Method for Stabilizing the Temperature Dependency of Light Emission of an Led

Abstract

Method for correction of the temperature dependency of a light quantity L emitted by a light emitting diode (LED), being operated in pulsed mode with substantially constant pulse duration t P , and measured in a light detector, using a predetermined parameter X, correlated to the temperature T of the LED in a predetermined ratio, whereby a correction factor K is determined from the parameter X, preferably using a calibration table, especially preferred using an analytic predetermined function, whereby the measured emitted light quantity L is corrected for the temperature contingent fluctuations of the emitted light quantity, whereby the parameter X is determined from at least two output signals of the LED, which are related to each other in a predetermined manner.

1 . Method for correction of the temperature dependency of a light quantity L emitted by a light emitting diode (LED), which is operated in pulsed mode with substantially constant pulse duration t P , and is measured in a light detector, using a predetermined parameter X related to the temperature T of the LED in a predetermined relation, whereby a correction factor K is determined from the parameter X, preferably using a calibration table, especially preferred using an analytic predetermined function, according to which the measured emitted light quantity L is corrected for the temperature contingent fluctuations of the emitted light quantity, whereby the parameter X is determined from at least two output signals of the LED, which are related to each other in a predetermined manner.  
     
     
         2 . Method for correction of the temperature dependency of the light quantity L emitted by a light emitting diode (LED) according to  claim 1  and measured in a light detector, whereby at first the temperature T of the LED is determined from the measured parameter X, preferably using a calibration table, especially preferred using an analytic predetermined function, and then, the correction factor K is determined from the temperature T, preferably using a calibration table, especially preferred using an analytic predetermined function.  
     
     
         3 . Method for temperature stabilization of a light emitting diode (LED), which is operated in pulsed mode with substantially constant pulse duration t P , whereby a predetermined parameter X, related to the temperature T of the LED in a predetermined relation, is used as a command variable, whereby the parameter X is determined from at least two output signals of the LED, which are related with respect to each other in a predetermined manner.  
     
     
         4 . Method according to  claim 1 , whereby the parameter X is determined as follows: 
 Operating the LED in pulsed mode such that the pulse duration tp remains substantially constant and the voltage at the LED alternates periodically between at least a first voltage U P1  and at least a second voltage U P2 ,    Measuring the average light quantities L(U P ) of the pulses with at least the voltages U P1  and U P2 ,    Determining the parameter X from the ratio of the light quantities.    
     
     
         5 . Method according to  claim 1 , whereby the parameter X is determined as follows: 
 Operating the LED in pulsed mode such that the pulse duration t P  remains substantially constant and the current flowing through the LED alternates periodically between at least a first value I P1  and at least a second value I P2 ,    Measuring the average light quantities L(I P ) of the pulses with at least the currents I P1  and I P2 ,    Determining the parameter X from the ratio of the light quantities.    
     
     
         6 . Method according to  claim 1 , whereby the parameter X is determined as follows: 
 Operating the LED in pulsed mode such that the pulse duration t P  takes substantially two different, substantially constant, values t PS  and t PL , and the voltage at the LED alternates periodically between at least a first voltage U P1  and at least a second voltage U P2 ,    Measuring the average light quantities L(U P ; t PS ) and L(U P ; t PL ) of the pulses with at least the voltages U P1  and U P2  and the pulse durations t PS  and t PL ,    Determining at least the differences D P1  and D P2  of the light quantities L(U P1 ; t PL ) and L(U P1 ; t PS ), as well as L(U P2 ; t PL ) and L(U P2 ; t PS ), and    Determining the parameter X from the ratio of the differences of the light quantities.    
     
     
         7 . Method according to  claim 1 , whereby the parameter X is determined as follows: 
 Operating the LED in pulsed mode such that the pulse duration t P  takes substantially two different substantially constant values t PS  and t PL , and the current flowing through the LED alternates periodically between at least a first value I P1  and at least a second value I P2 ,    Measuring the average light quantities L(I P ; t PS ) and L(I P ; t PL ) of the pulses with at least the current I P1  and I P2  and the pulse durations t PS  and t PL ,    Determining at least the differences D P1  and D P2  of the light quantities L(I P1 ; t PL ) and L(I P1 ; t PS ) as well as L(I P2 ; t PL ) and L(I P2 ; t PS ), and    Determining the parameter X from the ratio of the differences of the light quantities.    
     
