Abstract: A lighting apparatus emitting polychromatic light comprising light of at least two light-channels with different colors, wherein each light-channel is controlled by one modified pulse-width-modulated signal (modified PWM-signal), and each modified PWM-signal results from the modulation of one color-pulse-width-modulated signal (color-PWM-signal) with an intensity-pulse-width-modulated signal (intensity-PWM-signal) in order to control the brightness and color location of the polychromatic light.

Abstract: A lighting apparatus emitting polychromatic light comprising light of at least two light-channels with different colors, wherein each light-channel is controlled by one modified pulse-width-modulated signal (modified PWM-signal), and each modified PWM-signal results from the modulation of one color-pulse-width-modulated signal (color-PWM-signal) with an intensity-pulse-width-modulated signal (intensity-PWM-signal) in order to control the brightness and color location of the polychromatic light.

Abstract: A LED lighting system (100) employing a LED light source (115), a user interface (124, 128, 134, 138), and a controller (112). The LED light source (115) includes a plurality of colored LEDs emitting one of a plurality of spectral outputs as a function of one or more currents flowing through the colored LEDs, where each current has a variable time average flow. The user interface (124, 128, 134, 138) facilitate a user selection of one of the spectral outputs. The controller (112) controls the variable time average flow of each current flowing through the colored LEDs as a function of the spectral output selected by the user.

Abstract: An apparatus is directed to controlling a light source. The apparatus provides at least one light source that emits a light signal at a discrete frequency and a reference signal at the discrete frequency. The apparatus further includes a photodetector optically coupled to the light source and designed to receive the light signal. The apparatus additionally includes at least one lock-in system coupled to the photodetector and each light source that receives the light signal from the photodetector and receives the reference signal from the light source. Each lock-in system produces an intensity value of the light source based on the light signal and the reference signal. The lock-in system may include a frequency multiplier and a filter coupled to the frequency multiplier wherein the intensity value is the product of the light signal and the reference signal processed through the frequency multiplier, and filtered to remove non-dc portions.