Apple was granted a couple of eye-tracking patents this summer (01 & 02) and both of them stemmed from Apple's acquisition of Germany's SMI SensoMotoric Instruments which Apple Acquired back in July 2017. Today Apple was granted their third eye-tracking and yet again it stems from the work done by SMI.

Tom Sengelaub has been an Engineering Manager at Apple since the acquisition and was the Project Lead Virtual Reality Engineering Manager at SMI. Martin Haller, who joined Apple after the acquisition is a Computer Vision Engineer and was the Technical Lead for Automated Semantic Gaze Mapping at SMI.

Today the U.S. Patent and Trademark Office officially granted Apple their third eye tracking patent for 2019 titled "Eye tracking device and method for operating an eye tracking device."

The invention relates to an eye tracking device comprising an optical system, which comprises a capturing unit for capturing images of at least one part of at least one eye of a user.

The eye tracking device further comprises a processing unit for determining at least one property of the at least one eye, e.g. the gaze direction, based on the captured images. Moreover, the capturing unit is configured to capture a first image and a second image of the at least one part of the at least one eye of the user. The invention also relates to a corresponding method for operating an eye tracking device.

There are different eye tracking devices known from the prior art, like remote eye trackers or head-mounted eye trackers, as well as different eye tracking methods, like appearance-based eye tracking or model-based eye tracking. Such eye tracking devices usually capture images of an eye of a user and determine certain features of the eye on the basis of the captured images. Usually, from these images a pupil position or iris position is determined.

For example, the pupil position can be found by first searching for the pupil in the image and then calculating the pupil center, for example, by finding the center of the pupil contour points.

Some eye trackers also use active illumination for producing cornea reflections on the eye. By assuming that the cornea surface is a sphere and by determining the position of two or more such cornea reflections the cornea center can be determined.

Also, the gaze direction can be determined, for example, as a straight line through the cornea center and the pupil center. This straight line defines the optical axis of the eye and can be calibrated in a calibration procedure to take into account individual deviations of the line of sight from the optical axis of each individual user.

With regard to eye trackers and eye tracking methods in general there will always persist the need for enhancing accuracy and precision. The precision and accuracy of the gaze direction or other determined eye features mainly depends on how accurately eye features like the pupil or cornea reflections and their positions can be determined in the captured images.

Moreover, as eye trackers get integrated in more and more devices, like computers, cars, virtual-reality-glasses, and so on, it's also a need to provide very compact eye tracking devices and offering much flexibility.

Therefore, it is an object of the present invention to provide an eye tracking device and a method for operating an eye tracking device by means of which high precision and accuracy can be achieved and by means of which the eye tracking capabilities can be enhanced.

The eye tracking device may be a head-mounted eye tracking device, like an eye tracking spectacle device, or an eye tracker integrated in a helmet or also integrated in a head-mounted display device, in virtual reality glasses, in augmented reality glasses or other head worn devices.

The eye tracking device may also be a remote eye tracker, optionally integrated or coupled with other devices like a computer, displays, monitors, and so on. The capturing unit may comprise one or more cameras, light sensors, like image sensors, for example a CCD sensor or a CMOS sensor.

In general, the processing unit may be a processor, a controller, a microcontroller or any kind of integrated circuit. The optical system can comprise any optical elements like one or more lenses, prisms, beam splitters, mirrors, reflectors, light guides, collimators, and so on.

Apple's patent FIG. 1 below a schematic illustration of an eye tracking device; FIG. 2a is a schematic illustration of a first image captured by the capturing unit of the eye tracking device according to a first setting of the optical system of the eye tracking device; FIG. 2b a schematic illustration of a second image captured by the capturing unit of the eye tracking device according to a second setting of the optical system of the eye tracking device.

Apple's patent FIG. 5 above is a flow chart illustrating a method for operating an eye tracking device.

Apple's granted patent 10,437,327 was originally filed in Q4 2016 and published today by the US Patent and Trademark Office.

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