Modifying the 135mm Triplet from DIYPC

changing triplet

I have seen pics of it disassembled.

You turn the threaded retaining ring until it comes out. (This can be very difficult.)

Then all three lenses come out easily. There are two plastic spacers that fit between the lenses. You can experiment until you find the exact spacing you want. Then you just modify the old spacers or make some new ones. Put it back together and you are done.

Not varifocal, but easy.

But before you modify it, try it with a 15" LCD. I have seen pretty good results with a 15" and unmodified 450 mm fl triplet.
 
Re: changing triplet

Guy Grotke said:
I have seen pics of it disassembled.

You turn the threaded retaining ring until it comes out. (This can be very difficult.)



Tell me about it! I tried unscrewing that thing last night... its impossible... I hope I was turning it the right way (counterclockwise) I was thinking maybe Ill have to make a tool to do this using some thick aluminum sheeting...


But before you modify it, try it with a 15" LCD. I have seen pretty good results with a 15" and unmodified 450 mm fl triplet.

Ive tried it, (just holding the lens in my hand) and wasnt able to get the whole LCD into view and focussed. In my setup Im using the standard lenses from Lumen Lab (220 rear/330) front. I was able to get the whole image lit if I put the bulb closer to the rear fresnel (about 6" from it). All the reading Ive done about this lens has confused me a bit... Has anyone gotten corner to corner focus using this lens and a 15" LCD with the bulb the proper distance from the rear fresnel?

According to DIYPC you must use 330/330 fresnels unsplit with the bulb 5.5 inches from the rear fresnel to get this to work. IMO while this setup may "Work" it kinda flies in the face of all the optical theory Ive been trying to learn. Id rather not build something that I dont understand why it works because if there is a problem down the road it may be difficult or impossible to figure out due to the "unconventional" design of the projector. Thats why I figured Id go the "Modify the Lens" route.

There are pictures of the process "Diyeitor17" used to modify the 135mm triplet and his results here http://diyprojectorcompany.com/phpB...topic.php?t=381
and also on his website http://usuarios.lycos.es/diyeitor17/ Note that he is using 330/330mm fresnels.

Yes I saw this site before but he didnt really explain what he did...
 

Rox

Member
2004-07-25 10:06 pm
?
well, 330/330 isn´t the only way to go now, you can use the new 550mm fresnell with a 220 rear fresnell as well.

About the 15" and 135 triplet compatibility, well, everibody knows what I think.

GG can you tell us more about that 15" and 135 triplet succesfull setup? What about your projetor? (you have 135 triplet if i am not wrong...)

I think the 135 triplet ouners need to prove it works to all of us.
 
>> About the 15" and 135 triplet compatibility, well, everibody knows what I think.

Yes... I know what you think about this setup...

However.

What do you think about the Modified lens with this setup? Do you think it will work... or is it another sham (ala... the 135 is a replacement for the 80mm without completely redoing your projector)
 

Rox

Member
2004-07-25 10:06 pm
?
about the triplet mod on the 135 triplet, i beieve itis the best way to go with this lens and large panles (large=15 and up).

The FOV will be big enough to cover the lcf, but the performances in there will fall considerably. Anyway, those bad performances overal in full 15-17" lcd will be better than the overal performances in the non modified 135 triplet when used with large panels.
 
15" LCD with big triplet

I have used a 600 mm fl process lens to see perfect optical performance in my 15" LCD projector. (220 mm fl condensor fresnel 220 mm from lamp arc, 770 mm fl field fresnel with about 100 mm to LCD) That lens gives me red, green, and blue sub-pixels focussed clearly from center to corner with very dark screendoor between pixels.

With my 18" fl (457 mm) 135 mm diameter opaque projector triplet, I get more light on the screen, but the sub-pixels focus at either center or corners, not both. I still see the individual pixels and a lighter grey screendoor between pixels, over the whole screen.

From more than 4 feet away, I can't see much difference between the image quality, other than the opaque projector triplet image being brighter. I have one of the new 550 mm fresnels on order. I think that will get more light into the smaller process lens. I'll let you know.
 
I did a test last night with my current setup...

I currently have a 220 rear and a 330 front fresnel unsplit

I moved the bulb to 5.5 inches from the rear fresnel...

The throw distance is about 8 feet

Just holding the 135mm triplet in my hand... I noticed 3 things

1) The lens needed to be ~20 inches from the LCD to get a focused image

2) It seemed like I couldnt get the whole image to focus at once.

3) The corners were dark
 

tjh

Member
2004-12-30 5:35 am
RI, USA
Luca Brazzi said:
I did a test last night with my current setup...

I currently have a 220 rear and a 330 front fresnel unsplit

I moved the bulb to 5.5 inches from the rear fresnel...

The throw distance is about 8 feet

Just holding the 135mm triplet in my hand... I noticed 3 things

1) The lens needed to be ~20 inches from the LCD to get a focused image

2) It seemed like I couldnt get the whole image to focus at once.

