Function Of Illumination Research Articles

Shape measurement with modified phase-shift lateral shearing interferometry illumination and radial basis function.

Three-dimensional shapes of objects were evaluated with modified phase-shift lateral shearing interferometry illumination and radial basis function. A simple optical system was developed to create the fringe pattern based on the Murty interferometer. The phase shift was generated only by moving a plane-parallel plate along an in-plane parallel direction. A novel moving radial basis function method was presented to improve the quality of fringe patterns. And the proper calculation window size was given based on numerical simulation. Three-dimensional shapes of two kinds of objects were determined to verify the feasibility and effectiveness of the proposed method, and the reconstructed height distributions were in good accordance with the referenced data.

Correction to "Determination of Cell Doubling Times from the Return-on-Investment Time of Photosynthetic Vesicles Based on Atomic Detail Structural Models".

Cell doubling times of the purple bacterium Rhodobacter sphaeroides during photosynthetic growth are determined experimentally and computationally as a function of illumination. For this purpose, energy conversion processes in an intracytoplasmic membrane vesicle, the chromatophore, are described based on an atomic detail structural model. The cell doubling time and its illumination dependence are computed in terms of the return-on-investment (ROI) time of the chromatophore, determined computationally from the ATP production rate, and the mass ratio of chromatophores in the cell, determined experimentally from whole cell absorbance spectra. The ROI time is defined as the time it takes to produce enough ATP to pay for the construction of another chromatophore. The ROI time of the low light-growth chromatophore is 4.5–2.6 h for a typical illumination range of 10–100 μmol photons m–2 s–1, respectively, with corresponding cell doubling times of 8.2–3.9 h. When energy expenditure is considered as a currency, t...

Study of a full-wave equation-based seismic illumination analysis

Recently, the seismic illumination analysis has progressed considerably in methodology which has been developed not only from one-way wave equation-based illumination to full-wave equation-based illumination but also from conventional illumination analysis to directional illumination analysis with local plane-wave decomposition. Because of the inherent defects of the one-way wave equation, the full-wave equation-based seismic illumination methods have increasingly attracted more attention. However, full-wave equation-based wavefield includes both downgoing and upgoing waves, such as transmissive, turning, and reflected waves. This hybrid wavefield can mislead us in seismic illumination analysis. For the sake of a preferable seismic illumination analysis method, we separated upgoing and downgoing wavefields in the time domain using Poynting vector and defined the incident and reflected illumination analysis functions based on the separated wavefields. Furthermore, we applied these two new illumination functions in seismic illumination analysis with the Sigsbee2a model. Multiple-shot illumination results show that the full-wave illumination and incident illumination maps are consistent with the seismic migration image. Because of no interference caused by the interactions between upgoing and downgoing waves, the incident illumination is superior for illumination analysis. Successful application of the full-wave equation-based incident and reflected illumination functions in the actual acquisition direction design of marine seismic geometry verifies their applicability and reveals their excellent prospects.

Day of year, temperature, wind, and precipitation predict timing of bat migration

Many temperate-climate bats migrate tens to hundreds of kilometers from hibernacula to summer habitat each spring and in the opposite direction each fall. Understanding the timing of migration can help reduce the risk of disturbance via anthropogenic activities, guide effective management, and determine future impacts of a changing climate. We examined the influence of weather and day of year on the arrival and departure of Indiana bats (Myotis sodalis) monitored at a summer maternity colony site in central Indiana from 1998 to 2014, using emergence count data to track the timing of bat presence during the spring and fall migration seasons. We used an information theoretic approach to compare 23 models that predicted bat presence as a function of weather, climate, and lunar illumination; these models predicted arrival of the first Indiana bat and the first observation of a colony in spring, and the last observation of a colony and the last bat observed in fall. Bats embarked on spring and fall migrations to the maternity colony area at approximately the same time each year (arriving ∼3 April and departing ∼7 October) and variation was accounted for by changes in weather. Spring arrival and colony formation were predicted by higher temperatures ( = 22.5°C for colony formation) and precipitation and lower wind speeds, whereas lower temperatures ( = 25.9°C for colony breakup) and precipitation and higher wind predicted colony breakup and departure in fall. Spring migration coincided with periods of increased winds and, thus, we advocate for higher cut-in speeds for wind turbines during bat migration seasons. Resource managers should consider the entire time that bats are on the summer landscape when defining regulations and implementing conservation measures.

