Luminance

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Ronald Daiker - One of the best experts on this subject based on the ideXlab platform.

  • effect of Luminance and text size on information acquisition time from traffic signs
    Transportation Research Record, 2009
    Co-Authors: Thomas Schnell, Lora Yekhshatyan, Ronald Daiker
    Abstract:

    Although visual performance was measured in terms of visual response time in many psychophysical studies, such an approach has not been used in evaluating the effect of Luminance on traffic sign legibility performance. Traffic sign and retroreflective sign sheeting performance at night have been historically identified with the threshold (farthest) distance for legibility and in many cases from stationary vehicles with no restrictions on viewing time. Because traffic signs are not always read at threshold distances or threshold Luminances and because the time available to read traffic signs is usually limited in the real world, a proper assessment of sign legibility performance requires determining information acquisition times above threshold conditions. This study investigated the effect of (legend) Luminance and letter size on the information acquisition time and transfer accuracy from simulated traffic signs. Luminances ranged from 3.2 cd/m2 to 80 cd/m2 on positive-contrast textual traffic sign stimul...

  • effect of Luminance and text size on information acquisition time from traffic signs with discussion and closure
    Transportation Research Record, 2009
    Co-Authors: Thomas Schnell, Lora Yekhshatyan, Ronald Daiker
    Abstract:

    Although visual performance was measured in terms of visual response time in many psychophysical studies, such an approach has not been used in evaluating the effect of Luminance on traffic sign legibility performance. Traffic sign and retroreflective sign sheeting performance at night have been historically identified with the threshold (farthest) distance for legibility and in many cases from stationary vehicles with no restrictions on viewing time. Because traffic signs are not always read at threshold distances or threshold Luminances and because the time available to read traffic signs is usually limited in the real world, a proper assessment of sign legibility performance requires determining information acquisition times above threshold conditions. This study investigated the effect of (legend) Luminance and letter size on the information acquisition time and transfer accuracy from simulated traffic signs. Luminances ranged from 3.2 cd/m² to 80 cd/m² on positive-contrast textual traffic sign stimuli with contrast ratios of 6:1 and 10:1, positioned at 33 ft/in. and 40 ft/in. legibility indices, and viewed under conditions simulating a nighttime driving environment. The findings suggest that increasing the sign Luminance significantly reduces the time to acquire information. Similarly, increasing the sign size (or reducing the legibility index) also reduces the information acquisition time. These findings suggest that larger and brighter signs are more efficient in transferring their message to the driver by reducing information acquisition time, or alternatively, by increasing the transfer accuracy. In return, reduced sign viewing durations and increased reading accuracy are likely to improve roadway safety.

Thomas Schnell - One of the best experts on this subject based on the ideXlab platform.

  • effect of Luminance and text size on information acquisition time from traffic signs
    Transportation Research Record, 2009
    Co-Authors: Thomas Schnell, Lora Yekhshatyan, Ronald Daiker
    Abstract:

    Although visual performance was measured in terms of visual response time in many psychophysical studies, such an approach has not been used in evaluating the effect of Luminance on traffic sign legibility performance. Traffic sign and retroreflective sign sheeting performance at night have been historically identified with the threshold (farthest) distance for legibility and in many cases from stationary vehicles with no restrictions on viewing time. Because traffic signs are not always read at threshold distances or threshold Luminances and because the time available to read traffic signs is usually limited in the real world, a proper assessment of sign legibility performance requires determining information acquisition times above threshold conditions. This study investigated the effect of (legend) Luminance and letter size on the information acquisition time and transfer accuracy from simulated traffic signs. Luminances ranged from 3.2 cd/m2 to 80 cd/m2 on positive-contrast textual traffic sign stimul...

  • effect of Luminance and text size on information acquisition time from traffic signs with discussion and closure
    Transportation Research Record, 2009
    Co-Authors: Thomas Schnell, Lora Yekhshatyan, Ronald Daiker
    Abstract:

    Although visual performance was measured in terms of visual response time in many psychophysical studies, such an approach has not been used in evaluating the effect of Luminance on traffic sign legibility performance. Traffic sign and retroreflective sign sheeting performance at night have been historically identified with the threshold (farthest) distance for legibility and in many cases from stationary vehicles with no restrictions on viewing time. Because traffic signs are not always read at threshold distances or threshold Luminances and because the time available to read traffic signs is usually limited in the real world, a proper assessment of sign legibility performance requires determining information acquisition times above threshold conditions. This study investigated the effect of (legend) Luminance and letter size on the information acquisition time and transfer accuracy from simulated traffic signs. Luminances ranged from 3.2 cd/m² to 80 cd/m² on positive-contrast textual traffic sign stimuli with contrast ratios of 6:1 and 10:1, positioned at 33 ft/in. and 40 ft/in. legibility indices, and viewed under conditions simulating a nighttime driving environment. The findings suggest that increasing the sign Luminance significantly reduces the time to acquire information. Similarly, increasing the sign size (or reducing the legibility index) also reduces the information acquisition time. These findings suggest that larger and brighter signs are more efficient in transferring their message to the driver by reducing information acquisition time, or alternatively, by increasing the transfer accuracy. In return, reduced sign viewing durations and increased reading accuracy are likely to improve roadway safety.

