Optical Characteristics of LED's
The many different packages and types of LEDs generate different spatial radiation patterns. Precise knowledge of the angle-dependent distribution of radiation is necessary for some applications. For example, a full-color (red, green, blue) LED display may appear white when observed at a normal angle if all three colors are illuminated simultaneously. However, if the LEDs have a different spatial distribution of radiation for the individual colors a color change occurs when the display is observed off axis.