image height distant object 4.2 Flashcards
What happens for a distant object?
-Cant use formula for magnification since L=0
What are nodal points (N and N’)?
They are conjugate points along the optical axis of an optical system with unit angular magnification
-Can find retinal image height of a distant object using the nodal points
What does unit angular magnification mean?
light is undeviated
What do the nodal points mean?
ray directed at 1st nodal point leaves the system undeviated from the second focal point
What can we calculate for the standard emmetropic reduced eye?
- Can calculate the location of the nodal points
Position of N and N’= +5.56mm
Nodal points are coincident for a single surface/thin lens?
What is an alternative apporach for N and N’?
-Find radius of curvature given by: paraxial surface power: F= n’-n/r
60=(4/3-1)/r
- We find radius of curvature of +5.55mm
-means centre of curvature is +5.55mm to right of surface.
CofC at the same place as nodal points
I=0 therefore I’ needs to be =0
How do you calculate the h’ in a distant object in any single surface/thin lens?
h’= -ntan(angle)/ Fe
h’= -ktan(angle)’ (normal)
What equations are applied to a corrected reduced eye?
- h1’ = -ntan(angle) / Fsp = h2
2. M=L2/L2’=h2’/h2= K/K’
What are principal points P and P’?
conjugate points along the optical axis of unit transverse magnification
What is unit transverse magnification?
Incident ray height at first principal plane is same as height of exiting ray on second principal plane
What happens in a standard reduced eye of P and P’?
P and P’ = 0.00mmm - -
Where are the P, P’ on the reduced eye?
For a single surface or thin lens the principal point are always at the surface/lens of the system
-Ray heights are therefore always the same at P and P’
What does image height depend on?
the angle subtended by the object ands power of system
