EyeInfo Research Group

Build Your Own Head-Mounted Eye Tracker

A head-mounted eye tracker consists of two cameras, one for capturing the eye image (eye camera) and the other one for capturing the user's field of view (scene camera). Haytham works based on the dark pupil method and it needs an infrared (IR) image of the eye, therefore the eye camera should be infrared (night vision). You probably need some filters that can block all visible light but don't block infrared light. A cheep solution would be to use photography film negatives (Figure 6). Find some unexposed (black) processed film (there should be some black bits at the end of the old negatives), and use put them in front of the lens or the CCD of the camera. You can also buy some visible light cut off filters that look like black pieces of glass that is transparent for the light of certain wavelength range. I found these in eBay. Just remember to know the wavelength of the infrared leds that you are using to buy a appropriate filter.

Figure 6: Example of low-cost IR filter block.


Wireless Head-Mounted Eye Tracker

If you would like to have a wireless eye tracker, there are some wireless night vision IR pinhole cameras (e.g., link1 and link2) that work fine for the distance about 10 meters (Figure 7). I have used this cameras couple of years ago on Dias eye tracker, and they worked pretty well. You just need some AV adapter (EasyCap USB) that capture the analog image from the wireless receiver and convert it to digital.

Figure 7: Example of two wireless night-vision cameras.

 

I have also found some very tiny infrared cameras (Figure 8) from a Chinese Company and they can be used as both eye camera and the scene camera:

Figure 8: Other infrared cameras that you can used to build your now head-mounted eye tracker.

Find a plastic glasses frame and a small telescopic antenna (used as an arm) and mount the cameras on the frame (Figure 9). The good point of using the antenna is that it is very solid against the shakes and vibration, and on the other hand you can use the telescopic feature of the antenna (extensibility and twisting the element) to give some degree of freedom to the eye camera. Therefore the eye camera can be easily adjusted in front of the eye.

Figure 9: Example of the use of a telescopic antenna to mount the cameras on head-mounted eye tracker.

In Figure 10, you can see the images captured by the wireless cameras in the Haytham software, and the video of the wireless head-mounted gaze tracker.

Figure 10: Examples of some images captured during an eye tracking session.


Wired Head-Mounted Eye Tracker

Genius islim 321R is a light weight night vision webcam that provides a sharp IR image of the eye and is good for making a head mounted eye tracker. This webcam has the infrared leds on it and you don't need to add a light source for the eye. You can either use a cap or a glasses frame to mount the cameras on it. Use a piece of wire and mount the eye camera in front of one of the eyes (distance about 10cm). Place the scene camera as close as possible to the eye in order to reduce the parallax error, as shown in Figure 11.

Figure 11: An wired head-mounted eye tracker.

You can actually use the ball joint of the webcam on the eye tracker. Disassemble the joint, use the glue and attach the lower part of the joint on the cap, as show in Figures 12 and 13. :)

Figure 12: Example of a scene camera used by a wired head-mounted eye tracker.

Figure 13: Cameras used by the wired head-mounted eye tracker.


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