Lens Imaging System Research Articles

Opto-VLSI-Based Dynamic RF Signal Combiner

An Opto-VLSI based dynamic RF signal combiner structure is proposed and experimentally demonstrated. The structure utilizes an Opto-VLSI processor in conjunction with an optical fiber array, a photo-detector, and a 4-f imaging lens system to dynamically combine multiple analog RF signals into a single output RF port with a user-defined combination ratio. A proof-of-concept $2\times 1$ analogue RF signal combiner is experimentally demonstrated, and experimental results show that RF signal combination with arbitrary ratio can be achieved by uploading different optimized phase holograms onto the Opto-VLSI processor.

3D multi-layered film thickness profile measurements based on photometric type imaging ellipsometry

In this investigation, we describe an imaging ellipsometric method to measure 3D thickness profiles of a multi-layered film structure. Opposed to traditional imaging ellipsometry to improve the spatial resolution using high magnification objectives, we adopt a low magnification imaging lens system approximately 1x to extend the measuring area. In addition, photometric type imaging ellipsometry is implemented to reduce the acquisition time and memory usage. Before film thickness measurements, the incident angle of incoming light and polarization axes of the optical components were calibrated by hardware and software. Several specimens were successfully measured by the photometric type imaging ellipsometer and the repeatability for 15 consecutive measurements was less than 0.5 nm.

Wide Field-of-View Fluorescence Imaging with Optical-Quality Curved Microfluidic Chamber for Absolute Cell Counting.

Field curvature and other aberrations are encountered inevitably when designing a compact fluorescence imaging system with a simple lens. Although multiple lens elements can be used to correct most such aberrations, doing so increases system cost and complexity. Herein, we propose a wide field-of-view (FOV) fluorescence imaging method with an unconventional optical-quality curved sample chamber that corrects the field curvature caused by a simple lens. Our optics simulations and proof-of-concept experiments demonstrate that a curved substrate with lens-dependent curvature can reduce greatly the distortion in an image taken with a conventional planar detector. Following the validation study, we designed a curved sample chamber that can contain a known amount of sample volume and fabricated it at reasonable cost using plastic injection molding. At a magnification factor of approximately 0.6, the curved chamber provides a clear view of approximately 119 mm2, which is approximately two times larger than the aberration-free area of a planar chamber. Remarkably, a fluorescence image of microbeads in the curved chamber exhibits almost uniform intensity over the entire field even with a simple lens imaging system, whereas the distorted boundary region has much lower brightness than the central area in the planar chamber. The absolute count of white blood cells stained with a fluorescence dye was in good agreement with that obtained by a commercially available conventional microscopy system. Hence, a wide FOV imaging system with the proposed curved sample chamber would enable us to acquire an undistorted image of a large sample volume without requiring a time-consuming scanning process in point-of-care diagnostic applications.

High energy electron radiography system design and simulation study of beam angle-position correlation and aperture effect on the images

A beam line dedicated to high-energy electron radiography experimental research with linear achromat and imaging lens systems has been designed. The field of view requirement on the target and the beam angle-position correlation correction can be achieved by fine-tuning the fields of the quadrupoles used in the achromat in combination with already existing six quadrupoles before the achromat. The radiography system is designed by fully considering the space limitation of the laboratory and the beam diagnostics devices. Two kinds of imaging lens system, a quadruplet and an octuplet system are integrated into one beam line with the same object plane and image plane but with different magnification factor. The beam angle-position correlation on the target required by the imaging lens system and the aperture effect on the images are studied with particle tracking simulation. It is shown that the aperture position is also correlated to the beam angle-position on the target. With matched beam on the target, corresponding aperture position and suitable aperture radius, clear pictures can be imaged by both lens systems. The aperture is very important for the imaging. The details of the beam optical requirements, optimized parameters and the simulation results are presented.

Experimental demonstration of reduced tilt-to-length coupling by a two-lens imaging system.

The coupling between beam tilt and longitudinal path length readout in a setup representing a LISA test mass interferometer was reduced to below 2 µm/rad using a two lens imaging system. This was achieved by the use of a homodyne equal arm-length Mach-Zehnder interferometer and suppression of the dominating effects of higher order Gaussian modes and longitudinal actuator movement. The latter was subtracted using the phase signal of a large single element photo diode.

