I was looking on youtube last night and the recent discussion on levels, I came across some laser interferometer videos..
They did a good job of explaining the principle... If I have it right, essentially the device works like this...
You have the laser unit that emits a pure known wavelength of light... This goes into the interferometer unit... The interferometer unit splits the beam, with it sending one beam to the receiver unit and sending the other beam on it's way to the reflector.. The reflector some distance away reflects the beam of light straight back to the interferometer which also then shoots that beam back to the receiver unit... So there are two beams of light going into the receiver unit.
What the receiver unit does is look at where the two beams converge, and it will either produce a light spot of a dark spot depending on the distance the reflector is from the interferometer.. This is because light travels sort of as a wave... So if when the two beams hit the detector unit in the receiver both hit at the top of the wave or the bottom, they produce a light spot on the detector... If they are out by 180 degrees, it is dark... (or is it the other way around)...
So since the wavelength distance is known, the distance the reflector has to move to turn a dark spot into a light spot is also known and just has to be counted.. So 100 000 dark/light spot counts equals x amount of distance... Hence why the units are so extremely sensitive..
All well and good for measuring distance...
So how do they measure angles?
They did a good job of explaining the principle... If I have it right, essentially the device works like this...
You have the laser unit that emits a pure known wavelength of light... This goes into the interferometer unit... The interferometer unit splits the beam, with it sending one beam to the receiver unit and sending the other beam on it's way to the reflector.. The reflector some distance away reflects the beam of light straight back to the interferometer which also then shoots that beam back to the receiver unit... So there are two beams of light going into the receiver unit.
What the receiver unit does is look at where the two beams converge, and it will either produce a light spot of a dark spot depending on the distance the reflector is from the interferometer.. This is because light travels sort of as a wave... So if when the two beams hit the detector unit in the receiver both hit at the top of the wave or the bottom, they produce a light spot on the detector... If they are out by 180 degrees, it is dark... (or is it the other way around)...
So since the wavelength distance is known, the distance the reflector has to move to turn a dark spot into a light spot is also known and just has to be counted.. So 100 000 dark/light spot counts equals x amount of distance... Hence why the units are so extremely sensitive..
All well and good for measuring distance...
So how do they measure angles?
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