Blocking Filter Research Articles

2-nm narrow band pass f ilter in standard conf iguration evaporate coating machine

High sophisticated optical monitoring systems like the OMS 5000 from Leyboldoptics are commonly used in vacuum coating system to improve the capabilities and reliability of production processes concerning optical performance and repeatability optics. This letter describes a method to perform high end optical filters with additional backside blocking over a wide spectral range. The direct monitoring with intermittent measurement on a large area rotating substrate holder is used to facilitate a narrow band pass filter of 2-nm half bandwidth at 532 nm and high transmittance together with a complex blocking filter to retard disturbing radiation from the ultraviolet (UV) range to the near infrared range. The machine is an ARES 1 350 coating system with basically standard conf iguration. 2013 Chinese Optics Letters.

A Technique For Removing Second-Order Light Effects From Hyperspectral Imaging Data

The Hyperspectral Imager for the Coastal Ocean (HICO) instrument currently on board the International Space Station is a new sensor designed specifically for the studies of turbid coastal waters and large inland lakes and rivers. It covers the wavelength range between 0.4 and 0.9 μm with a spectral resolution of 5.7 nm and a spatial resolution of approximately 90 m. The HICO sensor is not equipped with a second-order blocking filter in front of the focal plane array. As a result, the second-order light from the shorter visible spectral region falls onto the detectors covering the near-IR spectral region above 0.8 μm. In order to have accurate radiometric calibration of the near-IR channels, the second-order light contribution needs to be removed. The water-leaving radiances of these near-IR channels over clear ocean waters are close to zero because of strong liquid water absorption above 0.8 μm. Through analysis of HICO imaging data containing features of shallow underwater objects, such as coral reefs, we have developed an empirical technique to correct for the second-order light effects in near-IR channels. HICO data acquired over Midway Island in the Pacific Ocean and the Bahamas Banks in the Atlantic Ocean are used to demonstrate the effectiveness of the new technique.

Application of Raman Amplification using a Reflector in Passive Optical Networks

We have studied Raman amplification in passive optical networks (PON). A use of a reflector, which reflects pump wave for Raman amplification, is proposed in this paper to mitigate pump power. The reflector also serves as a pump blocking filter for each subscriber. To clarify the effects of a reflector in PON, the wavelength dependence of Raman gain (or loss) and amplified spontaneous emission (ASE) has been investigated theoretically and experimentally. Raman amplification with a reflector is applied to both ordinary PON systems and wavelength division multiplex (WDM) PON systems as case studies. Finally, effects of Raman amplification with a reflector are discussed.

Design and Ground Calibration of the Helioseismic and Magnetic Imager (HMI) Instrument on the Solar Dynamics Observatory (SDO)

The Helioseismic and Magnetic Imager (HMI) investigation (Solar Phys. doi: 10.1007/s11207-011-9834-2, 2011) will study the solar interior using helioseismic techniques as well as the magnetic field near the solar surface. The HMI instrument is part of the Solar Dynamics Observatory (SDO) that was launched on 11 February 2010. The instrument is designed to measure the Doppler shift, intensity, and vector magnetic field at the solar photosphere using the 6173 A Fe i absorption line. The instrument consists of a front-window filter, a telescope, a set of waveplates for polarimetry, an image-stabilization system, a blocking filter, a five-stage Lyot filter with one tunable element, two wide-field tunable Michelson interferometers, a pair of 40962 pixel cameras with independent shutters, and associated electronics. Each camera takes a full-disk image roughly every 3.75 seconds giving an overall cadence of 45 seconds for the Doppler, intensity, and line-of-sight magnetic-field measurements and a slower cadence for the full vector magnetic field. This article describes the design of the HMI instrument and provides an overview of the pre-launch calibration efforts. Overviews of the investigation, details of the calibrations, data handling, and the science analysis are provided in accompanying articles.

