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Raytracing Nagler ultrawides patents

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#1 Vla

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Posted 24 February 2019 - 08:29 PM

I was kind of curious, and suspect a few others will be, what do Nagler's published prescriptions' raytrace look like. One more reason is that no complete raytrace of its patents exist (that I know of), and those partial ones (that I know of) are grossly inaccurate. Even Rutten and Venroij (1st ed.) present the first patented Nagler as having about 1.5mm longitudinal astigmatism in the outer 1/2 field area, while the actual one at 40 deg off is 0.23mm, for little over 2 waves p-v. Gross' "Handbook of Optics" is worse in this respect, etc. Main reason for this inaccuracy is raytracing entire field with a single exit pupil location, giving grossly distorted values (and ray spot plots) for the field points coming to different exit pupil locations. So here are complete, properly raytraced prescriptions, in their actual size, all 10mm f.l. and directly comparable (ExP is exit pupil distance from the eye lens, ACC is needed accommodation in diopters and DIST is rectilinear distortion). Accommodation of 1 diopter corresponds to ocular focus adjustment from infinity (field center) to about 1m distant object. 

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  • nagsi1.png
  • nagsi2.png

Edited by Vla, 24 February 2019 - 08:37 PM.

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#2 TOMDEY

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Posted 24 February 2019 - 09:51 PM

Hi, Vla! I may be a bit slow on the draw here... can you clarify... Is the feed coming in as idealized F/5 telecentric? That's what it seems from what I see up there. I vaguely recall (maybe incorrectly) that Al (may have) said something about the (telescope exit) pupil being at a range of "about a hundred" (inches, centimeters)? I doubt that it would make much difference, especially with that 10mm eyepiece focal length... just figured it's worth asking. I had tried to get the R/X long ago (decades)... just for yucks... and sorta did... don't remember what I did with that, probably nothing!

 

Anyway, nice analysis... what I had wondered about, way back then!   Tom



#3 Vla

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Posted 24 February 2019 - 11:10 PM

Hi Tom! It's in general what looks like telecentric over 22mm entry (chief) ray section for 10 and 20deg off, and telecentric or slightly diverging for 30 and 40deg. As you say, those small differences don't change the output significantly. Patent drawings show what looks like telecentric entry, but with such a short ray path shown there would be no difference if entrance aperture is a hundred inches away.

 

I should add, with respect to the odd one, the 1988(d), that the "alternative" box shows a bit tweaked (by me) prescription, in which predominant coma is replaced by predominant astigmatism (with reduced lateral color error). The original looks kinda awful with all that coma, but I speculate that it wasn't intended for f/5 systems. At, say, f/10, since the eyepiece's effective aperture is proportional to the f-ratio, and coma changes with the 3rd power of aperture (as opposed to 2nd power for astigmatism), the coma becomes nearly negligible, as shown in the "f/10" box. That strategy is used by Tal, which advertases its 80deg ep (designed by Klevtsov, and different than Naglers) as "practically free of astigmatism", and it is true with Tal's f/8 and f/10 Klevtsov's, for which they are recommended. At f/5, however, they (there is a simpler and a little more complex version) they exhibit - guess what - predominant coma.


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#4 evan9162

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Posted 24 February 2019 - 11:32 PM

Sooooo....which designs were actually put into production?  For the Type 1, it should be the first as the Type 1's were a 7-element design.  Every time I've seen a design drawing of a Type 2, it's been the 1988(a) prescription.  



#5 Vla

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Posted 25 February 2019 - 07:04 PM

Correct, that's what goes as Type 1 and 2 layout, although we can only guess whether the patented prescriptions went into production unchanged. But I think it's reasonable to assume that they are a good representation of the actual units. Another reasonable assumption is that Al Nagler didn't disclose in the patent documentation his best take, i.e. that the actual units are generally somewhat better than the patent prescriptions.



