Yesterday the US Patent & Trademark Office published a patent application from Apple that relates to methods and apparatus for using polarized light (e.g., infrared (IR) light) to improve eye-related functions such as iris recognition in Apple Vision Pro. It also improves the quality of imagery for AR/VR/MR applications such as virtual training environments, gaming, remotely controlling drones or other mechanical systems, viewing digital media content, interacting with the Internet, or the like.

In Apple's patent background they note that conventional eye camera systems use non-polarized light, which has several limitations. For example, non-polarized light may result in reflections from eyelashes and eyelids being captured in the images, which may make processing the images of the eye to perform tasks such as iris recognition and eye/gaze tracking more difficult.

As another example, when glints from the illumination sources fall into the iris region, the region may saturate and thus may not be useful for iris recognition.

As another example, the contrast of iris patterns (the contrast between different regions of the iris) may be low for some eyes.

Apple's invention/granted patent rectifies the negatives listed above that are important for delivering quality MR/AR/VR applications.

Eye Camera Systems With Polarized Light

Apple's granted patent covers methods and apparatus for using polarized infrared (IR) light to improve eye-related functions such as iris recognition are described. As an example, a head-mounted display (HMD) may include an eye camera system that includes one or more IR cameras that capture images of the user's eyes that are processed to perform iris recognition, gaze tracking, or other eye-related functions.

In embodiments, at least one light polarizing element may be located in the path of the light which is used to capture images of the user's eye (or other facial features). In some embodiments, the user's eye may be illuminated by IR light emitted by one or more LEDs of the HMD.

In some embodiments, at least one of the LEDs may be an LED package with an optical filter or filters as described herein. In some embodiments, at least one polarizer (e.g., polarizing filter) may be located at the eye camera sensor, in the eye camera optics, or as or in an additional optical element located on the light path between the eye camera and the user's eye.

Embodiments of the eye camera system may improve the performance of eye-related functions of the HMD including but not limited to iris recognition and eye/gaze tracking through the use of polarized light. Conventional eye camera systems use non-polarized light, which has limitations. For example, non-polarized light may result in reflections from eyelashes and eyelids being captured in the images, which may make iris recognition and eye/gaze tracking more difficult. For users with contact lenses or a smooth corneas, strong reflections of eyelash and eyelid may prevent the iris recognition and/or eye/gaze tracking from working properly.

As another example, when glints from the illumination sources (e.g., from non-polarized LEDs) fall into the iris region, the region may saturate and thus may not be useful for iris recognition. As another example, the contrast of iris patterns (the contrast between different regions of the iris) may be low for some eyes. Using polarized light in the eye camera system may overcome these and other limitations of using non-polarized light by reducing or eliminating reflections, reducing or eliminating glints, and/or improving contrast in the iris region.

Apple's patent FIG. 8 below graphically illustrates an IR eye camera with IR LEDs that illuminate the eye, according to some embodiments. Images of the iris captured by the eye camera may be processed, for example to perform iris recognition to determine if the person wearing the HMD is authorized to use the HMD. Images of the eye captured by the eye camera may instead or also be processed to determine the current visual axis and point of gaze of the user with respect to the display.

The images captured by the cameras may include glints, which are reflections of the IR light sources (e.g., arrays of LEDs) on the surface of the cornea. The images may also include reflections of the user's eyelashes and/or eyelids.

In addition, in regions of the images such as the iris, contrast may not be sufficient to efficiently perform functions such as iris recognition. Embodiments may use polarized IR light when capturing images to improve eye-related functions such as iris recognition and eye/gaze tracking.

In some embodiments, at least one of the LEDs may be an LED package with a polarizing filter or filters as described herein. In some embodiments, instead of or in addition to the polarized LEDs, at least one polarizer may be located at the eye camera sensor, in the eye camera optics, or as or in an additional optical element located on the light path between the eye camera and the user's eye.

Apple's patent FIGS. 9A and 9B above illustrate components of an eye camera system in an example HMD in which the eye camera #940 images a reflection of the user's eye #992 through an eyepiece or eye lens #920, and in which the LEDs #900 illuminate the eye through the eye lens.

FIGS. 13A and 13B illustrate enhancement of contrast using polarized light, according to some embodiments. FIG. 13A shows an iris image with lower contrast between the iris-pupil boundary captured with non-polarized light. FIG. 13B shows an iris image with lower contrast between the iris-pupil boundary captured with polarized light.

For more details, review Apple's granted patent 11861941