In Vitro Detection of UV‐Induced Damage of the Cornea, Lens and RPE

AbstractPurpose UV‐A and UV‐B radiation from sunlight is a major source of ocular oxidative damage. This paper describes in vitro methods that can be used to detect ocular damage from UV radiation.Methods Human corneal epithelial cells, lens epithelial cells, and RPE cells were cultured and Ultraviolet A/Ultraviolet B blocking filters and UVB‐only blocking filters were placed between the cells and a UV light source. Cells were irradiated with UV radiations at various energy levels, with and without filters. Cell viability after exposure was determined using the metabolic dye alamarBlue and by evaluating changes in nuclei, mitochondria, membrane permeability, and cell membranes using the fluorescent dyes Hoechst 33342, rhodamine 123, calcein AM, ethidium homodimer‐1, and annexin V. Images of the cells were taken with a Zeiss 510 confocal laser scanning microscopeResults The alamarBlue assay results of UV‐exposed cells without filters showed energy level‐dependent decreases in cellular viability. However, UV treated cells with 400 nm LP filter protection showed the equivalent viability to untreated cells at all energy levels. Also, UV irradiated cells with 320 nm LP filter showed lower cell viability than the unexposed control cells, yet higher viability than UV‐exposed cells without filters in an energy level‐dependent manner. The confocal microscopy results also showed that UV radiation can cause significant dose‐dependent degradations of nuclei and mitochondria in ocular cells. The annexin V staining also showed an increased number of apoptotic cells after UV irradiation.Conclusion UV‐induced damage can be evaluated to test the effectiveness of UV‐absorbing contact lenses and intraocular lenses with bioassays that measure change in in vitro cells

Convex-Programming Design of Linear and Nonlinear Phase Wideband Blocking Filters

Blocking filters are commonly used in array processing to excise targets from data when suitable target-free training data is not available. A drawback is the reduction of the effective size of the array by the order of the filter, motivating a search for the smallest filter that meets the design specifications. Common linear-phase approaches lead to convex optimization and efficient global solutions, but can be inefficient when the phase of the blocking filter is unimportant. Although direct magnitude-response optimization is nonconvex in general, for narrowband linear arrays optimal-magnitude blocking filters can be found using constrained optimization followed by spectral factorization. This approach cannot be directly applied to wideband arrays, as finite-support spectral factors do not generally exist in higher dimensions. Instead, a procedure is presented in which an approximate multidimensional spectral factor of an optimized spectral density is used as a target response in a second optimization stage. Linear and nonlinear-phase solutions are found and compared for both narrowband and wideband notch filters, with the nonlinear phase outperforming the linear phase in both notch width and passband error. The various optimizations are performed using second-order cone programming, an efficient class of convex optimization.

Possible Behavioral Avoidance of UV-B Radiation and Sunlight in Wood Frog (Lithobates sylvaticus) Tadpoles

Little is known of the ability of amphibian larvae to behaviorally avoid exposure to UV radiation. We examined whether wood frog (Lithobates sylvaticus) tadpoles avoid UV-B radiation and, more generally, sunlight. We found that wood frog tadpoles were located more often under a UV-B blocking filter (only after 60 min) or under shade than would be expected if their behavior was random. Our observations suggest that wood frog tadpoles may minimize exposure to UV-B, either by directly avoiding UV-B or coincidentally by choosing shade.

Wavelength Dependence of the Helioseismic and Magnetic Imager (HMI) Instrument onboard the Solar Dynamics Observatory (SDO)

The Helioseismic and Magnetic Imager (HMI) instrument will produce Doppler-velocity and vector-magnetic-field maps of the solar surface, whose accuracy is dependent on a thorough knowledge of the transmission profiles of the components of the HMI optical-filter system. Here we present a series of wavelength-dependence calibration tests, performed on the instrument from 2005 onwards, to obtain these profiles. We obtained the transmittances as a function of wavelength for the tunable and non-tunable filter elements, as well as the variation of these transmittances with temperature and the angle of incidence of rays of light. We also established the presence of fringe patterns produced by interferences inside the blocking filter and the front window, as well as a change in transmitted intensity with the tuning position. This thorough characterization of the HMI-filter system confirmed the very high quality of the instrument, and showed that its properties are well within the required specifications to produce superior data with high spatial and temporal resolution.

