Patent ID: 6937346

Claim:
A wavemeter for determining a wavelength of an incident optical beam, comprising: a first interference element having a first optical component and a second optical component, the first optical component providing a first path with a first effective optical length x, x >0, being arranged in said incident optical beam or in a part of it, and generating a first optical beam with a first optical power depending on the wavelength of said incident optical beam, the second optical component providing a second path with a second effective optical length l=x−d, x>d>0, being arranged in said incident optical beam or in a part of it, and generating a second optical beam with a second optical power depending on the wavelength of said incident optical beam, whereby said first and second optical powers oscillate periodically with increasing wavelength, and said second optical beam having a phase shift of approximately pi/2 with respect to said first optical beam, a first power detector detecting the first optical power, a second power detector detecting said second optical power, a second interference element having a third optical component and a fourth optical component, the third optical component providing a third path with a third effective optical length x′, x′>0, being arranged in said incident optical beam or in a part of it, and generating a third optical beam with a third optical power depending on the wavelength of said incident optical beam, the fourth optical component providing a fourth path with a fourth effective optical length l′=x′−d, x′>d>0, being arranged in said incident optical beam or in a part of it, and generating a fourth optical beam with a fourth optical power depending on the wavelength of said incident optical beam, whereby said third and fourth optical powers oscillate periodically with increasing wavelength, and said fourth optical beam having a phase shift of approximately pi/2 with respect to said third optical beam, wherein said first, second, third and fourth optical components are arranged such that said incident optical beam may experience a lateral shift, yet remain at least partial incident on each of said first, second, third and fourth optical components, a third power detector detecting the third optical power, a fourth power detector detecting said fourth optical power, and a wavelength allocator for allocating a wavelength to the incident optical beam based on the wavelength dependencies of the detected first, second, third, and fourth optical powers, wherein the second optical component and the fourth optical component are positioned diametrical to each other with respect to a surface of a plate.