Perger Prisms (1 Viewer)

[42za]

Hello All,

It is a pity that no Optics Manufacturer has picked up on the Perger Prism.

Here lies the potential to produce a really superior binocular , probably much better than any other binocular made today , (well , probably not as good as the Nikon WX , but I bet it could be made to at least equal the WX).

Imagine a binocular made to the highest standards without ANY plastic parts , a brass body , and the lenses and prisms made with superior modern glass and coatings , and NO RUBBER coverings , (they must use leather).

It will probably never happen , as I don't think the Chinese could do this , and the old established manufacturers are too commited to their present offerings.

But we can dream can't we ??.

o

Cheers.

 

[Chosun Juan]

Will it come with a team of bearers to cart it around for you ?

I'll take mine in CFRP thanks :t:





Chosun :gh:

 

[wllmspd]

I’d think that innovation in compact long focal length, wide angle eyepieces would have more impact? A lot of the bulk of the away is at the back!
Peter

 

[jring]

Hi,

the Perger prism system is patented - depending on whether Leica has gotten an exclusive license or not, it might not even be possible for others to build bins with Perger prisms...

PS: According to the patent filing history, the patent now belongs to Leica... see the entry from June 28th 2019...

https://worldwide.espacenet.com/pat...4542/publication/EP2463692A1?q=pn=EP2463692A1

Joachim

 

[Canip]

......
.......
It is a pity that no Optics Manufacturer has picked up on the Perger Prism.

Here lies the potential to produce a really superior binocular ......
......
......
......

You mean: no OTHER optics manufacturer than Leica.

Since 2014, the 3rd generation Leica Geovids all use the Perger prism. This prism has all the usual advantages of porro type prisms (total internal reflection etc.), plus a much smaller lateral beam offset than traditional porro prisms which allows for slimmer binocular bodies usually found in roof prism binoculars.

In the Geovid, the Perger prism produces a very bright image with good contrast.
However, from an optics perspective, I don‘t see any special „potential to produce a really superior binocular“ with the Perger prism that any traditional porro prisms (Porro I, Porro I reverse, Porro II) would not also have.

Maybe you know more about this?

Canip

 

[jring]

Hi,

no, a pair of normal bins with Perger prisms will not be better than a pair of Porro bins - except maybe for two less surfaces as Perger prisms tend to be cemented and Porros usually are not to make the instrument shorter.

And of course they are very well suited to projecting some info into the field of view by having a dichroic filter on one the cemented surfaces which will reflect just the color of the display back into the eye...

Joachim

 

[42za]

Hello,

I clean forgot about the Geovid as RF binoculars do not interest me at all (my bad).

So Leica owns the Perger patent , I think that we can now forget about ever seeing an "ordinary" Perger prism'd binocular because Leica has too much tied up in their roof prism technology and they are highly unlikely to jeopardise that.

Another dream bites the dust LOL.

Cheers.

 

[John A Roberts]

Attraction of Perger Prisms?
Apart from the novelty value, the attraction of using Perger prisms would be the combination of Porro like transmission,
without the degree of objective/ eyepiece offset of conventional Porro Type I prisms (as is noted by Canip in post #5)

On the introduction of the x42 HD-B Geovids, Leica noted that they have a 14 mm objective/ eyepiece offset which gives them their distinctive shape
(see the screen grab from the attached document)


An Alternative?
As I’ve previously indicated, another way to achieve Porro optical performance, with relatively minimised offset of the external light path,
would be by using conventional Porro Type II prisms, specifically as on some Canon IS binoculars *
see posts #4, 7 and 10 at: https://www.birdforum.net/showthread.php?t=379582

While the offset would be greater than with Perger prisms, it would seem to offer an opportunity for a canny marketer

* and interestingly in his prism patent, Perger considers his designs to be variations of Porro Type II prisms (see under ‘Abstract’ in the patent in the next post)


John

 

[John A Roberts]

Patents
As Joachim notes in post #4, the Perger prism design is patented by its inventor Andreas Perger (see the attached copy of the US patent, which includes 3 versions of the design)

And the design for the 3rd generation Leica Geovid rangefinder binoculars, using one version of the prism designs, is also patented (again see the attached copy)

However, while Leica is an assignee for the Geovid patent, it does not seem to be an one for the original prism patent
So while it may be possible for a manufacturer to obtain a licence to use Perger prisms, my suggested alternative would be cheaper if not quite as elegant


John

 

[Canip]

Patents
.........
.........
So while it may be possible for a manufacturer to obtain a licence to use Perger prisms ......


......

I was talking to Dr. Perger some time ago about this, and I think he would be thinking twice or three times before granting a license to a competitor of Leica.

