Intersection cross-cut: sensor-multi-wavelength-ppg ∩ algo-spo2-estimation

Axes: sensors × algorithms

5 corpus entries disclose both tags.

Earliest disclosure: 1974

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.

Aoyagi (1974) — two-wavelength pulse oximetry principle (1974)

  • id: aoyagi-1974-two-wavelength-pulse-oximetry
  • corpus: private
  • form factor: other
  • creator: Takuo Aoyagi (Nihon Kohden)
  • disclosure: Aoyagi T, et al. — the pulsatile two-wavelength (red/infrared) ratio method for non-invasive arterial oxygen saturation, presented at the 13th Annual Meeting of the Japan Society of Medical Electronics and Biological Engineering (1974); commercialized as the Nihon Kohden ‘Ear Oximeter OLV-5100’ (1975) and Minolta ‘Oximet MET-1471’ (1977). History documented in Severinghaus JW, Honda Y. ‘History of blood gas analysis. VII. Pulse oximetry.’ J Clin Monit 1987;3(2):135-138.
  • ip status: patented
  • sensors: sensor-spo2, sensor-ppg, sensor-multi-wavelength-ppg
  • algorithms: algo-spo2-estimation
  • prior art notes: Discloses the pulsatile two-wavelength ratiometric method that underlies every non-invasive SpO2 device: comparing the AC/DC ratios of light absorbance at (typically) red ~660 nm and infrared ~940 nm through pulsatile tissue to compute arterial oxygen saturation. Any wearable claim reciting ‘a first and second light source at distinct wavelengths and a photodetector configured to compute oxygen saturation from a ratio of pulsatile components’ reads on this. § 102 prior art for the SpO2 principle from 1974; the wrist/ring/earbud form-factor variants are obvious combinations under [[obviousness-template]].

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.

ISO 80601-2-61 — particular requirements for basic safety and essential performance of pulse oximeter equipment (2011/2017) (2011-08-15)

  • id: iso-80601-2-61-pulse-oximeter-equipment-2011
  • corpus: standards
  • form factor: other
  • creator: ISO/IEC (TC 121/SC 3 and IEC SC 62D)
  • disclosure: ISO 80601-2-61:2011 (revised 2017). ‘Medical electrical equipment — Part 2-61: Particular requirements for basic safety and essential performance of pulse oximeter equipment.’ ISO, 2011.
  • ip status: standards
  • sensors: sensor-spo2, sensor-ppg, sensor-multi-wavelength-ppg
  • algorithms: algo-spo2-estimation
  • prior art notes: Publicly-adopted standard defining pulse oximeter equipment (a device estimating SpO2 and pulse rate from light at two or more wavelengths through perfused tissue) and the accuracy/validation requirements for it. Prior art for wearable-SpO2 claims to the extent they recite the multi-wavelength pulsatile method or the SpO2-and-pulse-rate output described here; the equipment definition and method have been a published standard since 2011 (building on the [[aoyagi-1974-two-wavelength-pulse-oximetry]] principle).

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.

Public domain (CC0 1.0). The corpus IS the prior art commons.

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