High Ambient Light Conditions Research Articles

Light wavelength and pulsing frequency affect avoidance responses of Canada geese.

Collisions between birds and aircraft cause bird mortality, economic damage, and aviation safety hazards. One proposed solution to increasing the distance at which birds detect and move away from an approaching aircraft, ultimately mitigating the probability of collision, is through onboard lighting systems. Lights in vehicles have been shown to lead to earlier reactions in some bird species but they could also generate attraction, potentially increasing the probability of collision. Using information on the visual system of the Canada goose (Branta canadensis), we developed light stimuli of high chromatic contrast to their eyes. We then conducted a controlled behavioral experiment (i.e., single-choice test) to assess the avoidance or attraction responses of Canada geese to LED lights of different wavelengths (blue, 483 nm; red, 631nm) and pulsing frequencies (steady, pulsing at 2 Hz). Overall, Canada geese tended to avoid the blue light and move towards the red light; however, these responses depended heavily on light exposure order. At the beginning of the experiment, geese tended to avoid the red light. After further exposure the birds developed an attraction to the red light, consistent with the mere exposure effect. The response to the blue light generally followed a U-shape relationship (avoidance, attraction, avoidance) with increasing number of exposures, again consistent with the mere exposure effect, but followed by the satiation effect. Lights pulsing at 2 Hz enhanced avoidance responses under high ambient light conditions; whereas steady lights enhanced avoidance responses under dim ambient light conditions. Our results have implications for the design of lighting systems aimed at mitigating collisions between birds and human objects. LED lights in the blue portion of the spectrum are good candidates for deterrents and lights in the red portion of the spectrum may be counterproductive given the attraction effects with increasing exposure. Additionally, consideration should be given to systems that automatically modify pulsing of the light depending on ambient light intensity to enhance avoidance.

3D target detection and spectral classification for single-photon LiDAR data.

3D single-photon LiDAR imaging has an important role in many applications. However, full deployment of this modality will require the analysis of low signal to noise ratio target returns and very high volume of data. This is particularly evident when imaging through obscurants or in high ambient background light conditions. This paper proposes a multiscale approach for 3D surface detection from the photon timing histogram to permit a significant reduction in data volume. The resulting surfaces are background-free and can be used to infer depth and reflectivity information about the target. We demonstrate this by proposing a hierarchical Bayesian model for 3D reconstruction and spectral classification of multispectral single-photon LiDAR data. The reconstruction method promotes spatial correlation between point-cloud estimates and uses a coordinate gradient descent algorithm for parameter estimation. Results on simulated and real data show the benefits of the proposed target detection and reconstruction approaches when compared to state-of-the-art processing algorithms.

Non-line-of-sight imaging based on an untrained deep decoder network.

In recent years, low-cost high-quality non-line-of-sight (NLOS) imaging by a passive light source has been a significant research dimension. Here, we report a new, to the best of our knowledge, reconstruction method for the well-known "occluder-aided" NLOS imaging configuration based on an untrained deep decoder network. Using the interaction between the neural network and the physical forward model, the network weights can be automatically updated without the need for training data. Completion of the optimization process facilitates high-quality reconstructions of hidden scenes from photographs of a blank wall under high ambient light conditions. Simulations and experiments show the superior performance of the proposed method in terms of the details and the robustness of the reconstructed images. Our method will further promote the practical application of NLOS imaging in real scenes.

