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IE 577 > Vision > Flashcards

Vision Flashcards

1
Q

What is vision?

A

Transformation from light waves (electromagnetic energy) to recognition

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2
Q

What is considered to be the primary sensory system?

A

Vision.

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3
Q

What are the stimulus properites included in vision?

A

Stimulus properties include wavelength (color) and ampmlitude (brightness).

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4
Q

What is the energy at the source?

A

Luminous intensity.

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5
Q

What is the name for the energy reaching the object?

A

Illuminance.

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6
Q

What is the name for the energy refelcted off the object to allow for vision?

A

Luminance.

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7
Q

What does the cornea do?

A

Protects the eye.

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8
Q

What does the lens do?

A

It focuses images.

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9
Q

What does the retina do?

A

Nerve cells that receive the image in the eye.

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10
Q

What does the optic nerve?

A

The optic nerve transmits visual information from the retina in the eye to the brai

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11
Q

What are the main parts of the eye?

A
  • Cornea
  • Pupil
  • Lens
  • Retina
  • Optic Nerve
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12
Q

What does the pupil do?

A

The pupil is used for controlling the amount of light entering the eye through the change in the size of the pupil.

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13
Q

What is near sighted (myopia)

A

The inability of the lens to flatten.

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14
Q

How does age effect vision?

A

The lense becomes less flexible and has issues focusing. The lense also becomes discolored and the cornea can cloud (cataracts). With aging, less light through cornea, thus decreased effective illumination – less contrast sensitivity

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15
Q

What percentage of males are color blind?

A

7%

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16
Q

What two types of receptors are found within the retina?

A

Rods and Cones.

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17
Q

Which is more sensitive rods or cones?

A

Rods are more senstive an require less light than cones.

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18
Q

Which is provides more image detail, rods or cones?

A

Cones provide more detail as they are more dense, which you use to see details. Rods are less dense and have less detail.

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19
Q

Where are rods and cones located?

A

Rods are located on the periphery and cones are located in the center (fovea)

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20
Q

Which helps more in low light visibility, rods or cones?

A

Rods help more in low light conditions.

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21
Q

When viewing bleow the light threshold (scotpic vision), which is used cones or rods?

A

Only rods are used below the light threshold, so their is less detail.

22
Q

Are conse senstivie to glare?

A

Yes. They become hypersensitive when they receive little stimulation. Thus, they are sensitive to glare.

23
Q

Can rods determine color?

A

Rods don’t determine color, as they cannot discriminate wavelength.

24
Q

When do rods lose sensitivity?

A

Rapidly lose sensitivity when exposed to light (up to 30 min to regain)

25
Q

What is contrast sensitivity?

A

Contrast Sensitivity: the reciprocal of the minimum contrast between a lighter and darker spatial area that can just be detected: ability to see the difference between lighter and darker areas

26
Q

With movement, is there a decrease in contrast sensitivity?

A

Yes.

27
Q

What is contrast?

A

Contrast is the difference between the luminance of light and the dark areas to the sum of the luminance values: L = luminance of light area, D = luminance of dark area.

28
Q

What is the contrast formula?

A

Constrast = (luminance of light area - luminance of dark area) / (luminance + lumninance of dark areas)

C= (L - D) / (L + D)

29
Q

What is contrast sensitivity?

A

The higher the contrast sensitivity (CS) that an observer possesses, the smaller the min amount of contrast that can be detected Cm.

30
Q

What is sensitive to what amount of cycles/degrees?

A

Human eye most sensitive to 3 cycles/degree (spatial frequency).

31
Q

What is the contrast sensitivity formula?

A

Constrast Sensitivity (CS) = 1/Cm

32
Q

What is a visual field?

A

What is a visual field: The area that can be seen when the head and the eyes are motionless.

33
Q

What is the visual field for one-eyed vision when the eye is motionless?

A

Extends from 70 on the nasal side to 104 on the temporal side.

34
Q

What is the visual field for each eye when the eyes are allowed to rotate?

A

VF for each eye when the eyes are allowed to rotate, but not the head is about 166.

35
Q

What is the visual angle?

A

What is visual angle: The angle formed at the eye by the viewed object.

36
Q

What is the measurement of the visual angle?

A

Usually this is given in degrees of arc [1 (degree) = 60 (minutes of arc); 1’ = 60” (seconds of arc)] . Visual Angle (minutes of arc) = (57.3)(60)L/D

Where L = the size of the object measured perpendicular to the line of sight, and D = the distance from the front of the eye to the object.

This formula is for an angle of less than 10 degrees and assumes that the line of regard bisects L

37
Q

Under good viewing conditions, what is the visual angle?

A

Under good viewing conditions the visual angle should subtend at least 15 minutes of arc.

38
Q

Under degraded viewing condistions, what is the visual angle?

A

Under degraded viewing conditions (e.g. low light levels) the angle should subtend at least 21 minutes of arc.

39
Q

What is the minimum perceptible visual angle?

A

Minimum perceptible visual angle is approximately 1 second of an arc (e.g., a thin wire against a bright sky)

40
Q

What is the visual field for color?

A

Color is perceived for about 60 degrees on either side of a fixed point when the eyes are motionless

41
Q

Are all receptors in the retina equally sensitive to color?

A

Not all receptors in the retina are equally sensitive to color.

42
Q

What is color sensitivity with the eye motionless?

A
43
Q

What are three common issues with vision design?

A

1) Visual acuity
2) Visual defects
3) Color deceptiveness

44
Q

What are the visual defects?

A
45
Q

How is visual acuity measured?

A

It is measured with the Snell eye chart.

46
Q

What are the two types of color deceptiveness?

A

1) Color weakness
2) Color blindness

47
Q

What is color weakness?

A

Color Weakness: people are capable of seeing all colors, but tend to confuse some of them, ESPECIALLY under dim Light

48
Q

What is color blindness?

A

Color Blindness: People who are color blind tend to confuse red, green and gray. In some cases no color perception (3 in 100,000).

49
Q

What is focal vision?

A

Focal: fine detail and pattern recognition.

50
Q

What is ambient vision?

A

Ambient: peripheral vision for orientation and ego motion.

51
Q

Focal (aprox. 2 degrees of vision, i.e. fovea) and ambient vision appear to define separate resources in the sense that:

A
  • Support efficient time-sharing
  • Characterized by qualitatively different brain structures
  • Associated with qualitatively different types of information processing

IE 577 (16 decks)

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