Electronic structure and vacancy formation in photochromic yttrium oxy-hydride thin films studied by positron annihilation

In order to investigate the mechanism of the photochromic effect in yttrium oxy-hydride (YOxHy) thin films, Doppler broadening positron annihilation spectroscopy (PAS) was applied to probe the electronic structure and the presence of vacancies in YOxHy and related materials as a function of composition, UV illumination and thermal annealing. The Doppler S and W parameter depth profiles of a series of Y, yttrium di-hydride YH1.9+δ and Y2O3 thin films show strong systematic changes caused by the distinct differences in electronic structure of the metals Y, YH1.9+δ and the wide band gap insulator Y2O3. The Doppler broadening parameters of photochromic YOxHy (a semiconductor with a band gap of ~2.6eV) are intermediate to those of YH1.9+δ and Y2O3. In order to probe the nanostructural changes related to the photochromic effect, the S parameter of YOxHy was monitored during in-situ UV illumination. A small but systematic increase of the S parameter was observed, possibly induced by generation of cation mono-vacancies or small vacancy clusters involving generated anion vacancies. The changes did not relax during bleaching under dark conditions, showing that the structural changes are not directly responsible for the photochromic mechanism. For temperatures above around 90°C, thermal annealing leads to a substantial increase in the Doppler S parameter, pointing to the formation of vacancies by local removal of hydrogen. Simultaneously, the optical band gap increases, consistent with an increase in O:H ratios.

Determination of Cell Doubling Times from the Return-on-Investment Time of Photosynthetic Vesicles Based on Atomic Detail Structural Models.

Cell doubling times of the purple bacterium Rhodobacter sphaeroides during photosynthetic growth are determined experimentally and computationally as a function of illumination. For this purpose, energy conversion processes in an intracytoplasmic membrane vesicle, the chromatophore, are described based on an atomic detail structural model. The cell doubling time and its illumination dependence are computed in terms of the return-on-investment (ROI) time of the chromatophore, determined computationally from the ATP production rate, and the mass ratio of chromatophores in the cell, determined experimentally from whole cell absorbance spectra. The ROI time is defined as the time it takes to produce enough ATP to pay for the construction of another chromatophore. The ROI time of the low light-growth chromatophore is 4.5-2.6 h for a typical illumination range of 10-100 μmol photons m-2 s-1, respectively, with corresponding cell doubling times of 8.2-3.9 h. When energy expenditure is considered as a currency, the benefit-to-cost ratio computed for the chromatophore as an energy harvesting device is 2-8 times greater than for photovoltaic and fossil fuel-based energy solutions and the corresponding ROI times are approximately 3-4 orders of magnitude shorter for the chromatophore than for synthetic systems.

Freeform illumination design model for multiple light sources simultaneously.

In this paper, we have proposed an innovative model of freeform illumination design, which differs from the current model that covers almost all of the existing freeform illumination systems. In our model, a freeform illumination system is designed for multiple light sources simultaneously, rather than just for one certain source like the current model. All the sources have the same size, shape, intensity distribution, and other photometric characteristics, but are located at different positions or directions. Each source can individually achieve an illumination pattern on the target plane. All the patterns are expected to have the same size, shape, and illuminance distribution, but the position of each pattern has a linear relationship with the position or direction of the corresponding source. Two new (to our knowledge) illumination functions can be realized in our model, as the light sources are non-single and movable. The first one is the continuous scanning of the illumination pattern on the target plane, and the second one achieves a flexible, diverse, and controllable array of illumination patterns on the target plane. As an example, a coaxial freeform illumination system has been designed under the framework of this model, in which multiple collimated light sources are introduced simultaneously. The design method and process of the system are presented. The system is further promoted, and the two new illumination functions are explained in detail based on the design example.