FEI Titan 80-300 TEM

The FEI Titan 80-300 TEM is a high-resolution transmission electron microscope equipped with a field emission gun and a corrector for the spherical aberration (CS) of the imaging lens system. The instrument is designed for the investigation of a wide range of solid state phenomena taking place on the atomic scale, which requires true atomic resolution capabilities. Under optimum optical settings of the image CS-corrector (CEOS CETCOR) the point-resolution is extended up to the information limit of well below 100 pm with 200 keV and 300 keV electrons. A special piezo-stage design allows ultra-precise positioning of the specimen in all 3 dimensions. Digital images are acquired with a Gatan 2k x 2k slow-scan charged coupled device camera.

Bayesian-based aberration correction and numerical diffraction for improved lensfree on-chip microscopy of biological specimens.

Lensfree on-chip microscopy is an emerging imaging technique that can be used to visualize and study biological specimens without the need for imaging lens systems. Important issues that can limit the performance of lensfree on-chip microscopy include interferometric aberrations, acquisition noise, and image reconstruction artifacts. In this study, we introduce a Bayesian-based method for performing aberration correction and numerical diffraction that accounts for all three of these issues to improve the effective numerical aperture (NA) and signal-to-noise ratio (SNR) of the reconstructed microscopic image. The proposed method was experimentally validated using the USAF resolution target as well as real waterborne Anabaena flos-aquae samples, demonstrating improvements in NA by ∼25% over the standard method, and improvements in SNR of 2.8 and 8.2 dB in the reconstructed image when compared to the reconstructed images produced using the standard method and a maximum likelihood estimation method, respectively.

Wide-angle spectral imaging using a Fabry-Pérot interferometer

We show that wide-angle spectral imaging can be achieved with compact and cost-effective devices using Fabry-Pérot interferometers. Designs with a full field of view of 90°, in which the Fabry-Pérot interferometer is mounted either in front of an imaging lens system or behind a telecentric lens system, are presented and analysed. We show the dependency of the spectral resolution on the numerical aperture of the lens system and demonstrate its value as a design criterion.

Study the Fisheye Staring Video Surveillance System of nothing Blind-Zone Based on the DaVinci Chip

A staring and nothing blind-zone video surveillance system was designed based on the DSP chip of TMS320DM6467 and the fish-eye lens which has ultra-view field. This fisheye lens has 185 degree field of view, and make the system has 360 degree panorama and nothing blind-zone monitoring which used two fish-eye lens imaging system. Firstly, this paper designed the panorama imaging system, and then studied the calibration method for it. The hardware system used the multimedia imagery processing chip of TMS320DM6467 which has dual core processor and can processing the fish-eye image real time. The experiment shows the fisheye image had 360 degree sphere with nothing blind-zone for surveillance area and the hardware of processing center can work stable. This system can intelligent surveillance when upload the algorithm.

Design and optimization of the sine condition test for measuring misaligned optical systems

By taking a new look at an old concept, we have shown in our previous work how the Abbe sine condition can be used to measure linearly field-dependent aberrations in order to verify the alignment of optical systems. In this paper, we expand on this method and discuss the design choices involved in implementing the sine condition test (SCTest). Specifically, we discuss the two illumination options for the test: point source with a grating or flat-panel display, and we discuss the tradeoffs of the two approaches. Additionally, experimental results are shown using a flat-panel display to measure linearly field-dependent aberrations. Last, we elaborate on how to implement the SCTest on more complex optical systems, such as a three-mirror anastigmat and a double Gauss imaging lens system.

Unified theory of thermal ghost imaging and ghost diffraction through turbulent atmosphere

A unified theory is developed to investigate both thermal ghost imaging and ghost diffraction through turbulent atmosphere. A very simple analytical imaging formula is derived and contains several previously known results as particular cases. Numerical examples are given to show the effects of the turbulence strength, source parameters, and detector size on the quality of ghost imaging and ghost diffraction. Specifically, we find ghost imaging is more robust against the turbulence than ghost diffraction. A comparison of ghost imaging with a conventional lens imaging system is given to show the advantages or disadvantages of ghost imaging through turbulent atmosphere.