Optimal Modulation Technique for Underwater Visible Light Communication Using Rolling-Shutter Sensor

The visible light communication (VLC) technique using a rolling-shutter sensor-based commercial camera has an advantage in that the LED and camera mounted on an underwater device ( e.g. , drone, sensor) can be effectively used as a transmitter (Tx) and a receiver (Rx), respectively, under water. On the other hand, a suitable modulation technique has not been well considered to realize a VLC system using a rolling-shutter sensor in an underwater channel that includes high ambient light conditions. In this paper, we design VLC systems using phase-shift keying (PSK), non-return-to-zero on- off keying (NRZ-OOK), and orthogonal frequency division multiplexing (OFDM), and evaluate them through simulations and experiments. The results suggested that the VLC system using PSK or OFDM is more resilient than that using NRZ-OOK in an underwater channel with low-frequency ambient light, and that a VLC system using PSK or NRZ-OOK is more tolerant than that using OFDM in environments with high ambient light, resulting in pixel saturation. In conclusion, the present study has demonstrated that PSK is the most suitable modulation technique for a VLC system using a rolling-shutter sensor in an underwater channel that includes high ambient light conditions.

Preferences for and use of light microhabitats differ among and within populations of a polytypic poison frog

Abstract Anti-predator strategies can influence trade-offs governing other activities important to fitness. Crypsis, for example, might make conspicuous sexual display especially costly, whereas aposematism might reduce or remove such costs. We tested for correlates of anti-predator strategy in Oophaga pumilio, a polytypic poison frog with morphs spanning the crypsis–aposematism continuum. In the wild, males of visually conspicuous morphs display from conspicuous perches and behave as if they perceive predation risk to be low. We thus predicted that, given a choice of ambient light microhabitats, these males would use high ambient light conditions the most and be most likely to perch in high-light conditions. We found no evidence that differently colored male O. pumilio preferentially used bright microhabitats or that ambient light influenced perching in a morph-specific manner. Independent of light conditions, males from the most conspicuous population perched the least, but the most conspicuous individuals from a polymorphic population perched the most. These patterns suggest that preferences do not necessarily underlie among-morph differences observed in the wild. This could be explained, and remain consistent with theory, if risk aversion is shaped, in part, by experience.

Can microscale habitat-related differences influence the abundance of ectoparasites ? Multiple evidences from two juvenile coastal fish (Perciformes: Sparidae)

The ectoparasite communities of two juvenile Diplodus species, D. sargus and D. puntazzo, were studied in a rocky coast of the Central Tyrrhenian sea (Mediterranean Sea) where three neighbouring nursery areas showed a differential availability of microhabitats due to a gradual protection gradient capable of influencing local hydrodynamic conditions. Five parasite forms were detected on juvenile hosts: Peniculus fistula, the two larval forms of gnathiids (praniza and zuphea stages), Caligus sp. and Anilocra physodes. Among these species an increasing rates of infestation (up to 57%), from the less protected to the most sheltered site, was detected. The largest infestation rate occurred in the most enclosed site, where P. fistula was the most infective species, also capable of affecting the body condition of juvenile fishes. In addition, to investigate behavioural processes among infected fish, both gut content analyses and in situ HD video sequences were used. Our results demonstrate that ectoparasites cannot be considered as accidental food items, implying an active removal of parasites among conspecifics. The highest frequencies of cleaning interactions were recorded during high ambient light conditions, suggesting the role of visual displays as an important factor in stimulating cleaning interactions.

Enhanced optical discrimination system based on switchable retroreflective films

Reported herein is the design, characterization, and demonstration of a laser interrogation and response optical discrimination system based on large-area corner-cube retroreflective films. The switchable retroreflective films use light-scattering liquid crystal to modulate retroreflected intensity. The system can operate with multiple wavelengths (visible to infrared) and includes variable divergence optics for irradiance adjustments and ease of system alignment. The electronic receiver and switchable retroreflector offer low-power operation (<4 mW standby) on coin cell batteries with rapid interrogation to retroreflected signal reception response times (<15 ms). The entire switchable retroreflector film is <1 mm thick and is flexible for optimal placement and increased angular response. The system was demonstrated in high ambient lighting conditions (daylight, 18k lux) with a visible 10-mW output 635-nm source out to a distance of 400 m (naked eye detection). Nighttime demonstrations were performed using a 1.5-mW, 850-nm infrared laser diode out to a distance of 400 m using a night vision camera. This system could have tagging and conspicuity applications in commercial or military settings.

