# Talk:Aspheric lens

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Please don't move this page to "Aspherical lens" (which now redirects to this article). The universal term for these in the optics industry is (AFAIK) "aspheric lens" (or "asphere"). I just did a quick survey of a half dozen major optics vendors. Every single one uses the latter term.--Srleffler 12:54, 6 December 2005 (UTC)

I concur, the term Aspheric has entered into mainstream use in optometry. "The best ideas are common property." 02:16, 18 July 2007 (UTC)

Stubs are by definition short. Anything longer than about a screenful of text is not a stub.--Srleffler (talk) 15:32, 13 January 2008 (UTC)

## the current article is complete BS

CorvetteZ51 (talk) 12:53, 27 February 2008 (UTC)

Powerful words from someone who can't spell. I'm going to back out your change until you tell us what's behind it. Dicklyon (talk) 16:01, 27 February 2008 (UTC)
That may have been too harsh. His edit looks like it was done in good faith to me. Looking at the article, I can see that someone who primarily knows about ophthalmic optics might find it lacking. The section "Non-optical advantages of aspheric eyeglass lenses" is particularly bad, but I don't know enough about it to rewrite it. If CorvetteZ51 does know something about it, he may have a lot to add.--Srleffler (talk) 18:59, 27 February 2008 (UTC)
I thought it was harsh of him to call the article complete BS and then add unsupported claims to the lead, with a misspelling of a word that one knowledgeable in this field should be very familiar with. So I figured it was good to challenge him to fix it. Dicklyon (talk) 02:38, 28 February 2008 (UTC)
OK, most of the article is not BS. Eyeglasses only, aspherics offer a reduction in thicknesss of 20% or so, at the expense of increased off-axis astigmatism and different geometric distortion, as compared to a spherical base (front) curve.CorvetteZ51 (talk) 15:34, 28 February 2008 (UTC)
Do you know of a reference (print or online) that supports that? I don't doubt your claim, but it's helpful to Wikipedia to be able to back up the information that appears in the articles.--Srleffler (talk) 16:18, 28 February 2008 (UTC)
Apology accepted, as Stephen Colbert would say. So find us a good source and write that up. Dicklyon (talk) 16:16, 28 February 2008 (UTC)
my comments come from, reading hundreds of posts on Optiboard forum. I will try to cite something, but it is difficult, as there is much conflicting info, and lots of advertising copy. Apologies to everybody,BTW. None of my comments apply to photography lenses. CorvetteZ51 (talk) 15:56, 29 February 2008 (UTC)
That's what I was afraid of. We can't have you putting in stuff that learned from reading forums. That's just hearsay, not backed up by anything reliable. Dicklyon (talk) 18:07, 29 February 2008 (UTC)
D., you will find this interesting. http://www.opticampus.com/cecourse.php?url=lens_design/&OPTICAMP=f1e4252df70c63961503c46d0c8d8b60#asphericity

go down about 90% of the page, to 'Aspheric Lens Design'. Uf you have something more reliable, please indicate. CorvetteZ51 (talk) 11:55, 1 March 2008 (UTC)

Thanks, looks like an OK source. Dicklyon (talk) 16:04, 1 March 2008 (UTC)

## Confusing paragraph

What is this paragraph trying to say? The wording is very confusing. --Srleffler (talk) 19:16, 8 November 2008 (UTC)

Conflicts in the description of aspheric lenses and their use exist mainly from the discovery of use needing techniques to determine their improvement of optic systems, a subjective process that may involve deciding which "looks best", 1 or 2. Wholesale commercialization by manufacturers promoting products are confounding the advancements of study in this improvement of systems requiring delicate ray tracing techniques, understanding of aberrations, indices, impurities, entrance/exit pupils, and criteria generally studied in the field of Physics under academic scrutiny, but not limited from commercial, or ophthalmic applications.

