Last week Patently Apple posted a report titled "Apple Invents iDevice Displays with Ultrasonic Wave Technology that accepts Touch Commands under Water." Today the US Patent & Trademark Office published another patent application from Apple titled "Ultrasonic Polarizer" that covers the same subject matter but with different aspects of the technology.

Apple notes in their filing that "In some examples, water or other fluids in contact with the surface of the device will not act as a discontinuity to the acoustic waves and thus the acoustic touch sensing method can be effective for detecting the presence of an object (e.g., a user's finger) even in the presence of water drops (or other low-viscosity fluids) on the surface of the device or even while the device is fully submerged."

Technically speaking, Apple's patent application published today relates to polarizers for use in an acoustic touch sensing system to improve performance of the acoustic touch sensing system.

 Acoustic touch sensing systems can utilize one or more transducers coupled to a surface of a device, such as piezoelectric transducers, to transmit ultrasonic waves along a surface and/or through the thickness of an electronic device. As the transmitted wave propagates along the surface, one or more objects (e.g., finger, stylus, etc.) in contact with the surface can interact with the transmitted wave causing a reflection of at least a portion of the transmitted wave, which can be received by the transducers. Portions of the transmitted wave energy after interaction with the one or more objects can be measured to determine the touch location(s) of the one or more objects on the surface of the device (e.g., using time-of-flight (TOF) techniques).

In some examples, an acoustic touch sensing system can be configured to be insensitive to contact on the device surface by water, by using shear acoustic waves, for example. Thus, an acoustic touch sensing can be used for touch sensing in devices that are likely to become wet or fully submerged in water.

A polarizer disposed between the transducer and the surface in which the shear acoustic waves propagate can be used to filter compressional waves that may interact with water, thereby improving water rejection by the acoustic touch sensing system.

Apple's patent FIG. 2A illustrates an exemplary block diagram of an electronic device including an acoustic touch sensing system; FIGS. 5A and 5E illustrate exemplary system configurations and timing diagrams for acoustic touch sensing to determine position using a bounding box technique.

In patent FIG. 5 Apple notes that "Propagation of shear horizontal waves can be unaffected by water on surface #500 because low viscosity fluids and gases (such as water and air) have a very low shear modulus, and therefore do not perturb the boundary conditions that affect wave propagation."

Apple's patent application 20190243047 that was published today by the U.S. Patent Office was originally filed back in Q1 2019. This patent incorporates two provisional patents dating back to 2018. Considering that this is a patent application, the timing of such a product to market is unknown at this time.

Some of the Inventors

Ehsan Khajeh: Ultrasonic Sensing, Modeling, and Hardware

Aaron S. T.: Electrical Engineer, Advanced Sensing Technology

Brian King: Senior Technologist

Marcus Yip: Sensing Hardware Electrical Engineer

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