Changes in the objective amplitude of accommodation with pupil size.

We evaluate the effect of pupil size on objectively measured amplitude of accommodation (AA). Pupil diameter and wavefront aberrometry were obtained in 15 eyes when stimulus swept across the range of clear vision in steps of 0.5 diopters. Wavefront refraction techniques were used to compute objective AA as the maximum refractive change. Measurements were obtained monocularly under low and high ambient room lighting conditions with a fixed luminance of the fixation target. Amplitude of accommodation computations were performed taking into account just paraxial rays (paraxial AA) or including the effects of the change of spherical aberration during accommodation (minRMS AA). Mean pupil size values at low light level were 6.26 mm (relaxed) and 4.15 mm (maximum accommodation), whereas at the high light level, those values became 4.74 and 3.04 mm, respectively. The effects of both light level on accommodation were significant (p < 0.001), and accommodative miosis was slightly larger at low light levels. Mean minRMS and paraxial AA were always greater by more than 1 diopter in high than in low ambient lighting conditions (p < 0.01), indicating a significant impact of pupil size on AA. The influence of the ambient lighting on the objective AA is not only attributed to the increased effects of spherical aberration as the pupil dilates but mostly attributed to a decrease in the paraxial accommodation as pupil dilates.

Effect of Varying Displays and Room Illuminance on Caries Diagnostic Accuracy in Digital Dental Radiographs

In clinical practice, digital radiographs taken for caries diagnostics are viewed on varying types of displays and usually in relatively high ambient lighting (room illuminance) conditions. Our purpose was to assess the effect of room illuminance and varying display types on caries diagnostic accuracy in digital dental radiographs. Previous studies have shown that the diagnostic accuracy of caries detection is significantly better in reduced lighting conditions. Our hypothesis was that higher display luminance could compensate for this in higher ambient lighting conditions. Extracted human teeth with approximal surfaces clinically ranging from sound to demineralized were radiographed and evaluated by 3 observers who detected carious lesions on 3 different types of displays in 3 different room illuminance settings ranging from low illumination, i.e. what is recommended for diagnostic viewing, to higher illumination levels corresponding to those found in an average dental office. Sectioning and microscopy of the teeth validated the presence or absence of a carious lesion. Sensitivity, specificity and accuracy were calculated for each modality and observer. Differences were estimated by analyzing the binary data assuming the added effects of observer and modality in a generalized linear model. The observers obtained higher sensitivities in lower illuminance settings than in higher illuminance settings. However, this was related to a reduction in specificity, which meant that there was no significant difference in overall accuracy. Contrary to our hypothesis, there were no significant differences between the accuracy of different display types. Therefore, different displays and room illuminance levels did not affect the overall accuracy of radiographic caries detection.

The influence of ambient light intensity on in situ laser diffractometers

In situ laser diffractometers characterize the suspended particle size distribution (PSD) by measuring laser‐generated light scattered off small particles over a range of small forward angles. In environments with low particulate concentrations or high ambient light conditions the ratio of natural downwelling sunlight to scattered laser light sensed by the photodetectors is high and measurements are influenced. Here, we evaluate the effect of the ambient light field intensity on measurements made with a Laser In Situ Scattering and Transmissometry (LISST) 100X type B instrument. Paired light‐dark scattering distributions are recorded over a range of underwater light intensities in high‐turbidity and low‐turbidity water. Light measurements displayed large erroneous concentrations of particles in the smallest size bin (1.25–1.48 μm) and showed effects over the full range of the PSD. Ambient light was found to exhibit the same constant distribution over the instrument photodetectors in both water samples, although the magnitude of the response, in laser counts per unit ambient light intensity, was PSD dependent. A technique for postprocessing data to remove the influence of light is presented for moored deployment and vertical profile data collected at Lake Tahoe, California‐Nevada, United States. While measurements removed of the light effect were successfully reconstructed, the technique may not be applicable to data where the PSD or the LISST orientation relative to the sun direction change rapidly or when light intensities are high enough to quench the instrument photodetectors. Ambient light was found to have negligible effects on PSD measurements in Lake Tahoe was below intensities of ∼30 W m−2.

