Effect Of Diffraction On Retinal Image Flashcards Preview

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Flashcards in Effect Of Diffraction On Retinal Image Deck (30):
1

Production of 3d images of objects

Holography

2

Holography requirements

-coherent light
-maintain 'phase relationship' of two waves constant all through out
-extremely complicated interference

3

A hologram records

-light from the object (intensity)
-phase-difference between the 'reference' beam and beam scattered from the object

4

_________ causes interference pattern to be formed producing an image with 3D information

Phase-difference

5

Unlike conventional imaging, in holographic imaging, light from each point on the object will do what?

Reach all points on the film.

You can break a small piece off of holography film and still see entire image

6

Requires a __________ to view the holographic image recording.

Coherent source

7

Interference pattern recording on the film acts as _____________

Diffraction grating

8

Real image on holographic film

M=0. Usually not viewed

9

Virtual image on holographic film

M=-1
Virtual image behind the film are viewed, with light coming from it exactly same way light came from the actual object when the film was exposed

10

Hologram viewed horizontally

You will see 3D image

11

Hologram viewed vertically

You will see different colors

12

What are the types of holograms

Transmission and reflection

13

To analyze light passing through a slit and diffracted by a grating when collimated light is incident on it

Diffraction grating spectrometer
-used to identify planets

14

How does diffraction affect the retinal image?

For the eye, only a section passes through the pupil; the iris is an obstruction that diffracts the light. This diffraction blurs the image. For a system limited only by diffraction, the image radius for a point object is 1.22lambda/d

15

As pupil size increases, point spread function ______

Decreases

16

To fix diffraction affects in small pupil less than 3mm, use ________

Gaussian filter for adopization

17

What do you use in larger pupil to fix diffraction effects?

Adaptive optics

18

What causes the image to appear different than the object in aberrated lens?

Diffraction and aberrations

19

Aberrations increase with ________ pupil size

Increased

20

Diffraction decreases with __________ pupil size

Increased

21

Best retinal image quality is provided by a ___mm pupil

3mm

22

____ controls impact of ocular aberrations and diffraction on retinal image quality

Pupils size

23

You can have perfect optics, but what ultimately limits image quality?

Neural systme

24

Corneal transparency is a __________ phenomenon

Diffraction

25

When is the cornea opaque?

Irregular spacing

26

An array of equally spaced collagen fibrils acts as a _______, scattering light into discrete directions

Grating

27

A fibril spacing (d) smaller than the wavelength of light (lambda) will make the fibrils ____________ as light passes through undeviated

Transparent

If d< lambda then theta>90 degrees for all m>0. Therefore no diffraction orders exist except m=o. Under this condition, the fibrils diffract no light and appear transparent

28

Diffraction halos

Caused by cataracts, angle closure glaucoma, edema
-diffraction from regularly spaced epithelial or lens fiber cells

29

The ciliary corona is an entoptic _____________ phenomenon

Diffraction

30

Ciliary corona

-light entering eye is diffracted by small particles in the eye
-circular diffraction pattern on retina tens of degrees across
-innumerable needles of light, fanning out for the point object