Method of adjusting multiple light sources to compensate for variation in light output that occurs with time

A method for calibrating light system having a first light source and a second light source each producing light of having a different color which combine during an operating mode of the light system, said method comprising:

• (a) defining a first reference value for a characteristic of the light produced by the first light source;
• (b) defining a second reference value for a characteristic of the light produced by the second light source;
• (c) defining the first light source as a selected light source;
• (d) operating only the selected light source;
• (e) sensing the characteristic of the light produced by the selected light source and thereby producing a sensed value;
• (f) selecting either the first reference value as a selected reference value when the first light is the selected light source or the second reference value as a selected reference value when the second light is the selected light source;
• (g) comparing the sensed value to the selected reference value;
• (h) adjusting operation of the selected light source until the sensed value has a predefined relationship to the selected reference value;
• (i) defining the second light source as a selected light source;
• and
• (j) repeating steps (d) through (h).

A method for calibrating light emission apparatus having a first light source that produces white light, a second light source that produces a first color of light, and a third light source that produces a third color of light, said method comprising:

• operating the first light source to produce light at defined luminance level which is a first reference level;
• adjusting operation of the second light sources and the third light source until a correlated color temperature of a combination of light produced by all light sources has a predefined value;
• sensing a first characteristic of light produced by the second light source, thereby producing a second reference value;
• sensing a second characteristic of light produced by the third light source, thereby producing a third reference value;
• thereafter:
• sensing luminance of light produced by the first light source, thereby producing a first sensed value;
• comparing the first sensed value to the first reference value;
• adjusting operation of the first light source in response to comparing the first sensed value;
• sensing the second characteristic of light produced by the second light source, thereby producing a second sensed value;
• comparing the second sensed value to the second reference value;
• adjusting operation of the second light source in response to comparing the second sensed value;
• sensing the third characteristic of light produced by the third light source, thereby producing a third sensed value;
• comparing the third sensed value to the third reference value;
• and
• adjusting operation of the third light source in response to comparing the third sensed value.