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BOARDS > Geo Optics > Flashcards

Geo Optics Flashcards

1
Q

Vergence of light

A 
-=diverging 
\+=converging 
L=object vergence 
L’=image vergence 
L’=F+L
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2
Q

L<0

A

Real object

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3
Q

L>0

A

Virtual object

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4
Q

L’<0

A

Virtual image

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5
Q

L’>0

A

Real image

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6
Q

Object location

A

l=n1/L

N1=RI of material in which light travels before hitting lens (left)

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7
Q

Image location

A

l’=n2/L’

N2=RI after passing through the lens (right)

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8
Q

Concave

A

Interface wraps around lower medium
Always diverging
Does not matter which way light travels

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9
Q

Convex

A

Interface wraps around higher medium
Always converging
Does not matter which way light travels

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10
Q

Power of SSRI

A

F=(n2-n1)/r

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11
Q

Radius of curvature

A
  • if shape of lens surface is a C, it s a POSITIVE ROC

- if backwards C, negative ROC

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12
Q

Secondary focal points

A
  • location of image point when plane-polarized light (light from infinity) incident on interface
  • converging=to the right (real image)
  • diverging=to the left (virtual)
  • F’
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13
Q

Secondary focal length

A
  • distance from interface to F-
  • f’=n2/F
  • f’
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14
Q

Primary focal point

A
  • location of an object from which light can leave such that after interacting with interface, it exits as plane waves
  • F
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15
Q

Primary focal length

A
  • distance from interface to F
  • f=(-)n1/F
  • f
  • focal points inverse of lens power
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16
Q

What is the inverse of the lens power

A

Focal points

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17
Q

Nodal point

A

Point on the axis through which light passes undeviated

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18
Q

Flat surface

A
  • r=infinity, so F=0
  • n1/l=n2/l’
  • apparent depth questions are asking where the image is located relative to flat surface (objects apparent distance=image location)
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19
Q

Lateral magnification (linear mag)

A
  • ratio of image size to object size
  • AKA linear magnification
  • m=hi/ho=L/L’=l’/l
  • hi=height if image, ho=height of object
  • L=incoming vergence, L’=outgoing vergence
  • l’=image distance from lens, l=object distance

-l’/l ONLY if object and image in the same RI

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20
Q

Snells law

A

Relationship between angle refraction and angle of incidence
N1sin(theta)1=n2sin(theta)2

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21
Q

Total internal reflection

A

n20c will be totally internally reflected

  • gloat incident at an angle greater than 0c will be refracted internally
  • sin0c=n2/n1
  • example is viewing AC angle unaided, must have gonio lens to view
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22
Q

Power of thin lens

A
  • treated as 2 SSRIs
  • calculate power of each and then add them to get total power
  • F=F1+F2
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23
Q

Downstream vergence

A
  • when you place a lens some distance (x) in front of a screen, the vergence of light striking the screen is different than the vergence of light leaving the lens
  • Leff=L/(1-dL)
  • light loses vergence as it travels further away from the object
24
Q

Power and vertex distance

A
  • effective power of lens changes depending on where the lens is located in front of the eye
  • plus lenses=effectively weaker as they move closer to cornea. Hyperopes need more (+) in CL
  • minus lenses=effective stronger as they move closer to cornea. Myopes need less (-) in CL

Fc=Fg/(1-dFg_

25
Q

Any lens moving farther from the eye needs ____power

A

More +

26
Q

Any lens moving closer to the eye needs more _____ power

A

Minus

27
Q

Thick lenses

A

Can be thought of as 2 thin lenses representing the front and back lens surfaces, separated by some material

28
Q

2 approaches to thick lenses

A
  1. Thick lenses can be though of as 2 thin lenses, representing the front and back lens surface, separated by some material of index n equal to index of lens. Successive imaging
  2. Use Gauss system (probably dont do this): power of a thin lens that would be equivalent (optically) to a particular thick lens
    - Fv=F2 + F1/(1-(t/n2)F1)
29
Q

Aperture stop

A

Light limiter

  • physical entity that limits the amount of light passing into an optical system
  • anatomical aperture stop of eye=pupil
30
Q

Field stop

A

Limited the size of object that can be imaged by the system

31
Q

Entrance pupil

A

Image of aperture stop bu lenses in front of it

  • image of aperture stop formed by all of he lenses in front of it
  • if no lenses in front of it, the entrance pupil itself i the ap stop
32
Q

Exit pupil

A

Image of Ap stop formed by all lenses behind it

-if no lenses behind it, exit pupil itself is the ap stop

33
Q

Entrance port

A

Image of field stop formed by lenses in front of it

34
Q

Exit port

A

Image of field stop formed by lenses behind it

35
Q

Depth of focus

A

Internal surrounding the RETINA in which an eye sees an object as in forces
-pinhole=increased depth of focus. Distinguishes refractive errors from other problems

36
Q

Depth of field

A

Interval surrounding the fixation plane in which an object can reside and still be in focus

  • short focal length=increased depth of field
  • decreased ap size=increased depth of field and focus
37
Q

Field of view

A
  • extend of object plane that is imaged
  • angle or liner
  • angle of 1/2 illumination
  • minus lens=increased field of view
  • plus lenses=decreased field of view
38
Q

Field of fixation

A

Angle made from the optical axis by the entrance port as measured as the center of the eye (14mm from cornea)

39
Q

Stigmatic system

A

Point source produces point image

40
Q

Astigmatic system

A
  • pair of focal lines
  • power is differnet in different meridians
  • location of the vertical focal line is determined by the power in the horizontal median of the lens, and the location fo the horiztonal focal line is determined by the power in the vertical meridian of the lens.
  • vertical power produces horizontal image
  • horizontal power produces vertical image
41
Q

Cylindrical lenses

A
  • direction parallel to the axis of the cylinder is referred to as the axis meridian
  • direction perpendicular to the axis meridian is the power meridian
  • cylinder lenses always have zero power along one meridian
42
Q

Spherical lens

A

Symmetric

Power in each meridian is the same

43
Q

Contraocular view

A
  • view dr would have when looking at the patient

- vertical meridian labels 90 degrees, horizontal labeled 180 degrees

44
Q

Labeling cylindrical lens

A
  1. Specify location of axis using x

2. Specify power in a given meridian using the @ symbol

45
Q

Circle of least confusion

A
  • point of best focus for a lens
  • dioptrically 1/2 way between the 2 line images that are formed in the principle meridians
  • we are finding the point where the image is distorted equally in each meridian
  • when using spherical equivalent, we assume COLC will fall on retina

DIOPTERS

46
Q

Interval of sturm

A
  • distance between the 2 foci of he principle meridians
  • it is the linear distance between the locations of the horizontal and vertical line formations

LINEAR

47
Q

Induced sphere and cyl with tilted lenses

A
  • panto Tilt=rotating about the 180

- faceform=rotating about 90

48
Q

Panto tile of minus lens will induce

A

Minus cyl at 180

49
Q

Panto tile of plus lens will induce

A

Minus cyl x 090

50
Q

Faceform of minus lens will induce

A

Minus cyl at 090

51
Q

Faceform Ttilt of plus lens will induce

A

Minus cyl x 180

52
Q

Mirrors ROC

A

Minus number

53
Q

Power of mirrors

A

F=-2n/r

54
Q

Convex mirror

A

Diverging

55
Q

Concave mirror

A

Converging

56
Q

Lens mirror combo equation

A

F=2F1+F2

BOARDS (14 decks)

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