Limitations of laser diffraction for measuring fine particles in oligotrophic systems: Pitfalls and potential solutions

Sampling of suspended particulates in oligotrophic environments is inherently difficult because of low ambient concentrations. The performance of a Laser In Situ Scattering and Transmissometry (LISST) series particle size analyzer is evaluated for use in such low‐concentration environments. Five issues are studied for their effect on recorded particle size distributions: the instrument limits of detection, the kernel matrix used in the inversion of the scattered light distribution, the effect of particles sized outside the instrument inversion limits (1.25 μm–250 μm), the effect of ambient light conditions, and the effect of sampling in density stratified conditions. We evaluate a LISST‐100X type B instrument using a series of small‐scale lab experiments and concentrate mainly on fine particles (&lt;20 μm). Kernel matrix processing effects are shown to have large impacts on fine particle measurements, but accurate results can be obtained with the correct matrix choice. Concentration detection limits may be sufficient for the clearest fresh water environments but may be too high for accurate sampling in the oligotrophic open ocean. Large out of range particles (&gt;250 μm) show little effects on the size distribution, but small particles (&lt;1.25 μm) have large impacts. High ambient light conditions, typical in clear oligotrophic systems, create erroneously high concentrations of fine particles, and profiling in density stratified conditions is found to create incorrectly low concentrations. We present recommendations for the next generation of in situ laser diffractometers and advise consideration of the issues covered here before using current instruments in oligotrophic environments.

56.1: Sunlight Readability of Digital Micro Shutter Based Display Technology

AbstractThe Pixtronix DMS™ (Digital Micro Shutter) display technology intrinsically provides exceptional image quality due to its optical architecture, device construction and device operation. This technology, based on MEMS micro‐shutters formed on active TFT backplanes, has enabled the development of color sequential, time division gray scale, direct‐view displays achieving breakthrough performance in wide color gamut, high brightness, high contrast ratio and wide view angles, all at roughly 1/4 the power consumption of competing TFT‐LCD or AMOLED displays of the same size and luminance. In addition, DMS™ technology also presents very good sunlight readability in transflective color modes. This readability can be attributed to reflective properties of the DMS™ optical architecture. This reflective nature enhances viewing characteristics of transmissive color modes in high ambient lighting conditions. The reflective performance is obtained without compromising transmissive mode performance as is typically the case in some of the existing display technologies. This paper will explain the performance of DMS™ display in reflective and transflective modes under high ambient lighting conditions.

Bottlenose Dolphin (&lt;I&gt;Tursiops truncatus&lt;/I&gt;) Double-Slit Pupil Asymmetries Enhance Vision

Geometries of the iris, retinal cell distributions, and the optical characteristics of the lens and cornea have evolved to optimize the visual adaptations of the bottlenose dolphin (Tursiops truncatus) to the oceanic environment. Under high ambient light conditions, the operculum of the iris shields the lens and forms two asymmetrical slit pupils. Under these conditions, light entering the eye is channeled and focused onto the two areas of the retina having a finer retinal mosaic of ganglion cells (typically associated with higher image resolution). The paths of light determined by tracing rays in the reverse direction through these pupils coincide with a dolphin’s behaviorally observed preferred viewing directions. These rays aid in determining the interdependence between the graininess of the retinal mosaic and resolution spot sizes in the object space. For oblique forward and downward viewing directions in air, the larger temporal pupil admits light which passes through the weakly refractive margin of a bifocal lens, counterbalancing the optically strong cornea in air. In water, light passing through the optically strong lens core is focused from a wide lateral and downward field-of-vision. Although other explanations for comparable aerial and underwater vision remain plausible, a dolphin eye model incorporating a bifocal lens offers an explanation consistent with ophthalmoscopic refractive state measurements. The model is also consistent with visual acuity study results conducted in air and in water under both high and low ambient light levels. From insight gained after applying a common data analysis technique to visual acuity studies conducted by other researchers and tracing oblique rays through the asymmetric double-slit pupils, a re-examination of explanatory hypotheses for the paradoxical observations of comparable aerial and underwater vision is presented. Based in part on these findings and supportive evidence from dolphin vision researchers, the unique distinguishing characteristics of dolphin vision are summarized.