Orange Carotenoid Protein Picosecond Dynamics Changes with Photo and Chemical Activation

Orange carotenoid protein (OCP) is the only photosensory protein described to date having a carotenoid as the active chromophore. Upon strong green-blue (or white) illumination, OCP goes from the orange inactive state (OCPO) to the red active state (OCPR) [1]. OCPR interacts with the phycobilisome (PB), assisting in thermal energy dissipation. This dissipation diminishes the formation of reactive oxygen which damages the photosynthetic apparatus and leads to cell death [2]. OCP has a large conformational change as it goes from OCPO to OCPR, and this structural change is thought to be essential to the energy quenching interaction with the PB. However, the conversion from inactive to active state has been recently shown to also occur with high chaotrope concentrations. Specifically high concentration NaSCN produces a long lived red state in the absence of photoexcitation [3]. We suggest that both the susceptibility of OCP to large conformational change and its interaction with PB are associated with changes in the long range picosecond structural flexibility. We measure OCP protein flexibility changes with photoactivation and chemical activation using terahertz absorption spectroscopy. Temperature dependent terahertz time domain spectroscopy is measured in the 100 - 290 K range on OCP solutions as a function of illumination and NaSCN concentration. A rapid increase in the THz absorbance is observed in the 180-220 K range. We quantify the picosecond structural flexibility by both the net THz absorption and the dynamical transition temperature, which scales with structural stability. R.E.B acknowledges DOE award DE-FG02-07ER15902 and A.G.M acknowleges NSF awards DBI 1556359 and MCB 1616529, and DOE award DE-SC0016317 for support of the work.1. Wilson, A. et al. Proc. Natl. Acad. Sci. U. S. A. 105:12075-12080(2008).2. Wilson, A. et al. Plant Cell, 18:992-1007(2006).3. King, J.D. et al. FEBS Lett, 588:4561-4565(2014).

The Pattern of Retinal Ganglion Cell Loss in OPA1-Related Autosomal Dominant Optic Atrophy Inferred From Temporal, Spatial, and Chromatic Sensitivity Losses.

PurposeProgressive retinal ganglion cell (RGC) loss is the pathological hallmark of autosomal dominant optic atrophy (DOA) caused by pathogenic OPA1 mutations. The aim of this study was to conduct an in-depth psychophysical study of the visual losses in DOA and to infer any selective vulnerability of visual pathways subserved by different RGC subtypes.MethodsWe recruited 25 patients carrying pathogenic OPA1 mutations and age-matched healthy individuals. Spatial contrast sensitivity functions (SCSFs) and chromatic contrast sensitivity were quantified, the latter using the Cambridge Colour Test. In 11 patients, long (L) and short (S) wavelength–sensitive cone temporal acuities were measured as a function of target illuminance, and L-cone temporal contrast sensitivity (TCSF) as a function of temporal frequency.ResultsSpatial contrast sensitivity functions were abnormal, with the loss of sensitivity increasing with spatial frequency. Further, the highest L-cone temporal acuity fell on average by 10 Hz and the TCSFs by 0.66 log10 unit. Chromatic thresholds along the protan, deutan, and tritan axes were 8, 9, and 14 times higher than normal, respectively, with losses increasing with age and S-cone temporal acuity showing the most significant age-related decline.ConclusionsLosses of midget parvocellular, parasol magnocellular, and bistratified koniocellular RGCs could account for the losses of high spatial frequency sensitivity and protan and deutan sensitivities, high temporal frequency sensitivity, and S-cone temporal and tritan sensitivities, respectively. The S-cone–related losses showed a significant deterioration with increasing patient age and could therefore prove useful biomarkers of disease progression in DOA.

Perifoveal S-cone and rod-driven temporal contrast sensitivities at different retinal illuminances.

We evaluated a technique for measuring temporal contrast sensitivities to sine-wave modulation driven by S-cones and rods in the perifovea using triple silent substitution. Isolating stimuli for S-cones and rods were created using an eight-channel, four-primary LED stimulator that has been validated before. Sensitivities were measured at 10 different temporal frequencies between 1 and 28 Hz in three normal observers at 14 different retinal illuminances between 0.07 and 587 photopic troland (phot Td) and at three different retinal illuminances over the same range in one S-cone monochromat. The technique was further validated by measuring bleaching adaptation in two normal subjects, demonstrating sufficient isolation in rods. Good isolation was apparent from the differences in the temporal contrast sensitivity functions and the sensitivity-versus-retinal illuminance functions between S-cones and rods, and also from the results in the S-cone monochromats and the delayed recovery of rod sensitivities after bleaching. The results will help to determine optimal stimulus conditions in future studies. The results in the S-cone monochromat demonstrate the potential clinical value of our protocol.