Canip

 

[John A Roberts]

Hi Canip,

Well that’s not surprising
When I used ‘may be possible’, I was thinking in terms of it theoretically not being impossible, as opposed to in any practical way being likely!

John

 

[Canip]

:t:

 

[Rico70]

Hi John, I always like your very complete information and I believe that all the other friends interested in the subject also like it very much. :t:

But in this particular technical you are pointing out, and I notice a fundamental error that could lead to other deduction errors.

another way to achieve Porro optical performance, with relatively minimised offset of the external light path, would be by using conventional Porro Type II prisms

The "offset of the external light path" of Porro Type II is the same as for Porro Type I. The difference is how they are oriented in the frame-body, so they reach shapes like Geoivid (Perger - which is in fact a Type of Porro) or Canon (or in inverted Porro prism too).

 

[WJC]

Attraction of Perger Prisms?
Apart from the novelty value, the attraction of using Perger prisms would be the combination of Porro like transmission,
without the degree of objective/ eyepiece offset of conventional Porro Type I prisms (as is noted by Canip in post #5)

On the introduction of the x42 HD-B Geovids, Leica noted that they have a 14 mm objective/ eyepiece offset which gives them their distinctive shape
(see the screen grab from the attached document)


An Alternative?
As I’ve previously indicated, another way to achieve Porro optical performance, with relatively minimised offset of the external light path,
would be by using conventional Porro Type II prisms, specifically as on some Canon IS binoculars *
see posts #4, 7 and 10 at: https://www.birdforum.net/showthread.php?t=379582

While the offset would be greater than with Perger prisms, it would seem to offer an opportunity for a canny marketer

* and interestingly in his prism patent, Perger considers his designs to be variations of Porro Type II prisms (see under ‘Abstract’ in the patent in the next post)

John

“Apart from the novelty value ...”

Hi, John,

How many millions have been made off the “novelty value”? Good advertising need not be accurate or even meaningful; it has only to be believed.

I have been buzzing around bino forums ever since there were bino forums to buzz around and I have seen many inexperienced people dragged down the ever-more-costly rabbit hole. There is no doubt the Perger prism is of value; possibly more to the manufacturer than the observer. However, in CONSUMER optics perception is reality as “realities” differ from person to person. And all manufacturers know that.

Dr. Dick Buchroeder (optical engineer)—the biggest bino geek I know—has pointed out that while Nikon’s much touted WX is great for land based daytime observations, an early 1940s USED Navy 7x50 was its equal for astronomy, which was its original market.

Scanning bino forums, it would be easy for the newbie to come away with the notion that MAJOR improvements in binoculars come along every month or two. Thus, they are ever ready to spend their money to OWN those improvements, even though research has shown that the average observer really can’t SEE those improvements—what may look great in STATIC mathematical printouts rarely has the same influence on FLUCTUATING biological receptors. If it were so, the best binos would be 200x, have photographically flat fields, be devoid of chromatic aberration, weigh as much as 4 postage stamps, not suffer from jitters, and cost $.18.

In the last 100 years, there MAY have been a half dozen OPTICAL improvements that the average observer could actually detect and care about. :cat:

“Reality bites.” — Aristotle

Back in my hole, now.

Bill

 

[John A Roberts]

Hi Rico (post #13),

Thanks for your positive comments

A) The main advantage of the Porro Type II configuration as used by Canon is a less bulky prism assembly, and in turn the potential to enclose the prisms in a less bulky housing


B) However, it’s not the case that the offset of the external light column is the same in the Porro Type I and Type II configurations
For simplicity, consider the attached diagram:

- A to B and B to C, each represent a prism of equal size in the Type I configuration (as with the current Swarovski Habichts, and the Zeiss in the attached image), and

- A to B represents prisms in the Type II configuration i.e. with the first prism underneath, and what’s effectively the second prism, cut in half and placed on top (as with the Canon)


Since the diagram in effect shows a right angle triangle with two equal sides
(from the centre of A to the centre of B, then from the centre of B to the centre of C, with the hypotenuse from the centre of C back to the centre of A),
we can do a simple calculation
If we assume that the distance of the 2 equal sides is 5 units, then the offset:

- in the Type II configuration is 5 units (from the centre of A to the centre of B), but

- in the Type I configuration it’s 7.1 units (from the centre of A to the centre of C), which is 40% greater (i.e. 5x5 + 5x5 = 50; and 7.1x7.1 = 50)


C) Additionally, if I was going to market a modern/ roof prism styled Porro Type II binocular, I’d strongly consider using internal focusing by lenses in the eye piece
- instead of the almost universal practice of focusing by a lens in the objective