High-contrast organic light emitting diodes with a partially absorbing anode

To be legible in high-ambient light conditions, organic light-emitting-diode displays should be optically designed to have a minimal reflectance without significantly affecting their overall efficiency. We demonstrate the use of an anode consisting of a partially absorbing metal layer and a multilayer distributed Bragg reflector to simultaneously absorb rather than reflect incoming light and to take advantage of a weak microcavity effect in the diode to improve light outcoupling.

High-Bandwidth Underwater Communications

The rapid exchange of data with underwater sensors and systems is increasingly valuable for oceanography, oil exploration and other investigations of undersea phenomena. This paper reviews the potential, as well as the limitations, of acoustic, radio-frequency electromagnetic, fiber-optical and free-space optical techniques for high-bandwidth, undersea communication. In particular, we discuss the environmental and hardware attributes that bound the performance of free-space optical communications in a variety of undersea scenarios. Free-space optical approaches are capable of providing data bandwidths approaching 109 bits per second (bps) under suitable environmental conditions. More commonly, 10-100 × 106 bps can be achieved over ranges approaching 100 meters. Turbid water and high-ambient light conditions (primarily from downwelling sunlight) pose a serious challenge to performance at moderate and long ranges.

Stand-off Raman detection using dispersive and tunable filter based systems

Small, transportable Raman systems are being developed for stand-off Raman measurements at intermediate ranges (e.g. <20 m) for planetary measurements. Four variations of stand-off Raman systems are described that use a small telescope for light collection that is either fiber-optic or lens-coupled to a detection system. The performance of an acousto-optic tunable filter for wavelength selection and spectral imaging is tested by comparing signal-to-noise ratio and throughput to similar measurements using a conventional spectrograph, and by measuring a variety of organic and inorganic mineral samples at distances up to 15 m. We also determine optimal ICCD gate widths for acquiring remote Raman spectra under high ambient light conditions.

Positive-mode dichroic LC display

There is considerable interest in large electronic display boards for presentation of information to mass audiences. Among the various display technologies, the dichroic dye liquid crystal display is considered best suited for such an application because ot its low power and low voltage requirements, viewability over wide angle and under high ambient lighting conditions, and potentially low fabricating cost.

A New Approach to Computer-Generated Holography

A digital computer and automatic plotter have been used to produce a series of perspective views of a computer-stored three-dimensional object which is slightly rotated for each view. All of these views are combined together optically to produce a final hologram which can be viewed in high ambient light conditions. The reconstructed image appears three dimensional since each eye looks through a different holographic strip corresponding to a different view of the three-dimensional object. The net result is a technique requiring only seconds of computer time and some possibly automated optical manipulations to produce extremely high quality holograms of computer-stored three-dimensional objects.

"Performance characteristics of the RCA direct view storage kinescope"

The RCA Direct View Storage Kinescope is a cathode ray tube capable of providing a visual display of radar information at brightness levels that permit viewing under high ambient light conditions such as occur in aircraft cockpits. The radar information may be stored at this high light level for several minutes without appreciable loss of resolution. The storage time can be controlled over a wide range--from a fraction of a second to several minutes. Under one mode of operation, the information may be caused to decay gradually over the entire display area or it may be completely removed within a fraction of a second. Another mode of operation permits removal of information along a single line of the display. In this way, the radar data may be continually erased just prior to writing new data. Other features which make the Direct View Storage Kinescope desirable as a radar indicator are its high writing-speed, good half-tone rendition and good resolution (450 line limiting resolution on a diameter).