Patent Application
20190268994
Electrical lights have been used for evening and nighttime external lighting, i.e., streetlights, for over a century. Still there is an ongoing debate on best types of lighting to use when daylight is not adequate for our needs. Some people are primarily concerned about roadway safety and prefer street lighting such as metal halide or LED lights that can provide more blue light. Other people are concerned about the unhealthy or disturbing aspects of being exposed to too much blue light at night and prefer street lighting such as sodium vapor lights or LEDs that can provide more red light.
In accordance with an aspect of the invention, an electrical outdoor light provides light with a spectral power distribution that matches prehistoric nighttime lighting to which humans may have adapted. In particular, rather than producing light with a spectral distribution that is inherent to one specific light production process, an outdoor light may use multiple light sources or multiple phosphors in combination to produce light having a spectral distribution closely matching moonlight or firelight. Different types of streetlights or other outdoor lights may be used in different types of locations, e.g., moonlight SPD at roadways, commercial districts, and industrial districts or firelight SPD in residential neighborhoods, walk ways, and parks.
The drawings illustrate examples for the purpose of explanation and are not of the invention itself. Use of the same reference symbols in different figures indicates similar or identical items.
Outdoor and indoor lighting systems typically have different characteristics and goals. For example, indoor lighting systems often provide ten times or more luminance, have higher color rendering, and lower glare than outdoor lighting systems. Streetlights are generally desired to enhance people's safety, health, and comfort in outdoor environments. To the extent that we understand the effects of light on humans, many lighting characteristics play important roles in achieving such goals. For example, the spectrum of the light, the quantity or intensity of the light, the duration of exposure to the light, the time of day when exposure occurs, and an individual's history of light exposure may all influence the safety, health, and comfort of light exposure. Regarding spectrum, much of the debate regarding preferred street lighting focuses on the best correlated color temperature (CCT) for street lights. People concerned with visibility on the road tend to favor cool (high) CCT and favor types of lighting that generate light having a high CCT, e.g., metal halide and some types of LEDs. People concerned with health, for example, sleep disruption, tend to favor warm (low) CCT and favor types of lighting that generate light having a low CCT, e.g., High Pressure Sodium (HPS), Low Pressure Sodium (LPS), Halogen/Incandescent, and some types of LEDs. However, the CCT may not be an adequate description of the spectral character of light when determining advantages and disadvantages of specific lighting. In particular, a single number, while being attractive for simplicity, is non-definitive of lighting because many different underlying spectra can have the same CCT or appearance when the light source is looked at directly. Objects viewed under lighting with a specified CCT may, however, appear distinctly different when viewed under light with the same CCT but a different spectral power distribution. Further, specific spectral content or wavelengths of light, which may be present to differing degrees in light having the same CCT, may have significant biological impacts, making two lights having the same CCT differ greatly in desirability for street lighting. Spectral power distribution (SPD) is what one needs for a more complete description or characterization of a particular light source.
In accordance with an aspect of the current invention, a street lighting system produces a SPD matching a light source that humans have adapted to since prehistoric times. In particular, two nighttime light sources that humans have thrived under, long before there was electric light, are moonlight and firelight. While the CCT of both moonlight and firelight are similar respectively to “white” and “yellow” streetlights, the underlying spectra are very different. A streetlight containing properly chosen combination of LEDs can produce light with any SPD and could even be configurable, switchable, or programmable to match different choices of SPD for lighting or to evolve the lighting as a night progresses.
The SPD of moonlight may particularly be used in areas such as a major roadway where a whiter light may be desired, and the SPD of firelight may be used in areas such as in a neighborhood where a yellower light may be less disruptive. In general, the goal becomes not just choosing a light generation technique that has a desired CCT but creating a combination of light sources reproducing the spectral shape of prehistoric nighttime light. Light with the desired SPD may be achieved using modern lighting technology, e.g., with multi-color LEDs and/or multiple wavelength converters.