A Study on Effective Dimming Control Scheme Using Optical Spreading Codes in Visible Light Communication

In this paper, we proposed a new dimming control scheme by using direct sequence spreading coding (DSSC) scheme in visible light communication (VLC). VLC systems using LED lighting can provide illumination functions and communication services at the same time. In order to provide simultaneous illumination and communication services, dimming control should be considered. Dimming control means that LED lighting should maintain a constant brightness in accordance with user requirements while communication services are offered. In IEEE 802.15.7 VLC standard, on-off keying (OOK) and variable pulse position modulation (VPPM) are defined as pulse modulation schemes for dimming control. In particular, 4B/6B, 8B/10B block coding and Manchester coding schemes have been proposed for stable dimming control in OOK. However, in such a case, stable dimming control is possible although the communication performance is degraded. In order to solve those problems, we propose a VLC system based on OOK modulation with DSSC. The proposed system can simultaneously stabilize dimming control and improve communication performance by obtaining spread diversity gain. The simulation results show that the proposed system provides superior dimming and BER performances compared to conventional dimming modulation schemes.

Full-wave seismic illumination and resolution analyses: A Poynting-vector-based method

Illumination and resolution analysis provides vital information regarding the response of an imaging system to subsurface structures. However, generating the resolution function is often computationally intensive, which prevents it from being widely used in practice. This problem is particularly severe for the time-domain migration method, such as reverse time migration (RTM). To solve this problem, we have developed a fast full-wave-based illumination and resolution analysis method. The source- and receiver-side waves are extrapolated to the subsurface for simulating the imaging process. To create the relations linking the incident and scattering directions to the target wavenumber components, we have adopted an efficient Poynting-vector-based method for wavefield angle decomposition. By taking the approximation that the time-domain wavefield preserves the source spectrum during propagation, massive input/output and trace-by-trace Fourier transform can be avoided and the finite-frequency calculated broadband signal can be directly converted to the wavenumber domain for calculating the point spreading functions (PSFs). Combining these approaches, the resulting method avoids intensive calculations, massive input/output, and huge storage requirements commonly involved in generating the illumination and resolution functions. The method is highly efficient and particularly suitable to team with RTM for resolution analysis. Numerical examples are used to validate this method. We have determined how to calculate the acquisition dip response and PSFs, based on which, the quality of the depth image can be significantly improved.

Unequal error control scheme for dimmable visible light communication systems

Visible light communication (VLC), which has the advantages of a very large bandwidth, high security, and freedom from license-related restrictions and electromagnetic-interference, has attracted much interest. Because a VLC system simultaneously performs illumination and communication functions, dimming control, efficiency, and reliable transmission are significant and challenging issues of such systems. In this paper, we propose a novel unequal error control (UEC) scheme in which expanding window fountain (EWF) codes in an on–off keying (OOK)-based VLC system are used to support different dimming target values. To evaluate the performance of the scheme for various dimming target values, we apply it to H.264 scalable video coding bitstreams in a VLC system. The results of the simulations that are performed using additive white Gaussian noises (AWGNs) with different signal-to-noise ratios (SNRs) are used to compare the performance of the proposed scheme for various dimming target values. It is found that the proposed UEC scheme enables earlier base layer recovery compared to the use of the equal error control (EEC) scheme for different dimming target values and therefore afford robust transmission for scalable video multicast over optical wireless channels. This is because of the unequal error protection (UEP) and unequal recovery time (URT) of the EWF code in the proposed scheme.

