Maintaining stable optical output of solid state illumination system

A solid state illumination device comprising:

• a plurality of light emitting diodes (LEDs) configured to produce light at different wavelength ranges;
• a plurality of controllable electrical current sources, wherein each electrical current source is configured to provide electrical current to a corresponding one of the LEDs;
• a plurality of other optical elements arranged to filter and/or direct light from each respective one of the plurality of light emitting diodes along a corresponding light path to a single optical output of the illumination system;
• a plurality of temperature sensors, wherein each temperature sensor is configured to measure a temperature associated with a corresponding one of the LEDs;
• a computer-based memory that stores characterizing information that describes how one or more optical properties of each respective one of the LEDs in the solid state illumination device change with temperature;
• and
• a computer-based processor configured to:
• determine, based on one or more temperature measurements and based on the characterizing information for one or more of the LEDs, an amount by which electrical current to a LED should be adjusted in view of a change in temperature;
• and
• cause a corresponding one of the controllable electrical current sources to adjust the electrical current to a corresponding one of the LEDs based on the determination,
• wherein the computer-based memory of the solid state illumination device stores information that characterizes one or more optical properties of the other optical elements in the solid state illumination device, wherein the other optical elements comprise one or more optical filters in an optical path for each respective one of the plurality of LEDs,
• wherein the information that characterizes the one or more optical properties of other optical elements in the solid state illumination device comprises cutoff frequencies associated with the one or more optical filters, and
• wherein the amount by which the electrical current to the tested LED should be adjusted is determined, by the computer-based processor, based on the relationship:
• P(T,I)=∫λ1λ2sP1(λ,T,I)*T(λ,T,I)dλ
• where:
• T represents a measured temperature associated with the tested LED,
• I represents the tested LED's driving current,
• P(T,I) is power delivered to the optical output by the tested LED,
• λ represents the tested LED's wavelength,
• sP1(λ,T,I)represents a spectral intensity of the tested LED as a function of the
• LED's wavelength λ, temperature T and driving current I,
• T(λ,I,T) represents a transmission function (for any optical filters and/or other optical components in a light path of the tested LED), and
• λ1 and λ2 define a spectral band for the LED light that reaches the optical output.