In this paper, we present the first realisation and experimentation of a new eye tracking system using an infrared (iR) laser pointer embedded into a wireless smart contact lens. We denote this contact lens prototype as the cyclops lens, in reference to the famous hero of the X-Men comics. The full eye tracker device combines the smart contact lens and its eyewear, which provides a primary source of energy and the beam detection system. We detail the assembling and encapsulation process of the main functionalities into the contact lens and present how a gaze tracking system is achieved, compared to existing conventional eye-tracking ones. Finally, we discuss future technical improvements.

Most eye trackers nowadays are video-based, which allows for a relatively simple and non-invasive approach but also imposes several constraints in terms of necessary computing power and conditions of use (e.g., lighting, spectacles, etc.). We introduce a new eye tracker using a scleral lens equipped with photodiodes and an eyewear with active illumination. The direction of gaze is obtained from the weighted average of photocurrents (centroid) and communicated through an optical link. After discussing the optimum photodiodes configuration (number, layout) and associated lighting (collimated, Lambertian), we present prototypes demonstrating the high performances possibilities (0.11° accuracy when placed on an artificial eye) and wireless optical communication.

Most current eye-trackers are camera-based and rely on image processing. To improve gaze tracking accuracy, this paper presents a new approach based on a camera-less gaze tracking system using a smart contact lens. A scleral lens is fitted with photodetectors illuminated by specific spectacles. Photo-currents vary with eye movements as the light photodetectors received varies. The gaze direction is obtained then by computing a barycenter from the photo-currents by means of an integrated circuit implemented on the lens and powered using an inductive link. Experimental measurements with a prototype lens fitted with four infrared photodiodes and mounted on an artificial eyeball validate the method. Designed for the AMS 0.35-μm CMOS process, a 170 μW integrated circuit is proposed, including a subthreshold analog barycenter computation unit and an analog-to-digital converter. Monte Carlo analysis based on the circuit layout and measured photo-currents shows an accuracy of 0.2° can be achieved. This is 2.5 times better than current camera-based eye-trackers.

We present the design, fabrication, and test of a multipurpose integrated circuit (Application Specific Integrated Circuit) in AMS 0.35 µm Complementary Metal Oxide Semiconductor technology. This circuit is embedded in a scleral contact lens, combined with photodiodes enabling the gaze direction detection when illuminated and wirelessly powered by an eyewear. The gaze direction is determined by means of a centroid computation from the measured photocurrents. The ASIC is used simultaneously to detect specific eye blinking sequences to validate target designations, for instance. Experimental measurements and validation are performed on a scleral contact lens prototype integrating four infrared photodiodes, mounted on a mock-up eyeball, and combined with an artificial eyelid. The eye-tracker has an accuracy of 0.2°, i.e., 2.5 times better than current mobile video-based eye-trackers, and is robust with respect to process variations, operating time, and supply voltage. Variations of the computed gaze direction transmitted to the eyewear, when the eyelid moves, are detected and can be interpreted as commands based on blink duration or using blinks alternation on both eyes.

This paper presents a camera-less eye tracker. Composed of 2 parts, an instrumented contact lens and spectacles, its principle consists in computing a barycenter based on the light intensity variations received from the spectacles onto the lens. To demonstrate both the method and the achieved accuracy it yields, a prototype lens fitted with 4 infrared sensors has been fabricated and tested. Based on measured photo-currents, simulations, both behavioral and at transistor level (AMS 0.35 µm CMOS), show an accuracy of 0.1° can be achieved. Which is a significant improvement to the 1° camera-base eye trackers offer.