What does it mean ?
Retro-reflectivity is the correct term given to something that has the ability to return light back to it’s
source. Many items are reflective, white paper, metal foil, a mirror. All of these are reflective but the light reflecting
off them is scattered in many directions. Non have the ability to return a large proportion of the light hitting then back
into the direction from where it came.
Where will I have seen it?
When you’ve seen the Emergency Services on TV at an incident at night and the markings and tape on their
clothing shines bright white. This is because there is a source of light on or next to the video camera, this light is hitting
the retro-reflective material and is being reflected directly back to where it came from, (into the camera) The wearer therefore
becomes far more visible in dark or low light conditions. If you are a driver you will be well aware that road signs also
are made out of a retro-reflective material.
How Bright is bright ?
The performance level of Retro-reflective materials is measured in candle power. Official data says that white
clothing has only a performance level of up to 0.3 candle power, a vehicle license plate has 50, and a conforming retro-reflective
material has 500 candle power. There is of course a direct relationship between reflective index (candle power) and the distance
from which it can be seen, as the above drawing indicates.
How does it do it?
There are two main types of retro-reflective material, the achieve their retro-reflectivity by using a cube
corner prism or glass bead principal. In one the light is reflected off the faces of the prism in the other it is reflected
off the rear face of the bead.
We are not qualified to discuss the technical merits of either system here, only to say that both technologies
provide materials that can conform to the relevant standards for retro-reflective materials. If you would like more technical
information we suggest you look at either of these two sites.
www.reflexite.com / www.international.3m.com