Ian AshdownSunTracker Technologies Ltd.
Ian Ashdown
MSc - Computer Science
About
173
Publications
89,497
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781
Citations
Citations since 2017
Introduction
Independent research engineer with current projects and interests in in: 1) horticultural lighting; 2) climate-based annual daylight simulations; 3) radiative flux transfer (radiosity); 4) acoustic radiosity; 5) colorimetry and radiometry; 6) daylight harvesting techniques; 7) energy management systems for green buildings; 8) global illumination techniques (computer graphics); and 9) mesopic photometry.
Publications
Publications (173)
Melanopic dose rate and dose are calculated in a virtual environment. A computer generated model of an actual or planned building is used as the virtual environment. Indirect and direct spherical irradiances are calculated using convex polyhedra throughout the virtual environment, and each is multiplied by a melanopic conversion factor. The two are...
Given the complexity of architectural spaces and the need to calculate spherical irradiances, it is difficult to determine how much ultraviolet radiation is necessary to adequately kill airborne pathogens. An interior environment with Iuminaires is modeled. Spherical irradiance meters are positioned in the model and the direct and indirect spherica...
The present invention relates to the importance-directed geometric simplification of complex mesh-based representations of objects in virtual environments for radiosity-based global illumination simulations. By means of simplification, the time needed to solve the radiosity equation and so generate an accurate physically-based simulation can be mar...
Discussion of the need for horticultural luminaire manufacturers to provide photon intensity and spectral quantum distributions for their products.
Laser light emanates from optical components that are mounted on a substrate, each optical component being coupled to an optical fiber that delivers laser radiation combined from multiple lasers. A linear or elliptical diffuser is located to diffuse the light emanating from the optical components. The laser wavelengths excite plant photopigments fo...
Electric light sources typically exhibit temporal variations in luminous flux output, commonly referred to as “flicker.” Flicker, or temporal modulation, is known to influence the growth, health and behavior patterns of humans, and is also linked to growth, health and behavior patterns throughout the growth cycle of plants and animals. Control of p...
Overview of a mathematical approach to modeling spherical irradiance for UV-C air disinfection in complex architectural environments.
A system and method for a neural network that is trained to recognize patterns in the exitance convergence behaviour of a radiosity equation being solved for a set of finite element environments, and subsequently employed to monitor and predict the exitance convergence behaviour of novel finite element environments. The neural network is trained wi...
A means to automate, using fuzzy logic, the classification of spectral power distributions of optical radiation for lighting systems, and more particularly horticultural lighting systems, is presented. After inputting the spectral power distribution of optical radiation from one or more light sources, radial basis function weights for the spectral...
A biological lighting system to provide temporally- and spatially-modulated photon flux output and spectral power distributions to plants on a circadian and circannual basis, or circadian and life cycle basis, to maximize effective and efficient growth in a horticultural setting. The photon flux or irradiance output and the spectral power distribut...
A dense array of sensors positioned in a virtual environment is reduced to a sparse array of sensors in a physical environment , which provides sufficient information to a controller that responds to environmental conditions and parameters in the physical environment in substantially the same manner as it would to the same environmental conditions...
Spectral irradiance distributions are calculated within a virtual environment based on arbitrary light source spectral power distributions. Architectural, horticultural and aquacultural lighting control systems use the calculated results to control both the intensity and spectral power distribution of the electric light sources. Energy consumption...
I have been presenting “Going Green” to various Illuminating Engineering Society chapters in Canada for the past year. Beginning as an overview of the topic, it has evolved into a preview of the forthcoming document, ANSI/IES RP-45-21, Recommended Practice: Horticultural Lighting. (I am the chair of the IES Horticultural Lighting Committee, which h...
Investigation of the photomorphological effects of near-infrared radiation (730 nm) on Petunia x hybrida and Ocimum basilicum v. "Sweet Genovese", demonstrating that plants respond to radiation outside of the accepted Photosynthetic Active Radiation (PAR) range of 400 nm - 700 nm.
An analytical approach to quantifying the contribution to astronomical light pollution of various high-intensity discharge lamps and LEDs modules based on their spectral power distribution.
Laser light emanates from optical components that are mounted on a substrate, each optical component being coupled to an optical fiber that delivers laser radiation combined from multiple lasers. A linear or elliptical diffuser is located to diffuse light emanating from the optical components. The laser wavelengths excite plant photopigments for pr...
