CurtPalme.com Home Theater Forum

tse · Joined: 03 May 2006 Posts: 1014 Location: Sweatbucket, Fl.

I need to find a short throw lens for a DLP projector that has LED light source. The DLP is the 0.96" diagonal, the throw distance is 112", and the lens needs to be 0.9 to 1.1. You would think this would be easy but the DLP lens has to be located almost 2" from the DLP imager. There is some type of prism gizmo between the DLP and the end element of the lens.

I"ve tried a few different lenses and those for LCD and LCoS projectors can't get close enough to the imager to focus. The DLP lenses are made for the 0.67" diagonal imager so the lenses end up being like 0.7 or 0.8 with the projected picture being too big at the required throw distance.

Any ideas?

Scott

mp20748 · Posted: Fri Nov 12, 2010 12:30 pm Post subject: Re: Lens for DLP/LED projector

Spanky Ham · Joined: 22 Mar 2006 Posts: 5643 Location: Comedy Central

CJ used to have a couple of DLP lenses.

tse · Joined: 03 May 2006 Posts: 1014 Location: Sweatbucket, Fl.

Hi Mike,

Thanks for the offer. That is very kind of you.

The lens in your picture is a 1.5 - 2.2 : 1 throw lens. That means picture width (minimum) = projector distance from screen / 2.2 and picture width (max) = distance from screen / 1.5. So if projector is 10' from the screen the picture can be adjusted from 4.55' to 6.67' wide. I'm sure you know this I'm just mentioning it for reference.

I need a lens that is more like 0.9 - 1.1 : 1 so the picture width is about the same as the projector distance from the screen.

The size of the DLP plays a part in this, too. Larger imager means larger projected image. Alot of the DLP imagers are 0.67" diagonal so would be 0.536" wide (if 4:3 aspect) and 0.583" wide (if 16:9 aspect). The imager that I'm dealing with is 0.96" diagonal or 0.814" wide. As far as I know only native 1400x1050, 1920x1080, and 1920x1200 DLPs are this size.

Apparently the different projector technologies require the rearmost lens element to be located at different distances from the imager with LCD and LCoS having a very small distance and the DLP types are much further away. I'm pretty sure that only a lens designed for DLP projectors will work because of this.

A custom mounting arraignment will have to be made. Probably every manufacturer has their own way of mounting the lens to the projector. Check out my lens positioning set-up.

Scott

garyfritz · Joined: 08 Apr 2006 Posts: 12026 Location: Fort Collins, CO

Nice, Scott! Is that some spit and baling wire I see just behind the lens??? Laughing

**AnalogRocks** · Posted: Fri Nov 12, 2010 4:35 pm Post subject:

Whoa.....where's the duct tape? Very Happy

dturco · Posted: Fri Nov 12, 2010 5:04 pm Post subject:

Rube Goldberg would be proud Smile

mp20748 · Posted: Fri Nov 12, 2010 5:31 pm Post subject:

Hey Scott. I'm not sure if there's a particular lens set for DLP and something different for LCD.

I took a few shots showing where the lenses fit into three different digital projectors. I'm thinking based on what I'm able to see looking into the projectors themselves is that it all depends on where the lens is mounted to the assembly. I'm sure I'm most likely wrong on this, because I very little experience with the lenses on these projectors.

Anyway, I'll make a few calls and see what's out there concerning lenses. I'll see if I can get a picture first and send you.

Barco SIM 6 Ultra 2 - LCD

Uploaded with ImageShack.us

Uploaded with ImageShack.us

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Christie Digital Mirage - DLP

Uploaded with ImageShack.us

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Panasonic WXGA 6000 - DLP

Uploaded with ImageShack.us

No problem at all if we can help with this. We/they know you'll do the same for us.

.

tse · Joined: 03 May 2006 Posts: 1014 Location: Sweatbucket, Fl.

It looks like the DLP projectors are similar. There is a thick chunk of glass between the back of the lens and the actual DLP imager. That keeps the back of the lens from getting too close. Some lenses can't get close enough to focus. I think those are the ones made for LCD. There is nothing to keep the lens from getting close to those. That has been the problem that I've ran into while checking out a few different lenses. They just can't get close enough to focus.

And all you guys making fun of my lens positioner, phhffffft! Mr. Green

Whaddda ya want from an electron pusher? Imma notta optical expert.

Scott

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

Actually, I do have two lenses which MIGHT be of some utility.

They're the two Minolta DLP zoom lenses made for the early generation 3 chip DLP machines. One is the 1.5 to 3.0:1 lens and
the other is the 4.0 to 7.0:1 lens.

Scott, you're welcome to use them if you want.

CJ

pbody140 · Joined: 10 Jun 2006 Posts: 5 Location: ORLANDO

.9 to 1... ive been looking for one of those for some time... let me know when you find it!

only other option is navitar or similar...