more or less I'm trying to make a ps1 screen based projector fit inside fit inside a full tower mod I've got in the works. Because the screen is a lot smaller than the frensels used for thos 15" projectors, I was wondering if I could use something like this - http://www.rolyn.com/html/page_3__v..._catid_2__companyid_64329__lineid_1005__.html Will it be too small? There are some other frensels on that site in addition, could I've read on lumenlab that you can remove the lense from an old slide projector like this one - http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=15256&item=7506701661&rd=1 anyone have any idea if this would work? I'm more concerned with getting a good quality image. I was thinking of widening my case anyways. thanks in advance - mobi.
Other than the fact that the price for the fresnel in the link is outrageous, as long as it is slightly larger than your PSone screen, you should be all set. I just posted this pic elsewhere, but I'll post it here too...It should help a little with what you're trying to do. Basically, your light originates from the source (light bulb, which has a ballast to ignite it), then is reflected so that the light is not lost by being diffused around the container. The light then travels from the reflector (and the light bulb) to the tempered glass, where light, but not heat, is transferred. After that, it enters the collimator Fresnel, where the light is made to be perpendicular to the lens (distributing the light evenly through the assembly). Then, it passes through the stripped LCD panel (obviously without a backlight), and then goes into the condensor Fresnel, where the image is thus condensed, and sent into the triplet lens, which inverts the image again, and attempts to remove distortion (a three lens assembly removes distortion much more efficiently than one lens alone), and also is used to focus the image. My other suggestion is that, because focal length is what actually determines the size of your box (along with the LCD), You may find it is a better solution to find a fresnel from an overhead projector, and figure out the focal length on that. As of now, the focal length you have on the lens is 152 mm (which, coincidentally, is the same as the C.A. in this case ). If you want to enlarge or shorten it, the physical size of the lens won't matter, you will need to find one with a focal length that fits your needs. OK, so my suggestions in a nutshell: 1. 250-300W Metal Halide light bulb 2. The lens you have linked (but see if you can't get a better price for two) 3. Precut tempered glass 4. Triplet lens (I suggest the one from LumenLab) 5. Reflector from LumenLab (the Ikea napkin ring thing)
thanks for the response. a couple more qs I have - I noticed that the fresnel kit that lumenlab has contains 2 different focal length fresnels. Is this needed or can I use 2 identical fresnels. Also, I found some el cheapo fresnels on ebay here - http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=67919&item=5767774775&rd=1. They could probably fit in my case, but might be a little long. Since they're made of pvc could I trim the excess area? Would this degrade my image in any way, or it just a bad idea? I thought about rotating the lense so it would fit tall and the lcd would be fit in there wide. I'm assuming fresnels are circular, is this correct? also, the I assume that you try to best match the focal length with the lense's, so I assume that I would need this lense - https://secure.lumenlab.com/shop/group.php?id=9 thanks again for helping - I'm going to get the log going soon.
AFAIK, you can use two identical fresnels, it's just that having the longer focal length one gives DIY projectors slightly more room to work with. As far as the eBay fresnels are concerned, go for it. They have a focal length of 300mm, and if they aren't quite right, then you're not losing much. If you want to cut them, my suggestion would be to mark up the lines (measure twice, cut once) on the fresnel in wet erase marker, then take a bare wire long enough to go over the length of the lens, then attach that bare wire to a DC power source, and use it to melt right through in a perfectly straight line. BTW, you are correct, the magnifying part of a fresnel is circular, and can be cut to just fit what you need.
