Notice of Pre-AIA or AIA Status
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
Claim Objections
Claim 12 is objected to because of the following informalities: “during the light measurements” should be “during the subsequent light measurements” to mirror claim 5 and avoid indefiniteness issue. Appropriate correction is required.
Claim Rejections - 35 USC § 103
In the event the determination of the status of the application as subject to AIA 35 U.S.C. 102 and 103 (or as subject to pre-AIA 35 U.S.C. 102 and 103) is incorrect, any correction of the statutory basis (i.e., changing from AIA to pre-AIA ) for the rejection will not be considered a new ground of rejection if the prior art relied upon, and the rationale supporting the rejection, would be the same under either status.
The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action:
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.
Claim(s) 16, 18-20 is/are rejected under 35 U.S.C. 103 as being unpatentable over “Lisogurski”, US Publication 2013024855.
Regarding claim 16, Lisogurski discloses a method comprising:
receiving a skin perfusion value [0040: pass light through blood perfused tissue; 0042: determine blood oxygen saturation… identify pulses and determine pulse amplitude; Under the Broadest Reasonable Interpretation, a skin perfusion value encompasses physiological parameters derived from blood perfused tissue such as SpO2 or pulse amplitude);
generating first light measurements with a light sensor of a wearable at a first and a second sampling rate [0062: system may sample at a high rate during a period of interest and at a low rate during other periods.].
However, Lisogurski does not explicitly disclose that the sampling rate changes because the SpO2/perfusion value crossed a threshold. It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to configure Lisogurski’s “first and second modes” of 0119 to include the “high and low sampling rates” of 0062. The motivation would be to optimize power consumption while maintaining/improving SNR by lowering the sampling rate when perfusion is high [and signal quality is naturally good], and increasing the sampling rate when perfusion drops outside the desired range to recover signal fidelity.
Regarding claim 18, Lisogurski discloses wherein generating the first light measurements with the light sensor includes: (1) driving a light source to emit illumination light [0070+: light drive circuitry generating light drive signals]; and (2) measuring returning light with the light sensor, wherein the returning light is a portion of the illumination light [0067+: detector receiving light after passing through tissue; 0040+: light passing through blood-perfused tissue and being photoelectrically sensed].
Regarding claim 19, Lisogurski discloses wherein generating the first light measurements at the first sampling rate includes having a first sampling frequency of driving the light source and measuring the returning light with the light sensor at the first sampling frequency [0072+: drive cycle with coordinated light emission and detection at a given frequency; 0153+: “The signal may be sampled at a first rate”; 0160+: sampling rate relates to “the amount of time between ‘on’ periods” — establishing a first frequency of driving and measuring], and wherein generating the second light measurements at the second sampling rate includes having a second sampling frequency of driving the light source and measuring the returning light with the light sensor at the second sampling frequency different from the first sampling frequency [0154+: “the system may receive a signal and sample it at a second sampling rate. For example, the period between samples may be increased or reduced”; 0160+: decreasing the duration of the ‘off’ periods -- i.e., increasing the emitter firing rate relates to an increased sampling rate].
Regarding claim 20, Lisogurski discloses wherein the skin perfusion value is received from a memory of the wearable and perfusion data includes a sampling rate of the light measurements and an offset value associated with the predetermined value range [0050: “Selections and variations of cardiac cycle modulation techniques may also be based on empirical data, user input, lookup tables, historical information”; 0042: “The system may use information from external sources (e.g., tabulated data…) to determine physiological parameters”].
Claim(s) 1-15, 17 is/are rejected under 35 U.S.C. 103 as being unpatentable over “Lisogurski”, US Publication 20130324855, in view of “Kim”, “Low-Power Photoplethysmogram Acquisition Integrated Circuit with Robust Light Interference Compensation”.
