Drive circuit for light-emitting diode in pulse oximeter
First Claim
1. A drive circuit for use in a pulse oximeter for measuring a degree of oxygen saturation of arterial blood in a living tissue, said drive circuit comprising:
- at least two light emitting elements different in wavelength for irradiating said living tissue containing said arterial blood;
a light receiving element for receiving light irradiated from said light emitting elements and traversing said living tissue directly and indirectly to said light receiving element;
means for intermittently applying an inverse bias voltage across said light emitting elements;
means including at least one inductor for applying an inverse electromotive voltage across said light emitting elements, said means for applying an inverse electromotive voltage being connected to said light emitting elements and to said means for intermittently applying an inverse bias voltage; and
signal processing means which is capable of calculating a ratio of a change of light absorption of at least two wavelengths transmitted alternatively from said light emitting elements,wherein said ratio is based on signals output from said light receiving element and said ratio represents said degree of oxygen saturation of said arterial blood.
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Accused Products
Abstract
Disclosed is a drive circuit for driving a light emitting diode in a pulse oximeter comprising at least two light emitting elements different in wavelength for irradiating a living tissue containing an arterial blood; a light receiving element for receiving light containing one of a reflected light and a transmitted light irradiated from the light emitting elements; a power supply for applying intermittently an inverse bias voltage toward the light emitting elements; and an inductor for applying an inverse electromotive voltage to the light emitting elements, the inductor being connected to the light emitting elements in parallel, wherein a ratio between light absorption change with respect to two wavelengths obtained from optical outputs of the light receiving element so as to obtain a degree of oxygen saturation of arterial blood.
254 Citations
31 Claims
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1. A drive circuit for use in a pulse oximeter for measuring a degree of oxygen saturation of arterial blood in a living tissue, said drive circuit comprising:
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at least two light emitting elements different in wavelength for irradiating said living tissue containing said arterial blood; a light receiving element for receiving light irradiated from said light emitting elements and traversing said living tissue directly and indirectly to said light receiving element; means for intermittently applying an inverse bias voltage across said light emitting elements; means including at least one inductor for applying an inverse electromotive voltage across said light emitting elements, said means for applying an inverse electromotive voltage being connected to said light emitting elements and to said means for intermittently applying an inverse bias voltage; and signal processing means which is capable of calculating a ratio of a change of light absorption of at least two wavelengths transmitted alternatively from said light emitting elements, wherein said ratio is based on signals output from said light receiving element and said ratio represents said degree of oxygen saturation of said arterial blood. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
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Specification