Talk:Ring laser gyroscope

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old stuff[edit]

I just deleted:

"External link:

Optical Kerr-effect in fiber-optic Brillouin ring laser gyroscopes"

This article discusses some specialized detail of laser gyros. It is certainly of no interest for anybody who read this article in order to find out what a laser gyro is. Simon A. 07:45, 24 Jun 2004 (UTC)

The text says " The angular position is measured by counting the interference fringes". Is this really correct? Can the device really directly measure angular position? Isn't that an impossibility? Doesn't it rather measure angular _velocity_, and not position (then integrating the velocity over time to yield the angular position)?

Yes. It measures absolute position exactly that way. Dennis 03:50, 30 Jan 2005 (UTC)

First paragraph mentions a "bulk optic ring", isn't this referring to the other type, the fibre optic gyro which used a long fibre cable coiled into a ring? --Kjw 00:10, 20 February 2006 (UTC)[reply]

This page really needs more links, there is nothing to back up the text. This is annoying as the information is good, but cannot be quoted as a reliable source. Thanks, Sam Mcmadkat 11:54, 25 May 2007 (UTC)[reply]

Error[edit]

This article doesn't properly distinguish between the fiber gyro which IS a direcct application of the Sagnac effect (and works exactly the way described, but with multiple turns) and the much more sensitive LASER gyro which is incorrectly described. Anyway I'll change those parts. (soon) —Preceding unsigned comment added by 82.95.146.159 (talk) 22:35, 23 January 2008 (UTC)[reply]

It is also factually inaccurate to say ring laser gyros are "often referred to as air data inertial reference units." A ring laser gyro can be a component of an ADIRU, but it is not in and of itself an ADIRU. That is like saying a transmission is often referred to as a car. —Preceding unsigned comment added by 166.70.56.136 (talk) 17:43, 4 June 2009 (UTC)[reply]

I'm not sure where to put this, but what about the Northrop Zero Lock Gyro? They solved the lock problem by running the opposing beams through separate channels in the Gyro. — Preceding unsigned comment added by 216.182.109.118 (talk) 04:44, 10 February 2013 (UTC)[reply]

I'm going to add material about the Multioscillator RLG (another name for the Northrop device). BTW, the "separate channels" are not different holes in the block but instead two senses of circular polarization running along the same optical path.IrlSmith (talk) 16:46, 23 October 2019 (UTC)[reply]

Common doubt[edit]

I believe that this page doesn't answer to some people's questions. They argue that to observe a frequency shift you must have a relative motion. So the article should better point out how this device does not violate Einstein's special theory of relativity. Their questions can be found for example here: http://www.youtube.com/watch?v=eu4ZrzG-7ik — Preceding unsigned comment added by 93.56.200.244 (talk) 19:35, 14 September 2011 (UTC)[reply]

The effect does not need relative motion or for that matter SR or GR as I see it..., it just needs a split coil with rotation around its center,or an understanding of the apparatus.

SR has a bit of understanding to the Lorentz transform which pins "c" to an event propagation time in both inertial and non inertial frames of reference in SR.. That is why the terms of 1-v^2/c^2 etc pop up because no matter what you do, "c" is constant/or the event will take time "distance/c" for the observer to observe - so even if you move towards or away the receiver there is that "c" lag to propagate the event, not c+v or c-v.

Galileian would fix "t" as the same in both frames (inertial and non inertial) while Relativity fixes "c" in all frames and says t can be different. Hence "red shift, blue shift etc" are all defined because that limitation is "c" being pinned to a constant in SR (no c+v and c-v).

For a particular "monochromatic" wave, "c" is constant. We could break it up into phase and group velocities (if you like slower modulated signals) but if you are travelling towards a source and "c" is constant, you would see a shift in freq and wavelength- even if the source is moving away at the same speed as you are moving towards it - inertial or non intertial frame of reference - because a "is_light and is no_light" will still travel at "c" (not c+v and c-v etc) , both for phase and group because "c" is constant (the fundamental point connecting Relativity with Lorentz transforms)- there is no "faster light" or "slower light".

