Flashcards in Lecture 6 Deck (22)
what does the law of parsimony recommend for using a model eye?
using the simplest model that is adequate for an application
what is the name of the #1 schematic eye and how many surfaces does it have?
what is the name of the #2 schematic eye and how many surfaces does it have?
Le Grand full theoretical schematic eye
what is the name of the #3 schematic eye and how many surfaces does it have?
Gullstrand number 2 schematic eye/Gullstrand-Emsley schematic eye/"Simplified eye"
what is the name of the #4 schematic eye and how many surfaces does it have?
Reduced schematic eye
1 surface (combined cornea and lens)
what happens to the cardinal points when you reduce the number of surfaces in a schematic eye?
the cardinal points are unchanged - all have the same function
if you wanted to study the back vertex power, which schematic eye would you choose?
Le Grand = needs to have 2 surfaces for the cornea and be the simplest option (so not #1)
if you wanted to study accommodation, which schematic eye would you choose?
Gullstrand #2 or Simplified eye = need to have surface for lens and be the simplest (so not 1 or 2)
what is the anterior focal length for the schematic eyes? what is the posterior focal length?
anterior = -16.67mm
posterior = 22.22 mm
(eq. power = 60D)
what is the 1st focus for the focal points?
axial object position for which the image will be formed at infinity
what is the 2nd focus for the focal points?
axial image point of an infinitely distance object
what are the nodal points?
any incident ray which passes through the 1st nodal point leaves the system as though from the 2nd nodal point and parallel to the incident ray (unchanged direction but maybe displaced)
what do the principal points do?
locate the front and back surfaces of an equivalent thin lens
where is the 1st principal point?
located where the exiting rays parallel to the optical axis intersected the refracted rays coming from the 1st nodal point
where is the 2nd principal point?
located where the incident rays parallel to the optical axis intersect the refracted rays converging to the 2nd focal point
what are cardinal points?
3 paris of points that define an equivalent thin lens whose paraxial performance is identical to the original thick lens or combination of lenses (eye) = F,F',P,P',N,N'
what is the depth of the first nodal point relative to the anterior corneal surface?
7.05mm (N' is 0.3mm away from N)
what is the reduced surface representing?
the "balance of power" between the cornea and crystalline lens
where does the reduced surface sit in the reduced eye?
about 1.67mm behind the (anterior) corneal plane
where is the pupil in the reduced eye?
considered to coincide with the reduced surface (in reality it is about 2mm behind the reduced surface)
what is the spherical refracting surface in the reduced eye?