#6 faackanders2

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Posted 25 February 2019 - 07:34 PM

I was kind of curious, and suspect a few others will be, what do Nagler's published prescriptions' raytrace look like. One more reason is that no complete raytrace of its patents exist (that I know of), and those partial ones (that I know of) are grossly inaccurate. Even Rutten and Venroij (1st ed.) present the first patented Nagler as having about 1.5mm longitudinal astigmatism in the outer 1/2 field area, while the actual one at 40 deg off is 0.23mm, for little over 2 waves p-v. Gross' "Handbook of Optics" is worse in this respect, etc. Main reason for this inaccuracy is raytracing entire field with a single exit pupil location, giving grossly distorted values (and ray spot plots) for the field points coming to different exit pupil locations. So here are complete, properly raytraced prescriptions, in their actual size, all 10mm f.l. and directly comparable (ExP is exit pupil distance from the eye lens, ACC is needed accommodation in diopters and DIST is rectilinear distortion). Accommodation of 1 diopter corresponds to ocular focus adjustment from infinity (field center) to about 1m distant object. 

What is 1988d?  It looks alot worse than 1988a,b, & c.



#7 lylver

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Posted 26 February 2019 - 07:56 AM

I should add, with respect to the odd one, the 1988(d), that the "alternative" box shows a bit tweaked (by me) prescription, in which predominant coma is replaced by predominant astigmatism (with reduced lateral color error). The original looks kinda awful with all that coma, but I speculate that it wasn't intended for f/5 systems. At, say, f/10, since the eyepiece's effective aperture is proportional to the f-ratio, and coma changes with the 3rd power of aperture (as opposed to 2nd power for astigmatism), the coma becomes nearly negligible, as shown in the "f/10" box. That strategy is used by Tal, which advertases its 80deg ep (designed by Klevtsov, and different than Naglers) as "practically free of astigmatism", and it is true with Tal's f/8 and f/10 Klevtsov's, for which they are recommended. At f/5, however, they (there is a simpler and a little more complex version) they exhibit - guess what - predominant coma.

You didn't think coma is usefull but ... Nagler are mainly designed for fast newton.

 

Tal, on the contrary provides some corrector or coma partially corrected optics.



#8 evan9162

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Posted 26 February 2019 - 10:59 AM

Correct, that's what goes as Type 1 and 2 layout, although we can only guess whether the patented prescriptions went into production unchanged. But I think it's reasonable to assume that they are a good representation of the actual units. Another reasonable assumption is that Al Nagler didn't disclose in the patent documentation his best take, i.e. that the actual units are generally somewhat better than the patent prescriptions.

 

Its possible multiple prescriptions made it to production.  I don't think the T2 is a scaled design, the physical size and eye relief of the 3 models indicates they are all at least somewhat different. 

 

At one point, I had all 3 - I've since sold the 16, but still have the 20 and 12, so I've done some comparison between the 3. 

 

The 16 has the least amount of eye relief of the 3, and is physically the smallest.  It's also the "least good" of the 3 - there doesn't seem to be anything wrong with the views (good contrast, sharpness, and edge performance), it just seems to lack that "oompf" that makes the views pleasing.  Can't quite put my finger on it - but it did make it easy to sell to make room for the others.  I remember the Smyth group was quite flat on the outside surface.

 

The 12 and 20 both have about the same amount of eye relief (the 20 might have a couple mm more).  For whatever reason, the 20 seems to have a noticeably larger AFOV than the other two - but that's just how it "feels" when looking through them (the larger eye lens and body may lead to that impression).  The 20's Smyth group is definitely more curved on the outside surface.  I'll have to check the 12 to see what the curve on the Smyth group looks like.

 

Like you said - it's entirely possible the patent disclosure doesn't have the actual prescriptions that went into production.



#9 Vla

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Posted 04 March 2019 - 10:32 AM

What is 1988d?  It looks alot worse than 1988a,b, & c.

