. 2014 Sep 14;2014:303670. doi: 10.1155/2014/303670

Table 1.

Summaries of proposed and previous approaches.

Category			Method	Advantages	Disadvantage
Gaze tracking on 2D screen	Wearable device [9, 10, 15]		Eye images are acquired by wearable gaze tracking device.	The accuracy of gaze estimation is usually higher than that by nonwearable device.	Application is restricted to interaction with a 2D screen.
Gaze tracking on 2D screen	Nonwearable device [11–14]		Eye or face images are acquired by nonwearable gaze tracking device.	User convenience is higher than that by wearable device.	Application is restricted to interaction with a 2D screen.

Gaze tracking in 3D space	Wearable device [16–21]		Scene and eye images are acquired by wearable device.	The allowable range of head rotation is large, because the wearable gaze tracking device is moved according to head movement.	User inconvenience increases by wearing the device including two cameras for gaze estimation and frontal viewing.
	Nonwearable device	Frontal viewing camera sensing visible light [16]	Scene and eye images are acquired by nonwearable devices.	User convenience is higher than that by wearable device.	Complicated algorithm is required to recognize the object in the visible light image given by frontal viewing camera.
	Nonwearable device	Frontal viewing camera sensing NIR light (proposed method)	Scene and eye images are acquired by nonwearable devices.	The object in the frontal viewing image can be easily detected and recognized using the NIR camera and NIR LED pattern.	Additional NIR LEDs must be attached to the outer boundary of the object to be recognized.