Point Spread Function Filtering for Radially Variant Blur Restoration

In this paper, we present a point spread function (PSF) filtering technique for solving the radially variant blur restoration problem. Radially variant blur is generated by a spherical single-element lens imaging system (SSLIS) that is embedded in an experimental camera module. The restoration of this category of blur is carried out in a polar coordinate system using polar PSFs at different fields of view (FOVs). However, restoration using large PSFs tends to introduce severe ringing artifacts in the restored image owing to the nonsparse nature of these PSFs. We show in this paper that the PSF filtering technique can effectively minimize ringing artifacts by filtering out some PSF pixels with an intensity lower than the threshold intensity. As a result, a nonsparse PSF becomes a sparse PSF, which is for good restoration results. The effectiveness of the PSF filtering technique was validated by visual comparison using three test images captured by the SSLIS camera module. In addition, a systematic way to determine the optimal filtering coefficient for a PSF at any FOV within the FOV range is also introduced.

Real scene capturing using spherical single-element lens camera and improved restoration algorithm for radially variant blur

A camera module employing spherical single-element lens imaging system (SSLIS) is introduced in this study. This type of imaging system can be used in compact digital cameras or mobile phone cameras, and it provides the advantages of simple design, reduced device bulkiness, and reduced manufacturing costs. When compared with conventional camera modules, our system produces radially variant blurred images, which can be satisfactorily restored by means of a polar domain deconvolution algorithm proposed in our previous study. In this study, we demonstrate an improved version of this algorithm that enables full-field-of-view (FOV) image restoration instead of the partial FOV restoration obtained via our previous algorithm. This improvement is realized by interpolating the upper and arc-shaped boundaries of the panoramic polar image such that the ringing artifacts around the center and four boundaries of the restored Cartesian image are greatly suppressed. The effectiveness of the improved algorithm is verified by image restoration of both computer simulated images and real-world scenes captured by the spherical single lens camera module. The quality of the restored image depends on the overall sparsity of all the point spread function (PSF) block Toeplitz with circulant blocks (BTCB) matrices used to restore a radially blurred image.

Imaging beamline for high energy proton radiography

Proton radiography is a new tool for advanced hydrotesting. This article will discuss the basic concept of proton radiography first, especially the magnetic lens system. Then a scenario of 50 GeV imaging beamline will be described in every particular, including the matching section, Zumbro lens system and imaging system. The simulation result shows that the scenario of imaging beamline performs well, and the influence of secondary particles can be neglected.

NASCA Report 2: Longitudinal Study of Relationship of Exposure to Space Radiation and Risk of Lens Opacity

The NASA Study of Cataract in Astronauts (NASCA) was designed to measure the impact of exposure to space radiation on progression rates of cortical, nuclear, and posterior subcapsular cataract in U.S. astronauts who have flown in space and comparison groups of astronauts who had not flown in space, and subjects with a history of military aviation. We present our analyses of 5 years of data with an average of 3.8 exams per subject. All subjects had digital lens images with the Nidek EAS 1000 Lens Imaging System. Because of high variability and skewness of opacity measures, nonparametric methods were used to test for association between rates of opacification and space radiation exposure. First, median regression was used to collapse longitudinal data into robust estimates of progression rates (opacity severity compare to time for each eye of each subject). To quantify and test for a radiation effect, median regression with the dependent variable being the maximum of the two slopes (OD and OS) per subject was then used, adjusting for the confounding variables of age, nutritional, and sun-exposure histories. Median regression showed evidence of an association between the rate of cortical progression in the worse eye with radiation dose and age. The estimated median progression rate from space radiation being 0.25 ± 0.13% lens area/Sv/year (P = 0.062). We found no relationship between radiation exposure and progression of aggregate area of posterior subcapsular cataract or nuclear progression rates. However, longer follow-up may be needed to further understand any impact of space radiation on progression rates for posterior subcapsular cataracts and nuclear cataracts, and to characterize changes to visual acuity.

Endoscopic imaging of Cerenkov luminescence

We demonstrate feasibility of endoscopic imaging of Cerenkov light originated when charged nuclear particles, emitted from radionuclides, travel through a biological tissue of living subjects at superluminal velocity. The endoscopy imaging system consists of conventional optical fiber bundle/ clinical endoscopes, an optical imaging lens system, and a sensitive low-noise charge coupled device (CCD) camera. Our systematic studies using phantom samples show that Cerenkov light from as low as 1 µCi of radioactivity emitted from 18F-Fluorodeoxyglucose (FDG) can be coupled and transmitted through conventional optical fibers and endoscopes. In vivo imaging experiments with tumor bearing mice, intravenously administered with 18F-FDG, further demonstrated that Cerenkov luminescence endoscopy is a promising new tool in the field of endoscopic molecular imaging.

