Transcript Document 7601868

Chapter 10
深度與大小
深度知覺之線索取向
(cue approach to depth perception)
• 尋找視覺影像（proximal stimulus）中與環境的深度
（distal stimulus）有關的線索訊息（cues ），我們透
過經驗建立這些深度線索與實際深度的關連性，而造
成深度知覺。
眼球運動線索
（Oculomotor cues）
• 根據我們對於眼球位置與眼球肌肉緊張度的感受，
而產生的深度線索
– 限近距離有用（手臂距離）
• Convergence
– 因需觀看近物，兩眼球向內移動
– 感受到的
convergence 愈多，
表示物體距離愈
近
– 雙眼線索
眼球運動線索
（Oculomotor cues）
• Accommodation
– 隨物體距離不同，水晶體形
狀會改變以利聚焦
– 水晶體愈平，表示距離愈遠
– 單眼線索
單眼線索 (monocular cues)
• 圖畫線索（pictorial cues）
– Alberti’s window
單眼線索 (monocular cues)
• 遮蔽（occlusion）
– 提供相對距離線索
– 被遮蔽者較遠
• 相對高度
– 底部較高的離觀察者較遠
– 但是，物體若落在水平線以上，那麼底部較
低的較遠
Fig. 8-3, p. 170
單眼線索 (monocular cues)
• 相對大小
– 小的比較遠 (demo-monster)
• 透視匯聚(perspective convergence)
– 匯聚端較遠
單眼線索 (monocular cues)
• 熟悉的尺寸
– 原本較大的被認為較遠
– 雙眼觀察則沒有這種錯覺
單眼線索 (monocular cues)
• 空氣透視（atmosphere perspective）
• 不清楚的比較遠
Fig. 8-5, p. 171
單眼線索 (monocular cues)
• 質地遞變
– 密的較遠
單眼線索 (monocular cues)
• 陰影
– 陰影的特性協助瞭解物體在空間中的位置
「遮蔽」與「相對
高度」線索衝突
• 運動線索(movement-produced cues)
– 觀看者運動而產生的深度線索（單眼）
• 運動視差（motion parallax）
– 遠的物體動得慢，近的物體
動得快link
– 比凝視點近的物體，其移動
與運動方向相反；比凝視點
遠的物體，其移動與運動方
向相同
• Deletion & accretion
Fig. 8-10a, p. 173
Fig. 8-10b, p. 173
Table 8.1 Range of effectiveness of different depth cues
雙眼深度訊息
• 雙眼像差（Binocular disparity）
– 左右眼的影像差異
Figure 8.11 Location of images on the retina for the “Two Eyes: Two Viewpoints” demonstration. (a) Both
images are on the fovea when the left eye is open. (b) The images are on different places on the retina
when the right eye is open.
雙眼深度訊息
• 立體感（stereopsis）
– 對應點（corresponding retinal points）
• 兩個網膜上連結相同皮質區域的點
– horopter
• 是一個想像的圓，通過凝視點，而其上的每個物
體會落在兩眼網膜的對應點
Figure 8.13 (a) When the lifeguard looks at Frieda, the image of Frieda, Susan, and Harry fall on
corresponding points on the lifeguard’s retinas, and the images of the other swimmers fall on
noncorresponding points. (b) The locations of the images of Susan, Frieda, and Harry on the lifeguard’s
retina.
• 不在horopter上的物體，會落在雙眼網膜的
非對應點（noncorresponding points）
– 形成像差角（angle of disparity）或絕對像差
（absolute disparity）
– 離horopter愈遠，像差角愈大
Horopter
Absolute disparity
for Carole (how far
an object is from
the horopter)
Absolute disparity
for Frieda
Horopter
• 交叉型像差（crossed
disparity）: 落在
horopter之前的物體形
成交叉型像差，顯示
物體比horopter近
• 非交叉型像差
（uncrossed disparity）:
落在 horopter之後的物
體形非成交叉型像差
（網膜上的落點向
內） ，顯示物體比
horopter遠
• Relative disparity is the
difference between the absolute
disparity of two objects.
