On-demand heart rate estimation based on optical measurements

An apparatus for determining a heart rate from a heartbeat signal present in a first signal generated by a heartbeat sensor, the apparatus comprising:

• at least one memory configured to store computer executable instructions, and
• at least one processor coupled to the at least one memory and configured, when executing the instructions, to:
• compute an autocorrelation function (AF) of data samples of the first signal over a first time period;
• compute an squared difference function (SDF) of the data samples of the first signal over the first time period;
• compute a combination function representative of the computed autocorrelation function and the computed squared difference function;
• process a second signal to evaluate motion of the heartbeat sensor during the first time period, the second signal indicative of a motion of the heartbeat sensor with respect to one or more directions;
• determine whether the data samples of the first signal over the first time period pass a first set of confidence checks, the first set of confidence checks comprising at least determining whether the motion of the heartbeat sensor during the first time period satisfies a motion-related criteria;
• upon determination that the data samples of the first signal over the first time period pass the first set of confidence checks, compute a first estimate of the heart rate from the combination function;
• compute a Discrete Fourier Transform (DFT) for data samples of the first signal over a second time period;
• compute a second estimate of the heart rate from the DFT;
• and
• determine the heart rate based on the first estimate and the second estimate.

A computer-implemented method for determining a heart rate from a heartbeat signal present in a first signal generated by a heartbeat sensor, the method comprising:

• processing a second signal to evaluate motion of the heartbeat sensor during a first time period, the second signal indicative of a motion of the heartbeat sensor with respect to one or more directions;
• determining whether data samples of the first signal over the first time period pass a first set of confidence checks, the first set of confidence checks comprising at least
• determining whether the motion of the heartbeat sensor during the first time period satisfies a motion-related criteria;
• upon determination that the data samples of the first signal over the first time period pass the first set of confidence checks,
• computing a first estimate of the heart rate from the data samples of the first signal over the first time period using a first heart rate estimation algorithm,
• computing a second estimate of the heart rate from the data samples of the first signal over the first time period using a second heart rate estimation algorithm, and
• determining the heart rate based on the first estimate and the second estimate.