Monthly average DLI values for a specified geographic location, or a greenhouse, polytunnel or other controlled environment at the specified geographic location, are calculated from historic reference data from weather stations. The calculations are a prediction based on the geographic similarity of the specified location to the locations of the we...
In an example, an expected sky condition is calculated for a geographic location, a time of day, and a date based on a mathematical model. A predicted distribution of direct and interreflected solar radiation within the environment is calculated based on the expected sky condition. Measurement data from one or more photosensors is obtained that pro...
Laser light emanates from optical components that are mounted on a substrate, each optical component being coupled to an optical fiber that delivers laser radiation combined from multiple lasers. A linear or elliptical holographic diffuser is located to diffuse the light emanating from the optical components. The laser wavelengths excite plant phot...
Spectral irradiance distributions are calculated within a virtual environment based on arbitrary light source spectral power distributions. Architectural, horticultural and aquacultural lighting control systems use the calculated results to control both the intensity and spectral power distribution of the electric light sources. Energy consumption...
A biological lighting system to provide temporally- and spatially-modulated photon flux output and spectral power distributions to plants on a circadian and circannual basis, or circadian and life cycle basis, to maximize effective and efficient growth in a horticultural setting. The photon flux or irradiance output and the spectral power distribut...
The present invention relates to the importance-directed geometric simplification of complex mesh-based representations of objects in virtual environment. By means of simplification, the time needed to solve the radiosity equation and so generate an accurate physically-based simulation can be markedly reduced. Further, geometric simplification is p...
Sustainable building lighting and energy modelling and control , and the associated computer graphics , including real-time dynamic lighting simulation , are concerned with : an optimized method for radiance modelling , including its application to predictive daylight harvesting , and the real time simulation of physically-based electric lighting a...
In an example, an expected sky condition is calculated for a geographic location, a time of day, and a date based on a mathematical model. A predicted distribution of direct and interreflected solar radiation within the environment is calculated based on the expected sky condition. Measurement data from one or more photosensors is obtained that pro...
In an example, an expected sky condition is calculated for a geographic location, a time of day, and a date based on a mathematical model. A predicted distribution of direct and interreflected solar radiation within the environment is calculated based on the expected sky condition. Measurement data from one or more photosensors is obtained that pro...
System and Method for the Optimization of Radiance Modelling and Controls in Predictive Daylight Harvesting
Both the WELL Building Institute and UL (Underwriters Laboratories) have released documents promoting the use of circadian lighting metrics in architectural building design. However, it may be prudent to take a step back and ask how these metrics will be implemented in the real world ...
A dense array of sensors positioned in a virtual environment
is reduced to a sparse array of sensors in a physical environment,
which provides sufficient information to a controller
that responds to environmental conditions and parameters
in the physical environment in substantially the same
manner as it would to the same environmental conditions
a...
In an example, an expected sky condition is calculated for a geographic location, a time of day, and a date based on a mathematical model. A predicted distribution of direct and interreflected solar radiation within the environment is calculated based on the expected sky condition. Measurement data from one or more photosensors is obtained that pro...
Bidirectional scattering distribution functions (BSDFs) are useful in modeling the distribution of daylight through building windows, but measured BSDFs are not readily available. For the purpose of calculating climate-based daylight design metrics, it is therefore reasonable to use analytic functions to represent BSDFs of common diffusion material...
LICASO™ and DAYSIM are daylighting analysis software programs that perform climate-based annual daylight simulations, including the calculation of annual daylight metrics. This white paper compares their performance in terms of accuracy and calculation times. Average illuminance and spatial daylight autonomy values agree to within 8 percent, while...
Investigation of the phytochrome photostationary state (PSS) metric as it applies to red and far-red LEDs for photoperiodic control of flowering plants in greenhouse environments.
Light pollution models used to predict sky glow typically assume 1,000 to 1,500 lumens per capita for urban centers, but neglect the contribution of automobile headlights (with an average 6,000 lumens per vehicle). This blog article analyzes the relative contributions of different light sources (roadway, parking lots, building exteriors, stadiums,...
Horticultural lighting these days is big business. As agricultural land becomes scarce, the weather becomes more unreliable, and the migration of people to megacities continues, it increasingly makes economic sense to cultivate plants indoors with electric lighting. The problem is that lighting designers and horticulturalists generally do not speak...
