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EP-4599317-B1 - EYE TRACKER COMPRISING A SHADOW MASK AND ELECTRONIC DEVICE

EP4599317B1EP 4599317 B1EP4599317 B1EP 4599317B1EP-4599317-B1

Inventors

  • NAJER, Daniel
  • SUAREZ, FERRAN
  • D'ALEO, Francesco Paolo

Dates

Publication Date
20260506
Application Date
20231201

Claims (14)

  1. An eye tracker (11) comprising: a shadow mask (100); a light emitting element (116); and a detection region (110) arranged at a first side of the shadow mask (100) in a plane which is parallel to a plane of the shadow mask (100); the light emitting element (116) being configured to emit electromagnetic radiation (16) towards an eye (107) arranged at a second side of the shadow mask (100), the shadow mask (100) comprising transparent portions (102) being transparent for the electromagnetic radiation (16) and opaque portions (101) being opaque for the electromagnetic radiation (16), the transparent portions (102) having a maximum width measured in a first horizontal direction; the detection region (110) being configured to receive electromagnetic radiation (16) emitted by the light emitting element (116), reflected by a cornea (108) of the eye (107) and transmitted by the shadow mask (100), the detection region (110) comprising a pixel array comprising a plurality of pixels (111), wherein a maximum distance P S between adjacent pixels (111) and the maximum width w A of the transparent portions (102) satisfy the following formula: 0.9 * w A ≤ P S ≤ 1.25 * w A , the maximum distance between adjacent pixels (111) being measured in the first horizontal direction.
  2. The eye tracker (11) according to claim 1, wherein the distance between adjacent pixels (111) is smaller than a projected minimum lateral displacement of electromagnetic radiation (16) reflected by the cornea (108) due to an eye movement.
  3. The eye tracker (11) according to claim 2, wherein the distance between adjacent pixels (111) is less than 100 µm.
  4. The eye tracker (11) according to any of the preceding claims, wherein an optical distance between the detection region (110) and the shadow mask (100) is less than 10 mm.
  5. The eye tracker (11) according to any of the preceding claims, wherein the detection region (110) and the light emitting element (116) are arranged on a common carrier (120).
  6. The eye tracker (11) according to claim 5, comprising a plurality of light emitting elements (116), the light emitting elements (116) being arranged in a region outside the pixel array.
  7. The eye tracker (11) according to any of the preceding claims, wherein the opaque portions (101) of the shadow mask (100) are transparent for visible light (20).
  8. The eye tracker (11) according to any of the preceding claims, further comprising a processing unit (124) configured to determine an eye movement from signals received by the detection portion (110).
  9. The eye tracker (11) according to claim 8, wherein the processing unit (124) is further configured to identify periocular features (104) based on the signals received by the detection portion (110), the processing unit (124) being configured to perform user authentication using the identified periocular features (104).
  10. The eye tracker (11) according to any of the preceding claims, wherein the shadow mask (100) is arranged at a first main surface (126) of a lens (121) and the detection region (110) is arranged at a second main surface (127) of the lens (121).
  11. The eye tracker (11) according to any of claims 1 to 9, wherein the shadow mask (100) and the detection region (110) are arranged at a first main surface (126) of a lens (121), further comprising a buffer material (115) between the shadow mask (100) and the detection region (110).
  12. An electronic device (25) comprising the eye tracker (11) according to any of the preceding claims.
  13. The electronic device (25) according to claim 12, further comprising a display element (113) emitting visible light (20), the eye tracker (11) being arranged on a light emission side of the display element (113) between the display element (113) and the eye (107).
  14. The electronic device (25) according to claim 12 or 13, being selected from smart glasses (122) and a head-mounted display (123).

Description

TECHNICAL FIELD The present disclosure relates to an eye tracker comprising a shadow mask. BACKGROUND Many applications use eye tracking for foveated rendering or for providing user interfaces based on an eye gaze direction. Attempts are being made to develop improved eye trackers. The article YOU HAORAN HY34@RICE EDU ET AL: "EyeCOD eye tracking system acceleration via flatcam-based algorithm & accelerator co-design", THE ADJUNCT PUBLICATION OF THE 35TH ANNUAL ACM SYMPOSIUM ON USER INTERFACE SOFTWARE AND TECHNOLOGY, ACMPUB27, NEW YORK, NY, USA, 18 June 2022 (2022-06-18), pages 610-622, XP058913674, DOI: 10.1145/3470496.3527443 ISBN: 978-1-4503-9427-7 describes an eye tracking system that uses a lensless camera. The article M. Salman Asif ET AL: "FlatCam: Thin, Bare-Sensor Cameras using Coded Aperture and Computation", 31 August 2015 (2015-08-31), XP055250990 describes a lensless camera that uses a coded aperture mask. It is an object of the present invention to provide an improved eye tracker. SUMMARY According to embodiments, the above object is achieved by the claimed matter according to the independent claims. Further developments are defined in the dependent claims. According to embodiments, an eye tracker comprises a shadow mask, a light emitting element, and a detection region arranged at a first side of the shadow mask in a plane which is parallel to a plane of the shadow mask. The light emitting element is configured to emit electromagnetic radiation towards an eye arranged at a second side of the shadow mask. The shadow mask comprises transparent portions being transparent for the electromagnetic radiation and opaque portions being opaque for the electromagnetic radiation. The transparent portions have a maximum width measured in a first horizontal direction. The detection region is configured to receive electromagnetic radiation emitted by the light emitting element, reflected by a cornea of the eye and transmitted by the shadow mask. The detection region comprises a pixel array comprising a plurality of pixels. A maximum distance PS between adjacent pixels and the maximum width wA of the transparent portions satisfy the following formula: 0.9*wA≤PS≤1.25*wA, the maximum distance between adjacent pixels being measured in the first horizontal direction. For example, the maximum width wA may be approximately identical with the maximum distance PS. According to further implementations, the maximum distance PS between adjacent pixels and the maximum width wA of the transparent portions may satisfy the following formula: 0.944*wA≤PS. Further, the following formula may be fulfilled: PS≤1.2*wA. For example, the distance between adjacent pixels may be smaller than a projected minimum lateral displacement of electromagnetic radiation reflected by the cornea due to an eye movement. In more detail, the distance between adjacent pixels may be less than 100 µm. According to embodiments, an optical distance between the detection region and the shadow mask may be less than 10 mm. For example, the detection region and the light emitting element may be arranged on a common carrier. The eye tracker may comprise a plurality of light emitting elements. The light emitting elements may be arranged in a region outside the pixel array. According to implementations, the opaque portions of the shadow mask may be transparent for visible light. The eye tracker may further comprise a processing unit which is configured to determine an eye movement from signals received by the detection portion. For example, the processing unit may be further configured to identify periocular features based on the signals received by the detection portion. In particular, the processing unit may be configured to perform user authentication using the identified periocular features. According to embodiments, the shadow mask may be arranged at a first main surface of a lens and the detection region is arranged at a second main surface of the lens. According to further embodiments, the shadow mask and the detection region may be arranged at a first main surface of a lens. The eye tracker may further comprise a buffer material between the shadow mask and the detection region. According to embodiments, an electronic device comprises the eye tracker as described above. For example, the electronic device may further comprise a display element that emits visible light. The eye tracker may be arranged on a light emission side of the display element between the display element and the eye. For example, the electronic device may be selected from smartglasses and a head-mounted display. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings are included to provide a further understanding of embodiments of the invention and are incorporated in and constitute a part of this specification. The drawings illustrate the embodiments of the present invention and together with the description serve to explain the principles. Other embodiments of the invention an