人機介面 視線軌跡追蹤 : 原理與應用

人機介面視線軌跡追蹤 : 原理與應用授課教師開課單位

Outline眼動儀類型應用領域與最新技術

– Application areas– State-of-the-art technologyEye tracker @NCCUCS 1.0

(wearable)Eye tracker @NCCUCS 2.0 (remote)Gaze-based HCI Demo ( 展示 )Conclusions

眼動儀類型侵入式

– 搜尋線圈法（ Search Coil ）– 眼電圖法（ Electro-Oculography ）非侵入式– 紅外線視訊（ Infra-red Video System ）– 光學式瞳位追蹤 (Optical-type Eye Tracking

Device)– 紅外線眼動圖法（ Infra-red Oculography ）– Purkinje 影像追蹤法（ Dual-Purkinje-

image ）

搜尋線圈法利用電磁感應的原理來測量眼球的移動

優點：有很好的空間和時間解析度缺點：需戴上侵入式鏡片受到眼球分泌物的影響固定磁場

搜尋線圈法四週固定磁場示意圖

眼電圖法利用電極的原理來測量眼球的移動缺點：

必須貼電極貼在皮膚上 皮膚角質分泌影響皮膚電阻

優點： 價格便宜

紅外線視訊系統影像追蹤的方法記錄眼球的移動缺點：

價格昂貴空間位置校正

優點： 可計算瞳孔移動位置和大小

光學式瞳位追蹤系統由攝影機所獲得的瞳孔影像，利用影像處理的方式，分析眼球的移動軌跡

優點： 使用者頭部與攝影機之間的相對位置不會改變

第四代追瞳器裝置

缺點： 頭盔因本身重量往下滑 光源讓人不舒服 配戴眼鏡無法使用

紅外線眼動圖法利用紅外線光源在眼角膜邊緣的反射差異，來檢測眼球運動狀況

缺點： 紅外線光對眼睛可能會造成傷害

優點： 測量範圍廣

Purkinje 影像追蹤法光源經過眼球組織不同的折射率，來計算眼球運動

缺點： 不能和眼球同步 價格極為昂貴

優點： 不易受眼瞼遮蔽準確度高

應用領域醫療 : 漸凍人等身體障礙者輸入介面EyeMusic - 創作音樂EyeDraw - 繪畫Usability: 網頁和廣告的使用性和實用性電腦 - 替代滑鼠，文字輸入遊戲 - eye tracking game心理學 - 眼球測謊儀閱讀 - text 2.0遠端遙控 - 遠端電視操控， EyeTech

基於影像之眼動追蹤An eye tracker is a device for measuring

eye positions and eye movements. The most popular variant uses video

images from which the eye position is extracted.Input source: visible spectrum vs. infrared

眼動 Eye MovementsEye movements are typically divided into

fixations ( 凝視 when the eye gaze pauses in a certain position) and saccades ( 掃視 when it moves to another position).

The resulting series of fixations and saccades is called a scanpath. ( 掃描路徑 )

掃描路徑實例

阿春眼動看護

EyeWriter Project

Web Design (U. of Manchester)

Heat map Gaze plot

Usability Study:Google Search Evaluation

Gaming

Driving Behavior

[Andrew T. Duchowski]

Character Input

EyeWrite [Andrew T. Duchowski]

Media ResearchThe Poynter Institute :

http://www.poynter.orgPublished first eye track study in

1991.More results published in 2000,

2004 and 2007.Eyetrack ’07:

http://www.poynter.org/content/content_view.asp?id=105035

Text 2.0

Research Communities

ACM SIG/CHIEye Tracking Research and

Applications (ETRA) Symposium: http://www.e-t-r-a.org/ COGAIN: Communication by Gaze

Interaction http://www.cogain.orgReferences:

http://www.cogain.org/downloads/

State-of-the-art Eye tracking Technology

Hi-Speed (SMI iView X™ Hi-Speed)Head-Mounted SystemRemote trackingIntegrated with LCD monitorWearable glasses

Mobile Eye Tracker 1.0 @ NCCUCS

eye camera

scene camera

Key ObjectivesLow-cost (NTD 10,000 vs.

1,000,000) MobilityEasily customized for specific

applicationsOn-line processingSampling rate?Accuracy?

System Architecture

Eye image

Preprocessing

Pupil detection

Gaze point projection

Scene image

Calibration

9 pairsof points

Calibration process

Pupil Detection (I):extracting feature points

Pupil Detection (II): Ellipse fitting using RANSAC

Pupil Detection (III):checking fitness measure

• Ellipse model:

n

bfScore

m

afScore

n

iiin

in

m

iiout

out

11

)(,

)(

20,sin

coscossinsincos cy

cxba

yxp

,0

,)(,1otherwise

PaThresholdapiff outbrightout

,0

,)(,1otherwise

PbThresholdbpiff indarkin

Number of bright vs. dark points inside and out the perimeter

Results

HCI Application: Eye Scrolling

HCI Application: Eye Gaming

HCI Application: Eye Typing

Mobile Eye Tracker 2.0 @ NCCUCS

Improve the pupil detection algorithm to alleviate corneal reflection problem.Enhance the accuracy by

compensating for head movement. Construct and test a remote eye

tracker.More HCI applications using the

remote eye tracker.Use the eye tracking device to

assist mobile user interface design.

Improved Pupil Detection

Allowing Head Movement

Remote Eye Tracker

Experimental Results (Wearable)Calibration

point

Original error Compensate for head

movement

(error/standard deviation)

1 98.17 32.91 (12.7)

2 137.54 55.89 (10.94)

3 108.20 29.69 (9.57)

4 76.30 28.79 (21.19)

5 113.30 22.49 (7.79)

6 117.86 34.83 (10.96)

7 116.53 33.31 (8.01)

8 112.56 16.03 (6.78)

9 146.73 26.49 (9.66)

1 cm = 38 Pixels

Accuracy (Wearable)

Experimental Results (Remote)Calibration point Original error Compensate for head movement

(error/standard deviation)

1 238.73 39.69 (24.6)

2 227.51 63.56 (22.82)

3 132.97 44.30 (21.49)

4 222.97 51.66 (30.94)

5 306.58 31.15 (16.71)

6 280.79 51.66 (21.83)

7 311.89 69.03 (41.57)

8 344.24 69.88 (31.71)

9 347.03 64.66 (24.41)

Accuracy (Remote Eye Tracker)

Demo: Web Browsing

Demo: Photo Viewing

Demo: Interactive Story Telling

Demo: Tic-Tac-Toe

Gaze Path AnalysisRecursive intersection

– Find the similarity between two scan paths

– Order of scanning is irrelevant– Suitable for processing fixation dataModified dynamic time warping

– Order of scanning is taken into account– Can handle both fixation and saccade

data

Recursive Intersection

Path 2

Path 1

Recursive Intersection: Example

Dynamic Time Warping (DTW)

Modified DTW (MDTW)

X-axisY-axis

time

MDTW Result

SummaryEye tracking device

– Low cost (<$10,000 NTD)– Head-mounted with mobile functionality– Remote eye tracking– Allow slight head movements– Accuracy: suitable for some HCI

applications, image viewing tasks, not high enough for reading

HCI applications