
Optics 47
2.6.2 Depth of field
If we focus the camera on a certain object O which is at a distance d
O
from
the camera, what we are doing is moving the lens system so that the image of
the object is formed exactly on the image plane, where the sensor is located.
Objects at distances larger or smaller than d
O
will have their images formed
behind or in front of the image plane, therefore they will appear blurry, i.e.
points will be imaged as circles, as Figure 2.22 showed. But if these circles are
sufficiently small, in particular smaller than the size of a single element cell of
the sensor (“the size of a pixel” if you will), then the objects will be perceived ...