Method of removing EMI noise from photoacoustic sensing signal and photoacoustic sensing apparatus employing the same

A signal processing device for removing electromagnetic interference (EMI) noise in a photoacoustic sensor signal, wherein the photoacoustic sensor signal is generated by a photoacoustic sensor based on an ultrasonic wave signal generated from an analyte to which an optical signal is directed, the signal processing device comprising:

• a switch controller that generates a first control signal and a second control signal, and provides the first control signal to an optical switch to control directing of the optical signal toward the analyte;
• an analog-to-digital converter (ADC) that converts the photoacoustic sensor signal into a digital signal;
• a selector that classifies the digital signal into one of a mixed signal and second EMI noise based on the second control signal of the switch controller, the mixed signal including a photoacoustic signal and first EMI noise;
• and
• a processor that analyzes the mixed signal and the second EMI noise to estimate information of the photoacoustic signal,
• wherein the switch controller synchronizes the second control signal with the first control signal,
• wherein the selector classifies the digital signal into the mixed signal based on the second control signal when the first control signal sets the optical switch to an ON state, and
• wherein the selector classifies the digital signal into the second EMI noise based on the second control signal when the first control signal sets the optical switch to an OFF state.

A photoacoustic sensing method for removing electromagnetic interference (EMI) noise in a photoacoustic sensor signal, wherein the photoacoustic sensor signal is generated by a photoacoustic sensor based on an ultrasonic wave signal generated from an analyte to which an optical signal is directed, the photoacoustic sensing method comprising:

• providing a first control signal to an optical switch connected to a light source to block or transmit the optical signal;
• generating a mixed signal that includes a photoacoustic signal and first EMI noise based on the photoacoustic sensor signal when the optical switch transmits the optical signal, and second EMI noise based on the photoacoustic sensor signal when the optical switch blocks the optical signal;
• and
• removing the EMI noise from the photoacoustic sensor signal based on the mixed signal and the second EMI noise to generate a photoacoustic signal.