Optics Basics
Optic Categories
The use of optics with LEDs is an essential part of enabling various types of LED lighting applications. Optics can be defined as devices used to control light output so it’s a usable source.
There are three basic categories of LED optics:
- Primary – usually attached directly to LED
- Secondary – usually fits directly over or around the LED
- Tertiary – usually some type of external device
| Light Control Diagram Using Different Optics |
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Optical Viewing Angle
Although LED light is directional, it can be controlled further, with optics and/or reflectors to concentrate the luminous flux to exactly what is needed. As previous discussed, every LED has a specified viewing angle. The way the LED is physically constructed and the type of optics used will have an effect on viewing angle.
Primary Optics
Primary optics are usually part of the LED package. Lenses integrated into LED packages, especially SMT and power packages, can cause the luminous flux from the LED to adopt a specific radiation pattern.
Secondary Optics
Secondary optics usually mount in a holder which is then positioned and mounted over the LED package. To understand the need for a secondary optic, assume that a given LED has a 90-degree viewing angle. If a different beam shape and angle are required for a particular application, secondary optics can used to provide that capability. Reflectors can manage reflected light and are fairly simple to design, manufacture, and implement.
Tertiary Optics
Tertiary optics encompass numerous types of optical devices that are application specific. These devices help diffuse, direct, and transport light. The following are some common device types:
- Light guides
- Light pipes
- Total Internal Reflection (TIR) devices
It is also important to remember that passives, electromechanical, and connector (PEMCO) products such as: connectors, cables, LED holders, etc. are an important part of the SSL solution.
Fixture Loss
Fixture loss refers to the light and power wasted from a light fixture. For example, an incandescent bulb radiates luminous flux in all directions and therefore wastes light and power just shining within the fixture. LED light, on the other hand, is directional, and can be controlled further with optics and reflectors to concentrate the luminous flux to where it is needed.
