Next Generation of Human Eye Simulator Prevents Eye Tracker Failures by Eliminating Unwanted Reflections with New IR Filter

Almalence introduces the next generation of its Human Eye Simulator, now making the simulator look exactly like a human eye by completely eliminating the unwanted pupil reflections in the IR specter.

A closer look at the evolution of how Almalence Human Eye Simulator looked like to the eye trackers in IR specter:

First generation:

In this IR capture from an eye-tracking camera, you can see the nicely defined glints. These are produced by eye-tracking system IR projectors and reflect off the synthetic cornea.

You can, however, also see some internal structure within the eye pupil. That structure is in fact the camera lens inside the eye simulator. Its presence in the captured image can distract the eye-tracking system. A real eye has no internal structures visible under IR illumination.

Second generation:

In the next generation of the Simulator, Almalence took care of the above issue by adding a conventional IR-cut filter.

Such filters are commonly sandwiched between the lens and the image sensor in digital cameras to prevent IR illumination to which the digital sensors are sensitive. The IR component of the light presents under some lighting conditions, and if not filtered out results in incorrect colors in the captured image.

Adding the IR filter to the Simulator worked very well for concealing the internal lens structure behind the pupil. Another issue remained though: under specific relative orientations of the simulated eye to the eye-tracking system, the surface of the filter was now producing a reflected image of the eye-tracking system itself.

In the image above, captured by an eye-tracker camera, you can see a reflection of that camera and its lens as well as the white background behind it.

Third generation:

In the third generation of the Simulator we implemented a custom-designed, non-flat, non-reflecting IR filter, achieving two major improvements over the previous design:

  1. No unwanted reflections inside the pupil, regardless of the simulator orientation.
  2. The non-flat surface has improved the overall MTF of the system and eliminated the unwanted reflections of the light from the IR LEDs that appear at some specific orientations and would blind the eye-tracking system.

With the design improvements made in the third generation Eye Simulator, Almalence achieved its robust operation and eliminated eye-tracking failures across all possible eye orientations and gaze angles, making the Simulator the ultimate solution for image capturing, optical profiling, and quality measurement of VR/AR head-mounted displays equipped with eye-tracking.