## Discussing the most current relevance

Amplification of details produced not so much by a point of focus, but by the concentration of light rays within an optical tube, still separated and not having crossed paths before coming to focus, compressed into tubes of successively smaller diameter, and remaining collimated from a distant source so an image has not yet converged, and light paths have not crossed Cardinal points (optics) summarily produce a better facsimile of an object from point to point without interference between each ray's particle waveform phase [1] at the final point of focus upon a grid of light sensors, ie. the macula.[citation needed]

Preserving the integrity of parallel light paths may involve not bombarding them into the same converging point. StationNT5Bmedia 18:13, 9 November 2008 (UTC)

Not non-sense, just hard to make sense of modern development . . . difficult to understand the context of ray tracing used here in reflecting telescopes as they increase the diameter of the reflecting lens, and improve on imaging systems. In particular improving designs like the Hubble Space telescope is a goal. StationNT5Bmedia 18:56, 9 November 2008 (UTC)

I removed the paragraph again. Let's work out wording here before reinserting it into the article. As it stands, I can't even tell what you are trying to say, much less evaluate whether it is correct. Either way, it is not supported by a reliable source. The reference you added seems to be a dead link, and you said in your edit comment that it is not a complete source anyway.
Please don't reinsert the paragraph until we discuss it further here. Note that the three-revert rule prevents an editor from repeatedly inserting or deleting the same material over and over again. Any editor who reverts edits on one article more than three times in a 24 hour period can be blocked from further editing.--Srleffler (talk) 21:19, 9 November 2008 (UTC)

There is also something wrong with the history. Newton made a telescope with at parabolic reflector in 1689.--Srleffler (talk) 21:43, 9 November 2008 (UTC)
Actually, Newton's was spherical according to this book. But I agree that the astronomical mirror stuff is probably out of place here. Dicklyon (talk) 22:43, 9 November 2008 (UTC)

Lord Oxmantown's team worked primarily on the metalurgy to create the surfacing machine that produced the larger diameter reflecting lens. His inclinations toward the end of the publication were towards testing parabolic form. Concerning modern ray tracing, and individual ray's particle waveform phases being collimated before reaching Cardinal points (optics) for higher definition and point to point traversal of successively smaller diameter optical tubes, there isn't any easier way to express these compound abstracts, except to try and put them together. In terms of pixels, high definition is considered to be 1920 X 1080. This is difficult at best to describe in terms of a distant source emitting individual collimated light rays that reach a complex lens system. StationNT5Bmedia (talk) 01:48, 10 November 2008 (UTC)

It's not a reflecting lens. It's a reflecting mirror, made of solid speculum. While it is aspheric, it is off-topic for this article because it is not a lens. It's an interesting paper, though. It's clear he was aware in advance of the desirability of a parabolic mirror for telescopes. His achievement in that regard was in developing a way to produce large mirrors that deviated from spherical form while retaining good optical figure (thereby having reduced spherical aberration). The rest of your paragraph above doesn't make any sense to me at all. It seems incoherent. It also looks like original research. Wikipedia does not publish original research. If you want to talk about this stuff in the article, you are going to have to cite a reliable source (assuming the material is actually relevant to the article, and otherwise suitable).

Visit http://www.photozone.de/mirror-lenses for an article entitled Mirror Lenses (Technology - Technology). It describes flaws in reflecting telescopes. StationNT5Bmedia (talk) 02:44, 10 November 2008 (UTC)

I'm familiar with photographic mirror lenses. They are discussed at Catadioptric system#Photographic catadioptric lenses. Reflecting optics work a lot better for telescopes than they do for camera lenses. Many of their defects are not relevant for astronomical photography.--Srleffler (talk) 04:47, 10 November 2008 (UTC)

Now, consider if the Hubble Space telescope were designed to retrieve 1920 X 1080 individual collimated light rays, and without "folding" them, avoid any interference between neighbors & fit each & all the rays onto a rectangle 2/3" in width, with a 16:9 aspect ratio for the new ATSC plasma screens, maintaining original ray particle waveform phase during the complex lens system processing, until it can converge onto the chip, and be digitally cinemagraphed. StationNT5Bmedia (talk) 02:51, 10 November 2008 (UTC)

