Effect Of Diffraction On Retinal Image

Question 1

Production of 3d images of objects

Answer 1

Holography

Question 2

Holography requirements

Answer 2

• coherent light
• maintain ‘phase relationship’ of two waves constant all through out
• extremely complicated interference

Question 3

A hologram records

Answer 3

• light from the object (intensity)

- phase-difference between the ‘reference’ beam and beam scattered from the object

Question 4

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

Answer 4

Phase-difference

Question 5

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

Answer 5

Reach all points on the film.

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

Question 6

Requires a __________ to view the holographic image recording.

Answer 6

Coherent source

Question 7

Interference pattern recording on the film acts as _____________

Answer 7

Diffraction grating

Question 8

Real image on holographic film

Answer 8

M=0. Usually not viewed

Question 9

Virtual image on holographic film

Answer 9

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

Question 10

Hologram viewed horizontally

Answer 10

You will see 3D image

Question 11

Hologram viewed vertically

Answer 11

You will see different colors

Question 12

What are the types of holograms

Answer 12

Transmission and reflection

Question 13

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

Answer 13

Diffraction grating spectrometer

-used to identify planets

Question 14

How does diffraction affect the retinal image?

Answer 14

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

Question 15

As pupil size increases, point spread function ______

Answer 15

Decreases

Question 16

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

Answer 16

Gaussian filter for adopization

Question 17

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

Answer 17

Adaptive optics

Question 18

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

Answer 18

Diffraction and aberrations

Question 19

Aberrations increase with ________ pupil size

Answer 19

Increased

Question 20

Diffraction decreases with __________ pupil size

Answer 20

Increased

Question 21

Best retinal image quality is provided by a ___mm pupil

Answer 21

3mm

Question 22

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

Answer 22

Pupils size

Question 23

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

Answer 23

Neural systme

Question 24

Corneal transparency is a __________ phenomenon

Answer 24

Diffraction

Question 25

When is the cornea opaque?

Answer 25

Irregular spacing

Question 26

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

Answer 26

Grating

Question 27

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

Answer 27

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

Question 28

Diffraction halos

Answer 28

Caused by cataracts, angle closure glaucoma, edema

-diffraction from regularly spaced epithelial or lens fiber cells

Question 29

The ciliary corona is an entoptic _____________ phenomenon

Answer 29

Diffraction

Question 30

Ciliary corona

Answer 30

• 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