Let’s Talk Optics: Secrets of LED Lighting Within professional lighting systems, there is frequent discussion surrounding the secondary optics applied to LED lights, utilized to focus, and direct light by altering its photometric distribution.

Inside an LED, illumination emanates from a diode enclosed within a casing known as primary optics. This casing influences the light’s form, but the resulting beam tends to be broad, diminishing in intensity as it extends from the origin, rendering it less suitable for some applications. Additional optical components are incorporated alongside the primary optics to produce more scattered or concentrated light, depending on the desired design specifications. These are necessary elements to focus light rays and maintain beam intensity while improving light distribution.

In addition to directing light, secondary optics offer creative ways to play with light beams and create different effects, thus improving the effectiveness of a lighting system in the environment.

In most cases, it is possible to find a reference regarding the optics in the product data sheets, identified with a series of values indicating the degrees of the beam angle. Commercially available are LEDs with optics starting from a value less than 10°, therefore very narrow, up to one greater than 60°, therefore very wide.

IRIS

Types of secondary optics
Secondary optics can be divided mainly into two families:
Lense
Lenses use principles of refraction and TIR – Total Internal Reflection. A notable advantage of employing a lens is the accuracy in regulating the direction of the emitted light beam.

The photometric solid distribution and light output of the system vary depending on the materials and surface treatment of the lens.

Reflectors
Reflectors utilize the principle of reflection; however, with each reflection of the light beam on the reflector surface, there is a loss due to the absorption of some of the light by the material upon which it is reflected.

IRIS

Materials of optics
Lense
Lenses made from thermoplastic materials, with the most prevalent options being:
PMMA (polymethyl methacrylate): This material offers high malleability during processing.
PC/APEC (polycarbonate): Known for its impact resistance, although it is more prone to scratches, making it suitable for products requiring high-strength properties.
Silicone: Resilient to high temperatures and less susceptible to yellowing over time.
Reflectors
Reflectors for LEDs, also fabricated using thermoplastic materials, specifically:
PC (Polycarbonate)
PCHT (Polycarbonate High Temperature)
An additional processing step, known as metallization, is required. This step involves depositing a reflective layer onto the surface of the reflector material itself.

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Lens or a reflector?

It is hard to determine a priori which type of secondary optic is superior to others because the evaluation depends on the specific application, the light source used, and the design specifications.

Lenses and reflectors are manufactured for high-power and mid-power LEDs, as well as COB LEDs. Therefore, the selection of optics is influenced only partially by the LED type.

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