It seems as a variation of (b), with separated, widely spaced Smyth doublet. Nagler probably wanted to lock in the design, which is the smallest of all, and has significantly less of exit pupil SA than the rest. I don't think he presented the best correction he could (he doesn't have to, since he's covered with a pretty common line in the patent: "it is to be understood that  the drawing and the specification are to be interpreted as illustrative rather than in a limiting sense."). But due to its much deeper in-focus position, the design could be marketed only as a separate line. Apparently, the little larger (b) had more going for it, including (probably) higher level of aberration correction possible.

 

As lylver implies, it is possible that he was thinking of an ep that corrects coma in Newtonians.



#10 Vla

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Posted 04 March 2019 - 10:46 AM

Its possible multiple prescriptions made it to production.  I don't think the T2 is a scaled design, the physical size and eye relief of the 3 models indicates they are all at least somewhat different. 

 

At one point, I had all 3 - I've since sold the 16, but still have the 20 and 12, so I've done some comparison between the 3. 

 

The 16 has the least amount of eye relief of the 3, and is physically the smallest.  It's also the "least good" of the 3 - there doesn't seem to be anything wrong with the views (good contrast, sharpness, and edge performance), it just seems to lack that "oompf" that makes the views pleasing.  Can't quite put my finger on it - but it did make it easy to sell to make room for the others.  I remember the Smyth group was quite flat on the outside surface.

 

The 12 and 20 both have about the same amount of eye relief (the 20 might have a couple mm more).  For whatever reason, the 20 seems to have a noticeably larger AFOV than the other two - but that's just how it "feels" when looking through them (the larger eye lens and body may lead to that impression).  The 20's Smyth group is definitely more curved on the outside surface.  I'll have to check the 12 to see what the curve on the Smyth group looks like.

 

Like you said - it's entirely possible the patent disclosure doesn't have the actual prescriptions that went into production.

Obviously, any, or all of the three, (a), (b) and © - and then some - could go into T2 series, as presented in the patent, or somewhat modified. Since they are all patented as 10mm f.l. change in f.l. is one more reason for relatively small modifications.



#11 Chris Lord

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Posted 04 March 2019 - 12:47 PM

I've recently got hold of a Russian patent by Ageev and Parko for an 80° design. My girlfriend speaks and writes fluent Russian and has translated it for me a few days ago.

So I've been ray-tracing their description in dbOptic. It's an interesting approach because all Seidel errors, 3rd & 5th order can be minimised. The Petzval surface can be flattened and Tangential Coma zeroed at 40° semi-field.
It's currently made in 12.5mm and 25mm focal lengths in Novosibirsk. Not found it on-line as yet.
It seems to be free of spherical aberration of the exit pupil, but I need to verify that.
I've flip ray-traced it, and direct ray-traced it. Yet to do an objective+eyepiece+eye ray-trace.
The prescription I've played with has AFoV=80° but the Geometric FoV=45°. Distortion= -7%.
I shall work some more on it tomorrow.
Chris Lord 🙂
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#12 MartinPond

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Posted 04 March 2019 - 01:45 PM

A hidden factor across the years

might be what element values can be affordably produced

at that time.   You can beat these performances for

micro-lithography or cinema work, but you need 

$100,000



#13 MitchAlsup

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Posted 04 March 2019 - 05:20 PM

A hidden factor across the years

might be what element values can be affordably produced

at that time.   You can beat these performances for

micro-lithography or cinema work, but you need 

$100,000

$100K for cinematic work,

$10M for photolithography in the 40nm range.



#14 MartinPond

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Posted 04 March 2019 - 05:28 PM

haha......yeah, probably.   Depending on how many chips,

   $10M might be worth it.

 

Amazing how some photolithography assemblies look like a super-Nagler.

Or some super microscope objectives.



