DIY Video Projector Part II

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i thin i found my favorite:

Philips ALUline...
 

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reflector for the big one's

Ok so the PAR desing is nice for the smaller single ended 150w CMD lamp. But what about the dubble ended one's or the single ended big one's (mogul based). 400w or 250w. Why design our own reflectors when these are used in reef holding! So i searched for a test on these reflectors and found a great article:

http://www.advancedaquarist.com/issues/mar2003/feature.htm

I couldn't believe the results of one of the reflector.

Diamond Light – Lumen Arc III:
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Look at the even light output!!!!!:

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Very great for people with a larger than 7" screen.

one drawback: The reflector is 19"x19". But maybe we can make a smaller design?

It can be bought for 149$ at http://www.coralfragz.com/drygoods.html
 
diyAudio Member
Joined 2003
2 frensels together make a big dual condenser lens, now inside of the double condenser structure cos u are using 2x plano convex lenses (frensels) we have a gap that gives us the paralelle rays and they are the rays that go through a lcd paralelle, this is ofcourse if u have the lcd inbetween the 2 fresnels, the other way is to have the lcd after the 2 frensels but in that way the fresnels have to be slightly bigger then the lcd as the rays are going through the lcd slightly offset to perpendicular of each pixel, depending on focal there are advantages and disadvantages in this system, also if u use paralelle rays before the frensel good luck in finding a condenser the same size as the reflector, as u know a condenser can intensify the lights intensity by 3x (dependant of the power), this will yeald us a brighter more intense light, its the same with using 2 frensels, 2 frensels are always brighter then just 1, if u wer to use the system above the light would be difused scatterd light, and also it wont have much intensity with just 1 frensel and just 1 condenser if u want to find one that big, the best way for projection and the eficentcy of using the majority of your light is a reflector with a focal point, the light reflected from the reflector will go back through its source, the frensel with also a focal point will gather the light directly from the focal point of your condenser while the condenser will gather all light from the point source of the bulb, an improperly matched condenser can loose us asmuch as 60% of our light, its just as important as our reflector, typically with the right matched condenser and reflector combo using a spherical reflector and a condenser u can achieve 80 - 90% from the source, ive been talking to a few optical engineers latley and im telling u that the majority of u guys in here are wasting upto 60% of your light by using the wrong configerations in your light engines, there are a few calculaions to take in mind, and these are what u need to know before u can even start to get any efiecentcy from your source, a spherical reflector with a short focal is the best for a ohp type system, this has to be calculated for size and focal by the specs on the light pattern generated by your bulb, also the condenser has to be calculated for the light pattern generated by the bulb so that u are gathering all of the light from the front of your source, also there is power thats an issue and condenser focal, with this system in mind it would far out do the parobolic reflector design in a reflector system no matter what lenses or configeration u used in projection, there is only 1 other thats better then a spherical system and thats an eliptical reflector, the reflector its self can gather 90% of the sources light where as a spherical can gather upto 65%, also an eliptical reflector has 2 focals, 1 for the bulb and 1 for the condenser, also the light doesnt go back through its source, so realy when u think about it with an eliptical reflector and a properly matched condenser its not that hard to get the 99% of light from your source, and its exactly what the pro projectors of today use.

Trev
 

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Best reflector

To do a test for parallel light rays on a light source, shine it on a wall. If it is a true source of parallel light, the light won't be bigger that the source. That is, a lamp and reflector (or a lamp, reflector and the first fresnel) will make a bright image on the wall that it the same size as the reflector (or fresnel).

If you move the light closer to the wall and further away from the wall, the image on the wall will NOT get larger and smaller. It will not get brighter and dimmer either.

Image a square hole in the wall of your house that sunlight comes through and you see a bright square of light on the opposite wall. This is VERY nearly parally light from the sun being masked off by the wall (and coming through the hole in the wall). If you used a movable wall (or a screen) and moved it closer to the wall with the hole and further that bright light square on it would not change in size or brightness.

Another good test while you are holding the light is to see what sort of shadows can be cast by the light. If you hold up an object between the light and the wall, you should get a VERY sharp shadow. The shadow should be the same size as the object and not get smaller or larger when you move it.

So that's the test for perfectly parallel rays of light, once you have a light source to play with.

As far as looking at a picture of a light source and trying to determine (before buying it) if it will put out parallel light, consider this:
Can you see the filament of the bulb when the light source is not pointed at you? Can you see reflections of the filament in the facets of the reflector when you are off-axis? If so, some of the light will be aimed at you when it is powered on.

As far as a perfect reflector goes, it is possible to use a point source or a line source. As long as light is coming from an exactly known location and is coming out in a known direction is can be focused to do anything you want (including parallel rays). A point source is better for this because all of the light is is going in a totally know direction. When the light hits a surface (like a mirror, curved or flat) you can control exactly where it is going to go because you know exactly what angle it is striking the surface and can design the surface (mirror) to bounce the light exactly where you want it to go.

With a line source, there is less known about the angle. When a bit of light hits your mirror, you don't know if the light came from one end of the filament or the other or near the middle some where, etc. The longer the filament is the higher the uncertainty is.

With a planar source of light, there is the unpredictable on both an x and y axis. The light ray that hits the mirror could have come from anywhere on the light source.
 
Ok thanx both. Sorry for my late reaction. I am getting more and more confused. I don't believe a "normal" reflector (spherical, parabolic) will do the trick with dubble and mongul based lamps.
But which will???? I will dig into it deeper or just do some tests.

Oh, i found some pdf on the optic of theater, film and disco spots.
it is in german, but look at it, because the pictures also explain a lot.

http://www.revolux.com/Wissenswertes/Scheinwerfersysteme.pdf


Ps. I have a question. I bough a wide converter lens van chinon (~1$) can I do anything with it? It realy looks like a projector lens. the diameter of the bottom is 4 cm and the diameter of the top is 5 cm. I know it is used to lower the focal lenght of an other lens, but can it be used on its own.
 
I found the design for the dubble ended bulbs!!!!!!!

It's is called a Dual paraboliod reflector and can be used for larger arced lamps (as is shown in the articel).

It is not easy yo make but, we have to try.

Here is the article
http://www.wavien.com/scientific/resources/IDMC_February_2003.pdf

And this is the reflector (build out of two half parabolic reflectors and one spherical)

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diyAudio Member
Joined 2003
Thats very much the same as the later model car's head lamps but its not offset, the shperical in the center while the parabolic or eliptical behind, u can do that system with a dual eliptical reflector system too thats even more eficient and has a better light control providing u can find the right focals, that system u have posted above would have a long focal, it would be good for fiber optic light guides and not so much projection unless u had a small lcd and room to spare, its a nice design though.

Trev
 
hey ace,

thx man, yeah i am from europe; i have 8 of this bulbs (Aluline 56) left here, if you are interested... normally they cost about 12 euros one bulb, but i got it on ebay for a very good price. the exact print on the package says: Philips Aluline Pro 50W and it has B15d socket

there a three types from Aluline: 111; 56 and 37

these are the diameters of the bulb in mm

just mail me if u are interested ak2kde@yahoo.de

i would need 2 cold mirrors with 85x65mm in size each...

do you have such mirrors and what will they cost? i am defently interested, may be we can trade bulbs with mirros or i think we will find another solution... what do u think bud? could you mail me some more infos about your cold mirrors? size price etc...

or do u know a good source in europe for cold mirros

as i only find firms and they don't sell to endusers :bawling:
 
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