3) The corners were dark

I don't really get where the 5.5" came from, I used diyetor17's plans and it worked well (though my throw is 12'), and his plans used 2 330 fresnels with the lamp ~20cm behind the 330rear. (http://usuarios.lycos.es/diyeitor17/)
 

tjh

Member
2004-12-30 5:35 am
RI, USA
Ok, makes sense now. No I haven't modified the triplet, but the design worked fine with a little tweaking. I would have gone with a pair of 330mm fresnels again (my current ones are too small) but I figured that since I was ordering fresnels I might as well get the right ones and order the new 550mm ones. But two 330's did work just fine for a while, no modification to the triplet needed.
 
tjh said:
Ok, makes sense now. No I haven't modified the triplet, but the design worked fine with a little tweaking. I would have gone with a pair of 330mm fresnels again (my current ones are too small) but I figured that since I was ordering fresnels I might as well get the right ones and order the new 550mm ones. But two 330's did work just fine for a while, no modification to the triplet needed.



So you get perfect corner to corner focus and brightness with an unmodified 135mm triplet on a 15" LCD using 2 330 fresnels unsplit?
 

tjh

Member
2004-12-30 5:35 am
RI, USA
Well I'm using a 14" LCD but about .5" is cut off on each side because the fresnels are so small (from an OHP as that was my original plan). I don't have a working digital camera anymore, so cant really post pics at the moment, but when the lens is perfectly focused I can see every pixel, center to viewable corner. I tend to leave it a bit out of focus though to fade the screen door effect a bit. When moved that slight bit the first things to go out of focus are the corners, so when compensating for screen door the corners are a bit more blurry than the center. With that in mind it would make sense if with 15" LCDs the corners are a bit blurry, but maybe not, I have no idea what the exact threshold is, or how to find out. I have always found though that each lens, be it fresnel or objective, has its own quirks, so it is usually best to use the equations as a guide and then just play with things a bit.

I haven't updated my site for a while because of the digital camera problem, but I'll try to borrow one or something and post some current pics, as well as some when the new fresnels arrive so you guys can compare b/t focus with a pair of 330s and a pair of a 220 and a 550. (Once those arrive of course.)

@Luca- About 20in from the LCD seems about right, I threw your data into a quick excel sheet I put together for this stuff and it spat out 21.73" for a 15" at a 8ft throw, so it should be somewhere around there. Maybe a bit further from where you were trying you could get the focus you want.

Edit: I also followed diyeitor17s instructions and used a heat gun to warp my front fresnel a bit, which may help. The biggest problem I found was that it was really hard to keep the bend consistent, and with the rapid heat changes I now get a few dark curves resulting from messing up the fresnel in those areas (light being directed in the wrong directions). As far as I can tell that may have helped with the corner focus, but it does suck having partial rings in the image now :xeye: Probably wouldn't suggest taking that route ;)
 

Rox

Member
2004-07-25 10:06 pm
?
well, i understan now :D

you have firstof all 14" LCD, then you say it is 0.5 inch smaller your fresnells each side, (does it mean 13"?) and finally you have relativelly short trhow. All this conditions make the lens work at a point very close to the expected FOV by the lens, and even that you say there is sighly blurr corners.

well, I believe your image is more than enough for that setup. But I think you can´t say it would work as good as now with a 15" and a something longer throw (not to talk about 17"...)

Anyway, I know it will be very soon tested with the new 550 fresnell and 15 and 17 users... so we can have an statistical sussesfull/wrong setups meassurent. More testers will show more realistic coclusion and if they are shown with atached images of the projections, even better. Good luck!!
 

tjh

Member
2004-12-30 5:35 am
RI, USA
Actually my throw is pretty long, 12 feet. So if your saying that the shorter the throw the bigger your LCD could be than it would be plausible to say that a 15" would be good with a throw of only 8' or so, but I'm not sure as I haven't tried that myself. Definitely can't wait to try the 550mm fresnels though! :D
 
Hey! Rox can/should keep on mentioning that the 135mm projection lens doesn't work for large panels at least until diyprojectorcompany.com accurately and precisely edits the product description on its online store. I almost trusted its claims and purchased it until I saw the problems mentioned by Rox and others and I'm sure future DIY'ers will be misled into purchasing a $120 lemon.
 
CCMCornell said:
Hey! Rox can/should keep on mentioning that the 135mm projection lens doesn't work for large panels at least until diyprojectorcompany.com accurately and precisely edits the product description on its online store. I almost trusted its claims and purchased it until I saw the problems mentioned by Rox and others and I'm sure future DIY'ers will be misled into purchasing a $120 lemon.



The thing is... there are still folks around claiming that it works well, although to date I have yet to see one single projector design that uses this lens (unmodified) with a 15" or larger LCD that is getting corner to corner focus.

I have one and would have tried to sell it, but I can use it on my next PJ which will be a 7" lilliput design (if I can get up enough nerve to strip the LCD that is ) :xeye: