Long throw projector workaround?

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    What is the best solution for a long throw projector (asides from buying a new projector)? I have a Optoma TW536 which has a throw ratio of 1.55-1.70:1. Even with the sandbox on the floor, I’m near my ceiling to get full coverage but then the kinect & support arm get in the way. Do I just have to go with a smaller box?



    Using a long throw projector is really tough as you noticed. They are designed to be 6 feet or more from their target area. A new Short Throw projector is definitely the way to go.

    Attached is an image to help explain the distances for each type of projector.
    Projector throw distances

    • This reply was modified 3 years, 4 months ago by mkaszuba.

    I did a lot of Google/YouTube research on this before we finally bought a cheap digital Pico projector. There are several YouTube videos showing the use of a mirror. You project onto the mirror which is at an angle facing the sandbox. The mirror projection doubles the distance so you can set the projector lower than 6 feet.
    We never actually tried this, but there are many others who have.
    Here is one video where the keystone settings on the projector are explained.
    $3 short throw projector lens mirror
    By Immerse 4K Cinema

    Oliver Kreylos

    With a long-throw projector, you basically have to use a mirror to fold the projection light path to get the throw distance you need in a compact package. Adding a mirror adds complexity and causes more rapid loss of calibration, which is why we recommend short-throw projectors.

    If you do put in a mirror, try lining things up such that the projection onto the sand is still on-axis, meaning that the natural image is as close to a rectangle as you can get. That way focus is more consistent.

    No matter how your image ends up, don’t use your projector’s digital keystone correction to rectify it. The AR Sandbox does its own keystone correction as a result of projector calibration, and it works much better because it works on the source 3D data instead of the generated 2D pixel image.

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