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Old Sep 2nd 2018, 02:42 AM   #1
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adding two (or more) light beams together

HI!

I'm new to this forum and I don't know if this question belongs here, if not please let me know.
I have a project (dormant since I didn't find the solution to this, yet) of modifying a 16mm film projector, one of the mods is to change the light source (incandescent bulb) for a LED, the most powerful LED on the market is an array can output about 35000lm (CLU550-3626C1-403M2G2-B24 from Citizen), but we want more. Then the question: is possible to add two (or more) light sources together pointed to the film and the projection lenses without having duplicate images or other unwanted effects and without a enormous lost of light power? if yes: how?
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Old Sep 3rd 2018, 02:10 AM   #2
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This led seems a very strange light source for a projector . The light emitting surface is many square cm !...

My understanding is the light source needs to be as close to a point source as possible to avoid blurring , It's not about choosing the most watts ...

Leds are not ideal for this ... The best will be a cree 15W , often used in torches.
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Old Sep 3rd 2018, 07:36 AM   #3
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Individual LEDs only produce a relatively modest light source,
which is why they are packaged as arrays when it is desired to produce any significant illumination from them.

It would be possible to combine the light from lots of LEDs into a single narrow beam,
but this would require a not insubstantial arrangement of mirrors and/or lenses.
You may find that the unwieldy bulk of any LED solution might make it impractical.
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Old Sep 6th 2018, 09:11 AM   #4
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Originally Posted by Woody View Post
Individual LEDs only produce a relatively modest light source,
which is why they are packaged as arrays when it is desired to produce any significant illumination from them.

It would be possible to combine the light from lots of LEDs into a single narrow beam,
but this would require a not insubstantial arrangement of mirrors and/or lenses.
You may find that the unwieldy bulk of any LED solution might make it impractical.
The LED array I mention before is 200W nominal, 350W if I can keep the temperature below 100C, I have the idea of using up to 3 of them if possible, so yes, I'm expecting something bulky just from the point of view of the cooling system
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Old Sep 6th 2018, 10:49 AM   #5
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I have quickly knocked together a sketch
Blue are LED panels
Green are lenses (Fresnel)
Black are Mirrors
Red are "light rays".
Note the lenses are arranged to focus the led panels through the focus of a parabolic mirror.

There is probably a better way to do this,
this was just a chuck some ideas at the paper and see what might work.
Attached Thumbnails
adding two (or more) light beams together-mirror.jpg  
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Old Sep 7th 2018, 12:20 AM   #6
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Originally Posted by Woody View Post
It would be possible to combine the light from lots of LEDs into a single narrow beam,
This is incorrect ...

There is absolutely no way any lens arrangement , or mirrors or anything else can make a narrow beam from a defused led source ....

If leds could replace incandescent in projectors, manufacturers would have done this a long time ago , leds are 5 times more energy efficient.

The laws of optics prevent this , if the light source is not a point , multiple images are inevitable .

The error in the diagram above is that it shows the light from the led panels (in green) converging and passing through a point , this does not happen.

Last edited by oz93666; Sep 7th 2018 at 12:24 AM.
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Old Sep 7th 2018, 02:38 AM   #7
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The green double ended arrows are representing lenses.
the led panels are shown in blue.

However, it is quite possible I am mistaken,
It is many years since I did this sort of thing at school.
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Old Sep 7th 2018, 04:48 AM   #8
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Originally Posted by Woody View Post
The green double ended arrows are representing lenses.
the led panels are shown in blue.
Ah yes ...I see now .

In that case the lens could not focus to a point . That led source is many square cms and each part is emitting light in a wide angle. Part of the light will travel as shown , perhaps a millionth of the total output.
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Old Sep 7th 2018, 05:47 AM   #9
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Oops yes Oz,
I hadn't recognised my unconscious assumption that the LED panels produce a parallel light beam.
I don't know anything about LED panels, so I don't know what their basic "beam" is like.
Perhaps eins can enlighten us...
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Old Sep 7th 2018, 10:00 AM   #10
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in the datasheet of the led (attached), p.8 you can see the radiation characteristic, from what I understand from this drawing we will have about 60% of the power in a +/-60 angle from the vertical axis of the led
I tried before to attach some photos of the previous version of this project, to show the lenses I'm using but for some reason the post was not published, I will try it again.
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File Type: pdf CLU550-3626C1_P3326_0915.pdf (751.2 KB, 1 views)
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