FUJINON COPY LENS won't do you any good?

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EasyPrey

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Joined 2003
#1
Just bought FUJINON COPY LENS, 240MM FL (http://www.surplusshed.com/pages/item/l3003.html) to use with my 10" LCD (OHP Panel actually) and it seemed that I can't use it without fresnel between panel and this triplet - lens angle won't catch all the screen - that's probably ok.

Even when I do, image became dimmer than if I wouldn't use it at all and just put 'outer' fresnel not close to panel but at it focal length point.

That is this set up (< - lamp, | - collimating fresnel, ! - lcd, | - fresnel2, () - triplet):
========
< | ! | ()
========
gives worse image than this (lamp, collimating fresnel, lcd, fresnel):
========
< | ! |
========

I wonder if I'm doing something wrong or it make sense (adding more glass reduces light coming through it) and we need triplet only for better controlling image focuse, ability to move setup, etc?
Personally I hope I won't need second fresnel with it - but it seems to come out differentely 🙁

Thanx!

P.S. I hope 'pics' are understandable. Didn't expect I'll love 'em so much 😀
 
#2
well i can tell u now there is nothing wrong with that copy lens, im using one and i dont have a problem with it, it must have somthing to do with your focals, it seams like to me u are focusing on the bulb rather then the lcd, in my last one i had it set up in such a way that with no lcd i was focused to the bulb due to modiftying focals, and when the lcd was in place it made the lcd brighter but i could see the bulb through the frensel, this isnt the way to go about it with a high class lens, lower class lenses distort the image therfore making this type of focal manipulation possible, but with a good lens u are out of luck, they only show what u give them so if your focals are out ajust them to work with the lens, to me it sounds your frensels focals are too long for the copy lens.

Trev
 
#3
Thanx Ace 🙂

I still don't get it. Do you have second fresnel between LCD and triplet? It seems to me this copylens angle is not wide enough to capture 10" lcd - that's why we need second fresnel to throw a less picture to lens focal point.
Is that correct?

And if I see sharp but dimmer picture with this lens _and_ fresnel - it means (accourding to your explanation) that focal is right for triplet but wrong for light source, isn't it?
 
#4
heya easy prey, to me the focal on the triplet is abit too short for that size lcd, with a frensel up the front of the lcd that will actually make things longer, i use only 1 frensel behind the lcd and always have, the frensels i use are also differnt types, they are page magnifiers wich are much thiner and brighter then a standard frensel, but they do have fewer rings if u get a crap quality one but most are ok and collimate light well, if i was u, id try to use just 1 frensel behind the lcd and see how that goes, make sure also the light is the right distance from the frensel so u have the right focal length for the frensel to work properly. Also are u using any mirrors?

Trev
 
#6
Actually that's exhactly what I'm doing 🙂 I'm using page magnifiers (they seem pretty decent to me 🙂 and Surplushed recently f%$%up my OHP fresnel shipment anyways, heh) and I don't use any mirrors - I've made kinda prototype using perforated board from Home Depot so I can sort of easyly move things inside.

I've calculated fresnel focal as 300mm, i.e ~12" and placed light source somewhere around this point.
When my copylens arrived I have removed second fresnel (after lcd) and put triplet at it's focal point ~10" (I understand that's exhactly what I had to do):
====================
< -----12"----- |! ------10"------ ()
====================

What I saw on screen was rounded version of my lcd with all corners cut - it was sharp but looked like picture of my lcd at len's focal point was too big for it.

When I put second fresnel back I saw whole picture :

=======================
< -----12"----- |!|-----12"+10"------ ()
=======================

but it was dimmer when without triplet at all. May be because projected image size became bigger actually anyways that's not important I hoped to use triplet and leave only one fresnel. May be I was wrong though..

You use first setup with your copylens and see 100% of your lcd, am I right?

Thanx, man 🙂
 
#7
You use first setup with your copylens and see 100% of your lcd, am I right?
Click to expand...

yup but my lcd is 7inches wide screen so its abit smaller then yours but not that much, with u having the corners cut that means the lens focal is too short for its feild of veiw so what we need to do is to make that copy lenses focal a tad longer, im suprised that the 10inch is too big for the lens actually, the whole image should fit, what i do as a fast way to see if i can project a certain size lcd thorugh a lens is look into the front of the lens at its focal distance away from the lcd and look through it at the widest angles to see if u can see the edges and corners of the lcd, that is a fast acurate way to soon see if the lenses feild of veiw is wide enough and a way i measured mine to see if it would work on this 7inch lcd i have, im getting more of those copy lenses in a couple of weeks from surpluss shed so ill run a few test to see if it should work or not, the copy lens i have now is in a position that i cant test it for a 10inch lcd other wise i would do it now for ya.

Trev
 
#8
Good advise, thanx - I'll try. I beleive I see area with d=~9". It means 7" should fit in it. Alhough if it's wide screen it might not 🙂

Anyways I'd appreciate if let me know about your test with 10" panel. Thanks in advance! 🙂

Btw, what kind of 7" u use? That Monitor/TV pane for $200 from ebay?
 
#9
ya i use the lilliput vga wide screen from ebay, it projects nice, its about 2-3x clearer then my tv if not more, and thats projected at about 140inches. If u are going to go smaller i dont recomend to go under 640x480 native in reso and not under 200:1 in contrast.

Trev
 
#14
Thanx 🙂

btw I made a mistake in this scheema:

=======================
< -----12"----- |!|-----12"+10"------ ()
=======================

it actually doesn't work :smash:

I've got image only if I do it this way:

=====================
< -----12"----- |!|-----11"------ ()
=====================

That is triplet is even closer to fresnel (or may be it just seems to be so).

That is using second fresnel and triplet doesn't actually increases the length of projector.
Another funny thing - I'm getting sharp image only when triplet is about 10-11" close to fresnel and it still cutting ~5% on both sides of screen! :hot:

If I move triplet further an inch or so - 100% of screen appears but image became out of focus.

Spent a day making sandwich of panel and fresnels just to know that may be I still don't need a second fresnel at all :smash:

looks like I have to go back to freaking school, heh 🙂
 
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