The literature on human-centric lighting explains that we have intrinsically photosensitive retinal ganglion cells (iPRGCs) in the retina of our eye, which synchronize ("entrain") the suprachiasmatic nucleus (SCN) in the brain. The SCN is the master clock for our circadian rhythms, and it determines when the pineal gland secretes melatonin, which i...
The BUG (Backlight-Uplight-Glare) rating system for outdoor luminaires presented in IES TM-15-11 is incorporated in the IDA/IES Model Lighting Ordinance and LEED v4 Light Pollution Reduction credit. However, an in-depth analysis reveals that not only is it not possible to measure the uplight limitations specified by TM-15-11, the effect they have o...
The International Dark-Sky Association recently reduced the maximum allowable CCT for its dark-sky Fixture Seal of Approval program from 4100K (neutral white) to 3000K (warm white) as a means of limiting light pollution. Unfortunately, it did not present any scientific analysis in support of this change, leaving it open to debate as to whether it w...
In the context of a predictive daylight harvesting system data values are input regarding a plurality of variable
building design parameters. The effects on a building's environmental characteristics are calculated based on
the data values regarding a plurality of building design parameters. At least one of the data values is changed
regarding vari...
There is a fascinating research paper called " Colour as a Signal for Entraining the Mammalian Circadian Clock " that has just been published in the open access journal PLOS Biology (Walmsley et al. 2015). While it is an exceedingly technical paper, the basic premise is this: the change in yellow-blue color ratio during twilight may be more effecti...
In various embodiments, an illumination system includes multiple light-emitting strings that are selectively
activated or deactivated to regulate an overall output of the array.
A controller, method and system, for controlling lighting responsive to ambient lighting conditions are
described. In particular, disclosed is illumination controller (110) for controlling illumination of a workspace
near a display (253). The illumination controller includes a memory device (113) storing a user's preference
for illumination of the...
A controller, method and system, for controlling lighting responsive to ambient lighting conditions are described. In particular, disclosed is illumination controller (110) for controlling illumination of a workspace near a display (253). The illumination controller includes a memory device (113) storing a user's preference for illumination of the...
Solid-state lighting is increasingly being used in horticultural applications, including greenhouses and indoor “vertical farms.” To meet the needs of the horticultural industry, SSL manufacturers and lighting designers will need to understand the spectral power distribution requirements of photosynthesis for optimal plant health and growth. Ian As...
Lighting design is based in part on the reasonable assumption that photometric units have precise definitions. The candela, for example, has a precise mathematical definition: " The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540×10 12 hertz and that has a radiant intensity in...
In accordance with certain embodiments, regions of spatially varying wavelength-conversion particle
concentration are formed over light-emitting dies.
In accordance with certain embodiments, regions of spatially varying wavelength-conversion particle
concentration are formed over light-emitting dies.
Lighting designers today will surely recognize the Kruithof curve, in which the color temperature of the light source is related to a range of illuminances that we find " pleasing. " In its modern form, the Kruithof curve has become supposedly irrefutable evidence that the correlated color temperature (CCT) of LED-based lighting should not exceed 4...
The IES Lighting Handbook, Tenth Edition (IES 2010), describes luminance as " perhaps the most important quantity in lighting design and illuminating engineering. " This is an accurate but curious description, as the editors neglected to include an entry for Section 5.7.3, Luminance, in the handbook's index. The section itself is a mere five paragr...
The blue light emitted from architectural white light LEDs is NOT harmful to the health of your eyes ... an examination of the medical literature and its interpretation in lighting design trade journals.
In accordance with certain embodiments, regions of spatially varying wavelength-conversion particle
concentration are formed over light-emitting diodes.
A method and apparatus for communicating information content by modulation of light in an illumination
system via a liquid lens optically coupled to the illumination system and capable of modulation of light
thereof, using resonant modes of the liquid lens. A modulation control system operatively coupled to the
liquid lens and to the information co...
Do you suffer from math anxiety? A surprising number of us do (e.g., Wigfield 1988). I would tell you the exact numbers, but you would need to understand statistical analysis … Fortunately, we can mostly muddle through our lives without having to deal with statistics, vector calculus, differential geometry, algebraic topology and all that. As an el...
A light-emitting device includes a light-emitting die and, at least partially surrounding the light-emitting die,
a phosphor element comprising (i) a binder and (ii) disposed within the binder, one or more wavelength conversion materials for absorbing at least a portion of light emitted from the light-emitting die and emitting
converted light havin...