• Absolute disparity
– Frieda: 0 °
– Carole: 26 °
• Relative disparity: 26 ° – 0 ° = 26 °
– Offering an advantage as an observer
shifts his fixation
• Stereoscope (1800’s)
Figure 8.16 The two images of a stereoscopic photograph. The difference between the two images, such
as the distances between the front cactus and the window in the two views, creates retinal disparity. This
creates a perception of depth when (a) the left image is viewed by the left eye and (b) the right image is
viewed by the right eye.
Fig. 8-18, p. 176
• 3-D movies
– A polarized filter allows only light
travelling in one position to pass
through. It is made of parallel
micro-sized slits that block out
all but one position of wave.
– A wave in the vertical plane
passes through a vertical
polarized filter.A wave in the
horizontal plane
passes through a horizontal
polarized filter, but would not be
able to pass through a vertical
polarized filter.
• There are two types of filters in 3-D glasses (i.e. vertical
and horizontal). So, one side allows only light travelling in
one position to pass through while the other side allows light
of the opposite position to pass.
• 3-D movies are filmed with a stereoscopic camera that
records video much like how the Pathfinder IMP above
records images. When a 3-D movie is played, two projectors
are used to display both perceptions. Each projects a video
polarized (with a filter) onto the screen. Wearing the 3-D
glasses, each eye can only take in light from one of the
projectors. Therefore, each eye receives a different image.
Your brain interprets these two separate images and
combines them into one 3-D picture.
• Next time you view a 3-D movie, take two set of glasses.
Place the right-eye filter and place it over the left-eye
filter. It's dark. That because the vertical and horizontal
filters are combined and no light can enter. They cancel
each other.
• 立體相機
• 裸眼觀看
Fig. 8-17, p. 176
Also see demo
• 純由像差造成的立體感
– 隨機點立體圖（Random dot stereogram）(Julez, 1971)
– 深度感只能歸因於像差
– 左右眼影像如何match？
對應問題（The correspondence problem）
• 根據單眼特徵作匹配？
• RDS 呢？
Depth Perception in Other Species
• Animals use the range of cues that humans
use.
• Frontal eyes, which result in overlapping
fields of view, are necessary for binocular
disparity.
• Lateral eyes, which do not result in
overlapping fields of view, provide a wider
view.
– This is important for watching for
predators.
Depth Perception in Other Species
• Locusts use motion parallax to judge
distance.
• Bats use echolocation to judge the distance
of objects in the dark.
– They emit sounds and note the interval
between when they send them and when
they receive the echo.
Figure 10.22 When a bat sends out its pulses, it receives echoes from a number of objects in the
environment. This figure shows the echoes received by the bat from (a) a moth located about half a meter
away; (b) a tree, located about 2 meters away; and (c) a house, located about 4 meters away. The echoes
from each object return to the bat at different times, with echoes from more distant objects taking longer to
return. The bat locates the positions of objects in the environment by sensing how long it takes the echoes
to return.
深度知覺的生理基礎
• A neuron in the parietal cortex of a monkey
Figure 8.20 Top: gradient stimuli. Bottom: response of neurons in the parietal cortex to each gradient. This
neuron fires to the pattern in (c), which the monkey perceives as slanting to the left. (From Tsutsui et al.,
2002, 2005.)
• 雙眼深度細胞
（Binocular depth cell）
或像差選擇性細胞
（disparity selective cell）
– 當兩眼影像具有像差時
反應最佳
Figure 8.21 Disparity tuning curve for a disparity-sensitive neuron. This
curve indicates the neural response that occurs when stimuli presented
the left and right eyes create different amounts of disparity. (From Uka
& DeAngelis, 2003.)
– 單眼養育的貓，皮質雙眼深度細胞數量甚少
– 敏感期（sensitive period）為六個
Connecting Binocular Disparity and Depth
Perception
• Experiment by Blake and Hirsch
– Cats were reared by alternating vision
between two eyes.
– Results showed that they:
• had few binocular neurons.
