Apple wins a Touch ID Under Display patent focused on an optical imaging system that operates in the 'Shortwave Infrared' Band
Apple has been working on a Touch ID system designed to be set under the display since at least 2013 (patent published in 2015). We've covered a series of patents since then (01, 02, 03, 04, 05 and 06). Apple analyst Ming-Chi Kuo first predicted that this feature would emerge in 2022 and then changed it again to it emerging in 2023. While we await this feature to arrive in a future iPhone, today the U.S. Patent and Trademark Office officially granted Apple yet another patent relating to Touch ID under the display that focuses on the use of "shortwave infrared" technology.
Apple's granted patent officially covers an optical imaging system that is configured to operate in at least the shortwave infrared band and is positioned behind, and/or integrated within, the display of the electronic device.
More specifically, the optical imaging system, when in operation, is configured to produce a flood illumination of an object or part of an object in contact with an input surface of the display in the shortwave infrared band. In addition, the optical imaging system is configured to receive and quantify surface and/or subsurface reflections—if any—that result from the flood illumination in the shortwave infrared band.
The phrase “surface reflection” that is found in this patent refers to a change in polarity of at least one direction of propagation of an optical wavefront (e.g., a ray of light) as a result of interaction with an interface between two different media having differing refractive indices.
A surface reflection can include both specular reflection components (e.g., components reflected at the same angle relative to a surface normal to the interface) and diffuse reflection components (e.g., components reflected at a different angle relative to the surface normal to the interface).
Further, the phrase “subsurface reflection” found in this patent refers to one or more scattered or refracted components of an optical wavefront (e.g., a ray of light) passing through, or within, a non-transparent or translucent medium. A subsurface reflection, as described herein, includes predominantly diffuse reflection components.
As a result, when a user of the electronic device touches the input surface of the display (for example to interact with content shown on the display), the optical imaging system can obtain an image and/or otherwise determine one or more properties of that user's finger.
For example, the optical imaging system can be configured to, without limitation: obtain an image of the user's fingerprint; determine a vein pattern of the user; determine blood oxygenation of the user; determine the user's pulse; determine whether the user is wearing a glove; determine whether the user's finger is wet or dry; and so on.
The optical imaging system can be any suitable optical imaging system, including both single-element sensors (e.g., photodiodes, phototransistors, photosensitive elements, and so on) and multi-element sensors (e.g., complementary metal oxide semiconductor arrays, photodiode arrays, and so on).
As noted above, in many embodiments, an optical imaging system is configured to operate (e.g., to receive and/or emit light) in at least the shortwave infrared band. As used herein, the phrases “shortwave infrared band” and “shortwave infrared light” and similar phrases refer, generally, to the band of infrared light including wavelengths between and including approximately 1,100 nm (1.1 μm) to 3,000 nm (3.0 μm).
For example, in some embodiments, an optical imaging system can be configured to emit and/or receive light having wavelengths of approximately 1450nm ±50nm. In other embodiments, an optical imaging system is configured to emit and/or receive light having wavelengths of approximately 1950nm ±50nm. In still other embodiments, an optical imaging system is configured to emit and/or receive light having wavelengths of approximately 1200nm ±50nm.
Apple's patent FIG. 1A below depicts an electronic device that can incorporate a display stack suitable for through-display imaging; FIG. 1B depicts a simplified block diagram of the electronic device of FIG. 1A.
Apple's patent FIG. 2A above depicts an example simplified cross-section of the display stack of FIG. 1A, taken through line A-A, depicting an optical imaging system operating outside the shortwave infrared band; FIG. 3B depicts an example arrangement of pixels of a display stack incorporating an optical imaging system operable within the shortwave infrared band; FIG. 5 is a simplified flow chart depicting example operations of a method of capturing an image of an object touching a display; FIG. 6 is a simplified flow chart depicting example operations of a method of determining an optical property of an object touching a display.
For more details, review Apple's granted patent US 11600103 B2.
- Giovanni Gozzini: Director of Engineering
- Moe (Mohammad) Yeke Yazdandoost: Tech Lead Sensing System Architect