using a shader to change focus

imagine im using a projector and im too close to the projector surface to bring things into focus, can i create a shader program that will modify its input so that things are in focus on the screen?

rason for this is i created a multi touch dj platform, i carefully selected an expensive projector with the correct throw ratio, but the minimum distance was a bit of a lie. i can see things fine on the screen apart from the text in the middle, i cant quite read anything below 10pt unless its on the side. i would like for the dj software i made to have a shader that will adjust the focus.

please tell me thats possible, ive no doubt in my mind that it is, just cant think how.

I’m pretty sure (unless I’m misunderstanding you question) that no matter what, shaders/filters can’t compensate for out of focus optics…once it passes through that lens you don’t have much you can do to it to bring it back into focus…of course you can bring it out of focus, but bringing it back in is a bear of a challenge