BIOSENSOR

• US 20160081626A1
• Filed: 11/30/2015
• Published: 03/24/2016
• Est. Priority Date: 05/30/2013
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: TAKAHASHI, EIJI
• Granted Patent: US 10,123,744 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A61B 5/02427 Details of sensor
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7225 Details of analog processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation A61B5/30, A61B5/316 take precedence; transformers for specific applications H01F38/00; amplifiers H03F

Abstract

There is provided a biosensor capable of improving the S/N ratio of a final photoplethysmographic signal regardless of the change in a noise component such as extraneous light.

A biosensor includes a driving signal generation unit for generating a pulsed driving signal, a light-emitting element for emitting light in response to a generated driving signal, a light-receiving section including a light-receiving element for outputting a detection signal in accordance with the intensity of light received and an amplification unit for amplifying a detection signal output from the light-receiving element, a filter unit for removing a pulse wave component from a detection signal output from the light-receiving section to obtain a baseline signal, and a differential amplification unit for taking a difference between a detection signal output from the light-receiving section and a baseline signal obtained by the filter unit.

Claims

1. A biosensor comprising:

a light-emitting element configured to emit light in response to a pulsed driving signal;

a light-receiving element configured to output a detection signal based on an intensity of light received;

a filter configured to remove a pulse wave component from the detection signal to acquire a baseline signal; and

a difference acquisition circuit configured to amplify a difference between the detection signal and the baseline signal to generate an amplified pulse wave component including biological information.

2. The biosensor according to claim 1, further comprising an envelope extraction unit configured to extract an envelope of the detection signal output from the light-receiving element,

wherein the filter removes a pulse wave component from the envelope of the detection signal to generate the baseline signal.

3. The biosensor according to claim 2, further comprising a high-pass filter coupled between the light-receiving element and the envelope extraction unit and configured to selectively pass detection signals of frequencies equal to or higher than a predetermined frequency, including the pulse wave component to the envelope extraction unit.

4. The biosensor according to claim 2,

wherein the envelope extraction unit includes an ideal diode circuit configured to equivalently eliminate a diode forward voltage drop, and

wherein the envelope extraction unit rectifies the detection signal output from the light-receiving element using the ideal diode circuit, removes a high-frequency component from the rectified detection signal, and extracts an envelope of the rectified detection signal.

5. The biosensor according to claim 4, wherein the ideal diode circuit includes an operational amplifier configured to receive a detection signal from the light-receiving element and a diode having an anode terminal connected to an output terminal of the operational amplifier and a cathode terminal connected to an output of the ideal diode circuit and a feedback loop of the operational amplifier.

6. The biosensor according to claim 1, wherein the filter is a band elimination filter configured to selectively block passage of the detection signal, among a plurality of detection signals, in a frequency band including a pulse wave component to acquire a baseline signal.

7. The biosensor according to claim 1, wherein the filter is a low-pass filter configured to selectively pass a detection signal, among a plurality of detection signals, of a frequency lower than frequencies including a pulse wave component to acquire a baseline signal.

8. The biosensor according to claim 1, further comprising an amplitude adjustment unit configured to adjust an amplitude of a signal to be input into the difference acquisition circuit based on an amplitude of the baseline signal generated by the filter.

9. The biosensor according to claim 1, further comprising an envelope extraction unit including a diode with an input coupled to the light-receiving element to receive the detection signal, and a resistive element and capacitive element each coupled to the output of the diode and ground.

10. The biosensor according to claim 9, wherein the filter includes an operational amplifier with an inverting input coupled to an output of the operational amplifier and a non-inverting input coupled to the output of the envelope extraction unit.

11. The biosensor according to claim 10, wherein the filter further includes a pair of resistive elements coupled in series between the non-inverting input and the output of the envelope extraction unit, a first capacitive element coupled to a node between the pair of resistive elements and the inverting input, and a second capacitive element coupled between the non-inverting input and ground.

12. The biosensor according to claim 11, wherein the difference acquisition circuit includes an operational amplifier with a non-inverting input coupled to an output of a diode, the diode having an input coupled to the light-receiving element to receive the detection signal, and an inverting input coupled to the output of the filter.

13. The biosensor according to claim 12, wherein the diode comprises an internal resistance value corresponding to an amount of attenuation of the baseline signal.

14. The biosensor according to claim 1, further comprising a microcontroller having an A/D converter configured to convert the amplified pulse wave component into digital data with a predetermined sampling period.

15. The biosensor according to claim 14, wherein the microcontroller includes a computation unit configured to process the digital data to obtain the biological information.

16. A method for detecting biological information, the method comprising:

emitting light by a light-emitting element in response to a pulsed driving signal;

detecting light by a light-receiving element;

outputting, by the light-receiving element, a detection signal based on an intensity of the detected light;

filtering the detection signal to remove a pulse wave component and acquire a baseline signal; and

amplifying, by a difference acquisition circuit, a difference between the detection signal and the baseline signal to generate an amplified pulse wave component including biological information.

17. The method according to claim 16, further comprising:

extracting an envelope of the detection signal output from the light-receiving element; and

removing a pulse wave component from the envelope of the detection signal to generate the baseline signal.

18. The method according to claim 17, further comprising filtering, by a high-pass filter, detection signals of frequencies equal to or higher than a predetermined frequency, including the pulse wave component.

19. The method according to claim 16, further comprising a converting, by an A/D converter, the amplified pulse wave component into digital data with a predetermined sampling period.

20. The method according to claim 19, further comprising, processing, by a computation unit, the digital data to obtain the biological information.