Patent ID: 8022631

Claim:
An illumination apparatus comprising: a light source comprising a lighting device which emits light and a phosphor material which converts at least a portion of the light emitted by the lighting device to light of a different wavelength; and a controller which adjusts a ratio of current on time to current off time of a current waveform supplied to the lighting device whereby a contribution of light emitted by the phosphor to a color of the light emitted by the light source is modified, the controller comprising: memory storing software instructions for modifying a pulse width in the waveform, memory for receiving data which is used for determining a modification to the pulse width, and a clock generator for timing the pulse; the controller having a first mode in which pulses having a first width and a first frequency are generated and a second mode in which pulses having a second width are generated, the second width being shorter than the first width, the pulses in the second mode having a frequency which is the same as the first frequency.