Improving the rectifying properties of metal/semiconductor junction using novel material: Zam-zam

In this work, a 1.42μm thin layer using zam-zam water has been formed as a thin interlayer to modify the Schottky barrier height (SBH) between Au contacts and Si substrates. Better rectifying ratio (2.14×105 at±1V bias) has been obtained according to Au/p-Si Schottky diode. The variations in the electrical characteristics of Au/zam-zam (ZZ) layer/p-Si Schottky diode have been investigated as a function of temperature, x-ray irradiation and illumination by using current–voltage (I–V) measurements. It has been found that the I–V characteristics of the Au/ZZ layer/p-Si Schottky diode strongly depend on temperature, x-ray irradiation and illumination. The temperature dependent of the junction parameters such as ideality factor and the barrier height has been explained by barrier inhomogeneities by assuming a Gaussian distribution of barrier heights at the interface of the junction materials. Furthermore, the I–V characteristic of the Au/ZZ layer/p-Si Schottky diode has showed a good illumination response like a solar cell.

Characterization and modeling of organic (P3HT:PCBM) solar cells as a function of bias and illumination

We investigated the response of roll coated organic solar cells at different bias voltages and illumination levels to implement a detailed impedance model. The technique used for the investigation is based on the combination of standard DC characterization with the impedance spectroscopy at different bias and illumination intensity conditions.We analyzed both fresh and intentionally degraded cells. The impedance spectra show different peaks evolutions, depending on the degradation of the cells. Moreover, the same trend appears by measuring the cell at different illumination levels. To describe the cell impedance behaviors we suggest an electrical model based on distributed elements. By fitting the model to experimental data, we extrapolate the parameters related to electron transport, recombination and accumulation. The main differences between fresh and degraded samples are underlined.

Daylight Sensing LED Lighting System

Adaptation of artificial light based on the available amount of daylight is known to be effective for energy savings. To achieve such daylight control, the state-of-the-art lighting systems use external photodetectors. The photodetector measures the combined contribution of artificial light and daylight, and closed-loop control schemes are used to determine the dimming levels of luminaires to produce the right amount of artificial light. In this paper, we propose LED luminaires that can perform the dual function of illumination and daylight sensing, obviating the need of additional photodetectors. We present a daylight sensing luminaire prototype and consider two driving protocols for sensing and illumination. An open-loop control scheme is then considered for daylight control. The proposed system is shown to be more robust to reflectance changes in comparison with a photodetector-based closed-loop lighting control system.

Effects of light variation on Schwalbe's line-based anterior chamber angle metrics measured with cirrus spectral domain optical coherence tomography.

Evaluate the impact of variations in ambient lighting conditions on the reproducibility/reliability of Schwalbe's Line (SL)-based anterior chamber angle (ACA) metrics using spectral domain optical coherence tomography (SD-OCT). Images were taken at Doheny Eye Centers-UCLA clinic, which were randomized, masked and graded twice by dual reading centre graders. Twenty-five normal/healthy participants with open angles Inferior angles were imaged using Cirrus SD-OCT under five light levels (foot-candles (fc) measured at camera-eye interface with Sper light-meter) with the instrument's corneal illumination function set to default level of 50 (CIdef) and low 5 (CIlow). Each eye was imaged 20 times, totaling 500 assessments. SL-angle-opening-distance (SL-AOD) and SL-trabecular-iris-space-area (SL-TISA) measured using custom ImageJ software. Intra-/inter-grader variability analyses were completed using Statistical-Package-for-Social-Science and Bland-Altman plots demonstrated limits of agreement for comparisons. Light level demonstrated a linear relationship with angle size, thus differences from highest to lowest light levels were compared. Decreasing light from 1.0 → 0.0fc at CIdef decreased SL-AOD from 394 µm +/- 137 µm → 356 µm +/- 137 µm (mean percent difference (MPD) = 10.71%,P < 0.001) and SL-TISA from 297 µm(2) +/- 114 µm(2) → 261 µm(2) +/- 109 µm(2) (MPD = 13.7%, P < 0.001). Decreasing from 1.0 → 0.0fc at CIlow decreased SL-AOD from 366 µm +/- 136 µm → 329 µm +/- 122 µm (MPD = 10.9%, P < 0.001) and SL-TISA from 271 µm(2) +/- 113 µm(2) → 234 µm(2) +/- 98 µm(2) (MPD = 15.8%, P < 0.001). There was 7.9/11.4% (both P < 0.001) difference for SL-AOD/SL-TISA between CIdef → CIlow at 1.0fc, and 7.7/9.4% (both P < 0.001) difference at 0.0fc. Intra-/inter-grader results showed high reproducibility for all metrics (MPD = 0.33-4.4%; CV = 0.96-1.36; PCC = 0.93-0.95(P < 0.001); R2 = 0.94-0.98). Bland-Altman plots did not demonstrate bias, with repeat-ability and agreement among measurements. Using Cirrus SD-OCT, we found that SL-based ACA morphometrics are exquisitely sensitive to changes in ambient illumination and also corneal illumination by the OCT instrument. Consistently imaging in the darkest room possible is recommended (≤0.2 fce).