Clinical characteristics and treatment outcomes of aggressive posterior retinopathy of prematurity

Objective To observe the clinical characteristics and treatment outcomes of aggressive posterior retinopathy of prematurity(AP-ROP).Methods Thirty-five eyes (18 patients) diagnosed with AP-ROP were studied from January 2006 to January 2011.All the patients were examined by 28 D optical lens,sclera compressor and wide-angle digital retinal imaging system (RetCam Ⅱ ).Laser photocoagulation with 532 nm wavelength using binocular indirect ophthalmoscope was used in all the infants within 12 hours after confirmed diagnosis. Thirteen eyes (37.1％) progressed to retinal detachment after laser photocoagulations were surgically treated,while 22 eyes (62.9 ％) underwent laser photocoagulation alone.Follow-up ranged from 6 months to 5 years,with a mean of 23.5 months.Results All AP-ROP lesions are located in zone 1 and posterior zone 2,with substantial dilated and tortuous retinal vessels.It is difficult to distinguish between the retinal vein and small arteries.There are shunts from vessel to vessel within the retina and no clear boundary between the vascularized and non-vascularized retina.Neovascularization lesions are flat and hard to be identified.There are no demarcation ridges.After laser treatment,22 eyes achieved good outcomes.Among 13 eyes who received vitrectomy,8 eyes achieved retinal reattachment after surgery,while 5 eyes developed total retinal detachment.Conclusion AP-ROP has specific clinical manifestations.Timely laser photocoagulation and early surgical treatment is necessary for AP-ROP. Key words: Retinopathy of prematurity/therapy; Laser coagulation; Vitrectomy

Focal depth of digital lensless Fourier transform micro-holographic system

Based on the Strehl criterion of coherent lens imaging system, the focal depth (FD) of lensless Fourier digital micro-holographic system is deduced. The FD expressions of the holographic systems with symmetrical and unsymmetrical reference point sources are obtained. The results show that the FD of lensless Fourier digital micro-holographic system is dependent not only on the optical wavelength and the numerical aperture of the recording system but also on the offset of the reference optical source, which is different from the FD of lensless Fourier digital micro-holographic system. The validities of the theoretical analysis are demonstrated by the computer simulations and experiments.

Analysis of Radially Restored Images for Spherical Single Lens Cellphone Camera

A spherical single lens imaging system for cellphone camera is proposed in this research. The overall thickness from the front surface of the lens to the image sensor is approximately 4.5 mm, which is competitive compared to 6~7 mm of current cellphone camera modules that use compound lens system. One defect of this spherical single lens that deteriorates image quality is radially variant blur, which is produced by one of the optical aberrations called field curvature. We describe a novel method of blur restoration that employs polar image and polar Point Spread Function (PSF) converted from Cartesian image and Cartesian PSF. The blurred image was radially segmented into several regions, to which polar PSFs at different field angles were applied. Results of visual and quantitative evaluation indicate that number of segmented regions and weighted average of β/ n ratios, i.e., ratio of bandwidth to the number Circulant Blocks (CBs) of the polar PSF Block-Toeplitz-with-Circulant-Blocks (BTCB) matrices affect the restored image quality and Mean Square Error (MSE). Evaluation results on restored images using different polar image resolutions revealed that high resolution obtains good pixel continuity, whereas low resolution results in radially expanding pixel vacancies.

Actual Image Effect Creation According to a Real Lens Imaging System

Nowadays, digital imaging device has become a popular item of our daily life. Even a cell phone can gives a high density image. People can enjoy taking a photo at anytime and anywhere, but such a mechanically simplified imaging device usually cannot mount an optical lens filter. Therefore the digital filtering effect is needed. Many image effect filters have been released by image processing soft maker or digital camera manufacture, but most of them were made just for funny, the resulting image is unnatural. This research focuses on the digital filtering effect, and it is realized according to a real optical lens imaging system. In this work, we prepared several optical filter lenses, and take photos with or without using them. Assuming the photo without using a filter is the real object, and then the photo using the filter is the observed filtering image, the digital filter can be derived by a division theoretically. Using these digital filters, the resulting filtering images are gotten. From these result, we find that some of the filtering effect is good, but some of the effects were not enough. Therefore, assuming the cause of these problems from the experimental results, show the direction for future research such as improving experiment approach or adopting nonlinear algorithms is also attempt.