Possible Behavioral Avoidance of UV-B Radiation and Sunlight in Wood Frog (Lithobates sylvaticus) Tadpoles

Little is known of the ability of amphibian larvae to behaviorally avoid exposure to UV radiation. We examined whether wood frog (Lithobates sylvaticus) tadpoles avoid UV-B radiation and, more generally, sunlight. We found that wood frog tadpoles were located more often under a UV-B blocking filter (only after 60 min) or under shade than would be expected if their behavior was random. Our observations suggest that wood frog tadpoles may minimize exposure to UV-B, either by directly avoiding UV-B or coincidentally by choosing shade.

Directly imaging damped Lyman α galaxies at z > 2 - I. Methodology and first results★

We present the methodology for, and the first results from, a new imaging program aimed at identifying and characterizing the host galaxies of damped Lyman-alpha absorbers (DLAs) at z>2. We target quasar sightlines with multiple optically-thick HI absorbers and use the higher-redshift system as a "blocking filter" (via its Lyman-limit absorption) to eliminate all far-ultraviolet (FUV) emission from the quasar. This allows us to directly image the rest-frame FUV continuum emission of the lower-redshift DLA, without any quasar contamination and with no bias towards large impact parameters. We introduce a formalism based on galaxy number counts and Bayesian statistics with which we quantify the probability that a candidate is the DLA host galaxy. This method will allow the identification of a bona fide sample of DLAs that are too faint to be spectroscopically confirmed. The same formalism can be adopted to the study of other quasar absorption line systems (e.g. MgII absorbers). We have applied this imaging technique to two QSO sightlines. For the z~2.69 DLA towards J073149+285449, a galaxy with impact parameter b=1.54"=11.89 kpc and implied star formation rate (SFR) of ~5 M/yr is identified as the most reliable candidate. In the case of the z~2.92 DLA towards J211444-005533, no likely host is found down to a 3-sigma SFR limit of 1.4 M/yr. Studying the HI column density as a function of the impact parameter, including 6 DLAs with known hosts from the literature, we find evidence that the observed HI distribution is more extended than what is generally predicted from numerical simulation.

8.1: Invited Paper: Enhancing the Visible with the Invisible: Exploiting Near Infrared to Advance Computational Photography and Computer Vision

AbstractSiliconbased digital camera sensors exhibit significant sensitivity beyond the visible spectrum 400–700nm. They are able to capture wavelengths up to 1100 nm, i.e., they are sensitive to nearinfrared NIR radiation. This additional information is conventionally treated as noise and is absorbed by a NIR blocking filter affixed to the sensor. We show that retaining instead of removing NIR information can significantly improve certain computational photography and computer vision tasks. Indeed, intrinsic properties of the NIR wavelength band guarantee that images can be sharper, less affected by manmade colorants, and more resilient to changing light conditions. The benefits of using NIR images in conjunction with standard color images in applications such as haze removal, skin smoothing, single and multiple illuminant detection, shadow detection, and material classification is discussed.

Spectropolarimetric Imaging of Laser-Induced Fluorescence

A compact wavelength and polarization agile acoustooptic tunable filter (AOTF)-based imager is used to obtain both spectral and polarization signatures from laser-induced fluorescence in a solution for the first time. This imager covers the visible to near-IR region from 400 to 800 nm, with a 10-nm spectral resolution at 600 nm, it uses an electronically tunable TeO 2 AOTF as a bandpass filter, and a nematic liquid crystal variable retarder to change polarization to obtain two orthogonally polarized images at each spectral wavelength. In this experiment, a blocking filter for the laser was not used before the camera. Here we present fluorescence measurement results for a dilute solution of fluorescein in acetone, using a 532-nm laser. Our results showed that for the vertically polarized exciting light, the fluorescence has a spectropolarimetric dependence in agreement with literature. This imager provides a simpler yet powerful tool to facilitate such measurements remotely with ability to extract both spectral and polarization information at each pixel of an extended sample image.

