Every light source requires an optic to work properly. According to Architecture Magazine, a compact fluorescent lamp can lose up to 70% of light when paired with an inadequate optic. LED fixtures are no different.
In order to take advantage of the light’s touted advantages – including increased efficiency – the proper optic is key. However, understanding optics can be confusing for those new to LEDs.
LED optics help shape, focus, and mix emitted photons. This ensures your plants receive adequate light to thrive. LEDs come with a built-in optic – called the primary optic – but can also be fitted with secondary optics designed to preserve light intensity over distance.
LED lights differ from incandescent bulbs in that they are directional. Incandescent bulbs illuminate in 360 degrees. A light emitting diode, however, is made from one or more die mounted on some type of heat-conducting material. This means the die is always partially blocked, so an LED can only illuminate at a maximum of 180 degrees.
Primary optics are small domes that cover the diode, which are easily visible on a typical LED fixture. Primary optics serve two purposes: to protect the light and to control the diode’s light output. Primary optics are attached during the manufacturing process, so they determine a light’s beam angle (a topic we discuss in depth here).
With most applications, an LED’s light distribution is too broad. This means that light intensity dulls over distance. This is a problem that can be corrected through the use of secondary optics.
Secondary optics serve multiple purposes: they magnify light intensity, direct light at a specific surface, enhance color, and improve beam uniformity. Various types of small lenses can be applied on top of emitters, which help focus the photons.
The two types of secondary optics used most often for LED lights are reflectors and total internal reflection (TIR).
Reflectors are easier to implement and much less expensive than other options, but tend to vary considerably in quality. How well a reflector works is dependent on factors such as shape, texture, and surface.
While reflectors may provide some help to those on a budget, they are not typically recommended for LED lights. The majority of incandescent lights use reflectors, but they pose certain problems when used with LED lighting. With LEDs, the majority of rays that come from the emitter’s center can bypass the reflector. This results in lost lumen output, and can sometimes contribute to issues like glaring.
For these reasons, reflectors are not commonly used for LED lighting. TIR optics are usually the preferred option.
TIR optics are cone-shaped refractive lenses placed inside a reflector. TIR optics can reach optical efficiencies as high as 92%. This efficiency is achieved by directing light from a source’s center, which is then sent out as a controlled beam.
TIR optics work well with LEDs for a number of reasons. TIR optics fit easily over primary optics, for one, and this allows them to direct light straight from the source. Therefore, less lumen output is lost and issues like glaring become less likely.
TIR optics are made from injected-molded polymer, so they can be tailored for different purposes. Various surface treatments – like ripple, frosted, or polished optics – can shape light distribution and widen beam angles. Some more modern TIR optics can even be made to filter out certain wavelengths, creating specific patterns or colors on different surfaces.
While TIR optics show a lot of promise, indoor growers hoping to incorporate them are at a slight disadvantage. TIR optics are currently much more prevalent in outdoor lighting, although they are gaining some traction as a viable choice for indoor fixtures. It is a technology indoor growers should keep an eye on in the coming years.
LED Optics: The Bottom Line
Optics are essential to light function. Primary optics play a big role in controlling factors like beam angle, but are often inadequate at controlling light intensity. This is why many growers choose to fit their lights with secondary optics. While reflectors are the inexpensive choices, TIR optics are generally better suited for LEDs specifically.
Factors like surface treatment, size, and shape can all impact how optics regulate light intensity, so do your research when deciding on the proper optics for your LED lights. Talking to your light’s manufacturer can help you make a decision.
We are always here to help growers at all levels gain the tools they need to thrive. If you have any questions about LED optics, feel free to reach out here and someone will be in touch soon.