Talk:Angular resolution

message: This page needs a picture for what a resolution angle is. I made a picture that *doesn't* help at all. But this is an example of what a picture of resolution angle should look like: 
: 
I would greatly appriciate it if someone drew a simple picture explaining what the resolution angle is physically. Fresheneesz 22:45, 20 March 2006 (UTC)
replies: text:  I updated that picture ^ Fresheneesz 23:41, 20 March 2006 (UTC)
thread_title: Picture

message: The article says:
:This factor is used to approximate the ability of the human eye to distinguish two separate point sources depending on the overlap of their Airy discs. 
I don't see how this could be accurate: the human eye has a much worse angular resolution than this formula would allow.  Look, let's do a rough estimate.  The diameter of the pupil of the eye is at most 10 mm (half of that in typical enlightenment conditions).  The shortest wavelength a human eye sees is about 300 nm.  From this, we get the angular resolution 1.22 * 300 nm / 10 mm = 3.66*10^-5.  But according to the eye article, a typicla human eye has an angular resolution of 7*10^-4, which is one magnitude larger.  I belive there are two limiting factors: one is the imperfect shape or material of the lens and the cornea, the other is the packing of photosensitive cells in the retina.  
On the other hand, I've read the statement that the size of the aparture is in fact a limiting factor (as well as the density of the cells on the retina) somewhere else too, so I'm in doubt.  – b_jonas 20:57, 11 May 2006 (UTC)
replies: text: There's a discussion of Rayleigh diffraction limit and the human eye (with refs) here (under the optometry stuff): http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/raylei.html#c2 164.54.53.165 17:22, 31 May 2006 (UTC)
replies: text: Thanks.  – b_jonas 13:55, 1 June 2006 (UTC)
thread_title:  Human eye 

message: What should be the units used for diameter, wavelength, and angle for the empirical formulas to work? They should be stated. From the lone example given, it appears that the diameter should be in meters? I did the calculations and the answer I got was 0.1196 so this has to be in meters in order to understand the answer given of 12cm.
In science discussions, never leave out the units.
:As defined angular resolution should be in radians, that is, it is a dimensionless value. That means that it should not matter what the units are, as long as everything is expressed in the same units. Apparently you entered the wavelength in meters, and then you get D in meters.
:
:However, the formula given under "Microscope case" produces a dimensioned value: a length. That cannot be an angular resolution. Something is wrong or inconsistent here.  --LambiamTalk 02:47, 7 October 2006 (UTC)
thread_title: Units?

message: This article is called "Angular resolution". Other possible names, such as "Spatial resolution" and "Resolving power" redirect to this article. It strikes me that "Spatial resolution" is more general than simply another name for "Angular resolution". For example, it commonly refers to the number of pixels a computer display holds, or the detail that can be seen in a photograph. It is also in much more common use by people concerned with human vision (such as optometrists, ophthalmologists, and psychophysicists) than "Angular resolution". Moreover, the text of the article states that "Angular resolution describes the resolving power of a telescope". Apart from this being unrasonably restrictive--something I will correct--it means that "Resolving power" is defined (via redirect) as "Angular resolution", which is in turn defined as resolving power! This all needs to be clarified.
Robert P. O'Shea 04:03, 25 October 2006 (UTC)
thread_title:  The name  of this article 

message: This article seems to be optical-centric whereas "Angular resolution" covers more than "optical components", "optical device", or "optical wavelengths" (re: for example the radio spectrum.) It looks like a little cleanup could be done to correct that. 69.72.7.204 16:53, 16 January 2007 (UTC)
thread_title: Optical?

