Hotspotting Issues

[ace3000_1]

drucal dracul dracul lol dont difuse the light, hezz is right, the lcd will diffuse it but with colour from each pixel, also the light from a lcd is polarised and not just normal scatterd light, to get light over a frensel perfectly even is not doable my man kind, its the science of it, as i said right now get yourself a proper reflector and condenser and u will see a major improvement, a frensel and light on its own is a waste of time and with that shop fitting reflector u have it will make it worse. All difusing the light will do is give u less light with no intensity and added heat.

Trev

[dracul]

I need to be sure that the lcd will even out the light for sure a lot.
I cant return the monitor and get my money back here once I get it. As you can imagine I am ready to throw in the towel and start saving for a commercial projector. What I dont want is spend another 300 bucks and end up with a crappy image. Which would be $800 out the window pretty much.

Have you tested this Ace? Is there a big difference in what the lcd does with the eveness of light?

[dracul]

Is there anything at all I can use to simulate what the lcd would do with the light? Anything?

[dracul]

I dont think tweaking the light engine will have a dramatic effect because the light hitting the first fresnel is reasonably even not as even as the 400 watt hqi but its good enough to get decent results. Thats my gut feeling after the manyyyyyyyyyyyy hours of screwing around. Also the new OHP projectors I saw in the stores displayed the same results which seems to point to the only logical possibility that the lcd will even things out a lot.
Btw, one OHP projector I saw had a reflector and condenser in it. I saw it when they changed the bulb. It was just as uneven as my setup maybe a hair better.

[ace3000_1]

dracul the condenser and reflector give u about 3-4x the brightness more then without it, ive fooled more hrs then what u could imagine with light engines lol, and im telling u this is the way to do it, get your lcd first, then fool with the optics, to get my light as even as i can i just have the lcd turned off, once u have it at its maxed out coverage and brightness turn the lcd on, i can garentee u that u wont see the brighter part in the middle compared to the outer edges not unless u have somthing like a billion lumens coming out of the 1 spot on the frensel, or it could be only noticable when u have a white screen like surfing the net, im glad u went out to see a comparison with a ohp, but ill tell u now ohp's are cheap, u can get way better results building your own light engine then the way ohps are made, pyramids is also a great way to even the light out and to make the edges brighter, i dont have a problem with edges in mine becuse of the condenser ive selected and becuase ive done my light engine in a different new way, with that being said it doesnt mean my new way will work for u, but its also saying it might aswell, just take your time, get your light engine parts, get the reflector, the condenser and your lcd, and have a fool around to get it right with the right parts and how it will be set up, do u know why the pro projectors have a more even light dracul? do u know how they do it? well for staters their reflector is bigger then thier lcd, then the condensers are also bigger, so what they have is a very big beam of light the same size as thier lcd the beam is condensed to the size of the lcd and nothing is made out to a wide beam, if u had the same lenses they had at the size for a 15inch lcd u could get the same results, but when u have such a tiny point sorce to go out to light such a big area u will get a hot spot in the middle cos thats where the light is coming from, the middle, so to make things better u make a pyramid that will light up the surrounding sides of the lcd to compensate for the brightness from the actuall light source, its been done , its been proved and even im going to use one on my small 7inch, u get a far brighter image and the light is much more even, even though i dont have that problem im still going to use one to utilise the maxium light i am getting from that bulb, every lumen counts, its just a matter of where u place it and where u want it to go.

Trev

[Hezz]

Dracul,

I have to concur with Ace. The cheapest and easiest way to increase the eveness is to enclose the light engine in a reflective trapazoidal shape and the best way to increase the brightness is to use a reflector and condenser lens. Without these items probably less than 10 % of the light from the bulb is getting to the fresnel. By the way the trapazoidal light pipe will also increase the brightness as well becasue it utilizes much of the off angle light creating a more diffuse light wave at the fresnel.

Check out crusers projects to get an idea what he is doing. Ace's new design seems to have a lot of merit but it might prove too expensive for LCDs of 15 to 17 inch size because of the higher coast of multiple large fresnels.

Hezz

[dracul]

have to concur with Ace. The cheapest and easiest way to increase the eveness is to enclose the light engine in a reflective trapazoidal shape

Ok. What do you recommend to use for material inside the pyramid? Mirror too much? So the trapezoid has how many sides 4 or more?
Ok. Ill check out aces threads. But damit they are longggggg...

[Hezz]

Dracul,

So far I think that cruser has come up with the easiest method. Using 1/4 inch thick acrylic sheet. Go to your local plastic sign shop and they usually sell small remnants for 1-2 USD a pound. Then make the tapazoid out of clear plastic and line it with reflective mylar sheeting which is the stuff used in hydroponic bays to reflect light. That is one option but you have to deal well with the heat because it can melt the mylar.

Method two is easier but somewhat less reflective. Get some lightweight aluminim sheeting which is as shiny as possible. Then bend it and fasten it with rivets or duct tape for temporary.

If you are using a small bulb HQI light then you can make a very high quality reflector for cheap from a PAR halogen sealed light bulb. Check the treads back a ways I beleive Mathias had the idea and the PAR bulb makes an effective reflector. However this will only work if you are using a small bulb.

Check out crusers thread on the bumble bee projector to see his methods.

Hezz

[ace3000_1]

hey hezz, there is actually some polish u can get for alloy magg wheels, in aust its called mr mag, its a metal polish with a medium cut back and to be honest ive never seen anything polish metal up like this stuff does, it will bring old oxidised alloy to a mirror finnish, its somthing i was going to use on my light engine instead of mylar but do u think i could find it here? lol, ive used it before on some quadrifilar antenas i used to make and i could see myself in the antenna radial everytime like looking in a mirror, so maybe this could be an option on the alloy for a mirror finish.

Trev

[Hezz]

Trev,

That is just the kind of stuff that I need. I went and bought some small pieces of stainless steel because I thought that it would polish better to a mirror finish. It does but it's a hard alloy to polish so the typical mag wheel polishes just break down and don't do anything. I'm leaning towards polishing aluminum. I know we can do it with the very fine grade grit that they use to polish telescope lenses. But it would be nice to find a single product that would work. I'll try and see if I can find any of this stuff. In fact I think they use a chemical deposation method to make very fine mirrors out of some aluminum alloy so it should polish to a very high quality finish.

Dracul,

Chech out Crusers thread called "Another quick peek" it is not all that long but has lots of photos of his light engine design.

Hezz