Yi Wang - One of the best experts on this subject based on the ideXlab platform.

  • different roles of subcortical inputs in v1 responses to Luminance and contrast
    European Journal of Neuroscience, 2021
    Co-Authors: Rendong Tang, Wenzhen Chen, Yi Wang
    Abstract:

    Cells in the primary visual cortex (V1) generally respond weakly to large uniform Luminance stimuli. Only a subset of V1 cells is thought to encode uniform Luminance information. In natural scenes, local Luminance is an important feature for defining an object that varies and coexists with local spatial contrast. However, the strategies used by V1 cells to encode local mean Luminance for spatial contrast stimuli remain largely unclear. Here, using extracellular recordings in anaesthetized cats, we investigated the responses of V1 cells by comparing with those of retinal ganglion (RG) cells and lateral geniculate nucleus (LGN) cells to simultaneous and rapid changes in Luminance and spatial contrast. Almost all V1 cells exhibited a strong monotonic increasing Luminance tuning when they were exposed to high spatial contrast. Thus, V1 cells encode the Luminance carried by spatial contrast stimuli with the monotonically increasing response function. Moreover, high contrast decreased Luminance tuning of OFF cells but increased that of in ON cells in RG and LGN. The Luminance and contrast tunings of LGN ON cells were highly separable as V1 cells, whereas those of LGN OFF cells were lowly separable. These asymmetrical effects of spatial contrast on ON/OFF channels might underlie the robust ability of V1 cells to perform Luminance tuning when exposed to spatial contrast stimuli.

  • V1 neurons respond to Luminance changes faster than contrast changes.
    Scientific Reports, 2015
    Co-Authors: Wen-liang Wang, Jian Ding, Louis Tao, Yi Wang
    Abstract:

    Luminance and contrast are two major attributes of objects in the visual scene. Luminance and contrast information received by visual neurons are often updated simultaneously. We examined the temporal response properties of neurons in the primary visual cortex (V1) to stimuli whose Luminance and contrast were simultaneously changed by 50 Hz. We found that response tuning to Luminance changes precedes tuning to contrast changes in V1. For most V1 neurons, the onset time of response tuning to Luminance changes was shorter than that to contrast changes. Most neurons carried Luminance information in the early response stage, while all neurons carried both contrast and Luminance information in the late response stage. The early Luminance response suggests that cortical processing for Luminance is not as slow as previously thought.

  • representation of surface Luminance and contrast in primary visual cortex
    Cerebral Cortex, 2012
    Co-Authors: Ji Dai, Yi Wang
    Abstract:

    In visual perception, object identification requires both the ability to define regions of uniform Luminance and zones of Luminance contrast. Neural processes underlying contrast detection have been well studied, while those defining Luminance remain poorly understood and controversial. Partially because stimuli comprised of uniform Luminance are relatively ineffective in driving responses of cortical neurons, little effort has been made to systematically compare responses of individual neurons to both uniform Luminance and contrast. Using large static uniform Luminance and contrast stimuli, modulated temporally in Luminance or contrast, we found a continuum of responses ranging from a few cells modulated only by Luminance (Luminance-only), to many cells modulated by both Luminance and contrast (Luminance--contrast), and to many others modulated only by contrast (contrast-only) in primary visual cortex. Moreover, Luminance--contrast cells had broader orientation tuning, larger receptive field (RF) and lower spatial frequency Preference, on average, than contrast-only cells. Contrast-only cells had contrast responses more linearly correlated to the spatial structure of their RFs than Luminance--contrast cells. Taken together these results suggest that Luminance and contrast are represented, to some degree, by independent mechanisms that may be shaped by different classes of subcortical and/or cortical inputs.

Yang Yang - One of the best experts on this subject based on the ideXlab platform.

  • improving the power efficiency of white light emitting diode by doping electron transport material
    Applied Physics Letters, 2006
    Co-Authors: Jinsong Huang, Weijen Hou, Yang Yang
    Abstract:

    Highly efficient white light emission was realized via the partial energy transfer from blue host polyfluorene (PF) to orange light emission dopant rubrene. A more balanced charge transport was achieved by adding an electron transport material, 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD), into the PF-rubrene system to enhance the electron transportation. Efficiency improvement by as much as a factor of 2 has been observed through the addition of PBD. These devices can easily reach high Luminance at low driving voltages, thus achieving high power efficiency at high Luminance (14.8, 13.5, and 12.0lm∕W at the Luminances of 1000, 2000, and 4000cd∕m2, respectively). Therefore, this performance is an important approach toward solid-state lighting application. The enhancement is mainly attributed to three factors: increased electron transport property of the host material, increased photoluminescence quantum efficiency, and the shifting of emission zone away from cathode contact. The reported efficiency is among the highest values reported in the white emission polymer light-emitting diodes.Highly efficient white light emission was realized via the partial energy transfer from blue host polyfluorene (PF) to orange light emission dopant rubrene. A more balanced charge transport was achieved by adding an electron transport material, 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD), into the PF-rubrene system to enhance the electron transportation. Efficiency improvement by as much as a factor of 2 has been observed through the addition of PBD. These devices can easily reach high Luminance at low driving voltages, thus achieving high power efficiency at high Luminance (14.8, 13.5, and 12.0lm∕W at the Luminances of 1000, 2000, and 4000cd∕m2, respectively). Therefore, this performance is an important approach toward solid-state lighting application. The enhancement is mainly attributed to three factors: increased electron transport property of the host material, increased photoluminescence quantum efficiency, and the shifting of emission zone away from cathode contact. The reported ...

