LED Light Beam Types Explained

LEDs have been widely used as the main light source for LED lighting lamps & fixtures. These LEDs have a much smaller footprint and are directional light rays compared to other light sources such as incandescent lamps. They usually come with primary optics attached but the light distribution pattern is wider than most applications. Since the distribution pattern is wide, the intensity/brightness decreases over distance. This is when we need to apply secondary optics to modify the output beam of the LEDs so it will efficiently meet our desired photometric specification.



Secondary optics consist of:



LensesLenses come in different materials, like Polymethyl Methacrylate (PMMA), Silicone plastic, Polycarbonate (PC) and Glass.Most lenses use optical grade Polymethyl Methacrylate (PMMA) lens and achieve a lighting efficiency of 93% with lens thickness of 3mm. Optical grade PMMA lens material is harder and more fragile compared to polycarbonate and allows for the use of high current and tolerance temperature of 80℃ conditions.Liquid Silicone lens is widely used to encapsulate on LED chips. In general, silicone lenses are small in size (around 3mm-10mm) in diameter. They have high temperature resistance feature to allow it to withstand reflow oven temperature around 150℃-225℃. Polycarbonate material offers excellent optical characteristics. It has advantage of high productivity and high light transmission. Higher tolerance of temperature up to 110℃. However, if it’s operated above this temperature, the lens may be damaged and out of shape. Glass lens has the characteristics of high light transmittance, high temperature resistance, corrosion resistance and saline-alkali tolerance. However, it’s not ideal material for LED lenses at the moment due to its heavier in weight, difficult to bend, and easy to break.



ReflectorsReflectors are typically metallic, cone-shaped and sit over the LED to alter the beam of light. However, they do not offer as much control as lenses. One significant advantage of lenses over reflectors is that the light source is covered, which reduces the harsh glare from LED light sources. Hyper-Reflective PC (HRPC) and aluminum material are often used in reflectors.



TIR Optic (Totally Internal Reflector)These lenses are typically cone-shaped, often called TIR lenses as a large part of the design relies on total internal reflection. TIR optics, which consist of a refractive lens nestled inside a reflector, capture and redirect an increased quantity of light emitted from an LED with optical efficiencies as high as 93%. The fundamental working principle is same for both TIR lenses and reflectors, but the TIR lenses enjoy greater control over light. With reflectors, a large amount of light doesn’t touch the reflector, and this light can’t be controlled in any way. Reflectors can be easily implemented and cheaper to manufacture than TIR optics, but the reflectors’ efficiency is clearly lower, compared to TIR optics. A TIR lens manages both direct and reflected light, whereas a reflector manages reflected light but leaves the direct light unmanaged.

Lenses play an important role in secondary optics.

The viewing angle or beam pattern is a vital attribute of lenses. The LED radiation pattern plays an important role in LED applications, which offers lighting designers increased flexibility when it comes to controlling the light in their applications.