How can I increase the throw distance for my Elmo HP-A305? Right now it sits less than a screen length away and I find that too close, especially when playing video games. I tried to put a regular convex lens in front of the beam that bounces off the mirror, but that just made the entire image impossibly blurry and unrecognizable. Does anyone have any experience in this area?
putting a lens in between the light source and the lcd panel isnt going to affect the throw distance. Throw distance is proportional to the distance from the lcd to the projection lens and the wall distance (this will give you some ratio by wich you can mutiply by the source image size to give you the wall image size)....thus the best thing to do is alter the projection lens...you can replace it with another one that will do the job better, or you can learn the wonderfull world of physics and determine one with the appropriate focal length that you can add to the current projection lens to increase the throw distance relative to size
i didn't put the lens between the lcd and light source.... i put it right after the current projection lens, which is right where the only mirror is on an OHP, the mirror that bends the light 90 degrees. i think adding a lens is the optimal way because replacing the current lens altogether sounds very risky.
replacing the lens isnt risky...its the best way to do it properly. When doing two lenses you put more "issues" into the optical system. There's also a greater chance of not being able to properly focus the image at the end
I think that Elmo 305 uses kind of an odd lens compared to other overheads. I have heard it called "Vari-focal" before.
Increasing the focal length on that setup might be more difficult than on an overhead with a conventional tripet lens and arm.
I could be wrong, I havent actually looked at one myself.
My triplet lens on my Dukane 680 is 327mm. Its one of the longer focal lenghts I have seen in a triplet. With a 10.4" diagonal
lcd panel(Sharp Projection panel) I get a 92"X69" ish image at
12.5 feet thow. I have decided not to use a 15" lcd like you are useing because of how much closer I would have to be to the screen. My guess is some where around 4 feet or so and thats just to close for my liking.
To use a standard triplet lens, you may have to chage the arm on your Elmo to one that moves up and down to focus. You would probably have better luck that way getting a longer focal length lens to work. It would have to be longer than the one I have.
I have also heard that a raw eyeglass lens on top of the trilet lens will increase focal length as well, I belive I read that a while ago on one of YWH's posts.
I think my solution for now will be to try and stay around 12" diagonal when I upgrade my LCD, I am currently looking for a suitable controller for a laptop screen.
Hope some of this helps
Increasing the focal length on that setup might be more difficult than on an overhead with a conventional tripet lens and arm.
I could be wrong, I havent actually looked at one myself.
My triplet lens on my Dukane 680 is 327mm. Its one of the longer focal lenghts I have seen in a triplet. With a 10.4" diagonal
lcd panel(Sharp Projection panel) I get a 92"X69" ish image at
12.5 feet thow. I have decided not to use a 15" lcd like you are useing because of how much closer I would have to be to the screen. My guess is some where around 4 feet or so and thats just to close for my liking.
To use a standard triplet lens, you may have to chage the arm on your Elmo to one that moves up and down to focus. You would probably have better luck that way getting a longer focal length lens to work. It would have to be longer than the one I have.
I have also heard that a raw eyeglass lens on top of the trilet lens will increase focal length as well, I belive I read that a while ago on one of YWH's posts.
I think my solution for now will be to try and stay around 12" diagonal when I upgrade my LCD, I am currently looking for a suitable controller for a laptop screen.
Hope some of this helps
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