Patent ID: 7253902
Filing Date: 2007-08-07
Classification: G01J

Abstract:
1. A radiation measurement device for determining a wavelength-related characteristic of radiation from a radiation source, the radiation measurement device comprising: a first beam dividing element located to input at least a portion of the radiation from the radiation source, and to output first and second portions of the radiation along first and second optical paths; a first wavelength-dependent optical element located along the first optical path; a first optical power-measuring detector located along the first optical path after the first wavelength-dependent optical element to receive radiation filtered by the first wavelength-dependent optical element such that the first optical power-measuring detector outputs a first signal having a first wavelength dependence that depends on the first wavelength-dependent optical element; a second optical power-measuring detector located along the second optical path to receive radiation transmitted along the second optical path; and a linear polarizer configuration comprising at least one linear polarizer, wherein: the second optical power-measuring detector outputs a second signal having a second wavelength dependence that is different from the first wavelength dependence; a signal ratio based on at least the first and second signals is indicative of at least one of a radiation wavelength, a change in a radiation wavelength, a radiation frequency, and a change in a radiation frequency, of the radiation from the radiation source; and the linear polarizer configuration is arranged such that the signal ratio is substantially insensitive to variations in a polarization orientation of the radiation from the radiation source, the linear polarizer configuration comprising at least one of: