I am struggling with a real-life optics problem. At work, I have a projector that makes an image too big for the screen. I think I can reduce the image to the required size by mounting a simple lens in front of the projector lens. However, I haven't been able to determine what lens I need, nor the distance at which I have to mount it.
Am I correct, at least in principle, that it should be possible to correct the image by mounting a simple lens?
What measurements do I need to collect, and how do I calculate the required lens and mounting distance?
I'm rather frustrated that I can't solve this myself. The problem is that I don't have a clear mental model of the optical system. When I've tried to research the optics of a projector/camera, I find much explanation of how focusing occurs, but very little explanation of how magnification occurs in a lens system.
Here are some details:
The projector is mounted 360 inches from the screen.
The projector has a zoom lens assembly which, at 360 inches, projects an image which is 84.7 to 154.1 inches tall.
The screen is 60-inches tall.
The image is height-constrained, so the widths of the image and screen don't matter.
The projector specifications say that the lens focal length is 24.0mm to 43.2mm.
All advice is appreciated.
By the way, I've labeled this question "camera" because my understanding is that a projector works just like a camera in reverse, so a camera expert should be able to figure this out. Let me know if I'm wrong about that.
I've done some research and I think I can partially answer my question. I now think that the image size cannot be corrected with a simple lens. If the image were out of focus, I might be able to correct that with a simple lens, but changing the size of the image requires more complicated optics.
On the other hand, I've learned that those complicated optics are exactly what happens inside a camera "conversion lens". So, now I'm pursuing the same solution, but I'm looking for a conversion lens assembly with the right specs, rather than a simple lens. I'm don't yet know how to determine the right specs, but I'm working on it.