Eye-safe laser-based lighting

Abstract

A laser-based light source includes a laser device configured to generate laser light of a predetermined laser wavelength and emit this laser light as a laser beam. A light-conversion device is configured to convert at least part of the laser light into converted light and a laser-output sensor is configured to determine a laser-output signal proportional to the output of laser light emitted by the laser device. Further, a converted-light sensor is configured to determine a converted-light signal proportional to the output of converted light emitted by the light-conversion device. A controller is configured to receive the laser-output signal and the converted-light signal, to determine a safe-to-operate parameter, based on the laser-output signal and the converted-light signal, and to control the operation of the laser-based light source based on a comparison of the safe-to-operate parameter with a at least one predefined threshold.

1 . A laser-based light source, comprising:
 a laser device configured to generate laser light of a predetermined laser wavelength and emit the laser light as a laser beam;   a phosphor light-conversion device configured to convert at least part of the laser light into phosphor converted light;   a laser-output sensor configured to determine a laser-output signal being correlated with an output of the laser light emitted by the laser device;   a phosphor converted-light sensor configured to determine a converted-light signal being correlated with an output of the phosphor converted light emitted by the phosphor light-conversion device; and   a controller configured to receive the laser-output signal and the phosphor converted-light signal and determine a safe-to-operate parameter of the laser device based on a ratio of the laser-output signal and the phosphor converted-light signal or based on phase delay between the laser-output signal and the phosphor converted-light signal, and control operation of the laser-based light source based on a comparison between the safe-to-operate parameter and at least one predefined eye-safety threshold or legislation.   
     
     
         2 . The laser-based light source of  claim 1 , wherein the laser-output sensor is formed by a laser driving current monitor configured to monitor the laser driving current. 
     
     
         3 . The laser-based light source of  claim 1 , further comprising at least one optical fiber configured to guide the laser light to the light-conversion device. 
     
     
         4 . The laser-based light source of  claim 3 , wherein the phosphor converted-light sensor is arranged at an end of the optical fiber which is remote from the phosphor light-conversion device. 
     
     
         5 . The laser-based light source of  claim 3 , wherein the phosphor converted-light sensor is arranged at a position along the optical fiber, and further comprising a decoupling device configured to couple the phosphor converted light out of the optical fiber and into the phosphor converted-light sensor. 
     
     
         6 . The laser-based light source of  claim 3 , wherein the optical fiber is provided with an electrical wiring for detecting damage to the optical fiber. 
     
     
         7 . A method of operating a laser-based light source, comprising acts of:
 generating laser light of a predetermined laser wavelength and emitting this laser light as a laser beam;   converting at least part of the laser light into converted light;   determining a laser-output signal being correlated with the output of emitted laser light;   determining a converted-light signal being correlated with the output of converted light; and   determining a safe-to-operate parameter based on the laser output signal and the converted light signal;   comparing the safe-to-operate parameter with a at least one predefined threshold; and   controlling the operation of the laser-based light source based on the comparison of the safe-to-operate parameter with the predefined threshold.   
     
     
         8 . The method according to  claim 7 , comprising an act of comparing the safe-to-operate parameter with a second predefined threshold. 
     
     
         9 . The method according to  claim 7 , comprising an act of determining the safe-to-operate parameter based on a ratio between the laser-output signal and the converted-light signal. 
     
     
         10 . The method according to  claim 7 , comprising an act of determining the safe-to-operate parameter based on the derivative with respect to time of the ratio between the laser-output signal and the converted-light signal. 
     
     
         11 . The method according to  claim 7 , comprising acts of modulating the emitted laser light in time; and determining the safe-to-operate parameter based on a ratio between the laser-output signal and the converted-light signal at different points in time. 
     
     
         13 . The method according to  claim 7 , wherein the act of controlling the operation of the laser-based light source based on the comparison of the safe-to-operate parameter with the predefined threshold comprises shutting down laser emission or switching it to a safe intermediate level or/and generating a warning. 
     
     
         13 . The laser-based light source of  claim 1 , wherein the safe-to-operate parameter of the laser device is further based signal strengths of the converted-light signal at different points in time, relative to a strength of the laser output.