Ear oximetry process and apparatus
Multi-wavelength incremental absorbence oximeter
Amplifier circuit having photoelectric converter
Noninvasive device for photoelectrically measuring the property of arterial blood
Light detecting circuit
Process and circuit arrangement for amplifying an input current
Pulse oximeter Patent #: 4759369
ApplicationNo. 06/897664 filed on 08/18/1986
US Classes:600/323, Oxygen saturation, e.g., oximeter356/41Oximeters
ExaminersPrimary: Coven, Edward M.
Assistant: Hanley, John C.
Attorney, Agent or Firm
International ClassA61B 5/00 (20060101)
AbstractA feedback control system is disclosed for use in processing signals employed in pulse transmittance oximetry. The signals are produced in response to light transmitted through, for example, a finger at two different wavelengths. Each signal includes a slowly varying baseline component representing the relatively fixed attenuation of light produced by bone, tissue, skin, and hair. The signals also include pulsatile components representing the attenuation produced by the changing blood volume and oxygen saturation within the finger. The signals are processed by the feedback control system before being converted by an analog-to-digital (A/D) converter (72) for subsequent analysis by a microcomputer (16). The feedback control system includes a controllable offset subtractor (66), a programmable gain amplifier (68), controllable drivers (44) for the light sources (40,42), and the microcomputer (16). The microcomputer receives signals from the offset subtractor (66), gain amplifier (68), drivers (44) and A/D converter (72) to produce signals that control the function of the subtractor (66) and drivers (44) in the following manner. Normally, the drivers (44) are maintained within a predetermined current range. In the event the microcomputer (16) senses an output from the converter (72) that is not within a predetermined range, the drive signal is adjusted to produce an acceptable signal. The magnitude of the offset removed by the subtractor (66), as controlled by the microcomputer (16), is maintained at a constant level when the converter (72) output is within a first predetermined range and is a predetermined function of the converter (72) output when that output falls within a second predetermined range.