How can an intervening lens correct an out-of-focus projected image?

[Loren Booda]

Why can an out-of-focus picture on a screen from a projector be corrected by an
intervening lens, while a lens cannot correct the out-of-focus image once
impinged on the screen?

 

[russ_watters]

When the light hits the screen, the direction the rays travel is not preserved due to the specular reflection. Replace the screen with a mirror and you can re-focus the light.

 

[charng]

An out-of-focus picture on a screen from a projector can be corrected by an intervening lens because the lens can manipulate the path of light rays before they reach the screen. This allows the lens to adjust the focus of the image and produce a clear picture on the screen. However, once the image has already been projected onto the screen, a lens alone cannot correct the out-of-focus image. This is because the light rays have already been scattered and cannot be redirected by the lens. In order to correct the image, the lens would need to be placed between the projector and the screen to manipulate the light rays before they reach the screen. Additionally, the quality and characteristics of the lens, such as its focal length and aperture, play a crucial role in achieving a clear and focused image on the screen.