Method and apparatus for accurately measuring the saturated oxygen in arterial blood by substantially eliminating noise from the measurement signal
First Claim
1. A pulse oximeter comprising:
- light-emitting means for repeating, successively, red light emission, infrared light emission, and no light emission, with respect to an object to be measured, in every data sampling cycle in measurement of a saturated oxygen in arterial blood;
light-receiving means for outputting a light-receiving signal obtained by receiving transmitted light and reflected light reflected from the object to be measured;
noise level detecting means for detecting, from the light-receiving signal, a noise signal level at the time of no light emission; and
signal generating means for processing the light-receiving signal to obtain a measurement signal having a level corresponding only to the red light emission and the infrared light emission by subtracting the noise signal level from the light-receiving signal.
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Abstract
A pulse oximeter includes a light-emitting device for repeating red light emission, infrared light emission, and no light emission with respect to an object to be measured every data sampling cycle in a measurement of a saturated oxygen in arterial blood, a light-receiving device for outputting a light-receiving signal obtained by receiving transmitted light or reflected light from the object to be measured; a noise level detecting device for detecting from the light-receiving signal a noise signal level at the time of no light emission in the light-receiving device, and a light-receiving signal generating device for obtaining a light-receiving signal of a level corresponding only to the red light emission and the infrared light emission by subtracting the noise signal level from each of light-receiving signal levels of the red light emission and the infrared light emission.
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Citations
23 Claims
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1. A pulse oximeter comprising:
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light-emitting means for repeating, successively, red light emission, infrared light emission, and no light emission, with respect to an object to be measured, in every data sampling cycle in measurement of a saturated oxygen in arterial blood; light-receiving means for outputting a light-receiving signal obtained by receiving transmitted light and reflected light reflected from the object to be measured; noise level detecting means for detecting, from the light-receiving signal, a noise signal level at the time of no light emission; and signal generating means for processing the light-receiving signal to obtain a measurement signal having a level corresponding only to the red light emission and the infrared light emission by subtracting the noise signal level from the light-receiving signal. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method for measuring a saturated oxygen in arterial blood, comprising the steps of:
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repeating, successively, red light emission, infrared light emission, and no light emission, with respect to an object to be measured, in every data sampling cycle in measurement of the saturated oxygen in the arterial blood; outputting a light-receiving signal obtained by receiving transmitted light and reflected light reflected from the object to be measured; detecting, from the light-receiving signal, a noise signal level at the time of no light emission; and obtaining a measurement signal having a level corresponding only to the red light emission and the infrared light emission by subtracting the noise signal level from the light-receiving signal. - View Dependent Claims (8, 9, 10)
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11. An apparatus for measuring light-absorbing material in blood comprising:
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light-emitting means for repeating red light emission, infrared light emission, and no light emission, with respect to an object to be measured, successively in every data sampling cycle in measurement of a light-absorbing material in blood; light-receiving means for outputting a light-receiving signal obtained by receiving transmitted light or reflected light reflected from the object to be measured; noise level detecting means for detecting, from the light-receiving signal, a noise signal level at the time of no light emission; signal generating means for processing the light-receiving signal to obtain a measurement signal having a level corresponding to the red light emission and the infrared light emission by subtracting the noise signal level from the light-receiving signal; storage means for storing, in each of a plurality of data sampling cycles repeated by the light-emitting means, the light-receiving signal corresponding to the red light emission, the infrared light emission, and the no light emission as well as the noise signal level corresponding to the no light emission; wherein the light-receiving means includes an integrating circuit for generating an integrated light-receiving signal by integrating the light-receiving signal from a light-receiving element included in the light-receiving means; and control means for starting integration and discharging said integrated light-receiving signal at said integrated circuit in synchronism with said data sampling cycles; and judging means for judging whether the noise signal level in each of the plurality of data sampling cycles is within a predetermined range, wherein when the judging means judges that the noise signal level is within the predetermined range, the signal generating means outputs the measurement signal having a level corresponding to the red light emission and the infrared light emission obtained by subtracting the noise signal level from the light-receiving signal.
