Eye-safe laser-based lighting

Abstract

The invention relates to a laser-based light source comprising a laser device ( 1 ) adapted for generating laser light of a predetermined laser wavelength and emitting this laser light as a laser beam; a light-conversion device ( 2 ) for converting at least part of the laser light into converted light; a laser-output sensor ( 7 ) for determining a laser-output signal proportional to the output of laser light emitted by the laser device ( 1 ); a converted-light sensor ( 6 ) for determining a converted-light signal proportional to the output of converted light emitted by the light-conversion device ( 7 ); and a controller ( 9 ) which is adapted for receiving the laser-output signal and the converted-light signal, for determining a safe-to-operate parameter, based on the laser-output signal and the converted-light signal, and for controlling 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. In this way, a laser-based light source is proposed which enables reliable eye-safety in an easy way.

1 . A laser-based light source, comprising
 a laser device for generating laser light of a predetermined laser wavelength and emitting this laser light as a laser beam;   a light-conversion device for converting at least part of the laser light into converted light;   a laser-output sensor for determining a laser-output signal being correlated with the output of laser light emitted by the laser device;   a converted-light sensor for determining a converted-light signal being correlated with the output of converted light emitted by the light-conversion device; and   a controller for receiving the laser-output signal and the converted-light signal, for determining a safe-to-operate parameter based on the laser-output signal and the converted-light signal, and for controlling the operation of the laser-based light source based on a comparison between the safe-to-operate parameter and at least one predefined threshold.   
     
     
         2 . The laser-based light source according to  claim 1 , wherein the laser-output sensor is formed by a laser-light photo diode adapted for receiving at least a part of the laser light. 
     
     
         3 . The laser-based light source according to  claim 1 , wherein the laser-output sensor is formed by a laser driving current monitor adapted for monitoring the laser driving current. 
     
     
         4 . The laser-based light source according to  claim 1 , wherein the converted-light sensor is adapted to receive at least a part of the converted light. 
     
     
         5 . The laser-based light source according to  claim 1 , wherein at least one optical fiber is provided which is adapted for guiding the laser light to the light-conversion device. 
     
     
         6 . The laser-based light source according to  claim 5 , wherein an optical fiber is provided which is adapted for guiding at least part of the converted light in a direction back from the light-conversion device to the converted-light sensor. 
     
     
         7 . The laser-based light source according to  claim 6 , wherein the converted-light sensor is arranged at the end of the optical fiber ( 8 ) which is remote from the light-conversion device ( 2 ). 
     
     
         8 . The laser-based light source according to  claim 6 , wherein the converted-light sensor is arranged at a position along the optical fiber ( 8 ), and a decoupling device is provided for coupling the converted light out of the optical fiber ( 8 ) and into the converted-light sensor. 
     
     
         9 . The laser-based light source according to  claim 5 , wherein the optical fiber is provided with an electrical wiring for detecting damage to the optical fiber. 
     
     
         10 . Method of operating a laser-based light source, comprising the following steps:
 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.   
     
     
         11 . The method according to  claim 10 , comprising the step of comparing the safe-to-operate parameter with a second predefined threshold. 
     
     
         12 . The method according to  claim 10 , comprising the step of determining the safe-to-operate parameter based on a ratio between the laser-output signal and the converted-light signal. 
     
     
         13 . The method according to  claim 10 , comprising the step 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. 
     
     
         14 . The method according to  claim 10 , comprising the steps 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.   
     
     
         15 . The method according to  claim 10 , wherein the step 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.