Distorted image?

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Hi,

I'm in the process of building a projector, using the "lcd in a box" setup (similar to the one at http://www.geocities.com/zark5150/projector.html) rather than the OHP based setup. I'm using a 5" TFT LCD from www.partsexpress.com, and a Delta 67 lens from allelectronics.com. The problem I'm having is that it's impossible to bring the corners of the display into focus, which sort of makes sense to me since I'm usin
 
oops

OK that was nice, my post got cut off and sent in the middle of typing (probably due to the ps/2 joystick I have hooked up that likes to send random extra keycodes.. but I digress...)

Aaaanyway..

The problem I'm having is that it's impossible to bring the corners of the display into focus, which sort of makes sense to me since I'm using a flat display and a curved lens (as oppossed to a fresnel), but I'm wondering why no one else seems to be having this problem? I noticed most of you are using the Delta IV lens, is there some difference between that and the Delta 67 I'm using that I'm not aware of? I do need to move the display back about 3/4 inch from the lens since the lens diameter is slightly smaller than the LCD panel.. does this have something to do with it?

Yes, I've triplechecked measurements and the center of the LCD is aligned with the center of the lens.

Forgive me if this question has already been answered, but I've read the vast majority of the threads and it didn't see this touched upon anywhere.

Thanks..
 
alot of people are have had that problem using the DELTA projection lenses... the guy you want to talk to is JP (uvodee),
he has gotten the delta 67 i believe to work fine with a 5" LCD.. i believe he used a fresnel between the light source and the LCD though, maybe try that?

Just curious, what sort of light source are you using?

Jay
 
I'm planning on using a 7-10k lumen or so LOA (haven't found one yet, prolly gonna make a walmart/home depot run in the next day or 2), but for now I'm testing with the built in backlight in a pitch black room.

Could this have something to do with it? My gut instinct is no, since the LCD is evenly lit either way, but hey, if I knew everything I wouldn't be asking questions here. :)
 
i would keep it simple!

i used a simple trick......

i used a frame(made of photoboard) between lens and lcd in order to have a rectangular projection through the lens, for each projector (i made 3 with loa's) i made 2 frames , one to watch tv and one that is needed when watching widescreen (smaller opening)
it also eliminated screendoor effect .
the angles are pretty square , there may be some curve (no distortion however), i noticed it when i delivered one projector to a customer, he projects more than 100 inche and i noticed it , but he did not complain!

for technical specs you need to ask gunawan.... his postings were a guideline allthough i have never recovered from his posting about fresnels...... sigh ................
 
photo board

some material we use to glue photo's onto used of conventions, tradeshows, presentations etc.... i will find out where out co. gets it from, i just take the used stuff hone whenever i need a piece......

it's slightly foamy, about 1/4 " think and usually comes in black
 
Gotcha. Apparently this stuff is pretty hard to come by, or is commonly known by another name, because I've searched a TON of camera/photography stores and only found "photoboard" available at http://www.castlecameras.co.uk/newlist.htm (Vinyl Photoboard, 40 leaves £8.90), but I'm not sure if this is even the same thing.. it looks like they might be talking about pages for a photo album.

Also, approximately how big should the frame be? The same size as the screen or...? I take it size does matter here if you're using 2 seperate ones for 4:3 and widescreen.
 
photo board

the board is about 1/4" think so they are not really pages.

the original name at office depot and office max is 'foam board"
around here you can get it quite easily.. i doubt however that you can order it by mail, the stuff is ratehr delicate and any mishandling creates an mark.


the boards i made had each a hole in it
one had a hole corresponding to the lcd panel size (5.6") but minus 1 mm on each of the 4 sides.
the other one had the size of the widescreen format projected on the lcd panel. i just measured it, deducted 1 mm of each side and cut the hole.
my panel is a 5.6" i needed the 1mm, otherwise the delta lens would had been exactly the same size as the panel and for some mysterious way, i cannot remember exactly, i decided the picture HAD to be smaller than the lens (read this Gunawan!!! very important)


but i guess if you work with a 4 or 5" lens, the latter is not important.
if you work like the pics i posted, i know you will succeed, it is actually much less complicated than most of us think.
 
Re: oops

delusion602 said:
The problem I'm having is that it's impossible to bring the corners of the display into focus, which sort of makes sense to me since I'm using a flat display and a curved lens (as oppossed to a fresnel), but I'm wondering why no one else seems to be having this problem? I noticed most of you are using the Delta IV lens, is there some difference between that and the Delta 67 I'm using that I'm not aware of? I do need to move the display back about 3/4 inch from the lens since the lens diameter is slightly smaller than the LCD panel.. does this have something to do with it?

I have a Delta 67, Delta 77 and a Fujinon. I ended up getting data sheets and info on the two Delta's, and found out that both of them are definitely designed for curved faceplate CRT's, and therefore you will be unable to use them with the flat lcd at all, even with adding fresnels or whatever. You would need some complicated optics to use them I think. I don't know about the Delta IV, some people seem to have used that OK, so it must be fine I suppose. The Fujinon is definitely for a flat CRT, and so works well. There was quite a bit of discussion on this about 6 months ago, search for Delta.
 
Uvodee, ah ok.. i know what foam board is, just hadn't seen it referred to as photoboard before.

Muzz, thanks for confirming my initial suspicions about the lens.

I'm gonna pick up some foam board, try to find a fujinon lens, and get down to some tinkering. :)

I also have a 2nd lens coming later today (http://sales.goldmine-elec.com/prodinfo.asp?prodid=6967) that I'll give a shot, but it looks like this is designed for a convex display as well.
 
me dumb, very dumb!

i have no idea what you are talking about
the screen fills up with clear image from left to right, top to bottom



Jean-Pierre




"there is always some one in this world that can make things cheaper, faster and better than you! "

my grandfather
 
Re: lens

MuzzMan said:


uvodee, you are using the delta 67? How?
How are you correcting for the out of focus edges of image?

I'm wondering the same thing. I tried the black photoboard mask (opening around 1mm < the usable size of the lcd panel on all 4 sides), and it did seem to help a LITTLE, but definitely didn't correct the out of focus corners enough to be watchable. I have a little less than a 1" gap between the lens and the lcd to allow it to focus and I tried placing the photoboard up against the lens opening, up against the lcd panel, and everywhere in between. One thing I haven't tried yet is to place a few pieces together to completely fill the gap between the lens and lcd and basically create a tunnel between them, but I'm rather skeptical that this will work as well.

Maybe I'll just go ghetto and use a page magnifier fresnel =)
 
getho

bulbs-fresnel-panel-foamframe-delta


this ist he only way i succeeded, maybe there are other ways nut i tried many set ups, for me this is the onl ly one that worked i still think i should use a 'better' fresnel but haven't found a glass one yet that is reasonable in price and shipping.
 
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