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Is there a way to set multiple focal lengths with one projector and software?

As shown in the following illustration, the image from one projector is partially in focus and partially out of focus.

enter image description here

Assuming that the screen output from the projector is viewed with the camera again, is there a way to correct the part out of focus with software?

pius lee
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    There is [a paper](http://hvrl.ics.keio.ac.jp/paper/pdf/international_Conference/2008/ACIVS2008_charmie.pdf) that describes an attempt to do this. Most people solve the problem with two projectors though because defocus blur correction produces ringing artifacts in the image. Choosing a small aperture projector lens (e.g. f/22) is an option too; both planes will be in focus but will be much darker than a wide aperture lens. – Wyck May 14 '21 at 03:57

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No this is not doable by SW only.

Because you would need to change the direction of light coming out from the projector's emitter so that after passing the optics will focus further away and SW can affect only Color change...

What you need is to tweak the projector optics changing the focal length of lenses. You can do that by adding another lens in front of projector (with the right focal length in the right distance). My bet you need concave lens (negative focal length) however You need to make sure the cooling of the projector itself will not be affected so it must not reflect too much light back, and also take in mind this will most likely create some color focusing problems. I would simply test this with holding such a lens in hand and see what happens with the image focus while moveing it ... however I got quite a lot of lenses at my disposal which I assume most people do not have.

However you can test this in SW by using any optic lab SW or even write you own and simulate the projector there ... after obtaining the proper parameters for your new lens you can purchase it at any optics (where eye glasses are made/sold) unless the focal length is not too weird...

Another option is to tweak the projectors lens system which is most likely a teleobjective so if you can slightly tweak the distance range between the lens mechanically which could do the trick however the lens movement range usually corresponds to their diameters and apertures so its possible such change will cut of some parts of screen (on the outer borders). Also this usually means loss of warranty as you need to mess up with the device itself and also if not done properly you could damage the lenses for good so I do not advise to do this unless really necessary.

Spektre
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  • If I use a specific lens, can I spray the image regardless of the focal length? Actually, what I want to do is to implement multiple focal lengths in one projector. If possible, without the help of hardware. Even if you can get a bad-focused image back to the camera, isn't there a way to correct it? – pius lee May 12 '21 at 14:48
  • @piuslee adding lens before the projector actually changes the focal length of the projectors. Yes distortions can be fixed but I doubt you will be able to do it fully as it would most likely require non spherical curvatures and possibly more than just single lens. However single Lens should improve the focus quite a lot (depending on its focal length and distance to projector) so just try it by hand and if good enough build some chasis for it (like 3D print or something). Having more focal lengths of the result might be possible by simply changing the distance of the lens to teleobjective – Spektre May 12 '21 at 15:27