Not quite sure what you're getting at there. Light rays do not really exist. They are a convenient abstraction for modeling, that represent some but not all of light's properties. The number of "rays" one considers in an optical system has nothing at all to do with the number of pixels on the detector. The performance of the system is limited by design and fabrication constraints, and by fundamental physics such as diffraction and conservation of etendue.--Srleffler (talk) 04:47, 10 November

2008 (UTC)

### the obsolete Hubble

These notes did not conclude with why the Hubble is obsolete. They continue to describe a flat array of sensors, each fitted with composite optical tubes that resist internal reflections but are durable in extreme conditions, where precision of the flatness of the sensor plate that contains the array was determined by a count of Newton rings. They go on to say that image details are limited only by available computing power, based on the software program running (256)^2 attributes per pixel in an array of 1920X1080 pixels at 30 fps. This optical system does not use any reflecting lenses, and the array being flat limits it's use solely to astronomical surveillance. StationNT5Bmedia (talk) 15:57, 10 November 2008 (UTC)

This topic migrates from aspheric to afocal, but unlike current material on digiscoping, the descriptions are not reflecting, less refracting, and more of a warp of electromagnetic flux that funnels into successively smaller diameters of re-collimated waveforms, ultimately reaching an array with enough energy to trigger components that begin the initial electronic processing used to interpret point-to-point facsimiles of objects several light years wide upon sensor arrays that detect infra-red, ultra-violet, and visible light spectrums. StationNT5Bmedia (talk) 20:36, 10 November 2008 (UTC)

"There is no competition", says the NASA contractor, Grumman-Northrop at the Goddard Space Center concerning the James Webb Space Telescope being scheduled for deployment in 2013 aboard Orion class vehicles. StationNT5Bmedia (talk) 23:13, 10 November 2008 (UTC)

I can't tell whether the text you have written here is an incoherent explanation of some other work, or original research, or complete nonsense. Fortunately, it seems to be completely off-topic for this article, so no further analysis of it seems necessary.--Srleffler (talk) 04:17, 11 November 2008 (UTC)

