Cheap planetarium/hemisphere projection lens

[weartronics]

Hi smogthemog - Yes, the overhead projector lens (the glass projection lens at the top, not the fresnel collimator in the base) is another great idea! I think this is a relatively wide-angle lens.

Also, I found several magnifying lenses here, some as big as the Discoscan lens!
http://www.amazon.com/dp/B000VL0C06/...qid=1213421685
Obviously they're not designed as projection lenses, but for $15 I wonder if they make any interesting beams?

[James Lehman]

Oops. Sorry! I feel like a moron.

James.

[weartronics]

Hi James,

If you do any experiment with the fresnel lens, please take a photo for us . Maybe not suitable for projection, but still might make an interesting effect!

weartronics

[Pangolin]

Can you send me any detailed specification for the Discoscan lens? I would like to know what entrance aperture and acceptance angle are necessary to achieve 180 degree scanning, and what effect the lens has on the beam divergence.

If you write to me privately, using our contact form, I will send you an outline drawing of the lens, and some pictures of it's intended application. The information is not highly detailed as, for most people in this industry, it hasn't had a need to be.

As for effect on the beam divergence, this is a tougher call. The lens itself increases the scan angle by a factor of 5.1. The divergence is also increased, although not by the same amount. The amount actually depends on the TEM mode of the beam itself, and other beam-quality-related criteria. In general, it may be necessary to pre-collimate the beam before entering the scanners, thus allowing you to control the divergence/spot size of the exiting beam (to some extent).

However, I think you are mistaken with regard to the scope of the AVI patent. I am seeing a lot of fear-mongering on this issue (intentional or otherwise), so I want to present a clear defense.

As an inventor and author of numerous patents yourself, you must be aware that the description of the invention (including figures) has no bearing on what is claimed. To my knowledge, AVI only have one patent (US 6,698,900 with possible derivatives in other world regions), which has only one main claim.

Well, I'll never claim to know everything, and it is always possible that I will be mistaken about something, especially if it does not pertain to my own company... But I myself never engage in fear mongering.

In this case, my guess is that you are referring to AVI's patent on their "Omnistar" product, which describes the creation of a laser display using a balloon-type projection surface.

If you search for "AVI" or "Audio Visual Imagineering" itself, as the "Assignee name", it may be true that you turn up only this one patent. But likewise if you search for "Pangolin" by itself as the "Assignee name", you would also turn up only one patent. This is because most of my own patents are not assigned to anyone (at this time), so there is only an "Inventor" listed as the owner. Of course, since I work for Pangolin (it could be argued that I am Pangolin), Pangolin has the full capability to go after those who infringe my patents.

In the same way, there are other relevant patents which are not ASSIGNED to AVI, but were invented by AVI principals or employees, and thus, may be applicable. For example, if you search for "Bacs" as the "Inventor name" instead of searching for "AVI" as the "Assignee name" you should turn up others.

Best regards,

William Benner

[weartronics]

Hi Bill,

I'm looking forwards to consider the Discoscan lens. I was hoping for complete specs to treat it as an optical system, but at least I can see the specs you have. If it's impossible to design a system around the lens without some experimentation, perhaps I can supply details of my application and you will be able to give some advice?

My defense above is only with reference to the AVI patent specifically (or "AVI's patent" as Buffo and you describe it). Like most basic technologies, I found that wide-angle projection is basically "sewn-up" in the patent arena. I certainly wouldn't advocate any commercial venture there!

Kind regards,

weartronics

[smogthemog]

Oops. Sorry! I feel like a moron.

James.

I may be able to help you there James, there are several living in my village. I will sort you one out and get it shipped over