieval

The Large Field of View Airborne Infrared Scanner is a newly developed multi-spectral instrument that collects images from the near-infrared to long-wave infrared channels.Its data can be used for land surface temperature(LST)retrieval and environmental monitoring.Before data application,quality assessment is an essential procedure for a new instrument.In this paper,based on the data collected by the scanner near the Yellow River in Henan Province,the geometric and radiometric qualities of the images are first evaluated.The absolute geolocation accuracy of the ten bands of the scanner is approximately 5.1 m.The ground sampling distance is found to be varied with the whisk angles of the scanner and the spatial resolution of the images.The band-to-band registration accuracy between band one and the other nine bands is approximately 0.25 m.The length and angle deformations of the ten bands are approximately 0.67%and 0.3°,respectively.The signal-to-noise ratio(SNR)and relative radiometric calibration accuracy of bands 4,9,and 10 are relatively better than those of the other bands.Secondly,the radiative transfer equation(RTE)method is used to retrieve the LST from the data of the scanner.Measurements of in situ samples are collected to evaluate the retrieved LST.Neglecting the samples with unreasonable retrieved LST,the bias and RMSE between in situ LST measured by CE312 radiometer and retrieved LST are−0.22 K and 0.94 K,and the bias and RMSE are 0.27 K and 1.59 K for the InfReC R500-D thermal imager,respectively.Overall,the images of the Large Field of View Airborne Infrared Scanner yield a relatively satisfactory accuracy for both LST retrieval and geometric and radiometric qualities.

An airborne pushbroom hyperspectral imager with wide field of view

An airborne pushbroom hyperspectrai imager （APHI） with wide field （42° field of view） is presented. It is composed of two 22° field of view （FOV） imagers and can provide 1304 pixels in spatial dimension, 124 bands in spectral dimension in one frame. APHI has a bandwidth ranging from 400 to 900 nm. The spectral resolution is 5 nm and the spatial resolution is 0.6 m at 1000-m height. The implementation of this system is helpful to overcome the restriction of FOV in pushbroom hyperspectral imaging in a more feasible way. The electronic and optical designs axe also introduced in detail.

3D depth-coded photoacoustic microscopy with a large field of view for human skin imaging

Photoacoustic （PA） microscopy comes with high potential for human skin imaging, since it allows noninvasively high-resolution imaging of the natural hemoglobin at depths of several millimeters. Here, we developed a PA microscopy to achieve high-resolution, high-contrast, and large field of view imaging of skin. A three-dimensional （3D） depth-coding technology was used to encode the depth information in PA images, which is very intuitive for identifying the depth of blood vessels in a two-dimensional image, and the vascular structure can be analyzed at different depths. Imaging results demonstrate that the 3D depth-coded PA microscopy should be translated from the bench to the bedside.

A novel trigger algorithm for wide-field-of-view imaging atmospheric Cherenkov technique experiments

The high-altitude detection of astronomical radiation(HADAR)experiment is a new Cherenkov observation technique with a wide field of view(FoV),aimed at observing the prompt emissions ofγ-ray bursts(GRBs).The bottleneck for this type of experiment can be found in determining how to reject the high rate of nightsky background(NSB)noise from random stars.In this work,we propose a novel method for rejecting noise,which considers the spatial properties of GRBs and the temporal characteristics of Cherenkov radiation.In space coordinates,the map between the celestial sphere and the fired photomultiplier tubes(PMTs)on the telescope's camera can be expressed as f(δ(i,j))=δ'(i',j'),which means that a limited number of PMTs is selected from one direction.On the temporal scale,a 20-ns time window was selected based on the knowledge of Cherenkov radiation.This allowed integration of the NSB for a short time interval.Consequently,the angular resolution and effective area at 100 GeV in the HADAR experiment were obtained as 0.2°and 10^(4)m^(2),respectively.This method can be applied to all wide-FoV experiments.

Dynamic measurement of beam divergence angle of different fields of view of scanning lidar

The laser beam divergence angle is one of the important parameters to evaluate the quality of the laser beam.It can not only accurately indicate the nature of the beam divergence when the laser beam is transmitted over a long distance,but also objectively evaluate the performance of the laser system.At present,lidar has received a lot of attention as a core component of environment awareness technology.Micro-electromechanical system(MEMS)micromirror has become the first choice for three-dimensional imaging lidar because of its small size and fast scanning speed.However,due to the small size of the MEMS micromirror,the lidar scanning system has a small field of view(FOV).In order to achieve a wide range of scanning imaging,collimating optical system and wide-angle optical system are generally added to the system.However,due to the inherent properties of the optical lens,it is impossible to perfect the imaging,so the effects of collimating and expanding the beam will be different at different angles.This article aims to propose a measurement system that dynamically measures the divergence angles of MEMS scanning lidar beams in different fields of view to objectively evaluate the performances of scanning lidar systems.

