A psychophysical model for visual discomfort based on receptive fields

© 2016, © The Chartered Institution of Building Services Engineers 2016. Visual discomfort is predicted from a luminance map with a model based on the receptive field mechanism in the human eye. A centre-surround receptive field is described by a Difference of Gaussians. Eight commercially available office luminaires are assessed for visual discomfort in a paired comparison experiment. The correlation between the subjective data and the receptive field model is optimized for three factors: the centre Gaussian width, the surround Gaussian width and the centre-to-surround weighing factor (WF). A centre and surround visual angle of 0.53 and 2.19 min arc, respectively, and a WF of 0.87 result in a coefficient of determination of 0.77. The model is validated independently with magnitude estimation data obtaining a coefficient of determination of 0.82. Where the standard unified glare rating method fails (coefficient of determination of 0.45), the receptive field model ameliorates predictability for visual discomfort. The model based on receptive fields is promising to replace current standard glare metrics, specifically when non-uniform luminaires are to be evaluated.status: publishe

Determination of the Diffusion Parameters of an Optically Thin Scattering Sample Through Time-resolved Transmission

The color-converting phosphor diffusers in white LEDs are optically thin and hence are hard to characterize. We show that separating of direct from diffuse transmission in time-resolved experiments results in less than 20% error in determining the diffusion parameters using the diffusion approximation

Systematic design of the color point of a white LED

\u3cp\u3eLighting is a crucial technology that is used in our daily lives. The introduction of the white light emitting diode (LED), which consists of a blue LED combined with a phosphor layer, greatly reduces the energy consumption for lighting. Despite the fast-growing market, white LEDs are still being designed with slow, numerical, trial-and-error methods. Here we introduce a radically new design principle that is based on an analytical model instead of a numerical approach. Our model predicts the white LED's color point for any combination of design parameters. In addition, our model provides the reflection and transmission coefficients of the scattered and re-emitted light intensities, as well as the energy density distribution inside the LED. To validate our model, we have performed extensive experiments on an emblematic white LED and found excellent agreement. Our model provides for a fast and efficient design, resulting in reductions of both design and production costs.\u3c/p\u3

Systematic design of the color point of a white LED

Lighting is a crucial technology that is used in our daily lives. The introduction of the white light emitting diode (LED), which consists of a blue LED combined with a phosphor layer, greatly reduces the energy consumption for lighting. Despite the fast-growing market, white LEDs are still being designed with slow, numerical, trial-and-error methods. Here we introduce a radically new design principle that is based on an analytical model instead of a numerical approach. Our model predicts the white LED's color point for any combination of design parameters. In addition, our model provides the reflection and transmission coefficients of the scattered and re-emitted light intensities, as well as the energy density distribution inside the LED. To validate our model, we have performed extensive experiments on an emblematic white LED and found excellent agreement. Our model provides for a fast and efficient design, resulting in reductions of both design and production costs

Accurate determination of the transport parameters of light in white light emitting diodes

The energy-efficient generation of white light has recently become an important societal issue. The technology of white-light emitting diodes (LEDs) is one of the most promising solutions to efficiently generate white light for home, office, and street locations, and even for remote locations without electric power grid [1]. One of the outstanding in the development of LED technology are understanding the scattering [2], the absorption and emission with analytical physical models [3, 4]. As a first example of the power of the physical understanding of multiple light scattering in LEDs, we describe straightforward tools to extract essential optical parameters

Tuning the color point of a white LED

White light is conveniently characterized by a color point that is represented on the color space. Color point of white LED is fixed by the design parameters (e.g. Phosphor type and concentration). When the design parameters are chosen, the color point of the white LED cannot be changed. Here, we show that wavefront shaping technique can be employed to reversibly tune the color point of a white LED without changing the design parameters