Process for stabilizing the optical output power of light-emitting diodes and laser diodes
AssigneeSensor Line-Gesellschaft fuer Optoelektronische Sensoren mbH
InventorsJoerg Plamper, Josef Engl
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Abstract
The invention relates to a method that can be used to compensate the influence of the temperature on the optical output power (light power) of light emitting diodes and laser diodes without the need to measure the temperature or light power. The method is based on the fact that the current flowing through a light emitting or laser diode and the forward voltage drop on the diode are at a constant light power independent of the temperature in a functional correlation that is often linear and can be obtained. If it is known, it must only be achieved during operation that the current and the forward voltage exhibit this correlation in order to eliminate the temperature effect on the light power.
Claims14
In a method for stabilizing the optical output power (light power) of a diode selected from the group consisting of a light emitting diode and a laser diode, the improvement comprising the step of maintaining the light power emitted by the diode substantially constant from solely a combination of the forward current and forward voltage of the diode, based on the assumption that at a constant light power the forward voltage is a particular function of the forward current.
A method for determining a particular function that yields a forward voltage of a diode, selected from the group consisting of a light emitting diode and a laser diode, from the forward diode current at a constant output light power, comprising the steps of:
- varying the temperature of the diode using a heating or cooling device;
- determining the emitted light power by means of a photodetector;
- and maintaining the emitted light power at a constant level by means of a control device and measuring the values of the forward voltage and the forward current of the diode at various temperatures.
A method for determining the parameters of a particular linear function that yields the forward voltage from the forward current of a diode selected from the group consisting of a light emitting diode and a laser diode at a constant light power, the method comprising tracing the time progression of the light power during a power-up procedure and setting the parameters such that the light power remains constant in spite of the increasing temperature of the diode after power up.
Dependencies are inferred from the claim text.