I have 3 of these laying around. I also have another 3 that are attached to my current old school CRT projector in my living room.

I am starting to collect the pieces to start my Lumenlab projector, and was wondering if one of these lenses would be a good choice. They have two adjustment knobs that allow for a lot of focus control. The lenses are just under 5" in diameter. They are made by US Precision Lens and are listed at 8 lbs each, but i swear they are over 10 lbs easy.


Shamelessly linked from: here.

Basically, I want to try to reduce the length of the projector, but I also want to use a 17" lcd which would require a longer length. I am hoping that the larger (5") size of this lens will be sufficient to cut down a couple inches. The table that I built to hold my current projector is 30" square on the base, so I am hoping that I can use this lens to build a 17" lcd projector WITHOUT having to fold it. (Mirrors scare me...)

Sorry for long first post that may seem like a dumb question. On the other hand, if this is a good lens and my projector turns out well, I'll have 4 or 5 extras laying around that I wouldn't mind sending away to good homes...

Thanks in advance for any responses. This website has been a constant source of information for me over the past month, and now that I'm a paid member, the hamsters in my head are spinning faster.

Unfortunately, those, and other lenses made for or salvaged from old CRT projectors will not work for this application. Those lenses have a very short focal length, as they were meant to sit directly on top of the CRTs they were projecting. They might work if you wanted to build a very small projector to play around with(like using a 3" casio LCD or something) but the focal length is just too short otherwise.

Sorry to burst your bubble...


-fly

Oh, no - didn't have much hope on this one. Thanks for the info!

I too have SEVERAL of the HD-6C-ML lenses that have been salvaged off of old CRT PJ's. These are very efficient 'FAST' lenses that already have focus adjustments (as well as corner focus correction). It would be cool to be able to take advantage of some of these Video Junkyard items.

I understand that this type of Delta CRT lens have VERY short focal lengths. They are designed to be mounted (more or less) directly on top of the CRT, only about 10-20mm away.

Would something like this work??



1. Point light source S400DD Lamp
2. Tempered glass isolation plate
3. 2 Fresnel lenses, a: 220mm FL collimator (condenser) and b: 220mm FL collector (field)
4. LCD module (17" Dell 1704FPT)
5. Correction Plate (220mm third fresnel??)
6. HD-6C (or other Delta CRT style) Projection Lens
7. Screen

A. Light Source with Spherical reflector
B. Light path

What are your thoughts??

Well, if by "work", you mean give you a nice clear bright projection of your "correction plate" then the answer is absolutely yes.

But no, there's no way. These lenses are perfectly sized for use with a 4" panel, and that's what I'm experimenting with now. But anything bigger or more than about 1" away from the rearward lens is totally out of the question.

You might be able to use that lens if you place a series of lenses before it. Although seriously you are better off to just scrap that idea and buy a triplet with the proper Effective Focal Length ( 12-24" ).

P.S. Is the housing of that lens Plastic or is it metal? I think I have a very similiar lens assembly here. I am just curious to know if they are the same. Also are the lenses themselves glass or plastic?

It looks like you have the glass deltas It should be a triplet just like mine with one vary short fl lens in the middle of 4.5" the front lens has a fl of 70" and the rear is a negative lens that is vary strong. If you want to use them and make a small PJ then the LCD will have to be the size of the rear glass.

The small LCD get better all the time the time. I saw one on a cannon camcorder it was 3.5" and vary high rez. On the one I had the tape drive was junk It had video in If I has known I might have tried to make a pj out of it.

The outside mounting cylinder is plastic, but the inner cylinder is metal. The lenses are glass. They came standard on a Barco Graphics 700. They also work on many other PJ's. I have 6 of the HD-6C-ML. They will also work on Sonys 10xx and 12xx series CRT PJ's.

I also have another (set of three) Noritar 14X Barco lenses that are all metal. Heavy suckers. These Noritar's were upgrades for the Barco Graphics line of PJ's and cost nearly $3000.00 when new. Will work on Barco Data/Graphics models, H/R, 400, 500, 600, and 700. The 800 series BD/BG (and above) series went to a 8" CRT.



I find it hard to 'scrap' any of these. The difference between these glass lenses and thier plastic counterparts is extreme in both brightness and sharpness. I'll hang onto them for somebody who wants to upgrade thier CRT PJ's old plastic Delta's.

After running CRT PJ's for years, I'm still not sure that I'll be happy with only 600:1 (at best) contrast ratio compared to 10,000:1.

