I just bought this lens on Ebay. I have a 17" transparency with a 550mmand 220 mm fresnels. Looks to have promise.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=7550227158&rd=1&sspagename=STRK:MEWN:IT&rd=1
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=7550227158&rd=1&sspagename=STRK:MEWN:IT&rd=1
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very nice
All you would-be designers should pay attention. In this one photo, rlwoodjr is showing you something you ALL should do: Start with a test bench setup, to validate your ideas and to get some real distances, etc. You have little chance of building an optimal projector if you skip this stage.
Process lenses are terrific: The have very precise focus corrected for flat fields (ie. like an LCD and a screen), superb color correction, and very wide field of view. The only negative is that they are usually not very wide, so you have to pay some attention to tuning those fresnel distances to get the light into the lens. With that projection lens, you should think about a projector design that lets you adjust the lamp-to-fresnel distance while it is running. Then you will be able to use the projector at different throw distances without losing too many lumens.
Your testbench image looks very good. I bet it would look even better if you mounted the lens in the center of a 2' by 2' piece of plywood or heavy cardboard to block all the light leakage.
BTW: Please don't be surprised when your LCD image is not as bright as your transparency image. LCDs lose at least 80% of the light passing through them.
All you would-be designers should pay attention. In this one photo, rlwoodjr is showing you something you ALL should do: Start with a test bench setup, to validate your ideas and to get some real distances, etc. You have little chance of building an optimal projector if you skip this stage.
Process lenses are terrific: The have very precise focus corrected for flat fields (ie. like an LCD and a screen), superb color correction, and very wide field of view. The only negative is that they are usually not very wide, so you have to pay some attention to tuning those fresnel distances to get the light into the lens. With that projection lens, you should think about a projector design that lets you adjust the lamp-to-fresnel distance while it is running. Then you will be able to use the projector at different throw distances without losing too many lumens.
Your testbench image looks very good. I bet it would look even better if you mounted the lens in the center of a 2' by 2' piece of plywood or heavy cardboard to block all the light leakage.
BTW: Please don't be surprised when your LCD image is not as bright as your transparency image. LCDs lose at least 80% of the light passing through them.
New setup
Yes the new lens holder is a 0.25" plywood face with a hole in it. It does block a little if the stray light.
I am testing at the throw distance I will be using. I will be using a folded design. I sure wish my current lumenlab projector could be as bright as the transparency. 🙂
Yes the new lens holder is a 0.25" plywood face with a hole in it. It does block a little if the stray light.
I am testing at the throw distance I will be using. I will be using a folded design. I sure wish my current lumenlab projector could be as bright as the transparency. 🙂
another good idea
>testing at the throw distance I will be using
That's another excellant point: You can't really tell how well a projector lens & condensor system will work together unless you test them at the throw distane you plan to use.
You could have a test bench where the image is perfect for a short throw distance, but then see dim or cut-off corners when you try it with the real throw distance. As the throw distance gets longer, you have to move the projection lens closer to the LCD in order to focus. That increases the required Field Of View angle, which is a critical limitation in many projection lenses.
>testing at the throw distance I will be using
That's another excellant point: You can't really tell how well a projector lens & condensor system will work together unless you test them at the throw distane you plan to use.
You could have a test bench where the image is perfect for a short throw distance, but then see dim or cut-off corners when you try it with the real throw distance. As the throw distance gets longer, you have to move the projection lens closer to the LCD in order to focus. That increases the required Field Of View angle, which is a critical limitation in many projection lenses.
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