• were unable to use binocular disparity to
perceive depth.
• Neural Responding &
Depth Perception
– DeAngelis et al. (1998)
• Monkey training: depth
created by images with
different absolute
disparity to each eye
• Monkey shifted its
depth judgment
because of a different
group of disparityselective neurons
activated.
– Primary visual cortex
 Ventral and dorsal
streams
大小知覺 (size perception)
• 大小知覺與深度知覺有關
Figure 8.25 (a) The visual angle depends on the size of the stimulus (the woman in this example) and its
distance from the observer. (b) When the woman moves closer to the observer, the visual angle and the
size of the image on the retina increases. This example shows how halving the distance between the
stimulus and observer doubles the size of the image on the retina.
Figure 8.26 The “thumb” method of determining the visual angle of an object. When the thumb is at arm’s
length, whatever it covers has a visual angle of about 2 degrees. The woman’s thumb covers half the width
of her iPod, so we can determine that the visual angle of the iPod’s total width is about 4 degrees.
Fig. 8-27, p. 182
• Holway & Boring (1941)
– 測驗刺激距離雖然會改變，但投射的視角大小維持不變
– 受試者調整比較刺激（固定位置於10ft處）的大小至與測
驗刺激相同
– 1-提供正常深度訊息
2-單眼
3-透過窺視孔
4-走道上加裝布幔
– 顯示大小判斷除運用視角訊息，還要仰賴深度知覺
測驗刺激實際大小隨距離遞增
– 太陽與月亮的大小感覺差不多
– 在飛機上看地面的房子像火柴盒
距不
離熟
悉
它
們
的
實
際
無
法
判
斷
或
用視角判斷
• 大小恆常性（size constancy）
– 即使距離改變，對於大小的知覺仍維持恆定
– 是考慮深度訊息後計算的結果—大小-距離調
節機制（size-distance scaling mechanism）
• demo
• S=K(R x D)
S-知覺大小，K-常數，
R-網膜影像大小，D-距離
– Emmert’s law
– Familiar size and texture gradient information
也都有助於維持大小恆常性
Fig. 8-30, p. 183
Emmert’s law:
K(R x D) = S
Fig. 8-31, p. 184
Fig. 8-32, p. 184
Fig. 8-33, p. 185
錯覺
• Muller-Lyer illusion
– 誤用大小恆常性調節機制 S=K(R x D)
• 但無法解釋啞鈴版或書本版的錯覺
– 線索衝突：大小判斷利用兩種線索
• 實際的線長
圖形的長度
• Ponzo illusion
– 誤用大小恆常性調節
機制
• Ames room
Fig. 8-40, p. 187
Figure 8.41 The Ames room, showing its true shape. The woman on the left is actually almost twice as far
away from the observer as the woman on the right; however, when the room is viewed through the
peephole, this difference in distance is not seen. In order for the room to look normal when viewed through
the peephole, it is necessary to enlarge the left side of the room.
• 月亮錯覺（Moon illusion）
– 表面距離理論（apparent distance theory）
• 地表附近有許多建築或其他結構，提供深度線索，所以
月亮看來較中天遠
– 角度大小對照理論(angular size contrast theory)
• 月亮在中天時，周遭背景較大，所以顯得較小
2005/6/23
Figure 8.42 An artist’s conception of the moon illusion showing the moon on the horizon and high in the sky
simultaneously.
Figure 8.43 When observers are asked to consider that the sky is a surface and are asked to compare the
distance to the horizon (H) and the distance to the top of the sky on a clear moonless night, they usually say
that the horizon appears farther away. This results in the “flattened heavens” shown above.
– 表面距離（apparent distance）理論
• 由窺視孔看，則使錯覺消失
– 大小對比理論
– 其他因子
• 空氣透視
• 顏色
• 輻輳作用
• 距離知覺的判斷也受所付出的努力影響
• 距離知覺的
判斷也受所
付出的努力
影響
Figure 8.44 Results of Witt et al.’s (2004) experiment. For each of the conditions, larger distance estimates
were associated with greater effort.