I was considering using a Dell 1704FPT LCD panel, I have one at work. The Dell does look darn nice as a 17" image. HOWEVER, when I go out to look at commercial LCD and DLP front PJ's that have 2000:1 and 3000:1 contrast ratio's I still miss the deep dark black levels and rich skintones of the CRT world.

I'm currently running a Sony 1272q (with rapidly aging tubes) on a 8' x 6' (4:3) Da-Lite screen. Sony rates it at 1600x1200 but I find that beyond 1280x1024 you run into overlapping scan lines and seriously reduced sharpness. It will do 1280x720 (720p) very nicely, and so so at 1440x960 at the very maximum of it's sharpness. It starts to lose it 960p though (scan doubled DVD). I can pick up a low hour used one for about $600.00 or re-tube my existing machine for about $150-200 per tube (used). About the cost of a 'high end' LL PJ.

Interesting read. So what are you going to do? Retube or build an LCD Projector?

Maybe both!!

I wish that I was as good at understanding optics as I am with electronics. The LL project could provide some much needed help there.

I will most likely build a LL LCD to run on a smaller screen (60 inch??) in my computer room for my fright simulator (ooops flight). I already have the LCD panel that I think will work well (the aformentioned Dell). I was just trying to do it on the cheap by using what I have on hand. It does look like a FUN project. I guess I'll break down and go for the Pro Triplet combo.

For the 'theater room' (basement) I will most likely either re-tube the 1272 or upgrade to something with fresh tubes and higher res like an NEC 9PG+. I'll probably do th LL project first though just to see how it compares with what I have.

Has anyone used any of the lenses from Edmund Scientific??

One other possible option that I had not yet considered is a retrofited overhead projector.

I want to use mine for flight sims too.

I "retrofitted"my OHP(Dukane 4000).Just used the top deck(w/glass and collimator fresnel)and the arm with triplet(see "1000w MH BLISS").I cut a hole in a coffee table and slid a 1000w halide monster underneath it.Overhead projectors have good lenses.Most of them will work well with Lumenlabs designs.

It is a shame not to use those lenses. There is some high rez car LCD I just saw with 1024/768 native for less than $200. If you go with some small LCD your PJ will be nice and small. It might be worth it to top off your $3000.00 lens with a top of the line LCD.

I love some of the new LCD displays they use to look flat and lifeless but some of them look better to me than most tubes I have ever seen.

Good luck

Where? What size? I'd love to get my mitts on one of those if my current LED + CRT lens + 4" LCD setup works OK.

An issue I ran into with the CRT lens was that many are made to focus on a curved CRT. When trying to focus on a flat LCD center or edges could be focussed. The other was blurry.

Really??

I have worked on dozens and dozens of CRT projectors over the years and I am not aware of any that have a curved surface on the CRT. All that I have ever seen are perfectly flat. Some PJ's can be converged be used on a curved/torus screen though. Thats one reason the Delta lenses have two focus rings, center and corner focus.

My Mits. lens was like that and and I just had a delta lens with the same problem. The delta I had did have the 2 focus points. Not matter how I adjusted same results. Not all the Delta's are the same. I actually contacted 3M and they had gave me the same feed back.

In review of the Mits CRT it is flat on the outer surface but the inner surface is curved.

I had found people on other websites having the same issues.
Quick search found these.
http://www.lumenlab.com/forums/lofiversion....php/t9480.html
http://www.greenspun.com/bboard/q-and-a-fe...l?msg_id=006hui
http://www.diyaudio.com/forums/showthread/t-19644.html

Somewhere I had seen a chart listing the Delta lens and which were for a flat CRT and which ones for a curved CRT.

I would love to see that chart if you can dig it up... I'm trying to use a delta II (which arizonavideo said he got to work, so hopefully when it arrives it will work with a flat image), but have noticed there are a wide variety of delta lenses on ebay, not to mention all the other brands.

Hey i hate to steal this diagram but it works perfectly for the idea i had as i was looking at this. If you put a small rear projection screen in the place of the third fresnel, wouldnt the image on the rear projection screen be projected by the lense just as if it was a mini crt? given it would take a lot of light to project "through" the screen and onto a wall. and also in this scenario the projection lense would have to be one for flat screens.

"Edit"

Well im gonna try it and see what happens on my 7" build i just realised last night that the delta II was a rptv lense somehow i missed that when i looked at surplusshed's website "dumb moment" gonna expermiment with that till a decent replacement lense comes in. i have a feeling that the brightness will be lowered since the light will be passing through an additional screen before the lense. oh well live and learn right?