Estimation of IFOV of Rosette Scan System

The methods of estimating the minimum allowed value of IFOV (instantaneous field of view) of the detector in a rosette scan system are investigated. The common method for the estimation of IFOV is described. A new method which uses the maximum distance between two neighboring petals as the estimated value of IFOV is developed and a comparison between the common method and the new method is given. It is concluded that the minimum allowed value of IFOV of rosette scanning is over estimated by the common method while this value can be calculated accurately with the new method.

Wide field-of-view metalens: a tutorial

Wide field-of-view(FOV)optics are essential components in many optical systems,with applications spanning imaging,display,sensing,and beam steering.Conventional refractive wide FOV optics often involve multiple stacked lenses,resulting in large size and weight as well as high cost.Metasurface lenses or metalenses promise a viable solution to realizing wide FOV optics without complex lens assembly.We review the various architectures of wide FOV metalenses,elucidate their fundamental operating principles and design trade-offs,and quantitatively evaluate and contrast their imaging performances.Emerging applications enabled by wide FOV metasurface optics are also discussed.

Radiation of lamp and optimized experiment using artificial light in the Arctic Ocean

A winter optical experiment by an artificial lamp was conducted in the Amundsen Bay of Arctic Ocean from November of 2007 to January of 2008. The radiation field emitted from an artificial lamp was measured and is introduced in this paper, and the optimized experiment project is discussed. It is demonstrated that the minimum size allowed of the lamp is determined by both the field of view （ FOV ） of optical instrument and the measuring distance from the lamp. Some problems that might influence on the experiment result often occur for a simple fluorescent lamp, such as instability, spatial nonuniformity, light divergence, effect of lamp temperature, etc. By the analysis of the light radiation, three kind of measures are proposed to control the quality of the experiment, i.e. keeping consistency of lamp size with FOV of instrument, calibrating in situ downwind, and conducting measurement in effective range. Among them, the downwind calibration is the key step to overcome most problems arose by the lamp. The experiment indicated that the reliable results can be obtained only when the optical measurement is coordinated with the radiation field of artificial lamp. The measured radiation property of the lamp was used to advise the field experiment to minimize measuring error. As the experiment by artificial lamp was the first attempt in the Arctic Ocean, the experience given by this paper is a valuable reference to the correlative studies.

Quantifying Design Parameters of Symbology Page for Automotive Head up Display

This paper gives an overview of studies on parameters displayed on the Automotive Head Up Display （A-HUD） including calculation and construction of symbology page based on study results. A study has been made on vital parameters required for car drivers and design calculations have been made based on design parameters like field of view, distance from the design eye position, minimum character size viewable from a distance of 1.5m between driver and the projected image, and optical magnification factor. lhe display format suitable for A-HUD applications depends upon the parameters required to be displayed. The aspect ratio chosen is 4：3. This paper also provides method to design the symbology page embedding six vital parameters with their relative positioning and size considering relative position between display device and optical elements which has been considered with a magnification factor of 2.5. The field of view obtained is 6.7° × 4.8°.

Robust design and analysis for opto-mechanical two array laser warning system

In the past three decades,laser warning systems(LWS)have emerged in great importance,as the development of laser-guided weapons,such as airborne Hellfire missiles,has increased,posing an imminent threat to vital areas and VIPs.The laser warning station(LWS)can detect,classify,identify,and give alarm from laser threat at a very short time with high sensitivity.Therefore,the designers of this system must take into account the detectability and field of view to cover the area to be secured.The main contribution in this research is an analytical design of LWS that consists of 24 detector elements,distributed in two arrays(2×12)circularly.Also,calculating the best distance between the detectors according to the laser beam spot size.In addition,enhancement laser warring sensor detection capability and detection performance FOV between the detectors to increase coverage area up to 360°.Moreover,decreasing dead zone area between the laser detectors element.Mathematical calculations and illustrations made to reach the best systematic design.

Mosaic line-scan camera based on FPGA

Because single line-scan camera loses light in the edge of the sensor when the field of view is large, a mosaic cam- era based on field programmable gate array （FPGA） is presented by putting multiple cameras arranged in a straight line to share the field of view and reduce the view angle of every camera. For detecting doping micro particles with the designed mosaic line-scan camera, a detection algorithm of the target＇s location in FPGA is proposed. Finally, the practicability and stability of the system were validated experimentally. The results of the experiment show that the camera can get images clearly with less light loss and can accurately distinguish the target and the background.

Review of bio-optical imaging systems with a high space-bandwidth product

Optical imaging has served as a primary method to collect information about biosystems across scales—from functionalities of tissues to morphological structures of cells and even at biomolecular levels.However,to adequately characterize a complex biosystem,an imaging system with a number of resolvable points,referred to as a space-bandwidth product(SBP),in excess of one billion is typically needed.Since a gigapixel-scale far exceeds the capacity of current optical imagers,compromises must be made to obtain either a low spatial resolution or a narrow field-of-view(FOV).The problem originates from constituent refractive optics—the larger the aperture,the more challenging the correction of lens aberrations.Therefore,it is impractical for a conventional optical imaging system to achieve an SBP over hundreds of millions.To address this unmet need,a variety of high-SBP imagers have emerged over the past decade,enabling an unprecedented resolution and FOV beyond the limit of conventional optics.We provide a comprehensive survey of high-SBP imaging techniques,exploring their underlying principles and applications in bioimaging.