     
         8 . Method according to  claim 4 , whereby the light quantities L(U P ) and L(I P ) are determined with a light detector, preferably a photo multiplier, a hybrid photo multiplier, an Avalanche photo diode or a photo diode with amplifier.  
     
     
         9 . Method according to  claim 8 , whereby the light quantities measured by the light detector are determined by one or more of the following process steps: 
 Carrying out the pulse amplitude spectrometry of the detector signals,    Measuring the average current flow in the light detector,    Measuring the charge quantity of the LED pulse generated in the photo sensitive layer of the light detector, preferably by means of spectrometry of the preferably already amplified charge signals triggered by the LED pulse.    
     
     
         10 . Method according to  claim 1 , whereby the LED comprises a series resistance.  
     
     
         11 . Method according to  claim 10 , whereby the series resistance is selected such that its resistance depends on the temperature T in a non-linear manner, preferably in a manner such that the dependency or at least the non-linearity of the dependency of the correction factor K from the temperature T is compensated for approximately by the temperature dependency of the series resistance.  
     
     
         12 . Method for stabilization of a light detector, preferably a photo multiplier, a hybrid photo multiplier, an Avalanche photo diode or a photo diode with amplifier, whereby the light detector is optically connected with at least an LED, whereby a least one LED is operated in pulsed mode, and whereby the output signals of the light detector are stabilized with a stabilizing factor, whereby the stabilizing factor is generated by the signals emitted by the at least one LED, and whereby the temperature dependency of the light emission of at least one LED is corrected with a method according to  claim 1 .  
     
     
         13 . Method for stabilization of the signals generated by a scintillation detector for measuring radiation, preferably ionized radiation, by the radiation absorbed at least partially in the detector, and depending on the operating temperature of the detector, whereby the scintillation detector has at least one light detector and at least one LED optically connected to the latter, whereby the stabilization factor for stabilizing the scintillation detector is generated from the signals emitted by the at least one LED, and whereby the temperature dependency of the light emission of at least one LED is corrected by means of a method according to  claim 1 .  
     
     
         14 . Method according to  claim 13 , whereby at least one LED is connected to the scintillator in a heat conducting manner.  
     
     
         15 . Method according to  claim 1 , whereby the signal processing is carried out digitally.  
     
     
         16 . Light detector, preferably a photo multiplier, a hybrid photo multiplier, an Avalanche photo diode or a photo diode with amplifier, with signal processing device, whereby at least an LED is connected to the light detector optically, whereby at least one LED is operated in pulsed mode, and the output signals of the light detector are stabilized with a stabilizing factor, whereby the stabilizing factor is generated by signals emitted by the at least one LED, and whereby the temperature dependency of the light emission of at least one LED is corrected by means of a method according to  claim 1 .  
     
     
         17 . Light detector according to  claim 16 , whereby the signal processing is carried out digitally.  
     
     
         18 . Scintillation detector for measuring radiation, preferably ionized radiation, whereby the scintillation detector has a light detector according to  claim 16 , which measures light generated by the scintillation detector at least partially.  
     
     
         19 . Scintillation detector according to  claim 18 , whereby the signals generated by the radiation absorbed in the detector at least partially and depending on the operating temperature of the detector are measured and are stabilized with a stabilizing factor S related to the temperature T of the scintillator in a predetermined ratio, whereby at least one LED of the light detector is connected to the scintillation detector in a heat conducting manner, and whereby the temperature contingent stabilizing factor S for stabilizing the scintillation detector is determined in a predetermined manner, preferably using a calibration table, in particular preferred using a predetermined functional dependency from the parameter X of at least one LED connected to the scintillation detector in a heat conducting manner, according to a method for correction of the temperature dependency of a light quantity L emitted by a light emitting diode (LED), which is operated in pulsed mode with substantially constant pulse duration t P , and is measured in a light detector, using a predetermined parameter X related to the temperature T of the LED in a predetermined relation whereby a correction factor K is determined from the parameter X, preferably using a calibration table especially preferred using an analytic predetermined function according to which the measured emitted light quantity L is corrected for the temperature contingent fluctuations of the emitted light quantity, whereby the parameter X is determined from at least two output signals of the LED, which are related to each other in a predetermined manner.