Patents: Diffractive Optic 2.0x & 1.8x Teleconverters

[Canon Rumors]

2.0x Teleconverter

1.8x Teleconverter

Patent Publication No. 2011-123336

• 2011.6.23 Release Date


• 2009.12.11 filing date


• Related 2011-123334

Example 1

• f =- 124.47mm


• = 1.95 magnification

Example 9

• f =- 251.89mm


• = 1.80 magnification


• Rear attachment lens


• Master a longer focal length


• Smaller than the front converter


• Because of the negative refractive power and degrade the curvature


• Without a diaphragm


• Beam passes through the upper and lower


• Can not compensate for the aberrations caused by light passing through the off-axis


• Magnification chromatic aberration only expanded


• Correcting the axial chromatic aberration in the most object side lens group, to compensate for inadequate performance of the chromatic aberration and curvature of the most image-side lens group


• Diffractive optics (DO lens = Diffractive Optics)


• For example, the material is UV cured resin, wavelength 530nm design degree


• Diffraction efficiency decreases at wavelengths other than orders for the design and will not require light fraction decreased, causing a flare


• Transmittance is reduced when used in multiple locations

Patent Technology

• Positive refractive power as a whole, group 4 consists


• Applicable to telephoto and telephoto zoom


• Share in compensating the chromatic aberration of magnification and lens and the next most image side lens


• Multi-layer diffractive optical element


• Than 95% diffraction efficiency across the visible light

Source [EG]

thanks Evgenii

cr

 

[Mt Spokane Photography]

One can only wonder just how good a TC would be with DO.  TC's are not huge and heavy beasts like the superzooms, where DO can give a huge reduction in size and weight.  If my TC's were 1/2 the size and weight, it would have little overall affect on the weight of my camera and lens.

However, for a lightweight mirrorless interchangable lens camera, they might make sense.

[lol]

If they can be made small enough, maybe they could be put into lenses more frequently like the announced 200-400 extender?

[UncleFester]

One can only wonder just how good a TC would be with DO. 

If it's worse than a standard TC, then it's not any good except for the cost savings for those who want it.

On a side note: any weight savings is just ridiculous when you figure in the weight of all the the gear associated with supers (telephotos - not zooms).

[Mt Spokane Photography]

One can only wonder just how good a TC would be with DO. 

If it's worse than a standard TC, then it's not any good except for the cost savings for those who want it.

On a side note: any weight savings is just ridiculous when you figure in the weight of all the the gear associated with supers (telephotos - not zooms).

DO optics has historically been more expensive, so cost savings isn't going to happen, thats why I wonder where it would find a use.  DO lenses have less contrast too, which is not what I want in a TC.

[NXT1000]

i really really do not understand what is the advantage of DO in a tiny little converter?

I thought DO is dead since 70-300 DO 3.5-5.6 lens.

[Haydn1971]

If they can be made small enough, maybe they could be put into lenses more frequently like the announced 200-400 extender?

Considering the 200-400mm is only a 1.4x TC, this seems a very plausible application for future lenses, a pair of 200-400mm perhaps, one 1.4x, the second 2.0x ?  Perhaps even a 70-300mm 2.0x with completely DO, that's gonna be a costly lens, but if sealed, potentially very useful lens in extreme environmental conditions.  Perhaps also there are other applications other than camera lenses, video, semi-conductor, medical perhaps

[dr croubie]

i really really do not understand what is the advantage of DO in a tiny little converter?

I thought DO is dead since 70-300 DO 3.5-5.6 lens.

ditto, shaving 100g off a 325g converter is a big % by itself, but nothing when you add on a 5kg lens on the other end.

maybe if they can make the tc pair well with some not-the-best lenses, it could actually correct some CA from the original lens? (ie, lens+tc gives better images than lens by itself, rather than worse as is normally the case). (if this is even possible). (would make the most sense for built-in TCs)

and it's not dead besides the 70-300DO and the 400f4DO, there were other patents here a few months ago for some wide-prime-DO lenses (which do make more sense in a reverse-tele Wide Lens). but for us consumers it may as well be dead until they make it, true.