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12. An apparatus for measuring light-absorbing material in blood comprising:
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light-emitting means for repeating red light emission, infrared light emission, and no light emission, with respect to an object to be measured, successively in every data sampling cycle in measurement of a light-absorbing material in blood; light-receiving means for outputting a light-receiving signal obtained by receiving transmitted light or reflected light reflected from the object to be measured; noise level detecting means for detecting, from the light-receiving signal, a noise signal level at the time of no light emission; signal generating means for processing the light-receiving signal to obtain a measurement signal having a level corresponding only to the red light emission and the infrared light emission by subtracting the noise signal level from the light-receiving signal; storage means for storing, in each of a plurality of data sampling cycles repeated by the light-emitting means, the light-receiving signal corresponding to the red light emission, the infrared light emission, and the no light emission as well as the noise signal level corresponding to the no light emission; wherein the light-receiving means includes an integrating circuit for generating an integrated light-receiving signal by integrating the light-receiving signal from a light-receiving element included in the light-receiving means; and judging means for judging whether the noise signal level in each of the plurality of data sampling cycles is within a predetermined range, wherein said judging means judges whether the noise level is within said predetermined range based on a comparison of a portion of said integrated light-receiving signal, corresponding to the no light emission, stored in the storage means with one of a maximum and minimum level a portion of previous integrated light-receiving signals corresponding to no light emission; and wherein when the judging means judges that the noise signal level is within the predetermined range, the signal generating means outputs the measurement signal having a level corresponding to the red light emission and the infrared light emission obtained by subtracting the noise signal level from the light-receiving signal. - View Dependent Claims (13, 14)
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15. An apparatus for measuring light-absorbing material in blood comprising:
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light-emitting means for repeating red light emission, infrared light emission, and no light emission, with respect to an object to be measured, successively in every data sampling cycle in measurement of a light-absorbing material in blood; light-receiving means for outputting a light-receiving signal obtained by receiving transmitted light or reflected light reflected from the object to be measured; noise level detecting means for detecting, from the light-receiving signal, a noise signal level at the time of no light emission; signal generating means for processing the light-receiving signal to obtain a measurement signal having a level corresponding to the red light emission and the infrared light emission by subtracting the noise signal level from the light-receiving signal; storage means for storing, in each of a plurality of data sampling cycles repeated by the light-emitting means, the light-receiving signal corresponding to the red light emission, the infrared light emission, and the no light emission as well as the noise signal level corresponding to the no light emission; wherein the light-receiving means includes an integrating circuit for generating an integrated light-receiving signal by integrating the light-receiving signal from a light-receiving element included in the light-receiving means; and judging means for judging whether the noise signal level in each of the plurality of data sampling cycles is within a predetermined range, wherein said judging means judges whether the noise signal level is within said predetermined range based on a comparison of a value obtained by subtracting a minimum level of portion of said integrated light-receiving signal corresponding to no light emission from a maximum level of a corresponding portion of a previous integrated light-receiving signal stored in said storage means, with a predetermined threshold level; and wherein when the judging means judges that the noise signal level is within the predetermined range, the signal generating means outputs the measurement signal having a level corresponding to the red light emission and the infrared light emission obtained by subtracting the noise signal level from the light-receiving signal. - View Dependent Claims (16, 17)
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18. A method for measuring light-absorbing material in blood, comprising the steps of:
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repeating red light emission, infrared light emission, and no light emission, with respect to an object to be measured, successively in every data sampling cycle in measurement of the light-absorbing material in blood; outputting a light-receiving signal obtained by receiving transmitted light and reflected light reflected from the object to be measured; detecting, from said light-receiving signal, a noise signal level at the time of no light emission; obtaining a measurement signal having a level corresponding to the red light emission and the infrared light emission by subtracting the noise signal level from said light-receiving signal; storing, in each of a plurality of data sampling cycles, said light-receiving signal corresponding to the red light emission, the infrared light emission, and the no light emission as well as the noise signal level corresponding to the no light emission; judging whether the noise signal level in each of the plurality of data sampling cycles is within a predetermined range, by comparing a portion of a current integrated light-receiving signal corresponding to no light emission with one of a maximum and a minimum level of portions of previous integrated light-receiving signals corresponding to no light emission; and outputting the measurement signal having a level corresponding to the red light emission and the infrared light emission obtained by subtracting the noise signal level from each of the light-receiving signals when the noise signal level is within the predetermined range. - View Dependent Claims (19, 20)
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21. A method for measuring light-absorbing material in blood, comprising the steps of:
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repeating red light emission, infrared light emission, and no light emission, with respect to an object to be measured, successively in every data sampling cycle in measurement of the light-absorbing material in blood; outputting a light-receiving signal obtained by receiving transmitted light and reflected light reflected from the object to be measured; detecting, from the light-receiving signal, a noise signal level at the time of no light emission; obtaining a measurement signal having a level corresponding to the red light emission and the infrared light emission by subtracting the noise signal level from the light-receiving signal; storing, in each of a plurality of data sampling cycles, the light-receiving signal corresponding to the red light emission, the infrared light emission, and the no light emission as well as the noise signal level corresponding to the no light emission; judging whether the noise signal level is within a range from a minimum level to a maximum level of a previous noise signal; subtracting a minimum value of a portion of said integrated light-receiving signal corresponding to the no light emission from a maximum value of said portion of said integrated light-receiving signal corresponding to the no light emission to obtain a subtraction value; comparing said subtraction value with a predetermined threshold level when said integrated light-receiving signal is not within said range; and outputting the measurement signal having a level corresponding to the red light emission and the infrared light emission obtained by subtracting the noise signal level from each of the light-receiving signals corresponding to the red light emission and the infrared light emission when the noise signal level is within the range. - View Dependent Claims (22, 23)
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Specification