DIY Video Projector Part II

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Experiment Re: Question

Hi,

I have done a little experiment with a 1.5 Volt flashlight inside
a toilet paper roll, and a slide on the end of that roll. I have seen
the slide projection on the wall, in a dark room.

Conclusion: Point light source can project a slide over a wall.

Advantages:

1. All the light from the slide goes to the wall = No light is lost after the slide.
2. It is easy to project the slide as a square i.e. side projection.
3. No need for a lens after the slide, actually no need for any lenses
beyond the point light source.


Chalenges:

1. Does it work with LCD?
2. Building a strong and uniform 'point light source'.


PS

The flashlight with its surrounding reflector wasn't a point light
source, and didn't produce an image. Only without it, and probably
also due to the fact that the lamp is so tiny, it was a point light
source, or close enough, and the image was projcected over the
wall.


zkuger said:
Hi,

I am kind of new here, so I apologize in advance
for this simple question, but I have just got to ask:

If you have a point 'light source', and you put it behind
an LCD panel, would it not just project the LCD image
over the wall? (like hand shadows)


I don't have an LCD panel yet, so I can't test it. But
I think that if a light beam pass the LCD strait, then
it is possible. On the other hand if a light beam that
pass the LCD is scattered in all directions then it isn't
possible.

If it is possible but the light source is not a point, than
many images would be cast on the wall from the many
virtual point light source, and so the image would not be
clear.

You can test it with a Laser beam or with a light beam
or with a point light source if you know how to make one.
 
this is what i use right now 400W HQI-TS

bright as hell but not effecient at all, that's why i decided to change to the cdm s
 

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look what i've found;

it is from this side:

http://www.led-lichtcenter.de/index.html?target=dept_142.html&lang=de

they put a normal 150W hqi in a reflector that is 65mm in dia

i'd love to test this one; but the bulb costs 174€

i wonder what they do with their damaged ones, may be i'll call the producer to ask if they sell their damaged ones
 

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ok, today i tried to take a few pictures to show the difference between the the 110mm and the 56mm.

i aimed at a white paper which was about 23cm away from the lamp (my focus of the first fresnel).

but all i got were hot fingers and nonshowing bright pictures on the camera. sorry i wasn't able to take it in picture to show the difference, but it is defently there.

so the main difference with the big refl i saw the side wire of the bulb in the projected lamp spot. with the small one it wasn't visible because the light spot was so intense...

now my thought and aim is, with a condensor lense in front of that i can evenly spread it onto the fresnel; but i wasn't able to additionally handle that; to be continued... :smash:
 
diyAudio Member
Joined 2003
so the main difference with the big refl i saw the side wire of the bulb in the projected lamp spot. with the small one it wasn't visible because the light spot was so intense...

Slize get the light from the big reflector to a point with a condenser, then focus the frensel to this point, only then u will have a brighter image with a big reflector, the big reflector will capture more light but we need to get this back to a point to work in an eficient manner, otherwise we are just loosing intensity. With a smaller reflector it is more intense, but u will capture less light then the big reflector.

Trev
 
Lampmixer

another question:

i am thinking about using two 150W lamps. But before i go and buy that stuff i thought about a way to make one spot out of two.
This subject has been discussed alot on this forum over the years.
But I haven´t seen any good solution yet. But the last idea I got is from all the 3 panel lcd projectors, they use a prism to mix together the red, green and blue color to a full color projectingbeam. I think this will work on diy-projectors also.

And if I have known this 2 years ago, I had probably not used the cdm-t lamp, because of this: 100W 12V halogen give 2400lm if you overvoltage them a little they give 4800lm and with this prismdesign I can get 3 times more = 14400lm and thats more than what the 150W cdm-t lamp give. 100W 12V Halogen bulbs are dirtcheap. So this could be a nice thing for diy-beginners.
 

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diyAudio Member
Joined 2003
mathias, u wont get 3x the light output, that takes a special prisim for this kind of combining, it take a dichric prisim, if the center lamp just shines the light into a normal prisim the light will get shinned strait back to its self from the other 2 reflecting halfs, so the 2 mirrors on the outside have to be dichoric so that light can pass through the prisim from the center lamp.

As for the cdm-t, if u get a phillips cdm-t they yeald 12500lm, a GE brand cdm-t will yeald 14000lm, this is also on the 4200k spectrum not the 3200, the GE also lasts 12000hrs.

Trev
 
that takes a special prisim for this kind of combining
Yes that is right, but this is the only lampmixer I have seen, and I don´t think there are any other way to do it. So if people can find special condensors they can probably also can find this type of prism and with it you will get 3 times more light.

And yes the Halogen thing is not as good as the cdm-t, but it´s much cheaper to start with and many people don´t want to start with HID-lamps.
 
diyAudio Member
Joined 2003
So if people can find special condensors they can probably also can find this type of prism and with it you will get 3 times more light.

The prisim required is a 45deg prisim, it is also dichoric, the back lamp can only output 50% of its light without some sort of light recyler, even with that said only 50% of the light can be reflected by the 2 side bulbs, so realy we can only get 50% out of each light, so in reality we will get 1.5x the light. It woiuld be way better to use 2 bulbs on a normal 60deg prisim to combine the light into 1 beam and then we would have roughly 2x the light output. No special condenser needed either, 2 pcx condensers will do the job fine.

Trev
 
heya Trev;

i buy bulbs on ebay with buy it now for 35€ plus 5€ for shipping:

http://cgi.ebay.de/ws/eBayISAPI.dll?ViewItem&item=3274792152&category=22515

they will send to germany and europe

and for the sockets i have someone who sells it private:

6€ one socket plus 4,55€ for shipping. I'll let him know your e-mail and ask him if he has got some left to sell, he shall contact you then...

Otherwise http://home.t-online.de/home/sinitzki/ they sell it for 7,50 a socket but they are hard to contact sinitzki@t-online.de

sorry got no more sources left then for sockets
 
mathias

mathias said:

So if people can find special condensors they can probably also can find this type of prism and with it you will get 3 times more light.


Yep they will find it probably and will pay A LOT of money. A friend of mine had 3 panel lcd projector and this thing got damaged by a fall and this prism got damaged not alone, but to replacement of this special prism costs 2000!!!$ :bigeyes: so he decided to buy a new one after all and sold it his broken pj on ebay for about 400$
 
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