Behavioral filter vent blocking on the first cigarette of the day predicts which smokers of light cigarettes will increase smoke exposure from blocked vents.

Filter vent blocking on best-selling light cigarettes increases smoke yield during standard machine testing but not in clinical investigations of smokers. The purpose of the study was to investigate the effect of (a) manipulating cigarette filter vent blocking and (b) blocking status of first cigarette of the day on carbon monoxide (CO) boost. Participants (n = 25; Marlboro Lights nonmenthol cigarette smokers, age range 21-60 years, minimum 15 daily cigarettes, and daily smoking for a minimum 5 years) completed the laboratory-based, within-subject, double-blind, cross-over design of 2 smoking sessions, one utilizing a smoking topography device, one without. Each session consisted of smoking 4 cigarettes; 2 with filter vents blocked and 2 with filter vents unblocked. Spent first daily cigarette filters collected between sessions were scored for evidence of filter vent blocking. Smoking cigarettes with blocked filter vents significantly increased CO boost in both laboratory sessions (p < .001). Those who blocked their first cigarette of the day (n = 10) had significantly greater CO boost when smoking a blocked cigarette, in relation to smoking an unblocked cigarette and in comparison with nonblockers (p = .04). Total puff volume was a significant predictor of CO boost when smoking unblocked and blocked cigarettes (ps < .04). Blocking filter vents significantly increased smoke exposure in relation to when filter vents are not blocked, particularly for those who block filter vents on their first cigarette of the day. Total puff volume predicted CO boost, and results suggest that smokers adjust their smoking behavior by cigarette blocking status. Those smokers who block filter vents may be increasing their exposure by 30%.

Mechanism of potassium-channel selectivity revealed by Na+ and Li+ binding sites within the KcsA pore

Potassium channels allow K(+) ions to diffuse through their pores while preventing smaller Na(+) ions from permeating. Discrimination between these similar, abundant ions enables these proteins to control electrical and chemical activity in all organisms. Selection occurs at the narrow selectivity filter containing structurally identified K(+) binding sites. Selectivity is thought to arise because smaller ions such as Na(+) do not bind to these K(+) sites in a thermodynamically favorable way. Using the model K(+) channel KcsA, we examined how intracellular Na(+) and Li(+) interact with the pore and the permeant ions using electrophysiology, molecular dynamics simulations and X-ray crystallography. Our results suggest that these small cations have a separate binding site within the K(+) selectivity filter. We propose that selective permeation from the intracellular side primarily results from a large energy barrier blocking filter entry for Na(+) and Li(+) in the presence of K(+), not from a difference of binding affinity between ions.

Highly Stable Molecular Layers on Nanocrystalline Anatase TiO2 through Photochemical Grafting

Well-defined molecular layers can be formed on the surface of nanocrystalline anatase TiO2 by photochemically grafting organic molecules bearing a terminal vinyl group. The molecular layers produced are shown to have minimal oxidation and are able to be patterned and uniformly grafted through optically thick nanocrystalline films. Stability tests show that the layers have excellent stability in deionized water at 80 degrees C, aqueous solutions at pH=1.0 and pH=10.3 at 65 degrees C, and acetonitrile for time scales approaching 1200 h. Degradation of the films in deionized water occurs using a AM1.5 full-spectrum solar simulator as an illumination source but is partially suppressed by filtering with a 400 nm UV blocking filter which blocks the above-bandgap light. A mechanism is proposed for the grafting reaction in which the surface hydroxyl groups trap photoexcited holes, facilitating reaction with the vinyl group.

