Research and other articles about the physics of light and LED light beams.
September, 2024 – Impact and visualization of scotomatic glare in central visual field perception – “We conclude that even off-axis light exposure may affect central visual field perception. Our results extend previous research on directed light interaction and contribute in explaining its incapacitating impact on human performance.”
2024 – LED Lighting Devices and Colorimetry – Detailed explanations of the physics of light and LEDs. LEDs are Lambertian radiators, whereas point sources are isotropic.
July 3, 2023 – LED Bulb Truth – This video shows the physics characteristics of incandescent, CFL, and LED. The narrator mentions the directed energy beam of LED and shows the spectral power distribution and flicker characteristics of LED light.
May 4, 2023 – Light field analysis for modeling and transmission characteristics of partially coherent light-emitting diodes – A discussion of the Lambertian spatial distribution of LED light and its semi-coherent properties.
January 22, 2023 – A Quest for New Metrics to Curb the Increase In Glare from LED Lighting – Lead author Dr. Peter Veto details the primary problems with LED light sources: unregulated peak luminance and inappropriate measurement techniques.
November 14, 2022 – Curved vs. Flat – A comparison of curved vs. flat surface radiation emitters.
August, 2022 – Radio Wave Packet – What you need to know about wireless technology.
December, 2021 – Is Street Lighting Damaging Our Health? – The first documented admission by an LED lighting company, Cree Lighting, that the industry has been using the wrong metrics to measure LEDs. (.pdf version)
June 7, 2021 – What is Peak Brightness – Confirmation by a writer in the LED display industry that LED brightness is measured with luminance in nits, not luminous intensity in candela.
June, 2021 – The Science of Goniophotometry – This article notes that care must be taken with lamps with narrow beams or an array of emitters.
October, 2019 – Derivation and Experimental Verification of the Near-field 2D and 3D Optical Intensities From a Finite-size Light Emitting Diode (LED) – Calculating peak intensities for the Lambertian shape generated by LEDs.
August, 2018 – Determination of a laser eye dazzle safety framework – Describes how a laser beam can cover part or all of an eye.
April 24, 2017 – Understand Luminous and Radiant Intensity, and Uniformity Characterization – Describes an averaged LED intensity.
July 1, 2016 – The Influence of LED Emission Characteristics on the Efficiency of Lighting Systems – Describes the difference between volume and surface LED emitters and describes the spatial emissions as a Lambertian or near-Lambertian.
February, 2016 – Analysis of uniformity of illumination of a freeform lens when combined with different optical sources – Discussion of how to uses lenses to achieve uniform illumination. Identifies that there are isotropic sources and Lambertian sources.
February 7, 2014 – Can Light Bend Around Corners? – Light interferes with itself, causing beam spread.
2013 – Radiance of the sun, a 1 mW laser pointer and a phosphor emitter – Discussion of homogenous and non-homogenous emitters and the importance of field of view. Includes discussion of safety limits.
2013 – Angular Distribution of Average Luminous Intensity of Low-power LEDs – LEDs emit non-uniform energy in a Lambertian shape, sometimes off-center.
2011 – Measuring Luminance with a Digital Camera – Explains how to use a digital camera to measure luminance from LED light sources.
January, 2009 – Electromagnetic Radiation from Organic Light-emitting Diodes – Shows a Light Intensity Diagram for an OLED with Lambertian shape.
2009 – Light-Emitting Diode Technology for Solid State Lighting – States that there are no known studies in the impacts of spikey spectral distribution on human perception and accurately predicts that LEDs will change the world.
2008 – Digital Billboard Recommendations and Comparisons to Conventional Billboards – Dr. Ian Lewin examines LED billboards. 300 nits is comfortable.
2008 – Modeling the Radiation Pattern of LEDs – LEDs emit non-uniform radiation.
2007 – Spherical Wave Propagation – Antennas emit radiation in a spherical wave that disperses following an inverse square law, so long as the antenna emits isotropic radiation. A flat surface antenna will instead emit a directed energy beam.
2007 – Luminance and Light Intensity Conversion
December 12, 2006 – Light Recycling Contributes to Brightness in Filament Lamps – Discussion of how light in a coiled tungsten filament reflects internally on the coils to create a non-uniform distribution of the light.
April, 2002 – Lecture 15 – LED Measurement Issues – Dr. A. A. Gaertner discusses measurement of LED light. Dr. Gaertner refers to traditional lighting as “point sources” and LED lighting as “Lambertian sources”.
Illuminance vs Luminance – Luminance is the light that his the eye. Luminance plus contrast is brightness. In the case of LEDs, the luminance is coming straight from the source without being reflected first.
Yujileds – Industry information about LEDs contains color many color temperature charts and other useful information.
Light Emitting Diodes Chapter 16 – Differentiates between “point sources” and “surface sources” for brightness.
Inverse Square Law, General – Quote: “Any point source which spreads its influence equally in all directions without a limit to its range will obey the inverse square law.” – LEDs are Lambertian Sources, not Point Sources, and the influence is not spread equally in all directions. Thus, LED radiation does not obey an inverse square law.