  • improving the power efficiency of white light emitting diode by doping electron transport material
    Applied Physics Letters, 2006
    Co-Authors: Jinsong Huang, Weijen Hou, Yang Yang
    Abstract:

    Highly efficient white light emission was realized via the partial energy transfer from blue host polyfluorene (PF) to orange light emission dopant rubrene. A more balanced charge transport was achieved by adding an electron transport material, 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD), into the PF-rubrene system to enhance the electron transportation. Efficiency improvement by as much as a factor of 2 has been observed through the addition of PBD. These devices can easily reach high Luminance at low driving voltages, thus achieving high power efficiency at high Luminance (14.8, 13.5, and 12.0lm∕W at the Luminances of 1000, 2000, and 4000cd∕m2, respectively). Therefore, this performance is an important approach toward solid-state lighting application. The enhancement is mainly attributed to three factors: increased electron transport property of the host material, increased photoluminescence quantum efficiency, and the shifting of emission zone away from cathode contact. The reported ...

Ruth Hamilton - One of the best experts on this subject based on the ideXlab platform.

  • photometric compliance of tablet screens and retro illuminated acuity charts as visual acuity measurement devices
    PLOS ONE, 2016
    Co-Authors: I A T Livingstone, C M Tarbert, Andrew Bastawrous, Duncan Middleton, Ruth Hamilton, Mario Giardini
    Abstract:

    Mobile technology is increasingly used to measure visual acuity. Standards for chart-based acuity tests specify photometric requirements for Luminance, optotype contrast and Luminance uniformity. Manufacturers provide some photometric data but little is known about tablet performance for visual acuity testing. This study photometrically characterised seven tablet computers (iPad, Apple inc.) and three ETDRS (Early Treatment Diabetic Retinopathy Study) visual acuity charts with room lights on and off, and compared findings with visual acuity measurement standards. Tablet screen Luminance and contrast were measured using nine points across a black and white checkerboard test screen at five arbitrary brightness levels. ETDRS optotypes and adjacent white background Luminance and contrast were measured. All seven tablets (room lights off) exceeded the most stringent requirement for mean Luminance (≥ 120 cd/m2) providing the nominal brightness setting was above 50%. All exceeded contrast requirement (Weber ≥ 90%) regardless of brightness setting, and five were marginally below the required Luminance uniformity threshold (Lmin/Lmax ≥ 80%). Re-assessing three tablets with room lights on made little difference to mean Luminance or contrast, and improved Luminance uniformity to exceed the threshold. The three EDTRS charts (room lights off) had adequate mean Luminance (≥ 120 cd/m2) and Weber contrast (≥ 90%), but all three charts failed to meet the Luminance uniformity standard (Lmin/Lmax ≥ 80%). Two charts were operating beyond manufacturer’s recommended lamp replacement schedule. With room lights on, chart mean Luminance and Weber contrast increased, but two charts still had inadequate Luminance uniformity. Tablet computers showed less inter-device variability, higher contrast, and better Luminance uniformity than charts in both lights-on and lights-off environments, providing brightness setting was >50%. Overall, iPad tablets matched or marginally out-performed ETDRS charts in terms of photometric compliance with high contrast acuity standards.

  • the Luminance response function of the human photopic electroretinogram a mathematical model
    Vision Research, 2007
    Co-Authors: Ruth Hamilton, M A Bees, Caroline A Chaplin, Daphne L Mcculloch
    Abstract:

    Abstract The Luminance–response function of the brief flash full-field photopic electroretinogram (ERG) rises to a peak before falling to a sub-maximal plateau – the ‘photopic hill’. The combination of on- and off-responses inherent in the brief flash photopic ERG suggests that this Luminance–response function could be modelled by the sum of a Gaussian function and a logistic growth function. Photopic ERGs to a Luminance series of brief flashes against three different background Luminances recorded from seven healthy adults showed the characteristic ‘photopic hill’ function for b-wave amplitudes which were satisfactorily fitted with the sum of a Gaussian curve and a logistic growth curve. As background Luminance increased, both components shifted to the right on the Luminance axis. The Gaussian component increased in amplitude while the logistic growth function component decreased in amplitude. The Luminance–response function of a complete congenital stationary night blindness patient had almost no logistic growth component.