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Visual Science: Binocular Vision > Binocular Vision: Lecture 16: Stereopsis 3 > Flashcards

Binocular Vision: Lecture 16: Stereopsis 3 Flashcards

1
Q
  1. How do you study STEREOPSIS?
    a. Binocularly are Called what?
  2. What are STEREOSCOPES?
A
  1. Present Stereoscopic Half-Views (Stereo Pairs) To each Eye INDEPENDENTLY
    a. STEREOGRAMS
  2. Instruments that alter the Relationship b/w Distance and Disparity by means of Mirrors, lenses, or Prisms so that Independent Images can be presented to each eye
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2
Q

Wheatstone Mirror Stereoscope

  1. What does it use to Place the 2 Separate Images into EACH EYE?
    a. What is one advantage of this?
A
  1. It uses 2 MIRRORS

a. It DOES NOT have a FIXED WORKING DISTANCE

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3
Q

Electronic Oscilloscope

  1. 2 Oscilloscopes are used to present what?
    a. these are Superimposed by what?
A
  1. Half-Views

a. by a Thin-Film Pellicle Beam-Splitter

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4
Q

Brewster Refracting Stereoscope

  1. What does it use?
    a. What does this do?

b. The + Lenses are decentered outward to produce what effect?
c. Decreasing the Separation by 2mm induces what? (Purpose)

A
  1. +5.0 D Lenses
    a. Places the FAR POINT of Accommodation at a Fixation distance of 20 cm.

b. a BASE-OUT Prismatic Effect
c. 1 PD of UNCROSSED DISPARITY (Used for Larger Disparities)

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5
Q

Free Fusion

  1. You can view a pair of pictures or photographs side by side and fuse them with what?
    a. What is this process called?
    b. It’s achieved by doing what?
  2. 2 half-views are printed in RED ink for one eye and Green (or Blue) ink for the other. These images can actually be Superimposed when printed into what?
A
  1. with VERGENCE EYE MOVEMENTS
    a. FREE FUSION
    b. Converging in front of or Diverging Beyond the Plane of the STEREOGRAM
  2. into a Single Target. Observer wears red/green-filtered glasses. Fusional Eye movements will bring the images into alignment
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6
Q

Synaptophore

  1. It’s a Stereoscope that allows the image intended for each eye to be presented along what?
    a. Even in the Presence of what?
    b. What does it assess?
A
  1. the Primary Line of Sight
    a. of Heterotropia and Heterophoria
    b. the Degree of sensory fusion and also provide VT.
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7
Q

How does Polaroid Filter Work?

  1. Half-Views of a Stereogram can also be separated w/o an instrument by means of what?
  2. They use polarizing filters to separate what?
    a. The Filters before each half-view of the stereogram are polarized at what?

b. Subject wears polarized filters in front of each eye at right angles, each eye can see what?

A
  1. Polaroid Filters (called a Vectographic Presentation or Vectogram)
  2. Each eye’s monocular view of the target
    a. At RIGHT ANGLES
    b. its own half-view of the target
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8
Q

Movie Theater 3D Glasses

  1. They use what polarized filters over:
    a. Left Eye
    b. Right Eye
  2. Projector projects 2 separate images on the film. The Left image is projected thru what?
  3. The 2 images have slightly different perspectives cuz they were recorded using a camera with what?
A
  1. a. Horizontally Polarized Filter
    b. Vertically polarized filter
  2. Thru a HORIZONTAL POLARIZER (right image thru a VERTICAL POLARIZER)
  3. With 2 Lenses. One for the left, the other for the right.
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9
Q

Liquid Crystal Shutter Stereo Goggles

  1. What do they have?
    a. How do they work?
  2. IF this is done at a rapid rate, what happens?
A
  1. Clear elements in their eyepieces that can be DARKENED until OPAQUE by the APPLICATION of an ELECTRICAL CURRENT
    a. 1 eyepiece, then the other, is Occluded alternately, so that one eye’s view of the computer screen, then the other, is revealed.
  2. (at like 15-Hz or higher alternation rate b/w the 2 eyes), the PERCEPT is that of a Single Fused image in Stereoscopic Depth
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10
Q

Line Stereogram

  1. Random-dot stereograms are made up of what?
    a. Some of the dots are displaced how?
  2. Monocularly, both views of the stereograms just look like what?
  3. When fused binocularly, the disparate part of the stereogram appears in depth, and a figure made up from what will do what?
A
  1. a Dense array of dots randomly filled w/either black or white.
    a. LATERALLY in one half-view to produce a Disparity
  2. Like Random Dots. There are no monocular contours to match in a random-dot stereogram
  3. Made up from the DISPARATE DOTS “pops out” in a DIFFERENT DEPTH PLANE
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11
Q
  1. how small of a Lateral Displacement(s) have to be used to create a 10 second of arc stimulus on the VIRTUAL DEPTH tests like the RanDot?
    a. From calculations (HDradians = change of S/d): you can see that generating a stereo test is not that simple if you want to test what?
  2. Bottom line: Our visual system is REALLY GOOD at detecting what?
A
  1. 0.02 mm
    a. really small disparities
  2. Differences in Monocular Visual Directions
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12
Q

