BIOLOGICAL SENSOR

• US 20160143549A1
• Filed: 02/02/2016
• Published: 05/26/2016
• Est. Priority Date: 08/07/2013
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: TSUCHIMOTO, HIROFUMI, Hayashi, Takanori, Saito, Kengo, Nakaji, Hiroyuki
• Granted Patent: US 10,588,522 B2
• Time in Patent Office: Days
• CPC Class Codes: A61B 2562/0238 Optical sensor arrangements for performing transmission measurements on body tissue
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/02427 Details of sensor
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7228 Signal modulation applied to the input signal sent to patient or subject; demodulation to recover the physiological signal modulation H03C

Abstract

A biological sensor capable of improving the signal to noise ratio of a detection signal obtained by a light-receiving element and amplified by an amplifier is provided.

The biological sensor includes a microcontroller that generates a driving signal, a light-emitting element that emits light in accordance with the driving signal, a light-receiving element that outputs a current detection signal based on an intensity of received light, and an amplifying circuit that converts the current detection signal into a voltage detection signal, amplifies an alternating current component of the voltage detection signal, and outputs an amplified detection signal. Furthermore, the microcontroller generates an offset signal that is applied to an offset circuit to offset the direct current component of the voltage detection signal and to obtain biological information by processing the amplified detection signal.

Claims

1. A biological sensor comprising:

a light-emitting element that emits light based on a driving signal;

a light-receiving element that outputs a current detection signal based on an intensity of received light including light emitted by the light-emitting element;

an amplifying circuit configured to convert the current detection signal into a voltage detection signal, amplify an alternating current component of the voltage detection signal, and output an amplified detection signal; and

a microcontroller configured to;

generate the driving signal,

generate an offset signal that is applied to a offset circuit coupled to the amplifying circuit to offset a direct current component of the voltage detection signal, and

obtain biological information based on the amplified detection signal.

2. The biological sensor according to claim 1, wherein the microcontroller is further configured to generate the driving signal as a pulse-form driving signal.

3. The biological sensor according to claim 2, wherein the microcontroller is further configured to generate the offset signal as a pulse-form offset voltage that is synchronized with the pulse-form driving signal.

4. The biological sensor according to claim 1, wherein the amplifying circuit comprises:

a first operational amplifier that converts the current detection signal into the voltage detection signal;

a second operational amplifier that amplifies the voltage detection signal to output the amplified detection signal; and

a capacitor connected between an output terminal of the first operational amplifier and an input terminal of the second operational amplifier.

5. The biological sensor according to claim 4, wherein the offset circuit is coupled to a path between the output terminal of the first operational amplifier and the input terminal of the second operational amplifier.

6. The biological sensor according to claim 5, wherein the offset circuit is coupled to a path between the output terminal of the first operational amplifier and the capacitor.

7. The biological sensor according to claim 1, wherein the offset circuit comprises a voltage dividing circuit that includes a plurality of resistors and that generates the offset voltage by voltage-dividing the offset signal generated by the microcontroller.

8. The biological sensor according to claim 1, further comprising a light-emitting element configured to output light of a different wave length from the light-emitting element,

wherein the microcontroller is further configured to generate pulse-form driving signals having mutually different timings for each of the plurality of light-emitting elements, and to generate pulse-form offset voltages independent from each other in synchronization with the respective pulse-form driving signals outputted at mutually different timings.

9. The biological sensor according to claim 1, wherein the microcontroller is further configured to:

extract a direct current component of the amplified detection signal, and

determine the offset voltage outputted by the offset circuit so that a deviation of the extracted direct current component from a target value decreases.

10. The biological sensor according to claim 9, wherein the microcontroller stops generating at least one of the driving signal and the offset signal when the deviation does not become less than or equal to a predetermined value as a result of the determined offset voltage.

11. A method for obtaining biological information, the method comprising:

generating, by a microcontroller, a driving signal;

emitting, by a light-emitting element, light based on the driving signal generated by the microcontroller;

outputting, by a light-receiving element, a current detection signal based on an intensity of received light including light emitted by the light-emitting element;

converting, by an amplifying circuit, the current detection signal into a voltage detection signal;

amplifying, by an amplifying circuit, an alternating current component of the voltage detection signal;

outputting, by an amplifying circuit, an amplified detection signal;

generating, by the microcontroller, an offset signal that is applied to a offset circuit coupled to the amplifying circuit to offset a direct current component of the voltage detection signal; and

obtaining, by the microcontroller, biological information based on the amplified detection signal.

12. The method according to claim 11, further comprising generating, by the microcontroller, the driving signal as a pulse-form driving signal.

13. The method according to claim 12, further comprising generating, by the microcontroller, the offset signal as a pulse-form offset voltage that is synchronized with the pulse-form driving signal.

14. The method according to claim 11, further comprising:

converting, by a first operational amplifier of the amplifying circuit, the current detection signal into the voltage detection signal; and

amplifying, by a second operational amplifier of the amplifying circuit, the voltage detection signal.

15. The method according to claim 14, wherein the offset circuit is coupled to a path between the output terminal of the first operational amplifier and the input terminal of the second operational amplifier.

16. The method according to claim 15, wherein the offset circuit is coupled to a path between the output terminal of the first operational amplifier and a capacitor connected between an output terminal of the first operational amplifier and an input terminal of the second operational amplifier.

17. The method according to claim 11, further comprising generating, by a voltage dividing circuit including a plurality of resistors, the offset voltage by voltage-dividing the offset signal generated by the microcontroller.

18. The method according to claim 11, further comprising:

outputting, by another light-emitting element, light of a different wave length from the light-emitting element;

generating, by the microcontroller, pulse-form driving signals having mutually different timings for each of the plurality of light-emitting elements; and

generating, by the microcontroller, pulse-form offset voltages independent from each other in synchronization with the respective pulse-form driving signals outputted at mutually different timings.

19. The method according to claim 11, further comprising:

extracting, by the microcontroller, a direct current component of the amplified detection signal; and

determining, by the microcontroller, the offset voltage outputted by the offset circuit so that a deviation of the extracted direct current component from a target value decreases.

20. The biological sensor according to claim 19, further comprising stopping, by the microcontroller, at least one of the driving signal and the offset signal when the deviation does not become less than or equal to a predetermined value as a result of the determined offset voltage.