rcd@opus.UUCP (Dick Dunn) (08/29/84)
> On a similar, but different subject,... can anyone explain >to me how a laser gyroscope works. I often heard mention of >it, buy I've never figured out how it might work. May as well toss it out for everyone. The principle is simple but it's a neat idea. Laser gyroscopes: The idea is to set up mirrors - / - - - - - - - \ typically four at the corners of a square - so | | that you can bounce light around inside the square. | | See crude diagram - the / and \ indicate mirrors; | * | - and | indicate light paths. Actually, you put a | | laser tube in each of the four light paths, and the | | whole thing acts like a big laser. Let some of the \ - - - - - - - / A | light leak out at "A"--that's the not-quite-completely silvered mirror in a normal laser. There's another mirror just beyond A. Now, some of the light circulates clockwise and comes out at A headed downward. Some of it circulates counterclockwise and heads out to the right at A. It hits the extra mirror and bounces back, hits the back side of the partially silvered mirror at A and heads downward. OK, at this point you've got two beams which are collinear but which came from opposite rotation. Now rotate the whole mess around (*). Since you're effectively changing the cavity length, you're slightly changing the frequency of the laser--up for one direction of beam travel, down for the other. Since you've got the two beams together, they beat with one another. Measure the beat frequency and you're there. -- Dick Dunn {hao,ucbvax,allegra}!nbires!rcd (303)444-5710 x3086 ...Nothing left to do but smile, smile, smile.
scottm@tektronix.UUCP (Scott Maxson) (08/30/84)
<> I think that the principle involved in laser gyroscopes comes from something called the 'Sagnac Effect'. As I recall, it has to do with how the angular momentum flux vectors of the electro- magnetic field transform under Lorentz transformations, the basic transformations of relativity. The argument is very elegant mathematically; I like to think (perhaps incorrectly!) that the counter-rotating beams of the laser gyroscope 'sample' the space they travel through differently because of the rotation and thus give diffent answers when asked what their wavelengths are. S. Maxson tektronix!scottm Portland, OR.