Obviousness

Based on the prior art cited in US patent 9,729,693, the claims appear to be obvious under 35 U.S.C. § 103. The patent combines known techniques for determining sensor data confidence with known methods for detecting if a wearable device is being worn, in a way that would have been predictable to a person having ordinary skill in the art (POSITA) at the time of the invention.

The analysis below focuses on independent claim 1, as claims 11 (apparatus) and 16 (system) are substantially similar in scope, simply restating the same method in the context of the device and a broader system.

Deconstruction of Independent Claim 1

The core of the method claimed is a multi-step process to confirm a wearable is worn before trusting its biometric data:

1. Check for Bright Light (Ambient Light Check): Determine if a first sample voltage is less than a threshold. As described in the patent's specification and claim 2, this is done with the device's light emitter off, effectively checking for overwhelming ambient light like direct sun. If the voltage is high, the device assumes it's not on a user.
2. Check for Dark, Reflective Surface (Proximity Check): If the first check passes, determine if a second sample voltage is greater than a threshold. This is done with the emitter on (per claim 3). This step confirms the sensor is against a surface that reflects its light (like skin) and not just in a dark environment.
3. Calculate Signal Quality Metric: If both voltage checks pass, the device proceeds to calculate a "signal quality metric" from the sensor's data (e.g., a PPG or pulse oximeter sensor, per claims 5 and 6) over a test period.
4. Confirm Signal Quality and "Worn" Status: The calculated metric is compared to a minimum threshold. If it exceeds the threshold, the device finally determines it is being worn by a user.

Obviousness Combination 1: US 2015/0265217 A1 (Hong) in view of US 2014/0247151 A1 (Sae-Ueng)

A POSITA would have found it obvious to combine the teachings of Hong and Sae-Ueng to arrive at the invention claimed in US 9,729,693.

• Primary Reference: Hong (US 2015/0265217 A1)
  Hong teaches the core concept of the '693 patent: a wearable sensor that calculates a "confidence score" for its physiological measurements to ensure data quality.

  • Teaches Steps 3 & 4: Hong explicitly discloses collecting physiological data, calculating a confidence score (equivalent to the "signal quality metric" in the '693 patent), and using this score to validate the measurement. (Hong, Abstract; Para.).
  • Teaches "Worn" Status Goal: Hong recognizes the problem of bad data when a device is not worn properly and teaches determining if the device is being worn. It suggests using an IR proximity sensor for this "on-wrist detection." (Hong, Para.).

• Secondary Reference: Sae-Ueng (US 2014/0247151 A1)
  Sae-Ueng teaches a simple and effective alternative for the "on-wrist detection" mentioned in Hong.

  • Teaches Step 1: Sae-Ueng explicitly teaches using an ambient light sensor to determine if a wearable device is being worn. (Sae-Ueng, Para.).

• Motivation to Combine and Reasoning for Obviousness:
  A POSITA starting with Hong's system for ensuring data confidence would be motivated to find a reliable and cost-effective way to perform the on-wrist detection that Hong suggests. Sae-Ueng provides an explicit suggestion to use an ambient light sensor for this exact purpose.

  Many wearable devices with PPG sensors (as discussed in Hong) already include a photodiode capable of measuring ambient light. The POSITA would have found it predictable and logical to use this existing hardware to implement Sae-Ueng's teaching. This leads directly to the claimed invention:

  1. The first logical step is to use the photodiode to check for high ambient light, as taught by Sae-Ueng. This is Step 1 of the '693 patent's claim.
  2. If ambient light is low, the device could be on a wrist or simply in a dark room. To distinguish these, a POSITA would find it a matter of basic engineering principle to turn on the device's own light emitter and check for a reflection. This is a well-known method for proximity detection and constitutes Step 2 of the claim.
  3. Only after these preliminary "placement" checks are passed would the system proceed with the more computationally intensive "confidence score" calculation taught by Hong, which corresponds to Steps 3 and 4 of the claim.

  The combination of Hong's confidence metric calculation with Sae-Ueng's use of an ambient light sensor for on-person detection renders the sequential method of claim 1 obvious. The specific two-voltage check is a predictable implementation of these combined teachings.

Obviousness Combination 2: US 9,167,995 B2 (Al-Ali) in view of US 2014/0247151 A1 (Sae-Ueng)

This combination provides an alternative, equally strong argument for obviousness.

• Primary Reference: Al-Ali (US 9,167,995 B2)
  Al-Ali teaches a method to determine a "confidence measure" for a physiological signal and to detect when a sensor is not attached to the body.

  • Teaches Steps 3 & 4: Al-Ali focuses extensively on analyzing a received physiological signal to determine a "confidence in the signal." (Al-Ali, Abstract; Col. 1, lines 17-21). This is directly analogous to calculating and checking the "signal quality metric."
  • Teaches "Worn" Status Goal: Al-Ali explicitly discloses a "sensor-off-body condition" detector, which determines if the sensor is attached to a patient by, for example, failing to detect a pulsatile signal over time. (Al-Ali, Col. 13, lines 52-60).

• Secondary Reference: Sae-Ueng (US 2014/0247151 A1)
  As before, Sae-Ueng teaches using an ambient light sensor for on-person detection.

• Motivation to Combine and Reasoning for Obviousness:
  A POSITA implementing Al-Ali's system would recognize that waiting to analyze a full data stream to determine an "off-body condition" is inefficient and wastes battery power. They would be motivated by a desire for efficiency to add a simpler, faster pre-check to see if the device is even in a position to acquire a signal. Sae-Ueng provides the ideal solution by teaching the use of an ambient light sensor.

  The motivation is to improve the system of Al-Ali by adding a power-saving front-end check. Combining the teachings would result in the exact sequence claimed in the '693 patent: first, perform the quick placement checks using ambient light (from Sae-Ueng), and only if those pass, proceed to the more complex signal confidence analysis taught by Al-Ali. This combination of known elements to achieve a predictable improvement in efficiency renders the claimed invention obvious.