## A questions unclear to me

Do modern $700+ DSLR lenses fit into "inexpensive consumer cameras" ? If no then what manufacturing method use companies like tamron and sony? The "See also" section lists Hyperbola and Parabola. While it's obvious at least the left surface of the lens shown on the picture is neither hyperbolic nor parabolic. Why the hyperbola and parabola are here? What's the typical shape of the lens surface? Is it а 3-4 degree polynomial, or just arbitrary NURBS, or what? Thanks in advance to anyone with the competence and willing to update the article. 77.50.135.136 (talk) 22:58, 1 May 2009 (UTC) No a$700 DSLR lens doesn't fit into an inexpensive consumer camera. If it contains a single molded asphere, they are charging way too much for it. Molded glass aspheres cost about $50 in small quantities; maybe half that in volume. Plastic lenses are cheaper. The shape is typically optimized for the particular application using a raytracing application on computer. One common formula for the shape of the surface is $z(r)=\frac{r^2}{R\left (1+\sqrt{1-(1+K)\frac{r^2}{R^2}}\right )}+\alpha_1 r^2+\alpha_2 r^4+\alpha_3 r^6+\cdots ,$ where the optic axis is presumed to lie in the z direction, and $z(r)$ is the sag—the z-component of the displacement of the surface from the vertex, at distance $r$ from the axis. $R$ is then defined to be the radius of curvature of the surface. Simple aspheres may have zero for all the alpha coefficients, in which case the surface is elliptical, hyperbolic, or parabolic depending on the value of $K$, which is called the conic constant. Other surface profiles can be used; in general the form is somewhat arbitrary. Optical software models propagation through NURBS surfaces, so in principle these could be used for aspheric lenses, but in practice they are not well suited to numerical optimization. NURBS is more useful for exporting lenses designed using some other definition of surface form (like the formula above), for use in a CAD program.--Srleffler (talk) 03:39, 2 May 2009 (UTC) Srleffler, thanks a lot! BTW$700 DSLR lenses are much more complex then just a single asphere. Look at this one (sony 18-250) I was keeping in mind when I was asking my question: http://www.photoreview.com.au/reviews/cameraaccessories/optical_diagram.jpg
77.50.135.136 (talk) 21:04, 2 June 2009 (UTC)
You answer your own question as if to beg to differ, and leave no quadruple tilge as requested when adding comments for your screen name to be identified. Identifying yourself would allow others to make comments on your talk page. When making any additions, please sign your comments with 4 ~ (tilge) characters. As to the questions, I have reviewed several blogs at the CloudyNights telescope review pages, and consistenly owners of quality telescope systems that have emailed the manufacturers often ask about the non-spherical surfaces, and some have received replies that you can read at the blog about the optical designs being a propriety priveledge & company secret with patents pending, so that many of the complex lens systems being studied that use aspheric, parabolic, and hyperbolic curvatures are tested for specific purposes at the manufacturer, depending on wavelength, coma, spherical abberation, chromatic abberation, refractive index, ect. The "best" fit is what makes it to the market place for consumers buying the product, and they are not perfect, but are the best known combinations that theory can employ. StationNT5Bmedia (talk) 03:50, 3 June 2009 (UTC)
He did sign his post properly. He isn't editing from a user account, so the software signs his message with his IP address instead of a username. This is normal.--Srleffler (talk) 04:01, 3 June 2009 (UTC)
Would that equation not be more simply expressed as (and I hope I don't fark this up, please double-check)
$z(r)=\frac{r^2}{R+\sqrt{R^2-(1+K)r^2}}+\alpha_1 r^2+\alpha_2 r^4+\alpha_3 r^6+\cdots ,$
i.e. move R into the brackets, and thence R^2 inside the sqrt. It reduces the nesting level of both brackets and fractions. Fatphil (talk) 16:20, 28 August 2012 (UTC)
That seems fine. The other form might be preferred because it makes the behaviour clear in the important limiting case where r/R is small.--Srleffler (talk) 04:06, 30 August 2012 (UTC)
Just to add a value to this last question, most literature use a variable "z" for curvature (z = 1/R) so as the colleague said, for evaluating formulation is more clear to use the first one, and contribution in the root is small. — Preceding unsigned comment added by 217.24.206.253 (talk) 13:21, 7 August 2013 (UTC)

## Define all quantities

The diagram needs to have definitions for all the quantities e.g. R is the radius of curvature, etc. —Preceding unsigned comment added by 128.250.51.155 (talk) 21:24, 7 February 2010 (UTC)

Yes, this is where math often fails in working with optics. Because the variables are measurements indexed in units defined by previous work, we're using values that rarely match calibrations used to categorize power, curvature, and other properties. The textbooks leave little comfort concerning the definition of quantities. Very few texts give a chart of definitions: they only include the inference from context building an equation. Most useful would be a legend of the math symbols, units, tolerances, and other properties. From the standpoint of engineering, a legend would seem more practicle & less theoretical. StationNT5Bmedia (talk) 15:34, 10 February 2010 (UTC)

## Wrong formula?

I am pretty sure this formula is wrong. z cannot be as defined as it does not reduce to a sphere for any value of k (with the As zero). I think z(r) is meant to be the Saggital Distance, often called SAG, not as it is at the moment "the z-component of the displacement of the surface from the vertex, at distance r from the axis". Billlion (talk) 14:44, 15 January 2011 (UTC)

That is what sag is, and the article says that z(r) is the sag. I'm pretty sure the formula is right.--Srleffler (talk) 15:50, 15 January 2011 (UTC)
Yes thanks, I am convinced now. I wrote out a quick derivation here [1] as I still haven't found it elsewhere. I wonder if anyone knows of a paper explaining why this series is a good one for optimising aspherical lenses? Billlion (talk) 14:57, 16 January 2011 (UTC)
I was confused by the term Sagittal Depth [2] "Sagittal Depth. Sagittal depth is the distance from the vertex of the contact lens surface to a chord drawn across the surface at a known diameter." Billlion (talk) 15:03, 16 January 2011 (UTC)