and some specs for those interested:
400 f5.6 - ~1.2kg - €1200
400 f4 DO - ~2kg - €6k
400 f2.8 ii - ~3.9kg - €10k

70-300 - 600g - €480
70-300DO - 720g - €1300
70-300L - 1050g - €1350

so you can't really tell how well the DO helps with weight and price because there's no direct comparison, the prime is bang in between the faster/slower versions, but it's definitely the shortest. (and the 400 f2.8 i was a lot cheaper than 10k, i think less than the f4 DO if anyone can confirm?)

same with the zoom, it's a bit heavier than the plain, and well below the L in weight, but the price is almost the same as the L for a lot lower IQ. it is a lot shorter than both though (in retracted at least).

[Mt Spokane Photography]

Perhaps also there are other applications other than camera lenses, video, semi-conductor, medical perhaps

Good Point, but its a TC for a camera lens being patented.  it won't apply to other things.


Patent Technology

•Positive refractive power as a whole, group 4 consists

•Applicable to telephoto and telephoto zoom

•Share in compensating the chromatic aberration of magnification and lens and the next most image side lens

•Multi-layer diffractive optical element

•Than 95% diffraction efficiency across the visible light

[Haydn1971]

One further thought, could it be possible that Canon have found a way to build a 2x TC that doesn't lose two stops so that the slower primes can still auto focus on mere mortal cameras ?

[macgregor mathers]

One further thought, could it be possible that Canon have found a way to build a 2x TC that doesn't lose two stops so that the slower primes can still auto focus on mere mortal cameras ?

As far as I understand, that's physically impossible. The TC doubles the focal length without enabling the aperture to be opened wider.

[/dev/null]

I don't think that the point here is to save weight or cost. They might reduce the size of the TC, but for an add-on TC that is not exactly an important point. For flip-in TC a la the announced 200-400 with integrated TC that might be more interesting, but the size, weight and price will still be dominated by the front elements.

It looks more as if the DO elements in these TCs are used to limit CA. Note that there have been some patents on long telephoto lenses where DO elements have been used in the rear parts of the system. These TC designs seem to be in the same spirit.

In any case, a patent does not mean that there will be any product - especially given that the TCs have been updated fairly recently.  ATM there are not even rumors about new DO teles even though the patent appeared something like 1/2 year ago.

BTW, the is NO WAY to build a rear-mounted 2x TC that does NOT loose 2 stops. A TC does nothing more than magnify the center of the image circle. Spreading the same amount of light over 4x the area means 1/4 of the exposure on the larger area, and with the magnification comes the DOF and so on. 1.4x TC=2x the image area=1 stop loss.

The "loss" of 2 stops is not a fault of the optical design, it's physics and unavoidable.

[drummstikk]

One further thought, could it be possible that Canon have found a way to build a 2x TC that doesn't lose two stops so that the slower primes can still auto focus on mere mortal cameras ?

As far as I understand, that's physically impossible. The TC doubles the focal length without enabling the aperture to be opened wider.

Ummm. . . yes. Physics.

Until they incorporate a di-lithium crystal lens element, a 2x converter will cost you two f-stops.

[Fleetie]

One further thought, could it be possible that Canon have found a way to build a 2x TC that doesn't lose two stops so that the slower primes can still auto focus on mere mortal cameras ?

As far as I understand, that's physically impossible. The TC doubles the focal length without enabling the aperture to be opened wider.

Ummm. . . yes. Physics.

Until they incorporate a di-lithium crystal lens element, a 2x converter will cost you two f-stops.

Well, maybe Canon can use some of the technology from this lens, to speed up their TCs:

http://www.experience-seminars.co.uk/images/pdf/canoniolens.pdf

:-)

[Mt Spokane Photography]

It looks more as if the DO elements in these TCs are used to limit CA. Note that there have been some patents on long telephoto lenses where DO elements have been used in the rear parts of the system. These TC designs seem to be in the same spirit.

Thats what I see in their list of advantages.  filing a patent is a expensive process, so, even if it does not become a released product, they likely want to keep ahead in DO technology.  They have the equipment and manufacturing processes.  There is a reason every time they spend thousands to file a patent.