If,likewise, you make the same assumption to "sound speed being constant" and drop the pin on time then...? the doppler effect would be called a "phase shift" etc but then you have to ensure that the observers measure "time" by sound ticks and not light/electromagnetic/watch/ visually (SR says ahh time shifted - if you measured time with sound ticks time would shift there too if "V_sound" was constant).

So to my dumb mind, the way I see it, if i was sending "waved water" down 2 semicircular pipes on either side of a circle and rotating the pipe assembly too about its center, "one side's water" would travel faster as the pipe is moving in the opposite direction, and the other slower - water source being on the pipe assembly always churning out that fixed "rate" of water waves, it is the apparatus itself "circular path" giving that non inertial frame of reference base needed to see the effect, would not happen if it was a straight line, and if it was a straight line between source and detector moving at same speeds, then there would be no "2 frames" in the SR case either. It is the apparatus "circular path" providing the non inertial frame between source and detector.

The special theory of relativity has no bearing on optical or non optical spectrum components so a signal from a single electrical source travelling over 2 distinct copper wires will show the same affect/phase shift. In other words the optics could be dumped for electrical measurements.

Or you could do it the "rpm/tachometer pendulum way", not bothering about standing waves and resonant modes etc. This was and perhaps is still one of the most common ways for speed control of motors: http://armymunitions.tpub.com/MM04868/MM048680086im.jpg

When you make edits, please do not delete comments by others.

 — Preceding unsigned comment added by 223.186.8.209 (talk) 10:39, 20 April 2017 (UTC)[reply]

External links modified (January 2018)[edit]

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Name?[edit]

When I frst read about this in an "Electronics Today" or "Electrnics Australia" magazine in the 1980s, this was called a "Laser Ring" gyro rather than a "Ring Laser". — Preceding unsigned comment added by 2001:8003:E448:D401:B4B3:B84C:B1D9:5248 (talk) 08:50, 23 August 2019 (UTC)[reply]

Fixing a dubious-tagged value[edit]

The peak dither rate was given as 1 arc second per second, and marked "dubious" with the following note in the text:
!--What is a typical lock-in rate? Much higher than that would possibly solve!!--
That is absolutely correct. I changed the value to a few degrees per second, based on the following:
The amplitude needs to be at least a few optical half-wavelengths of circumferential motion, i.e. a few arc seconds; at 400 Hz this implies a maximum rate of "a few" times 2 pi × 400 Hz ~ 5000 arc-seconds per second or 1.5 degrees per second.
And then I removed the "dubious" tag. I suppose one might say that that calculation represents "original" work, but it's pretty elementary.
I also added a paragraph about a non-dithered RLG, based on a book chapter on such instruments, which is the source of the material in the paragraph. OK, I fibbed; I wrote the paragraph with hardly any reference to the book, but the material is there in the chapter. I should know, I was one of the authors. Hmm. Does this make me guilty of self-citing? What should I do about it?
Finally, I removed the words "compared with RLG" near the end; the sensitivities of both depend on design and the FOG is generally worse than the RLG although the latter may have more long-term drift. IrlSmith (talk) 20:16, 23 October 2019 (UTC)[reply]

a phenomenon versus its measurement[edit]

A certain rate of rotation induces a small difference between the time it takes light to traverse the ring in the two directions according to the Sagnac effect.

So this happens only at a specific ω? I'm skeptical. Persuade me that this sentence would not be improved by excising "A certain rate of". —Tamfang (talk) 22:09, 10 July 2022 (UTC)[reply]

Too much jargon[edit]

I find this article hard to read, as it's filled with terms that aren't defined in the article. I couldn't even understand the first sentence. Can someone who understands these terms make the article easier to read? RteeeeKed 💬📖 05:04, 15 May 2023 (UTC)[reply]