13) Optical Lenses Flashcards
Optical lens
Optically homogeneous grandparent body
Types of thickness
Thin lenses
The thickness is smaller than the curvature
Tick
The thickness is neglible relative to curvature
Types of lenses by the shape of their surface
Spherical
They have 2 spherical ends
Cylindrical
Bound by 2 cylindrical ends
Type of lenses by the curvature
Biconvex
The shape looks like ()
Biconcave
Looks like rectangle with bite missing
Type of lenses by the refraction
You have converging
This is when it increases the convergence of the incidence and decreases the diverging
Diverging is vice Versa
Basic elements of the spherical lens
Principle optical axis _ Principle plane l Optical centre Focus Focal plane l Focal length
Optical power
This depends on the curvature
Positive is converging
Negative is diverging
Thin lens formula
1/F= 1/A 1/B
a is the object distance
b is the image distance
F is the focal length
Refraction of cylindrical lens
The cross section is rectangular this means that the rays are not refracted
Aberrations
This is the distortion of an image
Spherical aberrations
The rays further away from the axis are refracted more
The image of the point is blurry
Use compound lens
Chromatic aberration
The focal length different for rays of different colour
Point image is coloured
Use compound lens
Distortion
This is when the magnification is altered
Causes barrel
Use a compound lens
Field curvature
This is when the planar object is not image onto the plane
Image can’t be seen
Compound lens
Astigmatism
The point will appear as a eclipse or circle
Correction is using compound lens but it can’t be totally eliminated
Coma
This means the image appears as a off centre spot
Correction is use of a compound lens
Optical system of the eye coats the globe
The cornea
This is a transparent layer found before the iris and pupil
Iris
Coloured cells found before the lens
Pupil
A circular opening that can change its diameter to act as an apature
Optical system of the eye anterior and posterior
This is present behind the cornea but before the lens
Eye lens
This consists of a double convex transparent layer behind the pupil
The front and back have different curvatures
Optical system of the eye
The retina
Is the inner layer of sensitive light cells
Control of the radiant flux surface
The eyelid stood light beam from entering the eye
The pupil can change its diameter to let more or less light in
Optical system of the eye
The optical power of the eye varies
It’s around 60D when it focuses on objects that are further away
Around 74D when it focuses on objects closer to the eye
Image on the retina
This image is
Inverted
read
Diminished
Accommodation
This is the optical power needed to focus on an object that is much closer to the eye
This distance increases with age
Normal near point distance
This is the closest an object can be to the face for the eyes to sill focus and for it to still be comfortable