γH2AX: A potential DNA damage response biomarker for assessing toxicological risk of tobacco products

Differentiation among American cigarettes relies primarily on the use of proprietary tobacco blends, menthol, tobacco substitutes, paper porosity, paper additives, and filter ventilation. These characteristics substantially alter per cigarette yields of tar and nicotine in standardized protocols promulgated by government agencies. However, due to compensatory alterations in smoking behavior to sustain a preferred nicotine dose (e.g., by increasing puff frequency, inhaling more deeply, smoking more cigarettes per day, or blocking filter ventilation holes), smokers actually inhale similar amounts of tar and nicotine regardless of any cigarette variable, supporting epidemiological evidence that all brands have comparable disease risk. Consequently, it would be advantageous to develop assays that realistically compare cigarette smoke (CS)-induced genotoxicity regardless of differences in cigarette construction or smoking behavior. One significant indicator of potentially carcinogenic DNA damage is double strand breaks (DSBs), which can be monitored by measuring Ser 139 phosphorylation on histone H2AX. Previously we showed that phosphorylation of H2AX (defined as γH2AX) in exposed lung cells is proportional to CS dose. Thus, we proposed that γH2AX may be a viable biomarker for evaluating genotoxic risk of cigarettes in relation to actual nicotine/tar delivery. Here we tested this hypothesis by measuring γH2AX levels in A549 human lung cells exposed to CS from a range of commercial cigarettes using various smoking regimens. Results show that γH2AX induction, a critical event of the mammalian DNA damage response, provides an assessment of CS-induced DNA damage independent of smoking topography or cigarette type. We conclude that γH2AX induction shows promise as a genotoxic bioassay offering specific advantages over the traditional assays for the evaluation of conventional and nonconventional tobacco products.

改进型窄带阻挡滤光片

A design approach is described to achieve spectral blocking filters of any spectral width and optical density for narrow blocking bands. We give new criterions to find the necessary number of layers from the desired bandwidth and optical density, and give new estimate equations which describe the number of layers required for designing a blocking filter of given bandwidth, high index, and optical density. This approach can be useful for laser line blocking, night vision filters, and many other general applications.

Second harmonic imaging of chloroplasts using the two-photon laser scanning microscope

BackgroundSecond harmonic information reveals information about the structure of spatially oriented structures with an asymmetry. We study the second harmonic images of the grana and intergranal parts of chloroplasts in the leaves of the shade moss Plagiomnium affine. ResultsA two-photon microscope with blocking filters to suppress fluorescence generated both forward and backward second harmonic illumination to be captured. In the starch free chloroplasts of the single cell layered laminae strong second harmonic generation (SHG) from the granal regions was emitted. Upon illumination the chloroplasts changed their orientation affecting the SHG signal. Chloroplast is reoriented upon illumination. ConclusionsSHG signals were successfully obtained from the grana without any possible confusion from SHG starch grains due to their absence.

Visual function and performance with blue‐light blocking filters in age‐related macular degeneration

Some dispute has occurred over the use of blue-light-attenuating intraocular lenses in age-related macular degeneration (AMD), as they may reduce scotopic vision. This study aimed to determine if a blue blocking filter would affect performance during eye-hand coordination and mobility tasks in scotopic illumination, psychophysically measured scotopic sensitivity or colour discrimination in AMD patients. Scotopic measures performed with and without a blue-attenuating filter included a mobility obstacle course, manipulation of cylindrical blocks and a psychophysical dark-adapted full-field flash test. A navy and blue sock colour sorting task evaluated photopic colour discrimination. Subjects were 22 bilateral pseudophakes with early AMD and visual acuity >6/24. On average with the filter, there was a 13% increase in time during the block test. The differences in time and number of bumps with versus without the filter were not significant for the mobility course. Performance with and without the filter was well correlated for the blocks (r = 0.70), flash test (r = 0.83) and mobility (r = 0.66), and the regression slopes were not significantly different from unity. 77% of subjects misidentified at least one navy sock as black with the filter compared with 9% without, with a significant increase in such misidentifications with the filter. The difference in scotopic visual function or performance with versus without a blue-blocking filter most likely does not produce a clinically significant effect or risk; however, detection of navy colour may be impaired.

DC Blocker Algorithms[DSP Tips &amp; Tricks

This paper presents a nonlinear-phase, but computationally efficient, dc blocking filter that achieves ideal operation when output data quantization is used. In addition, we described an alternate dc blocking filter that, at the expense of larger data memory, exhibits a linear-phase frequency response.