Atmospheric Drag Perturbation in an Autonomous Orbit Determination for Satellite

In this paper, an autonomous orbit determination method for satellite using a large field of view star sensor is presented. The simulation of orbit under atmospheric drag perturbation are given with expanded Kalman filtering. The large field of view star sensor has the same precision as star sensor and a sufficient filed of view. Therefore ,the refraction stars can be observed more accurately in real time. The geometric relation between the refracted starlight and the earth can be determined by tangent altitude of the refraction starlight. And then the earth center can be determined in satellite body frame. The simulation shows that the precision of the mean square deviation of satellite’s position and velocity is 5m and 0.01m/s respectively. The calculated decrement of the semi-major axis in one day is close to the theoretical result, and the absolute error is in the range of decimeter when the altitude of orbit is 750 km. The simu- lateion of orbit of different initial semi-major axis shows that the higher the altitude of orbit is, the smaller the dec- rement of the semi-major axis is, and when the altitude of orbit is 1700 km the decimeter of the semi-major axis is 10-7 km.

Precise 3D shape measurement of three-dimensional digital image correlation for complex surfaces

Three dimensional-digital image correlation （3D-DIC） is a widely used optical metrology in the experimental mechanics community because of its reliability, practicality, and flexibility. Although the precision of digital image correlation （DIC） has been thoroughly studied theoretically and numerically, verification experiments have seldom been performed, especially fbr complex surfaces with a small field of view （FOV）. In this work, the shape of a 1-yuan coin was measured using 3D-DIC; the shape was complex due to the presence of many fine details, and the FOV was relatively small because the coin diameter was only 25 mm. During the experiment, a novel strategy for speckle production was developed： white paint was simply sprayed onto the surface. Black paint was not used; instead, taking advantage of the reflective nature of the coin surface, polarized light and a Polaroid filter were introduced, and the polarization direction was carefully adjusted, ensuring that the spray pattern was extremely thin and that high-quality speckle images with significant contrast were captured. The three-dimensional coin shape was also successfully determined for comparison using a stylus profiler. The results demonstrate that 3D-DIC provides high precision in shape measurement even for complex surfaces with small FOV. The precision of 3D-DIC can reach 1/7000 of the field of view, corresponding to about 6 ~tm in this experiment.

Multiscale label-free volumetric holographic histopathology of thick-tissue slides with subcellular resolution

Histopathology relies upon the staining and sectioning of biological tissues,which can be laborious and may cause artifacts and distort tissues.We develop label-free volumetric imaging of thick-tissue slides,exploiting refractive index distributions as intrinsic imaging contrast.The present method systematically exploits label-free quantitative phase imaging techniques,volumetric reconstruction of intrinsic refractive index distributions in tissues,and numerical algorithms for the seamless stitching of multiple three-dimensional tomograms and for reducing scattering-induced image distortion.We demonstrated label-free volumetric imaging of thick tissues with the field of view of 2 mm×1.75 mm×0.2 mm with a spatial resolution of 170 nm×170 nm×1400 nm.The number of optical modes,calculated as the reconstructed volume divided by the size of the point spread function,was∼20 giga voxels.We have also demonstrated that different tumor types and a variety of precursor lesions and pathologies can be visualized with the present method.

Evaluation of operator visibility in three different cabins type Far-East combine harvesters

The purpose of this study was to develop and evaluate a visibility evaluation system for the cabin type Far-East combine harvester.The human field of view has been classified into five levels(perceptive,effective,stable gaze,induced,and auxiliary)depending on the rotation of the human head and eye.The divider,reaper lever,gearshift,dashboard,and conveying component were considered as major viewpoints of the cabin type Far-East combine harvester.The visibility of the cabin type Far-East combine harvester was evaluated quantitatively using viewpoints and human field of view levels.The visibility evaluation system for the cabin type Far-East combine harvester consisted of a laser pointer,stepping motors to control the directions of the view,gyro sensors to measure horizontal and vertical angles,and I/O interface to acquire the signals.The visibility evaluation tests were conducted at different postures(‘sitting straight’,‘sitting with a 15°tilt’,‘standing straight’,and‘standing with a 15°tilt’)for three cabin type Far-East combine harvesters.The LSD(least significant difference)multiple comparison tests showed that the visibilities of viewpoints differed significantly as the operator's posture changed.The results showed that the posture while standing with a 15°tilt provided the best visibility.The average visibility scores at sitting postures were 22.3(straight)and 24.4(15°tilt),and the scores at standing postures were 18.7(straight)and 29.5(15°tilt).Also,the average visibility scores were observed in order from highest to lowest as reaper lever(44.6),divider(28.7),dashboard(23.1),conveying part(12.2),and gearshift lever(10.1).Most viewpoints of the cabin type Far-East combine harvester were out of the stable gaze field of the view level.Modifications of the cabin type Far-East combine harvester design will be required to enhance the visibility during harvesting operation and to improve safety and convenience of farmers.