#15 MitchAlsup

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Posted 05 March 2019 - 05:35 PM

See if you can google up::

 

Optical Lithography … 40 years and holding
John H. Bruning
Corning Tropel Corporation
Fairport, NY 14450
ABSTRACT



#16 MitchAlsup

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Posted 05 March 2019 - 05:40 PM

Most interesting image from the above paper.

 

Steppers.jpg


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#17 MitchAlsup

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Posted 05 March 2019 - 05:43 PM

Another useful image:

 

Stepper1.jpg


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#18 luxo II

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Posted 06 March 2019 - 06:31 AM

Thanks Vla.

 

So... in conclusion:

 

1. What is in the patents is good, however Al did not disclose the "secret sauce" - ie measurements of actual samples suggest the designs were tweaked further for production - but not disclosed in the patents. Not really surprising, any smart designer would do same to protect their intellectual property, though no doubt making sure the production designs are well documented internally in case they need to challenge a copycat - or an insider who leaked the design.

 

2. Design (d) also suggests Al had the idea of building-in some negative coma and field curvature to compensate for that of fast newtonians in 1988, and possible earlier (the secret sauce, as above) - while not much as to be offensive in the mass market f/10 SCTs from the likes of Celestron and Meade.

 

Off-axis the lateral chromatic error in (d) isn't fantastic, either.


Edited by luxo II, 06 March 2019 - 06:45 AM.


#19 Vla

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Posted 09 March 2019 - 08:08 PM

Sorry for late response, luxo II, this lithography stuff made made overlook your post. Lateral color in (d) can be easily minimized (as boxed alternative shows), but that's probably part of not showing all your cards to the other players. Same applies to ©, and to a smaller extent (b), where you see the red above the blue throughout the field. That is simple to remedy by using glass with little different dispersion (weaker for the positive elements, stronger for the negative). But in general, these prescription have to be close enough to the best Al had for not to allow for the possibility that someone else comes with a similar layout with substantially better performance.



#20 faackanders2

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Posted 10 March 2019 - 11:48 AM

Thanks Vla.

 

So... in conclusion:

 

1. What is in the patents is good, however Al did not disclose the "secret sauce" - ie measurements of actual samples suggest the designs were tweaked further for production - but not disclosed in the patents. Not really surprising, any smart designer would do same to protect their intellectual property, though no doubt making sure the production designs are well documented internally in case they need to challenge a copycat - or an insider who leaked the design.

 

2. Design (d) also suggests Al had the idea of building-in some negative coma and field curvature to compensate for that of fast newtonians in 1988, and possible earlier (the secret sauce, as above) - while not much as to be offensive in the mass market f/10 SCTs from the likes of Celestron and Meade.

 

Off-axis the lateral chromatic error in (d) isn't fantastic, either.

So d was better for fast scopes?



#21 TOMDEY

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Posted 11 September 2019 - 11:37 AM

Regarding Patents (in general) and Optical patents (in particular):

 

Part of the ~art~ of patenting is that you want to sufficiently disclose the inventive aspects of your innovation, without unnecessarily giving away the store. Lens design patents often (most often?) will not disclose the final, optimized, tweaked, production version... but just a more generic one or two that demonstrate what's special and unique. The figures do not have to be properly scaled, and are most-often intentionally cartoonish, and distorted away from optimum. Some patents even camouflage the final intended use of the gizmo!

 

e.g. My compact projector here >>> is presented as an ~e.g.~ overhead transparency projector, like was be used in conference rooms. But the actual application was for photogrammetry work stations for the ground stations. It used less light, could be placed on "regular" tables, and wound up saving a fortune in air-conditioning... and we delivered untold thousands of them!    Tom

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#22 SandyHouTex

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Posted 12 September 2019 - 12:09 PM

Sorry for late response, luxo II, this lithography stuff made made overlook your post. Lateral color in (d) can be easily minimized (as boxed alternative shows), but that's probably part of not showing all your cards to the other players. Same applies to ©, and to a smaller extent (b), where you see the red above the blue throughout the field. That is simple to remedy by using glass with little different dispersion (weaker for the positive elements, stronger for the negative). But in general, these prescription have to be close enough to the best Al had for not to allow for the possibility that someone else comes with a similar layout with substantially better performance.