## rotational symmetry

An aspheric lens in ophthalmic optics don't always have rotationally symmetric surfaces. For the correction of astigmatism an aspheric ophthalmic lens has a single aspheric surface with rotational symmetry, and a toroidal surface which is not rotational symmetric. Some lenses even have a non-rotationally symetric aspheric surface (eg. a biaspheric ophthalmic lens for the correction of astigmatism) The term "whose surfaces have a profile that is rotationally symmetric" should be removed. Its liam (talk) 12:26, 23 March 2011 (UTC)

## Ultra short throw projector lenses?

I am trying to figure out who manufactures ultra short throw lenses, and I'm trying to find some sort of history or discussion of how they are developed. I work with these on a regular basis and I am interested to know where the technology originates.

Since the lenses are permanent components of projectors, the projector manufacturers have no need or desire to tell where they get their lens assemblies from.

There are now several extremophile lens systems out there where the projected image is bent at nearly an 80-degree angle towards the bottom of the screen, from a wall mounted projector directly above the screen without any arm holding it out in space a meter or more away. I am really interested to know what the shape profile is of these lenses and how the lenses are being manufactured, and it would probably make a useful addition to this article as well.

DMahalko (talk) 10:24, 27 June 2011 (UTC)

Sounds like something that might well be proprietary: the projector manufacturers may well design their own lenses and have them custom-made.--Srleffler (talk) 00:37, 28 June 2011 (UTC)

## The label h is not correct

Shouldn't the h label in the diagram on the right side not be a r to fit with the formula? (Forgive me my ignorance, these are one of my first words on Wikipedia and I didn't find another place to put my comment) — Preceding unsigned comment added by Halirutan (talkcontribs) 02:28, 6 December 2012 (UTC)

Yes, you're correct, and this was exactly the right place to put your comment. I think the notation in the formula is better, since the surface profile is really a function of radius, not height. We should probably edit the image or replace it with a better one.--Srleffler (talk) 03:58, 6 December 2012 (UTC)
The Diagram has been modified by the original auther, so as part of tidying up the Reqdiagram page, I am removing the Diagram Requested tag. Egmason (talk) 10:44, 1 June 2014 (UTC)

## Ibn Sahl

There is a 'verification needed'. after the statement that Sahl first discovered Snell's law. This puzzles me as there are two bona fide references. The scame ststatement is in the article on Sahl. I suggest to remove the verifiication request. Objections? Karloman2 (talk) 20:00, 11 April 2014 (UTC)

"Verification needed" means that someone needs to actually go check the cited sources and verify that they say what the article claims. There was a problem a few years ago with an enthusiastic editor who added a lot of material about Ibn Sahl and other Islamic scientists and mathematicians to many Wikipedia articles. The editor's contributions contained many citations, but on closer examination many of the claims were not adequately supported. I presume the "verification needed" tag is a leftover from that incident, but some digging would be needed to figure out whether this claim is properly supported.
I certainly object to simply removing the verification request without further research. Either verify the claims, or remove the material altogether.--Srleffler (talk) 06:30, 12 April 2014 (UTC)
Dear Srleffler. I will leave this as is, and neither verify nor modify. I do not want to become involved in a controversy around this. (I am not a specialist in this field. I had heard a professor in the history of science state on the BBC radio that Ibn Sahl discovered Snell's law, and I wanted to know how Ibn Sahl expressed this without knowing trigonometric functions. It is well explained in the Ibn Sahl Wikipedia article.) I stumbled on this passage and I felt it is awkward as it is - still do - but did not want to change this before checking on the talk page. I believe the BBC professor but if there are strong feelings a about this, I leave it as is. Wkr.Karloman2 (talk) 07:25, 12 April 2014 (UTC)