Why IR illumination is necessary?

SimpleGazeTracker requires IR illumination because it makes pupil detection easier and more reliable. Figure 1 is an example of ocular image when participant is looking a PC display in a dark room (contrast is enhanced). Corneal reflection of PC display is overlaid on the pupil. Boundary between pupil and iris is quite unclear. It is difficult to measure the center of the pupil quickly and reliably from such images.

Figure 1

With using IR-pass filter, corneal reflection of PC display is reduced and measuring the pupil center becomes much easier (Figure 2).

Figure 2

Fgiure 3 is another example. Participant is looking on a PC display in a well-lit room. The light coming through a window is reflected by eye and eyeglass. Similar to a case shown in Figure 1, it is difficult to detect boundary between pupi and iris in such a case, too.

Figure 3

Adding an IR illumination, pupil can be detected much easily.

Figure 4

Inserting IR pass filter

FUJIFILM's IR pass filter is used for development. A sheet of 7.5x7.5cm costs approximately 1,000 JPY.

IR filter is cut round and is inserted in front of the camera sensor.