Pulse transducer with artifact signal attenuator

• US 4,198,988 A
• Filed: 07/26/1978
• Issued: 04/22/1980
• Est. Priority Date: 07/26/1978
• Status: Expired due to Term

• Current Assignee: John T. Polhemus, Lovelace Alan M Administrator of The National Aeronautics and Space Administration With Respect To An Invention of, Wilbur H. Cash Jr
• Original Assignee: John T. Polhemus, Lovelace Alan M Administrator of The National Aeronautics and Space Administration With Respect To An Invention of, Wilbur H. Cash Jr
• Inventors: Lovelace, Alan M. Administrator of the National Aeronautics and Space Administration, with respect to an invention of, Polhemus, John T., Cash, Wilbur H. Jr.
• Primary Examiner(s): Howell, Kyle L.
• Application Number:
  US05/928,137
• Time in Patent Office: 636 Days
• Field of Search: 128/665-667, 128/687, 128/689, 128/690, 330/126
• US Class Current: 600/479
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence

Abstract

In combination with a pulse transducer characterized by a source of light and a detector for light reflected from blood vessels of a living body, to provide heart signal consisting of a modulated dc signal voltage indicative of the pulse rate for the body, an artifact signal resulting from a reflection of light from the skin of the body, which includes both a constant dc signal component and a modulated dc signal component the amplitude of which is greater and the frequency of which is less than said heart signal, a signal attenuator circuit including an operational amplifier for canceling said artifact signal from the output signal of the pulse transducer.

Claims

1. In combination with a photoelectric transducer having an output terminal connected with an input terminal for a further signal processing circuit, and adapted to be worn on the arm of a human body for providing an output signal at a variable voltage value including a heart signal component resulting from reflection of light by blood vessels present in the arm and an artifact signal component resulting from reflection of light by the skin of the arm, an artifact signal component attenuator circuit for subtracting the artifact signal component from the output signal of the transducer, comprising:

A. a signal pick-off terminal connected to the output terminal of the transducer;

B. signal integrating means connected to said pick-off terminal for integrating the output signal of the transducer as the output signal is applied to the pick-off terminal, comprising first resistance means connected between the pick-off terminal and the output terminal of said transducer, and capacitance means having one side connected to ground and one side connected to the pick-off terminal, whereby an integrated output signal is applied to said pick-off terminal at a voltage value comprising an average value for the voltage of the transducer output signal;

C. an operational amplifier having an input connected to the pick-off terminal for providing an amplifier output signal comprising an algebraic negative of the integrated output signal; and

D. means for summing the voltage value of the transducer output signal with the amplifier output signal for thus unmasking the heart signal, including second resistance means connected in series between the output terminal of the transducer and the input terminal for the further signal processing circuit, and means connecting the output of the amplifier with the input terminal for the further signal processing circuit.