Ch 3. Rectilinear Propagation

Describe the properties of pinhole cameras

-image is inverted -image is in focus no matter where the image screen is moved (depth of focus) -image size is proportional to the distance to the screen -image brightness is inversely proportional to the distance to the screen (increased distance = decreased brightness) -image is in focus no matter where object is moved (depth of field)

Formula for vergence of a wavefront

L = n/r, where L in object space, n is index of refraction, r is distance from optical system

Formula for vergence altering power

L' = D + L , L' in image space, L in object space, D is vergence altering power of optical interference

define umbra

a complete shadow

Define pinhole

a small aperture

Define penumbra

an incomplete shadow, generally the result of an extended light source and an obstacle "shallow shadow" that surrounds the umbra

define depth of focus

extent over which the image plane can be moved and the image remains in focus

define depth of field

extent over which the object can be moved and the image remains in focus

Define rectilinear propagation

geometric optics principle that light travels in straight lines

Equation for finding the penumbra

h'p/x' = s/x where s is the size of the light source

Equation for finding the umbra

h/x = h'/ x + x'

formula for pinhole camera - object and image relationship

h/x = h'/x', where h' is image height, h is object height, x is object distance, and x' is image distance

What happens to an image as aperture is increased? As it is decreased?

larger holes decrease image sharpness (more peripheral rays) and smaller holes increase image sharpness as image quality limited by diffraction