| 摘要 |
The invention pertains to a method for controlling radiation power of a radiation source (26), comprising the steps of a) driving the radiation source (26) in a first mode comprising the substeps of al) determining a threshold current (Ithr)at which the radiation source (26) begins to radiate, a2) measuring the radiation power emitted by the radiation source (26), a3) driving the radiation source (26) with the threshold current (Ithr) increased with the a delta current (Idelta)for obtaining a predetermined radiation power Prl, wherein the delta current (Idelta) is calculated by subtracting the measured radiation power (Pm) from the predetermined radiation power Prl, b) driving the radiation source (26) in a second mode comprising the substeps of bl) determining the threshold current (Ithr),and b2) driving the radiation source (26) with the threshold current (Ith r) increased with the delta current (Idelta) for obtaining the predetermined radiation power Prt, wherein the delta current (Idelta) is calculated from the threshold current (It hr) by using a function F which is a model for the relation between the threshold current (Ithr) and the delta current (Idelta) and the radiation power. The relation between the delta current (Idelta) and the threshold current (Ithr) however changes during the lifetime of the radiation source. Therefore the method according to the invention further comprises the step of c) calibrating the function F, comprising the substeps of cl) determining the radiation power and the delta current (Idelta) at at least two different threshold currents (Ithr) when the radiation source (26) is driven in the first mode, and c2) updating at least one parameter of the function F by using the measurements in substep cl.
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