Light intensity is related with 3 factors, all about light power, angle and height. It’s a combination to form the light characteristics for different use case, especially in grow light world.
Here today, we introduce more details about LED optics which helps to shape the light beam angle.
PART 1: PRIMARY OPTICS
LED chip, sometimes people call it diode, is coated with silicon during the manufacturing process. This layer of coating is called PRIMARY OPTIC. The shape of primary optic functioning as a protective coating and determines the light beam angle which emitted from the diode.
Firstly, LED grow light companies will select different angles for their products in different growing scenarios. 90° is a common beam angle on LED grow lights, but some companies may use wider angles. Too wide of an angle reduces the intensity over distance, while too narrow of an angle can reduce coverage area.
Read more about LED beam angle here (Links)
Then, even though LED grow light distribution is at a specific angle, let’s say 120°, but it does not mean that the light will be at equally intense at all viewing angles. For example, if we use a CRIC (Common Relative Intensity Curve) to explain the Lumo-X XC series grow light, we can see that the intensity at 75° is about 50% of the original intensity, and 100% at the angle range between 0~5°. That why you need a PPFD map to plan your grow room.
For more about PPFD and PPFD map, click (links) here
So, this is the nature of LED primary optics. It is such an important concept that you have to know when you plan your lights distribution for an evenly light coverage, either in the greenhouse, grow room, Lumo-X emerald or black diamond series grow tents.
Talk about the LED grow light, in the past, some LED grow light companies only use primary optics but high-wattage diodes, 5 watts or even higher for example, to hold the intensity. But in recent days, the trend has been changed by using large amount of low wattage LED diodes on multiple light bars (Fluence Bioengineering SPYDR Series) or panel (Quantum Board) instead. The recent big name is Samsung 301B/H chips which the wattage could go down as low as 0.25W of each diode. Lumo-X LightCloudTM series is under this typical modern design which meet the recent days concept by using more than 2400pcs low power LED diodes in total to reach a very high PPF to meet the target of both a very even light distribution and high intensity at 1000 umol/s2 level at 12inch height.
Get more information about Lumo-X LightCloudTM series LED grow light here.
So, primary optics area ideal for even canopy coverage since they spread the light out wider than a narrower beam angle.
PART 2: SECONDARY OPTICS
With the forementioned concept, the secondary optics is another layer of architect to help to form a much more purposed light beam angle, which usually being categorized as 3 different types:
Cat. A: TIR(Total Internal Reflection) Lenses, the most common design
TIR optics are what most growers consider secondary optics. These are cone-shaped, injection-molded, refractive lenses inside a reflector that are placed over the diode.
TIR lenses focus the light in a more collimated distribution, meaning they concentrate the photons that would have been radiating out at a larger degree angle and narrows their beam angle. TIR lenses are more common with smaller chips, such as 1-watt, 3-watt, and sometimes 5-watt diodes, and are used to increase the diode’s intensity. However, this comes at a small cost. TIR optics will decrease a fixtures overall footprint size and optical efficiency. Furthermore, secondary lenses can decrease optical efficiency by about 8% via the reflection and refraction losses that occur in the optic.
Cat. B: Glass lenses, high quality magnifying design
Glass lenses are often used to focus the light from COB LEDs.
Learn more about different type of LED diodes just like SMD, COB… click the links here
Unlike a TIR lens (that work via reflection and refraction), a glass lens works similar to a magnifying glass in which the convex lens uses only refraction to concentrate the incoming light into a narrower beam.
Some growers consider glass lenses superior to lenses made with polymers since polymers can degrade, yellow or haze overtime due to outgassing and high-energy blue light, respectively. Hazing can reduce optical intensity, while the yellowing can change the color of the emitted wavelengths.
Cat.C: Reflectors, a much simpler and less expensive solution
Reflectors are sometimes used instead of TIR lenses to focus the light. A manufacturer might use reflectors because they are simpler and less expensive than TIR lenses. Unlike TIR lenses, reflectors surround the diode and are not placed on top of the diode.
The effectiveness of the reflector depends on the pattern, angle, and finish. Reflectors can be circular (cone-shaped) or paneled (4 flat sides) with varying angles. Steeper angled reflectors increase light intensity, while shallower lenses will throw the light out in a wider pattern. Most (all?) LED grow light reflectors use a film for the reflective surface, which can be optically superior
Efficiency losses with reflectors can occur in the pattern, angle, or finish. Different patterns may have varying degrees of efficiencies. And if the angles are too steep, this may decrease the optical efficiency. Furthermore, less glossy films or reflective materials reduce reflectivity and, ultimately, the amount of light reaching the plants.
Instead of using a glass lens over the COB to increase light intensity, some manufacturers incorporate reflectors around the COB. The reason of using reflectors instead of a glass lens is because some of the light escapes the sides of the reflector and is not as directed as when a glass lens is used. Some manufacturers might use a reflector design since it increases the light intensity while allowing even blending across the fixture’s footprint.
PART 3: THINGS YOU SHOULD KNOW BEFORE A PURCHASE
As explained, it is important to consider the beam angle in relation to the chip wattage, recommended height above the plants, size of the light footprint, and grow environment when comparing LED grow lights.
Here are few tips you should keep in mind: