What does it mean for the lens camera to be in focus?
motoole2
A lens is focused on a point if the rays emanating from that point all map to a single point on the sensor (as illustrated at the top of this slide). A lens is out of focus if the rays do not map to the same point.
Here's a demo of the thin lens model, where you have a single (thin) optical element acting like a lens. The position where the rays converge to a point is where the sensor needs to be to form an in-focus image. This, btw, makes use of the thin lens equation to describe the focusing properties of the lens.
What does it mean for the lens camera to be in focus?
A lens is focused on a point if the rays emanating from that point all map to a single point on the sensor (as illustrated at the top of this slide). A lens is out of focus if the rays do not map to the same point.
Here's a demo of the thin lens model, where you have a single (thin) optical element acting like a lens. The position where the rays converge to a point is where the sensor needs to be to form an in-focus image. This, btw, makes use of the thin lens equation to describe the focusing properties of the lens.
In practice, lenses are usually made of multiple lens elements, so things can get complicated. Here's another cool demo of a more realistic 2D ray tracing procedure, where you have multiple thick lenses. Try dragging around the light source. It even models the chromatic aberrations of lenses (the rainbow effects) where light of different colors will travel in different directions.