A report by CBS titled "Apple to remove pulse oximeter from watches to avoid sales ban," was published on January 15, 2024. The report noted that "Late last year, Apple halted sales of its Series 9 and Watch Ultra 2 Apple Watch models over a years-long patent dispute with health technology company Masimo, a maker of pulse oximeters. The tool measures the saturation of oxygen in the device wearer's red blood cells. Low blood oxygen levels can lead to serious health conditions, including damage to the brain, heart and other organs, according to Cleveland Clinic.

Apple pulled the watches from store shelves after the International Trade Commission (ITC) ruled that the watches' blood oxygen sensors violated Masimo's patents. The devices were banned on December 26. Apple appealed the decision and the ban was paused, allowing the tech giant to resume watch sales in the U.S."

Today the U.S. Patent and Trademark Office officially published a patent application from Apple titled "System and Method for Robust Pulse Oximetry using Asymmetric Distance-Dependent Calibration."

Apple's patent relates to systems and methods for robust estimation of a characteristic of a user's physiological signals. For example, the physiological characteristic can be oxygen saturation of the hemoglobin in arterial blood (SaO2) as estimated by a pulse oximeter (SpO2).

In some examples, an optical sensor may include multiple channels with asymmetries between respective emitters and detectors of the multiple channels.

For example, the different distances between different emitter and detector pairs (e.g., asymmetric distances among the multiple channels) can result in asymmetric effective distances in the expected distributions of possible light paths between the different emitter and detector pairs. Additionally or alternatively, the placement of light emitting components within the light emitter (e.g., the position and/or angle of the light emitting components) may also result in asymmetric effective distances in the expected distributions of possible light paths among multiple channels (e.g., even among those channels with otherwise uniform separation between respective emitter and detector pairs).

To improve accuracy of the estimation of a physiological characteristic (e.g., SpO2), different calibration relationships (e.g., modulation ratio R-to-SaO2 mappings) can be used that may be dependent on a characteristic of the optical sensor.

For example, different calibration relationships can be used that are dependent on a spatial characteristic (e.g., distance between the respective emitter and respective detector of a channel, die position and/or angle) and/or that are dependent on a wavelength characteristic of the light emitting components of the respective emitter of a channel. In some examples, a unique calibration relationship can be used for each channel.

In some examples, a common calibration relationship can be used for multiple channels with shared distance and/or wavelength characteristics. Utilizing asymmetric distance-dependent and/or wavelength-dependent calibration can improve robustness of pulse oximetry measurements (e.g., for improved accuracy of SpO2 estimates).

Apple's patent FIGS. 1A-1B below illustrate views of an exemplary electronic device including one or more optical sensors; FIG. 1C illustrates a cross-sectional view of exemplary wearable device including one or more light emitters and one or more light detectors; FIGS. 1D-1E illustrate alternative arrangements of light emitters and light detectors on the underside of an exemplary electronic device.

Apple's patent FIG. 5 above illustrates an example process for asymmetric distance-dependent and/or wavelength-dependent calibration ,

What may be important in this patent update is Apple's 23 new patent claims to bolster their invention. Whether this could assist Apple's legal problems with Massimo is unknown at this time.

To review Apple's 23 new patent claims and the full details of this invention overall, check out patent application 20240225496.

Today, Apple also updated their patent titled "Detecting Conditions Using Heart Rate Sensors," with 20 new patent claims.