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EP-4505236-B1 - EYE-IMAGING SYSTEM WITH SWITCHABLE HOT MIRRORS

EP4505236B1EP 4505236 B1EP4505236 B1EP 4505236B1EP-4505236-B1

Inventors

  • LUNDELL, Benjamin Eliot
  • KOLLIN, JOEL STEVEN
  • CHATTERJEE, Ishan
  • PACE, MARIA ESTHER
  • BOLAS, MARK THEODORE
  • KRESS, Bernard Charles
  • HELD, ROBERT THOMAS
  • GEORGIOU, ANDREAS
  • AHOLT, CHRISTOPHER CHARLES

Dates

Publication Date
20260506
Application Date
20230124

Claims (13)

  1. A head-mounted display system (400;600; 700; 800; 900), comprising: a frame; an eye-imaging camera (404; 606; 704; 802; 804; 902) supported on the frame; a switchable hot mirror array (408; 520; 602; 702; 810; 812) comprising a plurality of switchable hot mirrors (406, 408, 410, 412) configured to direct light reflecting from an eye (402; 604; 706) toward the eye-imaging camera (404; 606; 704); and a controller (414; 524) configured to control switching of a reflectivity of each of the plurality of switchable hot mirrors (406, 408, 410, 412), wherein the controller is configured to determine a most recent pupil position based on image data obtained by the eye-imaging camera, and control imagining of only the pupil by switching on only a subset of the plurality of switchable hot mirrors based upon the most recent pupil position.
  2. The head-mounted display system (600) of claim 1, wherein two or more switchable hot mirrors of the plurality of switchable hot mirrors are oriented at different angles to the eye-imaging camera (606).
  3. The head-mounted display system (800) of claim 1, wherein the eye-imaging camera (802, 804) is located at a side portion of a frame.
  4. The head-mounted display system of claim 1, wherein the eye-imaging camera is located at an upper portion of the frame.
  5. The head-mounted display system of claim 1, wherein the switchable hot mirror array is positioned within a visibly transparent support (512).
  6. The head-mounted display system of claim 1, wherein the eye-imaging camera comprises a line camera.
  7. The head-mounted display system (700; 900) of claim 1, further comprising an infrared light emitter (708; 806A-D, 808A-D; 904A, 904B, 906A, 906B) configured to direct infrared light toward the plurality of switchable hot mirrors.
  8. The head-mounted display system of claim 1, wherein the switchable hot mirror array comprises an array of switchable Bragg gratings.
  9. The head-mounted display system of claim 1, wherein the switchable hot mirror array comprises a polarization-selective mirror.,
  10. The head-mounted display system of claim 1, wherein one or more switchable hot mirrors of the plurality of switchable hot mirrors comprises optical power.
  11. On a computing system, a method (1000) of operating an eye-imaging system, the eye-imaging system comprising an eye-imaging camera and a plurality of switchable hot mirrors each configured to direct light reflecting from an eye to the eye-imaging camera, the method comprising in a first time period, controlling (1004) a reflectivity of a first switchable hot mirror to allow light from the eye to pass through and controlling a reflectivity of a second switchable hot mirror to reflect light from the eye to the eye-imaging camera; and in a second time period, controlling (1006) the reflectivity of the first switchable hot mirror to reflect light from the eye to the eye-imaging camera, further comprising determining a most recent pupil position based on image data obtained by the eye-imaging camera, and controlling imagining of only the pupil by switching on only a subset of the plurality of switchable hot mirrors based upon the most recent pupil position.
  12. The method of claim 11, wherein the plurality of switchable mirrors further comprises one or more additional switchable hot mirrors, and further comprising controlling the reflectivities of the plurality of switchable hot mirrors sequentially.
  13. The method of claim 11, further comprising outputting (1002) infrared light toward the plurality of switchable hot mirrors to illuminate an eye for imaging.

Description

BACKGROUND Display devices may utilize eye-imaging cameras to enable eye tracking as an input mode and/or for user authentication. Eye tracking may enable a display device to respond to movements of a user's eye, such as by displaying virtual imagery in appropriate locations, and/or detecting eye gestures as user inputs. However, positioning eye-imaging cameras on some devices may pose challenges. For example, a head-mounted mixed-reality display device may comprise a see-through display that combines projected virtual imagery with a view of a real-world environment. In such a device, positioning an eye-imaging camera in front of a user's eye may occlude a view of the real-world environment. On the other hand, positioning the eye-imaging camera on a frame of the device may provide only an oblique view of the user's eye, thereby making eye tracking more challenging for some gaze directions. A display device utilizing an eye-imaging camera is known from US 10 168 531 B1. SUMMARY The invention is defined by the independent claim. Preferred embodiments are defined by the dependent claims. This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure. Examples are disclosed that relate to using an array of hot mirrors in an eye-imaging system. One example provides a head-mounted display system comprising a frame, an eye-imaging camera supported on the frame, a switchable hot mirror array comprising a plurality of switchable hot mirrors configured to direct light reflecting from an eye toward the eye-imaging camera, and a controller configured to control switching of a reflectivity of each of the plurality of switchable hot mirrors. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a user wearing an example head-mounted display device comprising an eye-imaging camera.FIG. 2 shows the head-mounted display device of FIG. 1 in more detail.FIG. 3 schematically shows an example eye-imaging system comprising a single hot mirror.FIGS. 4A-4D schematically show operation of an example eye-imaging system comprising an array of switchable hot mirrors.FIGS. 5A-5D schematically illustrate an example method of making a switchable hot mirror array.FIG. 6 shows an example eye-imaging system comprising hot mirrors arranged at varying angles.FIG. 7 shows an example eye-imaging system comprising switchable hot mirrors configured to direct illumination light toward an eye.FIG. 8 shows an example head-mounted display device that includes left and right-side eye tracking sensors respectively arranged on left and right-side portions of a device frame.FIG. 9 shows an example head-mounted display device that includes an eye tracking eye-imaging camera arranged on a nose bridge portion of a frame.FIG. 10 shows a flow diagram depicting an example method of imaging an eye.FIG. 11 shows a block diagram of an example computing system. DETAILED DESCRIPTION As mentioned above, positioning eye-imaging cameras on some head-mounted devices may pose challenges. For example, some head-mounted mixed-reality display devices may position an optical combiner close to a user's eye to mix virtual projected images with a view of a real-world background. As such, a frame that supports the combiner (which may take the form of an eyeglasses frame in some examples) may be positioned at oblique angles to a user's eye. Thus, a camera positioned on such a frame may not have a clear view of the user's pupil when the user's gaze is directed away from the camera. As one possible solution to this problem, two or more cameras may be used for each eye to image the eye from different angles. While such an arrangement may provide for unobstructed imaging of the eye from a wider variety of angles, the use of multiple cameras increases device cost and complexity. As another possible solution, a hot mirror may be placed in front of the eye to reflect infrared light toward a camera positioned obliquely to the eye. A hot mirror is a dichroic reflector that reflects one or more wavelengths of infrared light (which may include near-infrared) while being transparent to visible light. In such a configuration, the mirrors and the camera are not visible to the user, yet the image formed on the camera's image sensor may appear as though it originates from a camera directly in front of the user's eye. The hot mirror may be formed on a surface of a transparent substrate, or embedded within a transparent support. However, as the hot mirror would be angled relative to the eye (e.g. to reflect light upward or to the side toward a frame-mounted camera), to provide for a suitably wid