GHOST IMAGES Flashcards
1
Q
Cause of ghost images
A
Light incident on a lens will be reflected by one or both surfaces
2
Q
Catoptric Image
A
Formed through reflections
3
Q
Catadioptric image
A
Formed through reflection and refraction
4
Q
When are ghost images troublesome
A
When the vergence of the image is similar to the lens vergence
5
Q
Ghost image 1
A
- total internal reflection in front of lens
- most troublesome
- AR coating is only solution
6
Q
Ghost image 2
A
- reflection of cornea on back surface of lens
- high power negative lenses
- resolved with AR coating / BVD change
7
Q
Ghost image 3
A
- reflection of cornea on front surface of lens
- high powered plus lenses
- resolved by lens form, AR coating and BVD change
8
Q
Ghost image 4
A
- reflection sources behind lens on back surface
- common with tinted lenses/ larger aperture
- resolved with back surface AR coating/ smaller frame
9
Q
Ghost image 5
A
- reflection sources behind the lens on front surface
- common in tinted lenses/ larger aperture
- resolved with back surface AR costing/ smaller frame
