Intersection cross-cut: watch ∩ sensor-multi-wavelength-ppg

Axes: form_factor × sensors

4 corpus entries disclose both tags.

Earliest disclosure: 1988-10

These entries are the direct inputs to OBVIOUSNESS_TEMPLATE.md. Any patent claim combining these two elements is anticipated or rendered obvious by the chain below.

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Mendelson & Ochs (1988) — reflectance-mode pulse oximetry / skin-reflectance PPG (1988-10)

• id: mendelson-ochs-1988-reflectance-pulse-oximetry
• corpus: academic
• form factor: other
• creator: Yitzhak Mendelson / Burt D. Ochs
• disclosure: Mendelson Y, Ochs BD. ‘Noninvasive pulse oximetry utilizing skin reflectance photoplethysmography.’ IEEE Transactions on Biomedical Engineering 1988;35(10):798-805.
• ip status: public-domain
• sensors: sensor-ppg, sensor-spo2, sensor-multi-wavelength-ppg
• algorithms: algo-spo2-estimation, algo-hr
• prior art notes: Establishes pulse oximetry by reflectance (light source and detector on the same side of the tissue) rather than transmission — the geometry every wrist, forehead, ring, chest, and earbud PPG/SpO2 wearable uses, since those sites cannot be transilluminated. Any wearable-SpO2 claim reciting ‘a reflectance photoplethysmography sensor’ or ‘a light source and photodetector arranged on a common surface against the skin’ reads on Mendelson & Ochs 1988. Anchor for the reflectance-PPG/SpO2 cross-cut on non-fingertip sites.

Apple Watch (1st generation, 2015) — wrist green-PPG heart rate and activity (2015-04-24)

• id: apple-watch-original-2015
• corpus: private
• form factor: watch
• creator: Apple Inc.
• disclosure: Apple Inc. ‘Apple Watch’, announced September 2014, available 24 April 2015 — a wrist-worn device with a green/infrared photoplethysmography heart-rate sensor against the dorsal wrist, accelerometer and gyroscope, and activity/exercise tracking.
• ip status: patented
• sensors: sensor-ppg, sensor-multi-wavelength-ppg, sensor-accelerometer, sensor-gyroscope
• algorithms: algo-hr, algo-step-count, algo-calorie-estimation, algo-activity-classification
• prior art notes: Discloses a wristworn device with a dorsal-wrist green-LED photoplethysmography heart-rate sensor (with IR for low-perfusion conditions), inertial sensors, and continuous HR/activity tracking. Anticipates wristworn-PPG-HR claims to the extent they postdate April 2015; combined with the much earlier PPG principle ([[hertzman-1937-photoplethysmography]]) and wrist form factor, the combination is in any case obvious under [[obviousness-template]]. Product-side anchor for the watch × PPG cross-cut.

Masimo W1 (2022) — first FDA-cleared continuous wrist medical-grade pulse oximetry watch (2022-05)

• id: masimo-w1-2022
• corpus: private
• form factor: watch
• creator: Masimo Corp.
• disclosure: Masimo Corp. ‘Masimo W1’ health-tracking watch, announced May 2022 — a wrist-worn device performing continuous medical-grade pulse oximetry (SpO2), pulse rate, perfusion index (PI), pleth variability index (PVi), respiratory rate from the PPG, and HRV, using Masimo’s SET/rainbow signal-extraction algorithms. (FDA cleared as a continuous-monitoring medical device.)
• ip status: patented
• sensors: sensor-ppg, sensor-spo2, sensor-multi-wavelength-ppg, sensor-accelerometer
• algorithms: algo-spo2-estimation, algo-hr, algo-hrv, algo-respiratory-rate
• prior art notes: Discloses a wrist-worn device performing continuous medical-grade pulse oximetry — SpO2, PR, perfusion index, PVi, RR-from-PPG, HRV — using established signal-extraction methods, distinguished from consumer spot-check SpO2 by continuous operation and clearance for medical use. Anticipates wrist-continuous-medical-SpO2 claims from 2022; the underlying two-wavelength SpO2 method is much older ([[aoyagi-1974-two-wavelength-pulse-oximetry]], [[mendelson-ochs-1988-reflectance-pulse-oximetry]], [[iso-80601-2-61-pulse-oximeter-equipment-2011]]). Product-side anchor for the watch × continuous-SpO2 cross-cut.

HealthyPi Move (ProtoCentral, 2026) — open-source medical-grade smartwatch (2024)

• id: healthypi-move-2026
• corpus: open
• form factor: watch
• creator: ProtoCentral Electronics
• disclosure: ProtoCentral Electronics (Bengaluru, India). ‘HealthyPi Move’ fully open-source AMOLED smartwatch — Crowd Supply campaign launched 2024, units shipping 15 May 2026. Sensors: single-lead ECG, dual-site PPG (wrist + finger), SpO2, blood-pressure trending, EDA/GSR, heart rate, HRV, respiration rate (derived), body temperature, 6-axis IMU. Compute: Nordic nRF5340 (dual ARM Cortex-M33). Display: AMOLED, 300 mAh battery. Companion app: Flutter, runs on Android/iOS/macOS/Windows/Linux, all data stored locally. Hardware design, firmware (Zephyr RTOS on nRF Connect SDK), and companion app all open-source. https://www.crowdsupply.com/protocentral/healthypi-move
• ip status: open-permissive
• sensors: sensor-ecg, sensor-ppg, sensor-spo2, sensor-multi-wavelength-ppg, sensor-gsr, sensor-accelerometer, sensor-gyroscope, sensor-skin-temperature
• algorithms: algo-hr, algo-hrv, algo-spo2-estimation, algo-respiratory-rate, algo-pwv-bp-estimation, algo-sleep-staging, algo-activity-classification, algo-step-count
• prior art notes: Discloses, as fully open-source hardware and firmware (CC and MIT-style licensing across components), a wrist-worn smartwatch with the full consumer-medical sensor stack: single-lead ECG between back-of-watch electrode and a finger-touch electrode; multi-wavelength reflectance PPG with SpO2 and BP-trending; EDA/GSR; skin temperature; 6-axis IMU; on-device Zephyr-RTOS application; AMOLED display; all-local data storage via cross-platform Flutter app. Anticipates wrist-multi-sensor-watch claims from 2024-2026 to the extent they recite combinations of these elements; as open prior art it is unencumbered and any patent claim reciting these combinations must distinguish over HealthyPi Move’s specific implementation. The product-side anchor for the ‘open watch with the full sensor stack’ cross-cut.