How do laser interferometers measure distances greater than 1wavelengt

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SUMMARY

Laser interferometers measure distances greater than one wavelength by utilizing phase differences across multiple interference fringes. While a single phase shift can only reach 180 degrees, the technique of phase unwrapping allows for the calculation of larger distances by interpreting the continuous phase changes beyond this limit. This method is essential for precise measurements in metrology and is supported by various resources that explain the underlying principles in detail.

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blin1994
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Hi,

My question is how do do laser interferometers measure distances of more than one wavelength?
I know they rely on phase difference to calculate distances but phases only differ at 180 degrees at max so how do interferometers factor in going over 180 degrees in phase difference to calculate larger distances?


Thanks
 
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blin1994 said:
Hi,

My question is how do do laser interferometers measure distances of more than one wavelength?
I know they rely on phase difference to calculate distances but phases only differ at 180 degrees at max so how do interferometers factor in going over 180 degrees in phase difference to calculate larger distances?


Thanks

Google "Phase unwrapping", for example:

http://earth.esa.int/landtraining07/D1LB4-Rocca.pdf
http://www.acsu.buffalo.edu/~jlv27/index_files/Publications_files/PhaseUnwrapEncyclopedia.pdf
 

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