Method of Determination of RMS Exposure of Ex-tended Source Image by Microphotometry

Background. Among the parameters and functions to assess the quality of images formed by optical systems RMS spot diagrams parameter is used. This option is usually defined by beam ray-tracing going through optical system. There is a fundamental ability to regenerate RMS by microphotometry of image of real point light sources. However, the RMS of the image is distorted due to finite size source. The problem is that the separation of RMS components values, which are caused by the parameters of the light source and the optical system aberrations.Objective. The recovery of RMS aberration component based on the results of microphotometry of image of extended source of radiation generated with optical system to be tested.Methods. The mathematical tools polar calculations were used, axial and centrifugal RMS from distribution function of illumination in the image of the extended light source, close to the spot. The calculations of mentioned RMS types are conducted by the radii formulas for moments of inertia that are known in theoretical mechanics. Analogue mass they contain is spatial density of luminous flux in the optical image source. In calculating of RMS the source length is included using Huygens- Steiner theorem.Results. New mathematical observations for calculation of RMS including illumination distribution in the image of light sources are obtained. It was established that RMS of each type is Pythagorean sum of components, one of which is specified by the parameters of the source, and the other by the aberrations of the optical system. According to the results of the regenerated RMS from microphotometry of the image of source and the data on the source parameters aberrational component can be determined in each RMS type.Conclusion. The study confirms the possibility of determining the aberration RMS of the optical system according to the results of microphotometry of image of extended light source. The method allows creating new photoelectrical hardware for measuring distances to objects, and to create new types of ophthalmic devices.

Effects of nonequilibrium quasiparticles in a thin-film superconducting microwave resonator under optical illumination

We have illuminated a thin-film superconducting Al lumped-element microwave resonator with 780 nm light and observed the resonator quality factor and resonance frequency as a function of illumination and microwave power in the 20 to 300 mK temperature range. The optically induced microwave loss increases with increasing illumination but decreases with increasing microwave power. Although this behavior may suggest the presence of optically activated two-level systems, we find that the loss is better explained by the presence of nonequilibrium quasiparticles generated by the illumination and excited by the microwave drive. We model the system by assuming that the illumination creates an effective source of phonons with energy higher than double the superconducting gap and solve the coupled quasiparticle-phonon rate equations. We fit the simulation results to our measurements and find good agreement with the observed dependence of the resonator quality factor and frequency shift on temperature, microwave power, and optical illumination. Examination of the model reveals approaches to reducing optically induced loss and improving the relaxation time of superconducting quantum devices.

On the nature of the photocurrent in secondary-emission multipliers of atomic-beam tubes

The physical cause for origination of the photocurrent in secondary-emission multipliers (SEMs) after long-term studies in the operation mode used for stabilization of parameters of atomic-beam tubes is considered. A general expression for the spectral photon flux penetrating through the channel connecting the ionizer with the SEM due to reflections in the channel and impinging on the surface of the first dynode of the SEM is obtained. Estimates of three versions of simplification of the general expression for the spectral photon flux are performed for several δ, i.e., average values of fine irregularities (in μm) characterizing the surface roughness of the channel, including a specified class of the channel treatment quality, and radiation angles of incidence on the channel surface θ. The expression that is the closest to correct determination of the illumination function of the surface of the first SEM dynode by a absolute black body source, which is described by the Wien equation at radiation wavelengths λ ≤ 2 μm, is determined.