Background Flashcards

(49 cards)

1
Q

What is a (non-digital) image? (1)

A

f(x,y) = colour/intensity

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2
Q

What is sampling?

A

TODO

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3
Q

What is quantisation?

A

TODO

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4
Q

What is required for vision? (3)

A
  1. Light source
  2. Eyes
  3. Object that reflects/transmits light
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5
Q

Draw diagrams to represent the 3 types of viewing mechanisms (3)

A

TODO 19

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6
Q

What determines the spectrum of wavelengths arriving at the eye? (2)

A
  1. Spectrum of wavelengths emitted by light

2. Spectrum of wavelengths reflected/transmitted by object

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7
Q

What is light? (1)

A

Electromagnetic radiation

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8
Q

What is the range of wavelengths of visible light? (2)

A

700nm -> 400nm

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9
Q

What colour is light of wavelength 700nm? (1)

A

Red

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10
Q

What colour is light of wavelength 400nm? (1)

A

Violet

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11
Q

What wavelength is red light? (1)

A

700nm

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12
Q

What wavelength is blue/violet light? (1)

A

400nm

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13
Q

Why does the colour characteristic of light emitted vary for different illuminants? (3)

A
  1. Light is composed of multiple electromagnetic wavelengths
  2. Different wavelengths are emitted with different intensities
  3. The composition of these determines the colour characteristics
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14
Q

What is an illuminant? (1)

A

TODO

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15
Q

Why are incandescent light bulbs very red? (1)

A

Wavelengths in the red region are emitted with the HIGHEST INTENSITY

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16
Q

Draw a diagram of the human eye indicating the retina, fovea and optic nerve. (1)

A

TODO 26

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17
Q

What is the retina? (1)

A

An array of light detection cells

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18
Q

What is the fovea? (2)

A
  1. High resolution area of the retina

2. Highest density of cone cells

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19
Q

What does the optic nerve do? (1)

A

It takes signals from the retina to the visual cortex of the brain

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20
Q

How many light receptors are in the retina? (1)

21
Q

How many nerve fibres are in the optic nerve? (1)

22
Q

Why does the retina need to perform pre-processing?

A

There are 150M light receptors in the retina but only 1M nerve fibres in the optic nerve -> the amount of information received by the retina needs to be condensed to fit onto the optic nerve

23
Q

Name 3 ways the retina performs pre-processing. (3)

A
  1. Avg. multiple inputs
  2. Colour signal processing
  3. Local edge detection
24
Q

How is colour signal processing performed in the retina? (1)

25
What is colour signal processing in the retina? (1)
TODO
26
What is local edge detection in the retina? (1)
TODO
27
How is local edge detection performed in the retina? (1)
TODO
28
How are multiple inputs averaged in the retina? (1)
TODO
29
Draw a diagram indicating the types of cells in the retina. (5)
TODO 28
30
What are the light detectors in the retina? (2)
1. Rod cells | 2. Cone cells
31
What do cone cells do? (1)
Enable colour vision
32
How many types of cone cells are there? (2)
3
33
What's the difference between the types of cone cells? (1)
They are sensitive to different wavelengths of light (short, medium, long)
34
What is the macula? (1)
TODO
35
Where are the cone cells concentrated? (1)
The macula
36
Where is the macula? (1)
Centre of the retina
37
What is the density of cones in the fovea? (1)
150,000 per square mm
38
What is vision like outside the fovea? (2)
1. Lower resolution | 2. Monochromatic
39
What is the purpose of providing lower resolution area of vision outside the fovea? (3)
1. Provide peripheral vision - > stop you walking into things - > find things more easily
40
Is the way the retina averages multiple inputs uniform for the whole retina? (1)
No, outside the fovea more rods' inputs are combined per signal
41
How are rod and cone cells distributed over the retina? (2)
1. Tightly packed cones in the fovea | 2. Cones spread out and spaces filled with rods outside the fovea
42
Why is it more difficult to see detail in blue than other colours? (1)
We have less cones that receive short wavelength light (corresponding to Blue light) than cones that receive medium/long wavelengths
43
What is luminance? (1)
TOCHECK | Signal comprising signals from long + medium + short cones
44
What is the percentage distribution of the different cone types in the fovea? (3)
7% short 37% medium 56% long
45
What is the approximate ratio of long:medium cones? (1)
3:2
46
What percentage of cones are short outside the fovea? (1)
1%
47
Where is the least number of short cones in the fovea and how many are there? (2)
1. Central 1/3 degree of vision | 2. None
48
Why can we see a yellowish-red but not a greenish-red? ()
TODO 34
49
What is a digital image? (1)
Rectangular array of intensity/colour VALUES | i.e. a collection of numbers