As I’ve commented before, this gives the potential for a much more compact body. See both post #5 at: https://www.birdforum.net/showthread.php?t=377255
and the image comparing a Leitz 10x40 (pre-B) to a Leica x42 BA (it’s from Ken Rockwell's photographic site at: https://kenrockwell.com/leica/trinovid/10x40.htm )

The slimness would provide yet another distinction compared to the sameness of most current binoculars - again a marketing plus
And in doing so it could also potentially piggyback off positive association with the just released Leica ‘Retrovids’
(and both acknowledgement and a big round of applause has to go to Canip for coining such an apt descriptor: https://www.birdforum.net/showpost.php?p=3933332&postcount=107 )


John

 

[Rico70]

John, if the orientation of the prisms Type I is the same as the photo 1 you have attached, the offset left-right (A-B) will be exactly the same as that of the Type II (A-B).
So, it will be depending on the orientation of the prisms.


https://assets.catawiki.nl/assets/2019/1/29/c/1/6/c16dcb0c-2bd3-4cd1-85de-a48802423828.jpg

 

[John A Roberts]

Hi Rico,

We may be having a problem with terminology

A) Offset - is the amount of displacement of the coincident axis of the light path, before and after it has passed through a prism assembly

B) Orientation - occurs where there is offset, and is the way in which the objectives and eye pieces of the two telescopes of a binocular are positioned around the centre hinge


Most roof prisms have no offset. With Abbe-Koenig prisms there may be either no offset or a slight offset, depending on the designer’s preference
(the latter is useful with larger diameter objectives as it allows the eye pieces to still have a sufficiently narrow minimum IPD)

With Porro Type I and Type II prisms and with Perger prisms, there is always offset. However, the amount of offset varies with the particular prism design, as I explained in my previous posts


Offset is orientated in one of four ways, depending on the preference of the designer:
- objectives outside of eye pieces (the traditional Porro prism binocular choice to maximise 3D effect, which was the basis for Ernst Abbe’s 1893 patent)

- eye pieces outside of objectives (the classic inboard Porro configuration, to maximise compactness in smaller binoculars)

- eye pieces above objectives (including the Leica Perger prism Geovids, the Canon Porro Type II prism IS models, and the British Avimo Porro Type I prism binoculars in your attachment), and

- objectives above eye pieces (including the Bausch & Lomb Elite 8x50’s with Porro Type I prisms, as in my link in post #8 above)

- - - -

In post #13 you stated that: The "offset of the external light path” of Porro Type II is the same as for Porro Type I
However, as I’ve explained in post #15 that is clearly not the case

Now in post #16, you seem to be saying that the orientation determines the degree of offset. Again that is not the case
And in the diagram in my previous post, while Porro Type II prisms make the rectangular shape A to B, Porro Type I prisms instead make the ‘L’ shape from A to B and B to C


In summary, with specific components:
- Offset is a fixed amount (and it’s only a consideration if present, and if present the amount varies with the prism type), and

- Orientation is a matter of design choice (and is only possible if offset is present)


John

 

[Tringa45]

Good advertising need not be accurate or even meaningful; it has only to be believed.

According to Leica, the minmized offset of 14 mm offers "a fantastic 3-dimensional view".
That's a bit like saying a downsized IC engine offers fantastic performance advantages!

John

 

[Rico70]

We may be having a problem with terminology

A) Offset - is the amount of displacement of the coincident axis of the light path, before and after it has passed through a prism assembly

Sorry John, it's like you say and you have every reason.
AB = 5 => AC = 7 ... and there is no discussion on this.

But the point is not the width of the form factor. The width of the binoculars has nothing to do here. How has nothing to do with Canon binoculars (which however uses a width like SP prisms).
Here we are talking about the Leica Geovid HD 3000 binoculars, which is a rangefinder-ballistic for specific use. Here the question is:

Why did Leica use the Perger system for its Geovid RF binoculars?

Leica could safely use any type of prism, independently. But instead he used the Perger system.

The answer is that the RF binoculars need a display ...

...they are very well suited to projecting some info into the field of view by having a dichroic filter on one the cemented surfaces which will reflect just the color of the display back into the eye...

This in my opinion is the point.





I take this opportunity to wish everyone a happy new year.

Nobody's going to get me out of the beer tonight B

 

[John A Roberts]

Hi Rico,

Regardless of the prism type, all hand held laser rangefinder binoculars have an internally projected data display e.g.

• Porro Type I - Leica generation 1 Geovid (a rebadged Vector)

• Uppendahl - Leica gen 2 Geovid

• Perger - Leica gen 3 Geovid

• Abbe-Koenig - Zeiss 1st and 2nd gen Victory

• Schmidt-Pechan - Swarovski EL Range

. . . so the prism type is not a determining factor in relation to data display!


John