Regarding claim 1, Lisogurski discloses a wearable device [0040: oximeter may include a light sensor that is placed at a site on a patient, typically a fingertip… portable systems] comprising:
a light source configured to emit illumination light [0065: light source 130 may be configured to emit photonic signals];
a light sensor configured to generate light measurements of returning light, wherein the returning light is a portion of the illumination light [0066+: Detector 140 may be chosen to be specifically sensitive to the chosen targeted energy spectrum… light may enter detector 140 after passing through the subject’s tissue]; and
processing logic [0068: monitor 104 includes control circuitry 110, light drive circuitry 120, front end processing circuitry 150, back end processing circuitry 170] configured to:
generating the light measurements with the light sensor to produce oxygen saturation measurements [0042: system may process data to determine physiological parameters… determine blood oxygen saturation using two wavelengths of light].
when the light measurements are below a light threshold: (1) increasing a sampling rate of subsequent light measurements by the light sensor [0047: the quality of a low amplitude signal may be degraded by quantization noise; 0062: system may sample at a high rate during a period of interest and at a low rate during other periods; 0159: In some embodiments, the sampling rate may represent the number of samples taken during an ‘on’ period of the drive cycle modulation… In this embodiment, the firing rate of the emitters may not be modulated along with the analog-to-digital sampling rate. For example, at a low sampling rate, the system may sample once per ‘on’ period, while at a high sampling rate the system may take several samples per ‘on’ period and average them].
However, Lisogurski does not explicitly disclose (2) reducing an analog offset of the subsequent light measurements when the light measurements are below a light threshold.
Kim, also directed to PPG signal acquisition and processing systems for wearable/portable physiological monitoring applications, discloses reducing an analog offset of the subsequent light measurements when the light measurements are below a light threshold [Section 2.4 “Automatic Offset Compensation (AOC)… The range comparator generates information about whether the input signal is oversaturated, undersaturated, or not saturated based on comparison with the upper and lower threshold values… Depending upon this information, the compensator logic increases or decreases the compensation current”; Section 3 “If the monitored signal is higher or lower than the upper or lower threshold voltage… adjust the output offset to the desired value”]. In essence, Kim teaches that compensation is implemented using “an 8-bit current DAC that compensates a DC offset of up to 30 μA” [Section 2.4]; when the signal is undersaturated [i.e., below a lower threshold], the compensator logic decreases the compensation current [reduces the analog offset] to restore the output signal to the desired range [Section 2.4, Figure 12 showing “when the monitored signal is saturated, the AOC restores the output signal to the desired range”].
It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to modify the teachings of Lisogurski with the teachings of Kim – incorporating the Automatic Offset Compensation circuit using a current DAC to reduce the analog offset when the signal is undersaturated, as taught by Kim, would enhance the base device of Lisogurski by improving its ability to utilize the full dynamic range of the analog-to-digital converter. This prevents signal saturation and minimizes quantization noise for low-amplitude signals.
Regarding claim 2, Lisogurski discloses wherein generating the light measurements with the light sensor includes: (1) driving the light source to emit the illumination light [0070: Light drive circuitry 110… configured to generate a light drive signal that is provided to light source 130]; and (2) measuring the returning light with the light sensor [0074: detector current waveform 214 may represent current signals provided by a detector… when light is being emitted].
Regarding claim 3, Lisogurski discloses wherein increasing the sampling rate of the subsequent light measurements includes increasing to an increased sampling frequency of driving the light source and increasing the measuring of the returning light with the light sensor to the increased sampling frequency [0160: decreasing the duration of the ‘off’ periods (i.e., increasing the emitter firing rate) relates to an increased sampling rate].
Regarding claim 4, Lisogurski discloses wherein the light source is driven at a same current for generating the light measurements and for generating the subsequent light measurements [0159+: the firing rate of the emitters may not be modulated along with the analog-to-digital sampling rate].
