Patent ID: 6992774

Claim:
An apparatus for detecting a wavelength of electromagnetic radiation, the apparatus comprising: a first electromagnetic radiation detector for receiving a first proportion of electromagnetic radiation that has been redirected from a main electromagnetic radiation path; a second electromagnetic radiation detector for receiving a second proportion of electromagnetic radiation that has been redirected from the main electromagnetic radiation path; a third electromagnetic radiation detector for receiving a third proportion of electromagnetic radiation that has been redirected from the main electromagnetic radiation path; a filter arranged for filtering the second proportion of the electromagnetic radiation before it reaches the second electromagnetic radiation detector; an interferometric device arranged for causing the third proportion of the electromagnetic radiation to interfere with itself before it reaches the third electromagnetic radiation detector; and processing means coupled to receive a first signal from the first electromagnetic radiation detector indicating an intensity of the first proportion of the electromagnetic radiation detected by the first electromagnetic radiation detector, a second signal from the second electromagnetic radiation detector indicating an intensity of the second proportion of the electromagnetic radiation from the filter detected by the second electromagnetic radiation detector and a third signal from the third electromagnetic radiation detector indicating an intensity of the third proportion of the electromagnetic radiation from the interferometric device detected by the third electromagnetic radiation detector, the processing means determining a wavelength of the electromagnetic radiation based on the ratios of the first and second signals and the first and third signals.