Shortwave infrared optical imaging through an electronic device display
Systems and methods for through-display imaging. An optical imaging sensor is positioned at least partially behind a display and is configured to emit shortwave infrared light at least partially through the display to illuminate an object, such as a fingerprint, in contact with an outer surface of the display. Surface reflections from the object are received and an image of the object can be assembled.
1. An electronic device comprising:
a protective outer cover defining an interface surface and configured to receive a touch input from a finger;
a display positioned adjacent the protective outer cover; and
an optical imaging system positioned at least partially adjacent the display and comprising:
a light emitting element configured to emit shortwave infrared light, through the display and toward the interface surface; and
a photosensitive element optically isolated from the light emitting element and configured to receive, through the display, a reflection of the shortwave infrared light from the interface surface; wherein
the received reflection is used to construct a portion of an image of the finger.
2. The electronic device of claim 1 , wherein the received reflection is a surface reflection.
3. The electronic device of claim 1 , wherein the photosensitive element comprises a photodiode on a thin-film transistor layer disposed below the display.
4. The electronic device of claim 1 , wherein the light emitting element is configured to emit light at a wavelength of approximately 1450 nm.
5. The electronic device of claim 1 , wherein the photosensitive element is separated from the light emitting element, at least in part, by an opaque mask layer.
6. The electronic device of claim 1 , wherein the protective outer cover is optically transparent.
7. The electronic device of claim 1 , wherein the display is an organic light emitting diode display.
8. The electronic device of claim 1 , further comprising a waveguide positioned below the display and optically coupled to the light emitting element.
9. The electronic device of claim 8 , wherein the waveguide is configured to emit light through inter-pixel regions of the display.
10. The electronic device of claim 1 , wherein the light emitting element is coplanar with at least one pixel of the display.
11. A method of operating an optical imaging system positioned below a display of an electronic device, the method comprising:
detecting, by the display, a contact area of a touch input provided to the display;
illuminating the contact area with shortwave infrared light emitted by a light emitting element of the optical imaging system;
receiving one or more surface reflections of shortwave infrared light from the contact area; and
assembling an image of an object initiating the touch input from the one or more surface reflections.
12. The method of claim 11 , wherein the operation of illuminating the contact area with shortwave infrared light comprises emitting shortwave infrared light at least partially through the display.
13. The method of claim 11 , further comprising filtering the one or more received surface reflections of shortwave infrared light with a narrow field of view filter.
14. The method of claim 11 , wherein:
the one or more surface reflections correspond to valley features of a fingerprint; and
the object is a finger of a user.
15. The method of claim 11 , wherein the operation of illuminating the contact area with shortwave infrared light comprises emitting shortwave infrared light into a waveguide positioned below the display.
16. A method of imaging an input surface defined by a glass substrate, the method comprising:
illuminating the input surface with shortwave infrared light emitted from one or more light emitting elements;
receiving, at an array of photosensitive elements, one or more surface shortwave infrared light reflections from the input surface at the array of photosensitive elements after filtering the one or more surface shortwave infrared light reflections with a narrow field of view filter; and
assembling an image of an object in contact with the input surface based on the received one or more surface shortwave infrared light reflections.
17. The method of claim 16 , wherein the shortwave infrared light has a wavelength greater than 1400 nm.
18. The method of claim 16 , wherein the shortwave infrared light has a wavelength greater than 1900 nm.
19. The method of claim 16 , wherein the array of photosensitive elements is disposed adjacent to the input surface in a rectangular pattern.
20. The method of claim 16 , wherein the array of photosensitive elements is disposed between the input surface and the one or more light emitting elements.