Talk:Collimated beam

Small-angle non-collimation

The light reaching me from that part of the sun that I see at the left edge of the sun's disk is not parallel to that from the right edge, since they're half a degree apart. Is it because 1/2 degree is so small that it's considered collimated, or should the article's statement to that effect be considered an error? Michael Hardy 01:21, 8 Nov 2004 (UTC)

Corrected the article to reflect the non-collimated (deviation of +-0,5degrees) nature of the sunlight on earth. Santtus 13:00, 15 July 2005 (UTC)[reply]

I think that there is a problem due to the vagueness of any definitions available to me. The fact that the sun's distance is extremely large compared to any earth-bound imaging element makes the light from any point of the object arrive in a practically parallel rays to the sides of the said element. The opposite sides of the disk of the sun do arrive in differently aligned rays, however. What is it that collimated light means, actually? Santtus 21:25, 5 November 2006 (UTC)[reply]

Combine with Collimating Lenses?

I agree that this should be combined with and redirected to collimating lenses. axharr 21:36, 4 Nov 2006 (EST)

I very strongly disagree that the Collimating Lens stub should be merged into Collimated Light or vice versa. Collimating Lens topic needs to address the action and even the design of collimators, at a minimum using lenses with coherent light (a pretty easy place to start). An example or three with actual numbers would be appreciated, as well. Collimated light needs to be specific about the parallelism of rays in a collimated beam, interference patterns between coherent spherical wave fronts and (mutually) coherent plane (collimated) wavefronts and/or spherical wavefronts, etc. --Light should describe the beam, --Lens should describe the apparati. Onlyocelot 11:03, 21 April 2007 (UTC)[reply]

I strongly agree with Onlyocelot. These two topics are each worthy of their own text books. The lens and the light are related but two different things.

Great. Now we've ended up with a section in this article that says it covers lenses, but the text of that section only discusses mirrors and... flight simulators (which is just weird). Looks like a hack job was done in this respect. Any thoughts on what ought to be done now? KDS4444^Talk 00:29, 3 June 2015 (UTC)[reply]

A bibliography a propos of?

Collimators for Thermal Neutron Radiography an Overview by J.C. Domanus and J.F.W. Markgraf (Jan 1, 2001)

Areal parabolic collimators for the Keck II telescope (Lick Observatory technical reports) by Brian M Sutin (1995)

-vs-

Absorption and Scattering of Light by Small Particles (Wiley Science Paperback Series) by Craig F. Bohren and Donald R. Huffman (1998)

Interferometry in Speckle Light: Theory and Applications by P. Jacquot and J.-M. Fournier (Oct 27, 2000)

Stephenkoski 07:13, 2 May 2007 (UTC)StephenKoski[reply]

Concerning Laser collimation

The observation about laser light being automatically collimated is partially true and only for gas lasers. Diode lasers (far more common, e.g. laser pointers are diode lasers) are not collimated at all, so much that in most applications they are fitted with a collimating lens. —Preceding unsigned comment added by 193.205.81.1 (talk) 12:15, 8 November 2007 (UTC)[reply]

This may be a bit of an over-statement. Diode lasers are not highly collimated, and do have considerable beamwidth: different in the two directions, due to diffraction limiting as the exit window of the emitting zone is only dozens of wavelengths wide and a few high. But they are still fairly coherent, as revealed by speckle - again, limited mainly by the very short cavity with relatively high gain per unit length, which allows multiple optical modes to be amplified. They can still be focused to a point effectively smaller than emission wavelength for, e.g., writing CDs.

Long-cavity lasers are more collimated for several reasons, including but not limited to the long barrel that eliminates gain for divergent rays. And being usually more coherent, they can also be beam-expanded and then collimated to a much higher degree - enough to bounce off an extra-terrestrial mirror for ranging, e.g.

(Not an optical engineer, but spent lots of time with lasers of several kinds.) Cteno (talk) 22:13, 4 December 2023 (UTC)[reply]

Spatial coherence is all that actually matters. A singlemode laser diode may be highly divergent, but can be collimated just as well as a laser with a long cavity. For a singlemode laser, there is no fundamental difference between collimated and diverging or converging states; they are variations of the same thing, and you can transform freely between them.--Srleffler (talk) 16:43, 10 December 2023 (UTC)[reply]

Frequency of collimating a telescope

I think that the sentence "Most amateur reflector telescopes need to be re-collimated every few years to maintain optimum performance" is a bit misleading. Many amateur reflector telescopes are Newtonians/Dobs, and their users should probably better collimate them before every observing session, especially if the telescope was moved. --M. Tewes (talk) 19:45, 6 January 2012 (UTC)[reply]

Agreed... but in the context of this article does it need to be included at all? Whether and how often a telescope needs collimation should be mentioned in a page about dobs or telescope maintenance. Here we just need to describe what collimation is. I'd be good with either of these changes - reword or remove. I did not check the dob page(s). Walkingstick3 (talk) 13:25, 20 September 2017 (UTC)[reply]

You're replying to a post that is five years old...--Srleffler (talk) 03:45, 21 September 2017 (UTC)[reply]

Collimation relation to coherence?

These concepts seem similar at least on the surface, although nothing relating to collimation is mentioned in the article on coherence or vice-versa. I'd assume coherent light would by implication be collimated. --Rimmer7 (talk) 22:26, 27 September 2016 (UTC)[reply]

Not all coherent light is collimated. Spatial coherence is a prerequisite for good collimation, though.--Srleffler (talk) 04:28, 28 September 2016 (UTC)[reply]

Change of title

I see the article was renamed from "Collimated light" to "Collimated beam" with no discussion. I'm not sure this was a positive change. Light can be collimated without necessarily being a "beam". --Srleffler (talk) 01:07, 3 October 2018 (UTC)[reply]

I agree this is not an improved article title. The article has to be about collimation in theory and not what artificial devices happen to produce. The most collimated light is distant starlight, and that's a radial source, not a beam. On the other hand, any artificial source that is collimated has to involve a stop and thus must be a beam. Perhaps this unwarranted name change is an obsession with laser beams being a common source of collimated light. Optics gets to be a mad science as everything is a dual or special case of something else. Perfect collimation isn't achievable, but we have this article double-talk about whether a beam is collimated or not as a binary condition, when the degree of collimation is the physical aspect.

And why should the article even restrict collimation to light? Collimation applies to the entire EM spectrum (radio antennas, x-ray equipment, etc.).

"Collimation" redirects here now. The business about telescope collimation should be evicted from this article, as long as we're fault-finding. It's all confused. Richard J Kinch (talk) 10:57, 3 October 2018 (UTC)[reply]