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| 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. |
| Nonwearable device [11–14] | Eye or face images are acquired by nonwearable gaze tracking device. | User convenience is higher than that by wearable device. |
|
| 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. |
Frontal viewing camera sensing NIR light
(proposed method) | 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. |
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