To track saccadic movements, one needs to track the eye hundreds of time per second. Smooth pursuit is how we move when we track a moving object. They aim to get the image of an object to appear on corresponding spots on both retinas. Vergence shifts are small movements the help in depth perception. Saccadic movements are fast and happen when we need to shift gaze from one area to another. How often should we calculate the gaze direction? The eyes have several types of movements. This method provides high-speed data but is less accurate than camera-based tracking. For instance, some have tried to detect movements of the eye muscles. There are other eye tracking approaches that are less popular. This allows estimating of the fixation point of the user in real or virtual 3D space. If eye tracking cameras observe both eyes, one can combine the gaze readings from both eyes. Other vendors developed special-purpose chips that offload the processing from the main CPU. This allows estimating the direction of gaze from the observed eye. Processing is sometimes done on a PC, phone or other connected processor. The image captured by the camera is then processed to determine the location of the pupil. Whether we use dark or bright pupil, the key point is that the pupil looks different than the rest of the eye.
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It is like the “red eye” effect when using flash photography. If the IR light source is near the optical axis, it can reflect from the back of the eye. Thus, the camera sees the pupil as a dark area – no reflection – whereas the rest of the eye is brighter. Instead, it reflects back towards the camera. Outside the pupil area, light does not enter the eye. IR light also enters the eye through this pupil. We see the world when our retinal detects light entering through the pupil. The eye can’t detect the illumination but the camera can.
![how does eye tracking work how does eye tracking work](https://talktechnical21.files.wordpress.com/2018/12/eyeTracking1.jpg)
It is just outside the visible spectrum of 390 to 700 nanometers. The wavelength of the light is often 850 nanometers. IR illuminates the eye and a camera sensitive to IR analyzes the reflections. Most eye tracking systems use a camera pointing at the eye and infrared (IR) light. But how does it work? Let’s look at a high-level overview. Scientists and vendors have spent many year perfecting algorithms and techniques. Eye tracking can help advertisers understand what interests customers.Įye tracking is complex. Eye tracking can detect concussions in athletes and can even help people see better. Additionally, People with certain disabilities can use their eyes instead of their hands. Understanding gaze direction can lead to more natural interaction. Higher-resolution images at shown at the central vision area and lower-resolution outside it. Tracking gaze direction can deliver many benefits. Foveated rendering, for instance, optimizes GPU resources by using eye tracking data.
![how does eye tracking work how does eye tracking work](https://i0.wp.com/assistivetechnologyblog.com/wp-content/uploads/2016/08/Visible_light_eye-tracking_algorithm.jpg)
Eye tracking could become a standard peripheral in VR/AR headsets.