Tunable LED light array for horticulture

A horticultural lighting apparatus comprising:

• a plurality of light emitting diodes (LEDs) producing light with different colors, wherein the plurality of LEDs is controlled to produce a predetermined proportion of the different colors;
• a waveguide structure coupled to the plurality of LEDs causing a mixing of the light from the plurality of LEDs, wherein waveguide output light from the waveguide structure is a uniform intensity across the apparatus and has a uniform mixture of the different colors;
• and
• a brightness enhancing film coupled to the waveguide structure to generate output light, wherein the brightness enhancing film is structured to control a directionality of the waveguide output light;
• wherein the different colors of the LEDs are selected to coincide with, or overlap, a range of wavelengths to which photosynthesis has a high sensitivity compared to other wavelengths.

A method of calibrating a horticultural light source, comprising:

• providing a plurality of control signal values to an LED driver circuit selected from a plurality of LED driver circuits and associated with an LED, wherein each LED driver circuit is associated with a different LED, wherein the LED driver circuit provides a series of different driver currents and voltages to the LED and driver circuits not selected turn-off the remaining LEDs;
• measuring the light output intensity of the LEDs as a function of the series of different driver currents and voltages;
• storing a table for the selected LED and associated driver circuit representing the measured light output intensity as a function of the driver circuit currents and voltages;
• and
• repeating the providing, the measuring, and the storing for each of the plurality of LEDs and associated driver circuits.