Random Dot Stereogram (1)

  1. When combining 2 Monocular Images together, the Visual System must find what?
    a. This guides vergence Eye movements to bring these contours into alignment, and then determine what?
  2. If each Eye Fixates a different spot, the resulting percept will be of what?
  3. The More dots, the more possible pairings of dots b/w the 2 eyes, and the more possible what we could see?
A
  1. Matching portions (Matching CONTOURS) in EACH IMAGE
    a. the Relative Depth of the Contours
  2. a SINGLE DOT in a Different Depth Plane than the rest of the stereogram
  3. DEPTH PLANES we could see
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13
Q

Random Dot Stereogram (2)

  1. The Visual System doesn’t perform by Element-by-element (dot-by-dot) matching, but rather forms what?
    a. This pools together info from the ENTIRE STEREOGRAM to create what?
  2. The Perceived depth in Random-dot stereograms is typically slow to develop, gradually appearing over a period of what?
A
  1. A Global perception over a LARGER SPATIAL SCALE
    a. to create a GLOBAL INTERPRETATION of DEPTH and FORM
  2. Over a period of 500-1,000 ms.
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14
Q

Seeing Stereopsis in Random Dot Stereograms

  1. The Brains have to MATCH together similar dots in 2 patterned monocular views and assign each locus what?
    a. Next, the brain matches Large areas of the Binocular View of the stereogram, finding patches with SIMILAR DISPARITY and combining them to what?
  2. Line Stereograms use what kind of Stereopsis?
  3. What else happens?
A
  1. a DISPARITY (Local Stereopsis)
    a. to an OVERALL SHAPE IN DEPTH (GLOBAL STEREOPSIS)
  2. Local Stereopsis
  3. Crowding Effect
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15
Q

Global Stereopsis

  1. What is it?
    a. It’s more easily disrupted than what in patients with BINOCULAR VISION DISORDERS?
  2. Lesions of the INFEROTEMPORAL CORTEX produce what?
A
  1. It’s a HIGHER ORDER form of Stereopsis
    a. than Local Stereopsis
  2. produce selective Losses of Global Stereopsis
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16
Q

Autostereograms

  1. What are they?
  2. The Degree of Depth seen depends on what?
A
  1. Stereographic Figures that take advantage of Repeating features so that with FREE FUSION, the observer can fuse any one of the Repetitive Features together
  2. on the Convergence of the Observer and which Particular patterns are FUSED TOGETHER
17
Q
  1. Autostereograms: “Magic Eye”: Seeing stereo depth with a stereogram that does not have what?
  2. Correct Vergence: What is seen?
A
  1. does not have a Separate RE and LE Image. (which is why it’s called an “Autostereogram”)
  2. Large and Small Periods all seen at correct depth plane
18
Q
  1. Underconvergence by one period:

2. Overconvergence by one period

A
  1. Increased period produces uncrossed disparity

2. Increased period produces Crossed Disparity

19
Q

Stereopsis (1)

  1. The existence of 3 broadly tuned disparity channels that are selective for 1 of 3 things?
  2. In Spatial Vision, which Spatial Frequencies are PROCESSED FIRST? (Low or High)
  3. What about Disparities?
  4. Central Stereopsis Operates over what range?
    a. It’s Specialized to Detect what?
    b. Central Stereopsis is VERY SPECIFIC for matching what?
A
  1. ZERO Disparity, Crossed Disparity, or Uncrossed Disparity
  2. Low before High
  3. It’s believed that Coarse Disparities are processed before Fine Disparities
  4. OVER a NARROW +/- 0.5 degree Range at the FOVEA
    a. Small disparities (minutes of arc) at the FIXATION POINT
    b. For Matching SIMILAR PATTERNS in EACH EYE
20
Q

Stereopsis (2)

  1. Peripheral Stereopsis operates over what Range?
  2. Fine Stereo run by what system?
  3. Coarse Stereo run by what system?
  4. Global Stereopsis is Much more sensitive than Local Stereopsis to the Presence of what?
A
  1. +/- 7 degrees to 10 degrees
  2. Parvocellular System (P)
  3. Magnocellular System (M)
  4. of Abnormal Binocular Vision
21
Q

Clinical Stereo Acuity Tests

  1. Can be used to Measure stereo as low as what?
A
  1. as 15 arc seconds

TNO Test (Red/Green Anaglyphs) or Randot (Crossed Polarizers)

Visual Science: Binocular Vision (20 decks)

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