Near infra-red signal processing system

• US 5,853,372 A
• Filed: 08/14/1995
• Issued: 12/29/1998
• Est. Priority Date: 08/14/1995
• Status: Expired due to Fees

• Current Assignee: Advanced Body Metrics Corporation
• Original Assignee: Advanced Body Metrics Corporation
• Inventors: Britton, Stuart D.
• Primary Examiner(s): Nasser, Robert L.
• Application Number:
  US08/515,047
• Time in Patent Office: 1,233 Days
• Field of Search: 128/633, 128/4, 128/664-7, 128/672, 128/687, 128/690, 128/748, 600/310, 600/473-478, 600/485, 600/500, 600/503, 600/561
• US Class Current: 600/500
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives

Abstract

A signal processing system which utilizes a near infra-red sensor signal to monitor the heart pulse rate of a user. The signal processing system is used to control and monitor the output of the near infra-red sensor to which detects the rate of change of blood flow through arteries of the user. The system operates on the signal from the sensor to detect the pulse rate of the heart of the user. The system can be analog or digital in operation.

Claims

1. A signal processing system comprising,

signal detector means for producing electrical signals representative of the detection of a signal by said signal detection means,

first sample and hold means connected to said signal detector means to selectively sample and hold said electrical signals,

first differential amplifier means connected to said signal detector means and to said first sample and hold means and operative to produce a corrected signal representative of the difference between the electrical signals produced by said signal detector means and the signal selectively held in said first sample and hold means,

second sample and hold means connected to the output of said first differential amplifier means to selectively sample and hold said corrected signal,

second differential amplifier means connected to the output of said first differential amplifier means and to said second sample and hold means and operative to produce a signal representative of the difference between the signals produced by said first differential amplifier means and said second sample and hold means,

third sample and hold means connected to the output of said second differential amplifier means to selectively produce an output signal representative of the difference between the signals produced by said second differential amplifier means and said second sample and hold means, and

timing control means connected to each of said first, second and third sample and hold means to control the operations thereof.

2. The system recited in claim 1 wherein,

said signal detector means includes a transimpedance amplifier means for amplifying said electrical signal.

3. The system recited in claim 1 wherein,

each of said first, second and third sample and hold means includes,

switching means controlled by said timing control means,

energy storing means selectively energized via said switching means, and

amplifying means connected to receive a signal from said energy storing means.

4. The system recited in claim 3 wherein,

said energy storing means comprises capacitor means.

5. The system recited in claim 3 wherein,

the respective switching means included in each of said first, second and third sample and hold means is activated by said timing control means at different times relative to each other.

6. The system recited in claim 1 wherein,

said timing control means activates said first sample and hold means while said signal detector means is not activated.

7. The system recited in claim 6 wherein,

said timing control means activates said second and third sample and hold means in sequence while said first sample and hold means is not activated.

8. The system recited in claim 1 wherein,

said signal detector means includes a photodetector means for producing an electrical signal in response to an optical signal.

9. The system recited in claim 8 wherein,

said signal detector means includes a light emitting diode.

10. The system recited in claim 1 wherein,

said signal detector means includes an illuminating device for selectively providing an optical signal.

11. The system recited in claim 10 wherein,

said illuminating means comprises a light emitting diode (LED).

12. The system recited in claim 10 wherein,

said optical signal is in the near infra-red range.

13. The system recited in claim 1 including,

amplifier means connected from said signal detector to said first sample and hold means and to said first differential amplifier means to amplify said electrical signals.

14. A heart pulse rate detector comprising,

an optical sensor adapted to be mounted adjacent to a blood vessel in the body of a user to sense heart pulses in said blood vessel,

said optical sensor operative to produce a background signal in the absence of a heart pulse in said blood vessel and a pedestal signal in response to the sensing of a heart pulse;

first sample and hold means connected to said optical sensor to selectively sample and hold said background signal,

first differential amplifier means connected to said optical sensor and to said first sample and hold means and operative to produce a corrected signal representative of the difference between said pedestal signal produced by said optical sensor and the background signal selectively held in said first sample and hold means,

second sample and hold means connected to the output of said first differential amplifier means to selectively sample and hold said corrected signal,

second differential amplifier means connected to the output of said first differential amplifier means and to said second sample and hold means and operative to produce a signal representative of the difference between the signals produced by said first differential amplifier means and said second sample and hold means,

third sample and hold means connected to the output of said second differential amplifier means to selectively produce an output signal representative of the difference between the signals produced by said second differential amplifier means and said second sample and hold means, and

timing control means connected to each of said first, second and third sample and hold means to control the operations thereof.

15. The heart pulse rate detector recited in claim 14 including,

light emitting means adapted to be mounted adjacent to said optical sensor and to selectively provide illumination thereto.

16. The detector recited in claim 14 wherein,

said signal detection means includes an amplifier connected from said optical sensor to said first sample and hold means and to said first differential amplifier means.

17. The detector recited in claim 16 wherein,

said amplifier comprises a transimpedance amplifier.

18. The detector recited in claim 14 wherein,

said optical sensor includes a light emitting device and a light detecting device,

said light emitting device is connected to and selectively activated by said timing control means.

19. A signal processing system comprising,

signal detector,

first sample and hold circuit connected to said signal detector,

first connecting circuit,

first differential amplifier connected to said signal detector via said first connecting circuit and to said first sample and hold circuit and operative to produce a corrected signal representative of the difference between the signals produced by said signal detector and said first sample and hold circuit,

second sample and hold circuit connected to the output of said first differential amplifier,

second connecting circuit,

second differential amplifier connected to the output of said first differential amplifier via said second connecting circuit and to said second sample and hold circuit and operative to produce a signal representative of the difference between the signals produced by said first differential amplifier and said second sample and hold circuit,

third sample and hold circuit connected to the output of said second differential amplifier to selectively produce an output signal representative of the difference between the signals produced by said second differential amplifier and said second sample and hold circuit, and

timing controller connected to each of said first, second and third sample and hold circuit to control the operations thereof.

20. The system recited in claim 19 wherein,

each of said first and second connecting circuits comprises a voltage divider circuit.