We most often think of lighting design in terms of lumens, color temperature, and CRI, but there are occasional situations where a deeper analysis is required. One such situation is as close as your doctor's office: the examination room. An examination room is typically windowless and illuminated only by linear fluorescent lamps. In examining the p...
Lighting control systems are disclosed that enable a combination of functions comprising natural illumination
based lighting control, occupancy-based lighting control, and security control. One or more processors are
used in conjunction with one or more cameras and a plurality of luminaires, to perform a combination of
functions comprising natural...
In accordance with certain embodiments, regions of spatially varying wavelength-conversion particle
concentration are formed over light-emitting dies.
In various embodiments, a lens array comprises a plurality of aspheric lens elements each optically coupled
to a light-emitting element and producing an out-of-focus image thereof. The images combine to generate a
traget luminous intensity distribution, e.g., providing constant illuminance on a plane.
In accordance with certain embodiments, regions of spatially varying wavelength-conversion particle
concentration are formed over light-emitting dies.
Giving light … this phrase symbolizes a new philosophy of lighting design, a philosophy in the sense of how we think about the lighting design process. Much like the modernist movement in architectural design a century ago, it offers a reconciliation of lighting design practices with today's rapid technological advancements and societal changes. Th...
One of the joys of statistics is that you can never be proven wrong … deriving scotopic-to-photopic (S/P ratios for generic white light LED roadway lighting from luminaire photometric data.
In accordance with certain embodiments, a phosphor element at least partially surrounding a light-emitting
die is shaped to influence color-temperature divergence.
In accordance with certain embodiments, a semiconductor die is adhered directly to a yielding substrate with
a pressure-activated adhesive nothwithstanding any noplanarity of the surface of the semiconductor die or
non-coplanarity of the semiconductor die contacts.
Nine out of ten daylight simulation programs agree … and therein lies a story worth retelling. The story begins in the sixth century with the publication of Corpus Juris Civilis (" Body of Civil Law ") by order of the eastern Roman emperor Justinian I [Scott 1932]. Written in four volumes, it included the Digest, being extracts from the writings of...
In accordance with certain embodiments, regions of spatially varying wavelength-conversion particle
concentration are formed over light-emitting dies.
Lamp with a CRI of 90 or above, good. Lamp with a CRI of less than 80, bad. Is there anything else that lighting designers need to know about the Color Rendering Index (CRI) metric? To be brutally honest … no. Despite all that has been written on the topic over the past decade, the importance of CRI to everyday lighting design today is minimal at b...
A working group for the Illuminating Engineering Society (IES) recently published the TM-25 standard file format for disseminating source ray data. This presentation will inform the community of the results.
In accordance with certain embodiments, interior spaces are illuminated with a combination of harvested
sunlight and artificial light emitted by one or more light-emitting elements.
If you are involved with outdoor area or roadway lighting design, you will undoubtedly encounter such terms as mesopic multipliers, scotopic lumens, and S/P ratios, and you will sooner or later need to consider mesopic photometry in your design efforts. For example, you may encounter a government specification that states, " Luminaires must have a...
In accordance with certain embodiments, a semiconductor die is adhered directly to a yielding substrate with
pressure-activated adhesive notwithstanding any nonplanarity of the surface of the semiconductor die or noncoplanarity of the semiconductor die contacts.
Methods and apparatus are disclosed for providing optical emission feedback control for an illumination
system comprising mixed light including light from a first light source (135) and a second light source
(140). Each light source is driven by a drive current configured using a control and/or modification signal
associated with that light source....
Optical design requires accurate characterization of light sources for computer aided design (CAD) software. Various methods have been used to model sources, from accurate physical models to measurement of light output. It has become common practice for designers to include measured source data for design simulations. Typically, a measured source w...
Radiative flux transfer between Lambertian surfaces can be described in terms of linear resistive networks with voltage sources. In this paper we examine how these "radiative transfer networks" provide a physical interpretation for the eigenvectors of form factor matrices. This leads to a novel approach to photorealistic image synthesis and radiati...
The IES BUG rating system is useful for classifying outdoor
luminaires when considering light trespass, sky-glow, and glare in
accordance with the joint IDA-IES Model Lighting Ordinance (MLO).
There are, however, limits to what can be measured in the laboratory.
IES TM-15–11 requires that a luminaire with an uplight rating of U0
emits zero lumens i...