So if Al doesn't really patent what he sells, does he have a case if someone buys one of his eyepieces, takes it apart and gets all of the radii and types of glass he used.  Then that entity puts the info. into a lens optimization program and allows it to optimize the design, coming up with slightly different radii or glass types.  Does he have any patent infringement protection, considering he didn't patent what he sells?  I've always been curious.


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#23 TOMDEY

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Posted 12 September 2019 - 01:39 PM

So if Al doesn't really patent what he sells, does he have a case if someone buys one of his eyepieces, takes it apart and gets all of the radii and types of glass he used.  Then that entity puts the info. into a lens optimization program and allows it to optimize the design, coming up with slightly different radii or glass types.  Does he have any patent infringement protection, considering he didn't patent what he sells?  I've always been curious.

Hi, Sandy... well, let me put it this way:

 

I was with Kodak, back when Polaroid sued them for infringement on one or more of their instant-camera patents. Among those was how some rollers squeezed the chemicals out, or whatever... best I can recall. (The Kodak camera was way better than the Polaroid... but that didn't really enter into it.)

 

The court found in Polaroid's favor, and ordered EK to cease production and sale, destroy inventory, and pay a HUGE fine, may have been the biggest patent infringement settlement, at that time. Kodak complied... one more nail in the coffin. The judge even chastised Kodak (lawyers) for being "arrogant" and was on the cusp of seriously considering added punitive damages!

 

But - to answer your question --- no, it would (probably) be illegal for the referenced third party to do that. That is, if whatever the hypothetical guy sells violates the ~calims~ of the (or any other active) patents --- that's a violation. And most claims describe the inventive qualitative aspects of the concept. Not necessarily every nit in the marketed, optimized embodiment. So you have to scrutinize the claims. 1, 2, 3... etc. That's what the assignee has the right to exclude. A Patent awards the right to exclude... nothing more, nothing less.

 

PS: People reverse-engineer existing devices all the time. So far, so good. But whatever they sell cannot violate any active patents... any active patents, out there.

 

Now... one could build and market outside the jurisdiction of a patent... with impunity. But, if they try to sell those within the jurisdiction --- that's a violation. And many countries have intellectual property mutual agreements, that can in theory extend the effective jurisdictions. [Hmmm... now who do we know who might just be blatantly violating such agreements. Hmmm...]    Tom


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#24 Jon Isaacs

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Posted 12 September 2019 - 02:29 PM

So if Al doesn't really patent what he sells, does he have a case if someone buys one of his eyepieces, takes it apart and gets all of the radii and types of glass he used.  Then that entity puts the info. into a lens optimization program and allows it to optimize the design, coming up with slightly different radii or glass types.  Does he have any patent infringement protection, considering he didn't patent what he sells?  I've always been curious.

 

Al patented the first Naglers. 

 

That just made it easier for Meade to copy them. Since TeleVue didn't have the financial resources to defend their patent against Meade, the patent was really worthless. Today, I doubt they could defend a patent against Explore Scientific's mega corporation. 

 

Live and learn.

 

I think TeleVue depends on two things, innovation and top quality. The 13 mm Ethos is clearly a better eyepiece than the Explore Scientific clone, that quality in coatings, materials etc costs.

 

Explore Scientific has to cut corners because if they had the same quality, the price would be too close to TeleVue's. 

 

Jon


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#25 howardcano

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Posted 12 September 2019 - 02:53 PM

I have been a 30(b)(6) witness in a patent lawsuit, and know others who also have had the experience.  What Jon described is usually the case: it is rare that a small company can ever overcome a big company.  It simply isn't possible for the small company to prevail before it runs out of money.


Edited by howardcano, 12 September 2019 - 02:55 PM.

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