SST-50 homemade spotlight

[jspeybro]

Yep those are the part numbers that I got. For getting the lens distances right I moved the fresnel lens so that the image is focused then I moved the small lens so the cone fills the fresnel lens, then I repeat those two steps till it's good enough. A glare reducing enclosure would be nice but it would have to be light.

can you tell me the distance between the led die and the back of the first lens?
the same for the second lens would also be good to verify the calculation.

1 difficulty with calculating this setup is the use of the first lens which is quite thick. I will see how close a thin lens approximation comes to the reality. The thing is that this calculation would be correct if you use the principal planes of the first lens to measure/set distances, but that info is not available at the anchor website.

 

[EasyB]

can you tell me the distance between the led die and the back of the first lens?
the same for the second lens would also be good to verify the calculation.

1 difficulty with calculating this setup is the use of the first lens which is quite thick. I will see how close a thin lens approximation comes to the reality. The thing is that this calculation would be correct if you use the principal planes of the first lens to measure/set distances, but that info is not available at the anchor website.

The LED (not the dome) is about .5cm from the back of the first lens. The LED is about 35cm from the fresnel lens. I have some image size data that might help you too. The image is 17cm 3m from the fresnel lens and 28cm 10m from the lens.

 

[wechnivag]

Can you re-upload the photos on photobucket or imageshack? This is killing me!!

 

[ledlensert7]

just been searching through cpf for a maximium throw sort of project- wow i think this beats anything i had ever expected! that is amazing.

Another project added to the list!:naughty:

 

[LEDAdd1ct]

Wow, very cool build!

 

[Dannnn]

Amazing!! A carbon fiber shell would be great on that, and it's simple/cheap to do.

 

[vestureofblood]

Hi EasyB,

For this project did you focus the LED with the first small aspherical lens so that it was as tight as possible, meaning so it showed the image of the die?


Thanks

 

[finges]

Hi EasyB,

For this project did you focus the LED with the first small aspherical lens so that it was as tight as possible, meaning so it showed the image of the die?


Thanks

in the pictures, the aspherical lens is very close to the led, so, in my experience, it would create a very wide beam.
if the asperical lens is further away from the led the beam tightens till it shows the actuall projection of the die.
correct me if i'm wrong

 

[Walterk]

in the pictures, the aspherical lens is very close to the led, so, in my experience, it would create a very wide beam.
if the asperical lens is further away from the led the beam tightens till it shows the actuall projection of the die.
correct me if i'm wrong

The first lens close to the led, determines how much of the light is projected on the big lens.
A wider light beam inbetween led and the big lens, affects the effective aperture of the system exiting by the big lens, and thus throw.

I built a similar light, and made it focusable by moving the led, the lenses are fixated optimized for throw.
It is hard to predict the behaviour excatly when using two lenses, I've tried.
Having the big lens covered in light from the led is the most important part.
Using a small led (point source) gives a more narrow beam.

 

[Al Combs]

Hi EasyB,

For this project did you focus the LED with the first small aspherical lens so that it was as tight as possible, meaning so it showed the image of the die?


Thanks

+1 to Walterk's bead on it.

See post #55 for a good picture and #58 for a brief explanation. The small condenser lens next to the LED adjusts the size of the beam angle to match the clear aperture of the Fresnel lens. The Fresnel lens in front is for adjusting the focus on distant objects. Moving the condenser does have an affect on focus but its real function is to collect as much light as possible from the LED. The "tight as possible" aspect of the system is controlled the the Fresnel lens focal length.

Edit:

A short focal length lens collects most of the light from the LED and the large fresnel lens focuses it far away. The LED is actually inside the focal length of the small lens, creating a virtual image that the large lens sees.

I was just reading this post again and noticed EasyB explains the function of each lens below the 2nd picture in post #1.

 

[xul]

That tower is about 250 meters away.

So if it's a 30 meter high tower and 1/3 illuminated this is a field angle of 2{arcsin(10/250)} = 5 degrees.

BTW, this post is mathematically incorrect! I should write out the formulas before posting, no matter how simple I think they are.

 

[tobrien]

do you have a parts list? I'd love to attempt one lol

 

[hoffmyster86]

ok! wheres batman? hol cool.