Advantages of Lenses and Reflectors
LED with ancillary lens - defocused
Defocusing: The LED is moved closer to the lens. Lenses have the advantage of ermitting a circular, homogenous light beam.
Concave mirror (Reflector)
Optical path via reflector - focused
Reflectors can focus light over great distances.
Disadvantages of Lenses and Reflectors
LED with ancillary lens - focused
Lenses have the disadvantage that they cannot focus light over great distances. Though they excel in collecting light, about 70% of the original LED or lamp radiation does not reach the lens.*
* Average values. May vary +/- 15% depending on type of chip and batteries.
Concave mirror (Reflectors)
Optical path via reflector - defocused
1. project a hole in the center of the light cone when defocused,
2. don’t reproduce light homogeneously but in ring forms (due to the glass body design of the bulb),
3. can only focus 30 to 50% of the light to the front*. The rest of the light appears as a huge diffuse circle around the focal point. Of course, there’s no light system that yields 100% emittance. In all light control and collection systems, a certain amount of light is sucked up and absorbed, depending on the evenness and coating of the surfaces involved. Low-grade reflectors absorb up to 30% of the light*.