Disclosed herein are methods and systems for emitting light that can provide a desired light-induced
physiological stimulus and a desired luminous stimulus. The light can be controlled to vary the physiological
Page29
stimulus within a predetermined first range while maintaining the luminous stimulus within a predetermined
second range that is usef...
Disclosed herein are methods and systems for emitting light that can provide a desired light-induced physiological stimulus and a desired luminous stimulus. The light can be controlled to vary the physiological stimulus within a predetermined first range while maintaining the luminous stimulus within a predetermined second range that is useful for...
Inventors: Ian Ashdown, Michael Tischler, Philippe Schick, C Wade Sheen, Paul Jungwirth
In accordance with certain embodiments, an unpackaged inorganic LED die is adhered directly to a yielding
substrate with a pressure-activated adhesive notwithstanding any non-planarity of the surface of the
unpackaged inorganic LED die or non-coplanarity of the...
In accordance with certain embodiments, a semiconductor die is adhered directly to a yielding substrate with
a pressure-activated adhesive notwithstanding any nonplanarity of the surface of the semiconductor die or
non-coplanarity of the semiconductor die contacts.
This bibliography includes over 3,000 references to papers, articles, books, and theses on radiosity and related global illumination algorithms. The latest release is available from http://www.helios32.com.
The present invention provides a method and apparatus for optical feedback control for an illumination
device, wherein the control signal for each array of one or more light-emitting elements corresponding to
a particular color, is independently configured using a modification signal whose frequency is different for
each color. Electronic filters w...
Apparatus for determining intensity and peak wavelength of light of luminaire with UV LED, uses processing
system and sensing units, to perform determination based on functional relationships between different
intensities of light.
Light-emitting element e.g. organic LED, controlling method for e.g. roadway lighting, involves comparing
two data, and difference between data is determined, where forward current is adjusted to decrease difference
between data.
Most lighting simulation programs represent color as RGB triplets in a device-dependent color space such as ITU-R BT.709. Implicit in this representation is the assumption that interreflections between colored surfaces can be accurately calculated using three separate color bands. We demonstrate that while this assumption generally holds for most a...
A kinoform diffuser used in light control devices, has controllable diffusion characteristics such as off-axis
transmittance.
Red, amber, green and blue light source for optimizing illumination characteristics in e.g. personal computer,
has computing module computing drive parameters for driving source to attain illumination characteristics.
Lighting design and analysis software is used by professional lighting designers to calculate lighting levels for buildings and roadways. The software iteratively calculates distribution of light within the 3D model by calculating the direct illumination of each surface due to the electric lighting and daylight. The two basic approaches for these c...
The papers included in this volume were part of the technical conference cited on the cover and title page. Papers were selected and subject to review by the editors and conference program committee. Some conference presentations may not be available for publication. The papers published in these proceedings reflect the work and thoughts of the aut...
Feedback and control system for digitally-controlled luminaire, has control system, operatively integrated
with feedback system, that adjusts supply electric current of one or more light-emitting elements according to
adjustment factor.
Illumination system in factory, determines control parameters based on output of photometric sensor and
set of parameters defined by multivariate function with solution defining hyperplane representing constant
chromaticity.
Light-emitting element control system for use in lighting system i.e. illumination system, has converting
module operatively connected to power supply to provide drive current to light-emitting element units.
Light source for use as illumination device, data communication device, generates continuous carrier signal
for controlling desired light output of LEDs.
Projects
Projects (3)
Ultraviolet-C (100 nm to 280 nm) germicidal lamps have proven effective for surface and air disinfection for 50 years, but the only means of validating their performance is with field trials using bacterial cultures and UV-C radiation sensors. This fast-track project aims to modify our existing architectural and horticultural lighting design and analysis software (which has been in commercial use for 25 years) to model and predict the performance of upper-room germicidal luminaires, ceiling-mounted sterilization luminaires with far-UV excimer lamps and visible light LEDs, and in particular mobile UV-C and pulsed xenon lamp platform and autonomous robots.
Daylight and supplemental electric lighting are essential for photosynthesis and photomorphogenesis in plants, and yet the best advice available for greenhouse and vertical farm designers is, "The light level in the greenhouse should be adequate and uniform for crop growth."
This study seeks to bring the principles of climate-based annual daylighting and electric lighting design analysis software as developed for architectural environments to greenhouse and vertical farm design.