Well after playing around with my projector for a few days, and spending time researching lenses, heres my question.
Setting focal points, and having the correct setup of lenses, is somewhat easy, but how can I assure that my image will be in focus? I dont understand the mechanics of focusing an image, so at this point i'm lost. If there are any optics experts out there, and whom might know of a good website or something to explain this, I think that would greatly help out any deep DIY-ers out there! THANKS!!
David
Setting focal points, and having the correct setup of lenses, is somewhat easy, but how can I assure that my image will be in focus? I dont understand the mechanics of focusing an image, so at this point i'm lost. If there are any optics experts out there, and whom might know of a good website or something to explain this, I think that would greatly help out any deep DIY-ers out there! THANKS!!
David
Try...
http://www.howstuffworks.com
There is a lot about eye-glasses (corrective lens) but the general principles would be the same.
Zaner21
http://www.howstuffworks.com
There is a lot about eye-glasses (corrective lens) but the general principles would be the same.
Zaner21
If you are just concerned about DIY projector lenses, there are usually only two types used.
The first is and the most complicated is the triplet (projection lens). That's the lens that will take your image and make it huge on the screen. Inside a triplet contains (you guessed it), three lenses. Two biconvex (each shaped like this: () ) and one biconcave (shaped like this: )( ). They are fitted together: biconvex / biconcave / biconvex. The reason for using three lenses has to do with correcting for color shift and image sharpness. This lens has a diameter and a focal length (FL) and a viewing angle that you need to be concerned about.
The second lens is the fresnel lens. This is essentially a weird looking plano-convex (shaped like this: |) ). It is flat with ridges. You want to be concerned with the size of the lens, what it's made of, and the focal length. These lenses take light from a point (like the arc of a welder) and spread the light over the entire sheet (fresnel lens). So you get a bigger rectangle of light from a point of light. It also does the opposite by turning it around. It can take a rectangle of light and bring it back down to a point.
So the idea is to take a point light source (the arc from a metal halide bulb), spread the light over the entire surface of an LCD screen (using a fresnel), take the light coming from the LCD and shrink it back down to a point (from a second fresnel), and pass that light on to the projection lens to be projected onto a screen.
Do a search on here or at Lumen Lab for the math behind it. If you want more optics info, look at wikipedia. Good luck!
The first is and the most complicated is the triplet (projection lens). That's the lens that will take your image and make it huge on the screen. Inside a triplet contains (you guessed it), three lenses. Two biconvex (each shaped like this: () ) and one biconcave (shaped like this: )( ). They are fitted together: biconvex / biconcave / biconvex. The reason for using three lenses has to do with correcting for color shift and image sharpness. This lens has a diameter and a focal length (FL) and a viewing angle that you need to be concerned about.
The second lens is the fresnel lens. This is essentially a weird looking plano-convex (shaped like this: |) ). It is flat with ridges. You want to be concerned with the size of the lens, what it's made of, and the focal length. These lenses take light from a point (like the arc of a welder) and spread the light over the entire sheet (fresnel lens). So you get a bigger rectangle of light from a point of light. It also does the opposite by turning it around. It can take a rectangle of light and bring it back down to a point.
So the idea is to take a point light source (the arc from a metal halide bulb), spread the light over the entire surface of an LCD screen (using a fresnel), take the light coming from the LCD and shrink it back down to a point (from a second fresnel), and pass that light on to the projection lens to be projected onto a screen.
Do a search on here or at Lumen Lab for the math behind it. If you want more optics info, look at wikipedia. Good luck!
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