Regarding claim 5, Kim discloses wherein the light sensor includes a photodiode [Section 1: sensor system consists of photodiodes (PDs)], and wherein reducing the analog offset of the subsequent light measurements includes reducing an offset current that offsets a photodiode current generated by the photodiode during the subsequent light measurements [Section 2.2: photocurrent generated from the PD; Section 2.4: large DC offset current compared with the AC pulse current from the PD is compensated using the current compensator… current compensator includes an 8-bit current DAC that compensates a DC offset of up to 30 μA; the compensator logic increases or decreases the compensation current – when signal is undersaturated/below threshold, the compensation current is decreased, i.e., the offset current is reduced].
Regarding claim 6, Kim discloses wherein the offset current is generated by a digital-to-analog converter (DAC) driven by processing logic [Section 2.4: current compensator includes an 8-bit current DAC that compensates a DC offset], wherein the processing logic is configured to receive an adjusted signal that is a difference between the photodiode current and the offset current, the adjusted signal being measured as part of the subsequent light measurements [Fig. 1 showing the current compensator subtracting the offset current from the PD current before the TIA and ADC stages; Section 2.5: “Most of the DC current is compensated by the current compensator, and the remaining DC current is used for AEC” — confirming that the signal processed downstream is the difference between the total PD current and the offset compensation current].
Regarding claim 7, Lisogurski and Kim combined discloses when the light measurements are not below the light threshold: generating the subsequent light measurements at the sampling rate [Lisogurski, 0062: “the digitizer rate may be constant” in some embodiments; i.e., the system operates at its baseline sampling rate when no triggering condition is met]; and maintaining the analog offset for the subsequent light measurements [Kim, Section 2.4; Fig. 5 showing the up/down counting logic which maintains the current compensation value when the signal is “not saturated” i.e., within the acceptable threshold range].
Regarding claim 8, Lisogurski discloses a method comprising: generating light measurements with a light sensor of a wearable to produce oxygen saturation measurements [0040+]; and when the light measurements are below a light threshold: increasing a sampling rate of subsequent light measurements for generating subsequent oxygen saturation measurements [0047, 0062, 0159].
However, Lisogurski does not explicitly disclose reducing an analog offset of the subsequent light measurements. Kim discloses reducing an analog offset of the subsequent light measurements [Section 2.4+].
It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to modify the teachings of Lisogurski with the teachings of Kim as discussed above in reference to claim 1. Furthermore, this modification would enhance the base device of Lisogurski by improving measurement fidelity under low-signal conditions -- when perfusion is low or optical coupling is poor, the PPG signal becomes small relative to the DC offset; by reducing the offset current, the ADC can devote more of its dynamic range to resolving the small pulsatile signal, resulting in more accurate oxygen saturation determinations.
Regarding claims 9-15, these claims depend from claim 8 and add additional limitations that are disclosed by the combination of Lisogurski and Kim as explained above with respect to the corresponding limitations in claims 2-7. Furthermore, regarding claim 15, Lisogurski discloses wherein the light measurements are for photoplethysmography (PPG) analysis [0040: signal representing light intensity versus time… may be referred to as the photoplethysmograph (PPG) signal].
Regarding claim 17, this claim depends from claim 16 and adds additional limitations that are disclosed by the combination of Lisogurski and Kim as explained above with respect to the rejection of claims 1-7 above. It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to modify the teachings of Lisogurski with the teachings of Kim as integrating Kim’s offset compensation techniques would enhance Lisogurski’s method by ensuring that when the skin perfusion value dictates a change in sampling rate, the analog offset is simultaneously managed to prevent signal clipping -- maintaining high-fidelity PPG readings across varying perfusion levels.
Accordingly, Kim discloses wherein the first light measurements are measured at a first analog offset, and wherein the second light measurements are measured at a second analog offset that is reduced from the first analog offset [Section 2.4 “Depending upon this information, the compensator logic increases or decreases the compensation current”; when the signal drops below the threshold, the analog offset is reduced].
Conclusion
The prior art made of record and not relied upon is considered pertinent to applicant's disclosure. US 20190150854 discloses a wearable biometric device that can stop emitting light, delay measurement, retry later, or adjust timing/sampling parameters to conserve power and improve quality.
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/TSE CHEN/Supervisory Patent Examiner, Art Unit 3791
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