9- Spatial Vision Flashcards Preview

Perception > 9- Spatial Vision > Flashcards

Flashcards in 9- Spatial Vision Deck (32):
1

What is spatial vision concerned with?

Variations in luminance across space

2

What are the 2 characteristics of sine-wave grating

Frequency and contrast

3

Low spatial frequency grating looks like

Bars more spread out

4

High spatial frequency bars look like

Closer together

5

Lower contrast bars

Dimmer, paler

6

High contrast bars appear

Darker

7

A lens is used to form an image of a sine wave grating. What does the spatial frequency depend on?

Magnification of the lens

8

A lens is used to form an image of a sine-wave grating. What affects modulation depth

The quality of the lens

9

For a real lens, as spatial frequencyof the object becomes greater, what happens to the amplitude?

Gets smaller

10

What is resolution

An imaging systems ability to distinguish object detail

11

What is contrast

How faithfully the min and max intensity values are transferred from object to image plane

12

OTF:

MTF+ PTF

13

What does the MTF measure

The lens ability to transfer contrast at a articulate resolution from the object to image

14

As line spacing decreases what affect does that have on the lenses ability to transfer the contrast?

More difficult
MTF decreases

15

In an on axis optical system is there any change in phase with spatial frequency?

No

16

At low-moderate spatial frequencies do aberration have an affect?

Not as big as in high frequencies

17

What is the effect of optical defocus on SMTF?

Defocus results in a reduction in image quality at high frequencies

18

What is the effect of translucent optics on SMTF?

Overall reduction in overall reduction in image contrast at ALL frequencies
The image formed by the lens is highly degraded

19

For higher levels of defocus what happens to MTF

Decreases the then becomes negative

20

What happens to the image pattern with MTF is negative

Reversed contrast

21

What is the resolution limit

Spatial frequency at which the modulation transfer function first goes to 0

22

What is spurious resolution

Any resolution of higher frequency pattern

23

Point where the grating is first seen by the patient

Contrast threshold

24

What is the reciprocal of contrast threshold

Contrast sensitivity

25

What is the maximum sensitivity

4 cpd

26

What is the high frequency cut off

The point where the grating can no longer be resolved

27

What is the approximate high frequency cutoff?

60 cpd

28

How does the high frequency cut off relate to VA

It is the point where the details of the optotypes can no longer be resolved

29

What is the optical limitation of high frequencies

Manifests a high frequency limitation because of optical aberrations

30

What does the packing of retinal photoreceptor have to do with high frequency

A finer matrix is able to resolve better

31

What happens to high frequency cut off in uncorrected refractive errors

There is reduction in the high-frequency cutoff that manifests itself as decreases VA

32

How does the high frequency CSF cutoff relate to snellen acuity

It's the angle that just resolvable bars make with the eye is called minimum angle of resolution