VCSEL pair used as optical pointers in a contact lens for gaze tracking and visual target designation

Abstract

We present a new eye-tracking and target designation device based on a contact lens incorporating a pair of vertical-cavity surface-emitting lasers (VCSELs). We describe the operating principle, the manufacturing process and characterize the impact of the VCSELs encapsulation on their optical properties. We then describe how such device can be incorporated into an eye-wear or a visual augmented system. We compare two different detection set-ups, the first using a camera and the second a position sensitive device, both illustrating different laser beam detection modes. We analyze their performances in terms of angular accuracy, speed, compactness, manufacturability, compared to current conventional eye-tracking systems. We emphasize how the use of two VCSELs and the control of their orientation during the encapsulation can simplify their integration in host systems and improve the gaze detection performance. Finally, we describe various embodiments and discuss potential improvements that can be expected in future systems.

Fig 1. CLP presentation.

a) VCSELs pair prototype (1: encapsulated circuit. 2: left VCSEL. 3: right VCSEL. 4: capacitor). b) Back side. c) CLP mounted on the mock-up eye behind the primary antenna (green element) in the eyewear.

Fig 2. (a) CLP top view with the horizontal angular separation; (b) Side view with the vertical angular separation.

Fig 3. Pictures of the spots on the paper screen recorded at three distances of the CLP: 40 mm, 45 mm, and 50 mm.

Fig 4. Abscissa: Beam direction (horizontal).

Ordinate axis: standard deviations (in pixels) of the centroid positions in x over three CLP-screen distances, for a CLP sample. When this value is minimal, the screen is considered normal to the direction of emission of the VCSEL.

Fig 5. Example of waist detection (blue circle).

Fig 6. Camera characterization bench.

a) CLP on the mock-up eye, b) primary antenna. c) CMOS camera.

Fig 7. PSD eye-tracking test bench.

a) primary antenna. b) PSD, c) CLP mounted on the mock-up eye.

Fig 8. Voltage measurement as a function of the spot position on the PSD (after offset correction).

Fig 9. PSD measurements as a function of gaze direction for two CLP-PSD distances: (a) 1.5 cm and (b) 2 cm.

The continuous line represents the experimental data and the dashed line the fitted model.

Fig 10. New manufacturing design to control VCSEL eccentricities.

Top right image: the CLP in the lens blank before lathing. Bottom right: the final CLP. Left: cross-section of the CLP where a) is the front surface and b) the VCSEL and circuit housing.

Fig 11. New manufacturing design to control the VCSEL eccentricity.

a) top view CLP of the CLP, the arrow illustrates the meridian of the cross section depicted in b); b) cross-section showing the VCSE in its housing.

Fig 12. Eyewear in the camera configuration.

The camera is mounted on top the eyewear frame. The beam splitter allows positioning the camera virtually in front of the eye.

Fig 13. PSD compact eyewear.

PSD is mounted on top of the eyewear.

Fig 14. The angular orientation of the VCSEL on the contact lens can be chosen to facilitate positioning of the PSDs close to the eye and to extend the gaze range over which the eye is tracked.