message: The first equation in section "Explanation" has a variable "f" which is never defined. From a similar equation in the "SLR cameras" section of Airy disc, I'm thinking that it is the distance from the lens to the film/image sensor (equivalently, i think, the focal length of the lens). Whether this or something else is what is intended, I think a definition for "f" should be added to the section. Thanks Bayle Shanks 00:36, 21 February 2007 (UTC)
thread_title:  Define "f" 

message: Just spotted a small error on this page. Someone more Wikiable than me please correct it (my first ever Wiki contrib, I'm in a bit hurry now & sorry if I don't know all the etiquette...). 
Anyway: The first formula is correct. The second should follow from the first by multiplying both sides by f (the system focal length). The left side doesn't add up. Delta l (the minimum spatial resolution) is actually TAN(theta) * f. (This is just basic trigonometry.) The Rayleigh criterion only gives us sine theta, not tan theta. 
Therefore, to arrive at Delta l, we need to first inverse sine both sides of the first formula (to find theta in angular units), then TAN both sides and only then multiply by f.
Note that the current formula is approximately correct for small values of theta (i.e. high F-number / low numerical aperture / slow optics), as SIN(theta) is then roughly the same as TAN(theta). For a practical camera objective, F/3 or so, the error is about 1.36 %. Insignificant in most practical cases; therefore, the original formula remains a handy approximation. But let's have the correct formula there too, in case someone starts wondering.
192.100.124.219 18:45, 17 April 2007 (UTC)
thread_title:  Erroneus formula 

message: The pulse compression article currently says
: "Pulse compression is a signal processing technique mainly used in radar, sonar and echography to augment the range resolution as well as the signal to noise ratio."
The word "resolution" in that article was recently disambiguated from resolution to angular resolution.
The disambiguation page resolution claims that
: "Angular resolution, the capability of an optical or other sensor to discern small objects"
which is certainly what pulse compression is all about.
Is "range resolution" really a specific kind of "angular resolution", as implied by the disambiguation page, and so we should talk about it here in the "angular resolution" article?
Or is there a more appropriate article to point to?
Or should we start a range resolution article?
--75.19.73.101 (talk) 09:33, 15 December 2007 (UTC)
thread_title:  range resolution 

message: I noticed part of the description text below the picture box is missing, it says "Airy diffraction pattern generated by a plane wave falling on a circular aperture, such as" .. such as what?  —Preceding unsigned comment added by 86.80.116.169 (talk) 15:33, 18 July 2009 (UTC)
thread_title:  missing text 

message: There should be a figure showing two overlapping Airy Discs spaced such that they just satisfy the Rayleigh criterion.  This is a common figure and explains a lot in terms of how resolving power is defined.  hovden (talk) 14:27, Jul 19 2010 (ET)  —Preceding undated comment added 18:27, 19 July 2010 (UTC)
thread_title:  Rayleigh Crit. Figure Needed 

message: I feel like something is missing on this page. For telescopes and microscopes, the usual focus of attention is the objective since both of those are specialized devices. On the other hand, for e.g., a cell-phone camera focused at infinity, the diffraction limit (as I understand it) is preventing you from making the pixels and optics ever smaller. That is, for a telescope, the given formulat doesn't tell us anything about the image sensor. That can't imply that if I keep the entrance pupil diameter fixed, increase the power, and shrink and move the sensor closer to the lens, that I can keep the same angular resolution? (Unless that in so doing the image-space NA will increase?) 
What about the case in which you want exceptional angular or spatial object resolution on a small sensor? Shouldn't there be an equation involving the image- and object-space NA? —Ben FrantzDale (talk) 20:06, 23 September 2010 (UTC)
thread_title:  Subject and image resolution 

message: Would it be possible to create a sub-section in this article and define the concept "spatial intensity distribution".  I'm not a scientist myself, but the phrase keeps popping up in astronomical literature and I don't understand what it means exactly.  It occurs in this abstract on astronomical interferometry which is being used as a reference in the Betelgeuse article.  If one googles the string "spatial intensity distribution",  81,700 results are produced, yet nowhere have I found a definition that a lay person would ever understand.
I don't know if such a concept warrants a sub-section in itself.  The reason for my request is that I'd like to blue link such a sub-section from the Betelgeuse article.  Thanks for any help you can provide.--Sadalsuud (talk) 11:18, 14 June 2012 (UTC)
thread_title:  Spatial Intensity Distribution 

message: The history of breakthroughs in angular resolution is important: comparable to the history of developments in computer speed, data storage and determination of universal constants. 116.251.188.18 (talk) 03:42, 12 February 2016 (UTC)
thread_title:  History of 

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