The Crucial Role of Optics
By Bill Little
CTO LumenPros, Inc.
Optics play an important role in proper lighting and light distribution in any given environment. In the field of agriculture, like many commercial fields, uniformity is equally as important as output, and often even more critical. Many manufacturers simply put a clear cover over the bare LEDs and allow the raw lambertian distribution to provide the light. However, this often results in spotty, uneven light in an environment. It can work reasonably well at times, especially in mid to high ceilings, but in lower ceilings it results in poor light distribution.
Lambertian LumenPros T5 LumenPros RSR Technology
(bare LEDs 120 deg) Square Wide (T5SW)
As you can see above, while all three graphs are theoretically wide angles, the intensity varies greatly at angle. A general rule of thumb for intensity is that intensity is relative to the square of the distance. Therefore, in any downward facing layout, such as a barn, distribution center or factory, the SHORTEST distance for the light to travel is straight down, and therefore should have the lowest intensity.
Note that this is opposite in the Lambertian, where the highest intensity is straight down, results in hot spots in an application. The two IES Type 5 optics illustrated are designed for uniform light distribution, but at different heights.
This particular Type 5 Medium is designed for mid height ceilings, and a spacing that is roughly 2 - 2.2 times the mounting height.
This Particular Type 5 Square Wide is designed for lower ceilings, and a spacing that is roughly 4 times the mounting height. It can be used at highers ceilings at wider spacings as needed as well.
All approaches result in similar averages, however, the critical difference is the uniformity, and equally important, the reduction in peak intensity, or hot spots.
See the comparison below contrasting 150 watt LED fixtures with Lambertian and T5SW light distributions patterns at a common mounting height of 12 feet, and assuming the lumens are the same between fixtures. Note that while they have roughly the same average (20fc), the T5SW has a nearly 40% lower contrast ratio (max vs min). This means a more uniform and comfortable environment for both animals and humans.
Typical Lambertian
Point by Point 3D Visual Rendering
Note the wide variance Note the drastic difference
in intensities in hot spots and dark areas
LumenPros T5SW
Point by Point 3D Visual Rendering Note the much lower Note the much lower difference
variance in intensities. in hot spots and dark area
In a similar fashion, looking at common lower ceiling applications such as linear fluorescent and LED jelly jar replacements, we can examine these Lambertian distributions to the LumenPros RSR Technology in the same way assuming lumens are the same, and mounting height is 8 feet. Note that while the Lambertian ,may have a slightly higher average (5-10%), the RSR Technology yields a 68% lower contrast ratio (max vs min). This means dramatically better uniformity and a brighter “feel” to the environment.
Typical Lambertian (LED Tube or LED Jelly Jar)
LED Point by Point 3D Visual Rendering
Note the wide variance. Note the drastic unhealthy
in intensities. hot spots and dark areas
Lumen Pros RSR Technology
LED Point by Point. 3D Visual Rendering
Note the much lower variance Note the maximized uniformity
in intensities without hot spots
Uniform illumination typically results in better comfort levels for both animals and humans.
LumenPros engineers each lighting fixture to properly light an application with considerations of light output, quality of light, and optics. LumenPros has developed specific optical technologies such as its T5SW design for mid and high bay applications as well as the innovative RSR Optical Technology for low ceiling applications. As illustrated, optics play a critical role in the engineering of a lighting fixture and application design, and it is important to understand both and purchase products from a company that understands optics and doesn’t simply put “LEDs in a box”.