Optics Flashcards
Aperture stop
controls the amt of light passing through the optic system when viewing an object
- first lens in the telescope (objective lens)
Ex. pupils
Entrance pupil
image of aperture stop formed by the lens in FRONT of it
- if no lenses, aperture stop is the entrance pupil
Exit pupil
image of aperture stop formed by lenses BEHIND it
Where’s the exit pupil on a Galilean and keplerian telescope
- Galilean inside the telescope
- Keplerian outside the telescope
Field of view
- increased with minus lens
- decreased with plus lens
Depth of focus
interval surrounding the retina in which the eye sees an object as in focus
Depth of field
surrounds fixation plan in which object can reside and be in focus. Increases with decreased pupil size and decreased focal lengths (myope)
Pantoscopic tilt
rotating lens around 180 degree
meridian
induces minus cyl with axis 180 for a - lens and axis 090 for a + lens
Faceform tilt
rotating lens around 90 degree meridian induces minus cyl with axis 090 for - lens and axis 180 for + lens
Circle of least confusion
point of best focus for a lens
- located dioptrically halfway between the 2 line images that are formed in the principle meridians
Interval of sturm
the distance btw 2 foci of the principle meridian
Telescope Know this chart
Galilean/Keplerian
type of lens
exit pupil
FOV
Mag
Galilean
Lens: object (+) ocular(-)
exit pupil: inside
FOV: small
Mag: up to 4x
Keplerian
Lens: objective (+) ocular (+)
exit pupil: outside
FOV: Large
Mag: Up to 10x
What causes spherical aberrations?
spherical lens (both plus and minus)
- light located further away from the center bends more
How would you minimize spherical aberration
- prescribe an aspheric lens for higher powered Rx
- decr aperture/pupil
- AVOID biconvex lenses
- plus powered lens = steeper centrally, flatter peripherally
What is the power of the planoconvex thin lens whose curved surface has a radius of 3 cm?
+16.67
Nodal point
light passes undeviated
- located at the center of curvature
Consider a very simple eye model that consists of only a single spherical refracting interface (cornea) and a screen (retina). Assume that the radius of curvature of the SSRI is 6mm, and the axial length of the eye is 23mm. If an object, 35cm tall is placed 1m in front of the eye, how large is the retinal image?
5.9mm
A pt looks at an object embedded in a glass 30cm below the flat surface. What is the apparent depth of an object?
20cm