Apparatus and method for use in pulse oximeters

Apparatus for use in a pulse oximeter for generating and detecting two wavelengths of electromagnetic radiation comprising:

• (a) first means for generating pulses of electromagnetic radiation having a first wavelength, said pulses being generated at a first pulse frequency;
• (b) second means for generating pulses of electromagnetic radiation having a second wavelength, said pulses being generated at a second pulse frequency:
• (c) means for simultaneously exposing a selected extremity of a human being or an animal to the first and second pulses;
• (d) transducer means for producing an electrical signal which is representative of the electromagnetic radiation intensity at a selected location in the vicinity of the selected extremity, said transducer means being responsive to electromagnetic radiation of the first and second wavelengths;
• (e) first bandpass filter means centered at or near the first pulse frequency operatively connected to the transducer means for separating a first electrical signal from the electrical signal produced by the transducer means, said first electrical signal being representative of the intensity of electromagnetic radiation having the first wavelength at the selected location;
• and
• (f) second bandpass filter means centered at or near the second pulse frequency operatively connected to the transducer means for separating a second electrical signal from the electrical signal produced by the transducer means, said second electrical signal being representative of the intensity of electromagnetic radiation having the second wavelength at the selected location.

Testing apparatus comprising:

• (a) exposing means for exposing a test specimen to electromagnetic radiation of two different wavelengths, said means including:
• (i) first means for generating pulses of electromagnetic radiation having the first of the two different wavelengths, said pulses being generated at a first pulse frequency;
• (ii) second means for generating pulses of electromagnetic radiation having the second of the two different wavelengths, said pulses being generated at a second pulse frequency;
• and
• (iii) means for simultaneously exposing the test specimen to the first and second pulses;
• and
• (b) means for detecting the intensity of electromagnetic radiation at each of the two different wavelengths at a selected location in the vicinity of the test specimen, said means including:
• (i) transducer means at the selected location for producing an electrical signal which is representative of the intensity of electromagnetic radiation in the vicinity of said means, said transducer means being responsive to electromagnetic radiation of the first and second wavelengths:
• and
• (ii) means for separating the electrical signal produced by the transducer means into first and second electrical signals which are representative of the intensity of electromagnetic radiation in the vicinity of the transducer means at the first and second wavelengths, respectively, said means including first bandpass filter means centered at or near the first pulse frequency for producing the first electrical signal and second bandpass filter means centered at or near the second pulse frequency for producing the second electrical signal.