CHAPTER 10 ■ LEDS
LED Lens Clarities
There are three popular lens clarities (see Figure 10-6).
Water Clear
Water-clear LED lenses are sometimes simply called “clear.” The lens is a transparent epoxy that tends to
bend light unevenly like water. Water-clear LEDs are likely to be a bit brighter since the clear lens itself
neither absorbs nor disperses the light. The light output is usually straight ahead like a spotlight.
Water clear is a good choice for an indicator that will be viewed head on but shouldn’t be too apparent
from the sides. (A traffic light, for example.) Water clear is excellent for a long distance beam, such as an
intruder alarm. Sandwich, the line-following robot, uses them because they focus most of their energy on
the floor in front of the robot, like headlights.
White Diffused
White-diffused LED lenses are a milky or hazy epoxy. The light spreads out throughout the LED body,
making it equally bright and visible from all sides. The amount of “head-on” light is reduced since the semi-
opaque lens absorbs some of the light and spreads the light over a larger viewing angle. Because the LED is
dim white when off, there’s a significant visual difference when the LED lights up with color.
White-diffused lenses are excellent for indicators that need to be visible from the sides as well as the
front. Power, ready status, target acquisition, and error lights are good examples.
Colored Diffused
Color-diffused LED lenses are sometimes called “red diffused” or whatever the particular color. A color-
diffused lens spreads light uniformly much the same as a white-diffused lens. Unlike the white lens, the
epoxy is tinted so that the LED color is obvious even when the LED is off. This is useful if a bunch of LEDs are
adjacent to each other (“Is the red LED turned off?”). However, since the color doesn’t change from the off
state to the on state (only the brightness), it’s more difficult to tell in a bright room if the LED is lit.
Early LEDs were so weak in their light output that they couldn’t act as spotlights and couldn’t light up a
white-diffused lens. As such, colored lenses were the manufacturers’ best solution. Colored lenses provided
consistent color quality with decent illumination.
Figure 10-6. Water-clear, white-diffused, and color-diffused lenses