CurtPalme.com Home Theater Forum

[David_Web]

"The filter would act as a lens element itself and thus degrade the optical quality of the lens."
You could probably measure it with specialized gear. But I have a hard time believing that you will see a 1.5-2mm thick glass plate in front of the lens. It's the same as putting a filter in front of a camera lens. The distortion is minimal.
AR coating is just there to prevent a reflex from washing out the image.

I doubt we can machine a c-element to produce less distortion than the filter would.

You could take a normal peace of glass and test how bad it would be.


And at the moment as colored c-elements are a little scarce the alternative to a hardly noticeable distortion in the image to bad colors I know what I would choose.

[jkruger]

[Nashou66]

I think you could make colored optical perfect glass and some how adhere it to the tube face itself with out any visual effect , it have to be very very thin so it wont alter the focal point to much and allow the actual lens to do its job the way it was meant to in the system.

Athanasios

[David_Web]

I forgot the part where you said camera housing. So I believe you on that.

As you have experience i these kind of things what would be the best way?

Is the c-element worth it or would a filter suffice?


Then I guess you would have to factor in the hassle with changing the c-element. Doing a complete setup of mechanical, magnetics and electrical.
versus just putting on a filter.

Just throwing some Ideas out there. I guess a lot more people would add color filtering with the easier way. Which would probably be cheaper as well.

[jkruger]

There are lots of ways to get colors, some better than others. I've seen the film filters on the tube faces, candy color spray paint, tinted plastic, etc... I think the guys with 9"lc projectors would be quite happy to redo a setup if they could put in colored c-elements. Maybe not, but at least we could take a poll to find out how many are interested in them.

[Spanky Ham]

CJ has already replied, but I think he did some testing on some fliters about four or five years ago. The thread should be in the AVS archive. Would the filter make a difference if it was on the front of the lens or does it need to be at the c-element?

That is interesting about spraying colors on to the surface. That would be a good way to achieve a more exact color. It could also be the easiest to implement, if all you need was a spray on coating.

[bbfarmht]

Correct me if I'm wrong, but you don't want to spray because of difficulty in being able to achieve a uniform thickness throughout the surface of the lens.

[Spanky Ham]

That is true, but I think I am good enough to spray a pretty even thickness. The biggest reason for spraying would be cost. Some people might be more amenable to $15 for the coating as opposed to $200 plus for the c-elements. Maybe someone can answer my first question. I think CJ paid like $20 for those filters.

[-Pjackso]

Just a note:
If a external color application is used (a spray for example), it would need to be applied to the dry-side of the C-element. Otherwise, one would need to consider chemical interaction with the glycol.

[Spanky Ham]

No doubt. I have been curious about applying some sort of masking to either the tube or the inside glass. Since this is where most of the light scatter comes from that destroys ANSI cr, I hypothesize that this might make a difference in ANSI. TSE thinks I am smoking something:mrgreen:, but it would be an interesting experiment. One problem is what material or coating is long term stable in glycol?

[Tom.W]

It would be interesting to find out who owns the patent on the c element and when it expires. These could be made to the patent specs by just about anyone if the patent has expired. Large optical grade glass filters are very expensive and spray painting an optical surface will only degrade the transmission as far as I can tell.

[bbfarmht]

[Tom.W]

It's my understanding that if the patent is still in effect you would have to have a royalty agreement with the patent holder before any company could legally produce and sell these. I doubt if any company would risk a law suit from the patent holder.

If the patent has expired we should be able to find several company's that could easily make these for less than $100 each in bulk.

[jkruger]

I think this is it:
Go here: http://patft.uspto.gov/netahtml/PTO/srchnum.htm
Try searching patent #7,133,084

[Tom.W]

Try this link to the patent #

http://www.google.com/patents?id=KWZ7AAAAEBAJ&pg=PA1&lpg=PA1&dq=usa+patent+7133084&source=bl&ots=dViNAnK61B&sig=EWpviYxmfvyJzgELmE9eN30oFEI&hl=en&ei=wVugSZO8LsiLngfqv738DQ&sa=X&oi=book_result&resnum=3&ct=result

China could probably produce these as they ignore our patent rules...

[jkruger]

Sounds like we need to approach whoever is making them for VDC.

[Tom.W]

The question is did 3M sell the patent to VDC ? And thanks for the patent # as I searched for that for two hours the other day and couldn't find it...

[jkruger]

[huggy]

[jkruger]

If you are selling brand labeled knockoffs that's more likely to get someone's attention. Selling a couple of random plastic parts here and there is probably gonna fly under the radar.