I'm making an extremely crude, portable projector built off of a 35W HID Xenon spotlight/worklight. I'm aiming for light throw over picture clarity (it now can shine a spot more than 500 meters away!). Since the spotlight has a large 9" reflector I would like to focus the beam with something similar to a large magnifying glass, but obviously these are impossible to find (& pricey if you can). Does anyone know if I could use 2 fresnels to get the same effect? Any advice would be greatly appreciated!
Thanks, I already have a few smaller ones from there. I haven't seen any with large diameters (around 200mm) that's why I was curious about the fresnels.
fresnel projection lens
This is what you get when you send somebody $5-$30 for a "projection TV conversion kit" on eBay: A fresnel lens. You tape it to a cardboard box with a hole in it, place that in front of your TV, and voila! You get a really BAD upside-down and backwards image on your wall. You need a real lens if you want a decent image.
BTW, color LCDs lose about 80% of the light passing through them. Even the most efficient DIY designs use 150 Watt MH lamps that put out around 80 lumens per Watt. Your 35 Watt lamp will give you a very dark (or a very tiny) image.
This is what you get when you send somebody $5-$30 for a "projection TV conversion kit" on eBay: A fresnel lens. You tape it to a cardboard box with a hole in it, place that in front of your TV, and voila! You get a really BAD upside-down and backwards image on your wall. You need a real lens if you want a decent image.
BTW, color LCDs lose about 80% of the light passing through them. Even the most efficient DIY designs use 150 Watt MH lamps that put out around 80 lumens per Watt. Your 35 Watt lamp will give you a very dark (or a very tiny) image.
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