Streetlight 100, in the implementation of
Controller-driver 120 may or may not be programmable. Programmable drivers for lighting system are disclosed in U.S. Pat. No. 8,021,021, which is hereby incorporated by reference in its entirety. In some implementations, controller-driver 120 is programmable to select how light channels 110 are respectively driven in order to provide combined light 140 with a desired SPD, e.g., to provide the SPD of moonlight or firelight. For example, controller-driver 120 may change the drive levels to light channels 110 if the performance of light channels 110 changes, e.g., with temperature or over time. A programmable controller-driver 120 may also change the intensity or SPD of combined light 140 over time to improve lighting efficiency, to achieve a biological effect on people, flora, or fauna in the area illuminated, to adapt to changes in ambient light, e.g., to change emitted light 140 as the ambient lighting changes from twilight to evening to midnight to dawn, or to adapt to weather or atmospheric conditions.
Streetlight 100 may optionally employ one or more sensors 150 to sense weather or atmospheric conditions surrounding streetlight 100, to sense the characteristics of combined light 140 or of ambient light, or to sense operating parameters, e.g., temperature or age, of streetlight 100. Controller-driver 120 may use measurements from sensors 150 to calculate or produce drive levels as needed to produce a desired SPD and a desired total emitted power. For example, controller-driver 120 may adjust the SPD or the total emitted power for environmental conditions such as weather, e.g., fog, rain, falling snow, or other atmospheric conditions such as smoke from fires, or surface conditions such as accumulated snow or wet or dry pavement. Also, controller-driver 120 may be programmed to adjust the SPD or total power for flora and fauna considerations at certain times of year and/or in certain locations. For example, more or less illumination may be provided depending on whether flora has lost leaves during winter or has grown to block part of emitted light 140 during summer. In some situations, controller-driver 120 may switch the SPD of emitted light 140 between moonlight and firelight SPDs depending on the real time, local activities, or user preferences or to adapt the SPD of emitted light 140 based on the time of day or ambient lighting measured around streetlight 100.
In some implementations, streetlight 100 or 200 may approximate the SPD of firelight or moonlight over all or a major portion of the visible spectrum, about 380 nm to about 780 nm. In some other implementations, combined light 140 may include light ranging into infrared or ultraviolet wavelengths. In particular, a streetlight producing a moonlight SPD including ultraviolet light may produce visible florescence to better approximate actual moonlight.
Streetlight 100 or 200 as described above may be configured to optimize important aspects of combined light 140 such as the quantity, duration, timing, and beam shape, but an important advantage of streetlights 100 and 200 is emulation of the actual spectrum of moonlight and firelight, which, since prehistoric times, humans (and other living things) have been using to sense the night environment. Such optimization in streetlights 100 or 200 may be set and fixed by the characteristics of components, or the optimization of programmable drive levels may be determined based on inputs from sensors 150 or other devices that provide input information such as temperature, humidity, sound, air quality, emergency condition, smell, ambient light, time, pressure, or the spectral transmissivity of the air. Optimization may also be accomplished through learning algorithms both autonomous or from human intervention. One example of human intervention is to change the SPD and/or light level including encoding a time signature of combined light 140 when important astronomical observations are occurring.
Optimization may also be adapted based on knowledge of plant and animal life cycles that are sensitive to nighttime light. For example, photosynthesis generally includes light and dark cycles, and streetlight 100 or 200 may switch for measured periods of time to an SPD that extends the light cycle of photosynthesis or to an SPD that does not interfere with the dark cycles. People and animals have sleep cycles, and streetlight 100 or 200 may switch from a moonlight SPD used in the evening to a firelight SPD used during sleeping hours.
A further advantage of streetlights 100 and 200 is that the effect or character of emitted light 140 is intuitive to understand. In communities considering lighting choices, concepts such as CCT and SPD may not be generally understood descriptions for light, and warm and cool are often confusing to those not familiar with lighting design, particularly because warmer is designated with a smaller number than cooler. However, many people can easily relate to moonlight and firelight based on personal experience, and people may acquire a moonlight or firelight source with confidence that they understand what the source will produce.
Although particular implementations have been disclosed, these implementations are only examples and should not be taken as limitations. Various adaptations and combinations of features of the implementations disclosed are within the scope of the following claims.
This patent document claims benefit of the earlier filing date of U.S. provisional Pat. App. No. 62/634,416, filed Feb. 23, 2018, which is hereby incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62634416 | Feb 2018 | US |
