Photometric apparatus and method

• US 4,350,441 A
• Filed: 06/30/1980
• Issued: 09/21/1982
• Est. Priority Date: 06/30/1980
• Status: Expired due to Term

• Current Assignee: Baxter Travenol Laboratories Incorporated (Baxter International Inc.)
• Original Assignee: Baxter Travenol Laboratories Incorporated (Baxter International Inc.)
• Inventors: Wicnienski, Michael F.
• Primary Examiner(s): McGraw, Vincent P.
• Application Number:
  US06/164,357
• Time in Patent Office: 813 Days
• Field of Search: 356/40, 356/320, 356/323, 356/325, 356/407, 356/408, 356/434, 356/448, 324/140 D, 328/161, 307/358, 307/359, 307/494, 307/498, 250/565
• US Class Current: 356/40
• CPC Class Codes: G01N 21/3151 using two sources of radiation of different wavelengths G01N21/33 - G01N21/39 take precedence

Abstract

A photometric system for determining the absorbance ratio, in a sample, of two different wavelength lights. First and second lights, each having a different wavelength, are passed through the sample in alternation with each other. The radiation intensity from each light that has passed through the sample is detected. A comparator, up/down counter and digital to analog converter are coupled so that a scaling factor is derived which, when multiplied with an analog signal proportional to the intensity of the first light after it has passed through the sample, is equal to an analog signal proportional to the intensity of the second light after it has passed through the sample. The output of the counter comprises a digital word corresponding to the ratio of the absorbance ratio of the first light and the second light.

Claims

1. A photometric apparatus for determining the absorbance ratio in a sample of two different wavelength lights, said apparatus comprising:

means for providing a light of a first wavelength having, when said light is energized, a postsample intensity after said light is directed through the sample;

means for providing a light of a second wavelength having, when said light is energized, a postsample intensity after said light is directed through the sample;

means for alternately energizing said first and second lights;

means for detecting said postsample intensities of said first and second lights;

a comparator having two inputs and an output;

a digital to analog converter having two inputs and an output;

means coupling the output of said digital to analog converter to an input of said comparator;

means coupled to the other input of said comparator for providing a signal that is proportional to said detected postsample intensity of said first light;

means coupled to an input of said digital to analog converter for providing a signal that is proportional to said detected postsample intensity of said second light;

an up/down counter having an up/down input and an output;

means coupling the output of the comparator to the up/down input of said counter;

means coupling the output of the up/down counter to the other input of said digital to analog converter; and

means for clocking said up/down counter.

2. An apparatus according to claim 1, and further including a first sample and hold circuit coupled between said detector means and said other input of said comparator;

and a second sample and hold circuit coupled between said detector means and said first mentioned input of said digital to analog converter.

3. An apparatus according to claim 1, wherein said first light is green and said second light is red.

4. An apparatus according to claim 1

and further including a beam splitter positioned adjacent said first and second lights, with each of said first and second lights being directed substantially perpendicularly with respect to each other, and a holder for holding the sample, and

wherein said detecting means includes photodetector means positioned such that said sample holder is located between said photodetector means and said beam splitter, said photodetector means being operative for detecting said postsample intensities of said first and second lights.

5. A photometric apparatus for determining the absorbance ratio in a sample of two different wavelength lights, said apparatus comprising:

means for providing a light of a first wavelength having, when said light is energized, a postsample intensity after said light is directed through the sample;

means for providing a light of a second wavelength having, when said light is energized, a postsample intensity after said light is directed through the sample;

means for alternately energizing said first and second lights;

means for detecting said postsample intensities of said first and second lights; and

means for generating a first analog signal that is proportional to said postsample intensity of said first light;

means for comparing said first analog signal with an other signal and for generating a succession of scaling factors which

incrementally increase in value if said first analog signal is greater than said other signal,

incrementally decrease in value if said first analog signal is less than said other signal, and

remain constant in value if said first analog signal is equal to said other signal,

means for generating a second analog signal that is proportional to said postsample intensity of said second light; and

means operatively connected with said second analog signal generating means and said comparing means for generating a succession of said other signals by multiplying said second analog signal with each of said successive scaling factors and for transmitting said succession of said other signals to said comparing means,

whereby said scaling factor, once constant, comprises the ratio of the absorbance of said first light and said second light.

6. An apparatus according to claim 5

wherein said comparing means comprises a comparator having two inputs, one of which is operatively connected with said first analog signal generating means, and an output, an up/down counter for generating at its output said scaling factors, and means for coupling the output of said comparator to the up/down input of said counter, and

wherein said other signal generating means includes a digital to analog converter having one input operatively connected with said second analog signal generating means, another input operatively connected with said output of said up/down counter, and an output operatively connected with said second input of said comparing means.

7. A method for determining the absorbance ratio in a sample of two different wavelength lights, which comprises the steps of:

energizing a first light having a first wavelength;

alternately energizing a second light having a second wavelength;

directing the first light and the second light through the sample and detecting the radiation intensity of each light after it has passed through the sample;

generating a first analog signal that is proportional to the intensity of the first light after it has passed through the sample;

comparing the first analog signal with an other signal and then generating a succession of scaling factors which

incrementally increase in value if the first analog signal is greater than the other signal,

incrementally decrease in value if the first analog signal is less than the other signal, and

remain constant in value if the first analog signal is equal to the other signal,

generating a second analog signal that is proportional to the intensity of the second light after it has passed through the sample, and

generating a succession of the other signals by multiplying the second analog signal with each of the successive scaling factors,

whereby the scaling factor, once constant, comprises the ratio of the absorbance of the first light and the second light.

8. A method for determining the absorbance ratio in a sample of two different wavelength lights, which comprises the steps of:

energizing a first light having a first wavelength;

alternately energizing a second light having a second wavelength;

directing the first and second lights through the sample and detecting the radiation intensity from each light after it has passed through the sample;

providing to a comparator a signal that is proportional to the detected intensity from said first light;

providing to a digital to analog converter a signal that is proportional to the detected intensity from said second light;

coupling the output of said comparator to the up/down input of an up/down counter;

coupling the output of said up/down counter to another input of the digital to analog converter; and

coupling the output of the digital to analog converter to the other input of said comparator.

9. An apparatus for detecting the presence of hemoglobin in a fluid which comprises

means for providing a substantially green light having, when said light is energized, a postsample intensity after said light is directed through the sample;

means for providing a substantially red light having, when said light is energized, a postsample intensity after said light is directed through the sample;

means for alternately energizing said green and red lights;

means for detecting said postsample intensities of said green and red lights;

a comparator having two inputs and an output;

a digital to analog converter having two inputs and an output;

means coupling the output of said digital to analog converter to an input of said comparator;

means coupled to the other input of said comparator for providing a signal that is proportional to said detected postsample intensity of said green light;

means coupled to an input of said digital to analog converter for providing a signal that is proportional to said detected postsample intensity of said red light;

an up/down counter having an up/down input and an output;

means coupling the output of the comparator to the up/down input of said counter;

means coupling the output of the up/down counter to the other input of said digital to analog converter; and

means for clocking said up/down counter.

10. An apparatus according to claim 9, and further including a first sample and hold circuit coupled between said detector means and said other input of said comparator;

and a second sample and hold circuit coupled between said detector means and said first mentioned input of said digital to analog converter.

11. An apparatus according to claim 9

and further including a beam splitter positioned adjacent said green and red lights, with each of said green and red lights being directed substantially perpendicularly with respect to each other, and a holder for holding the sample, and

wherein said detecting means includes photodetector means positioned such that said sample holder is located between said photodetector means and said beam splitter, said photodetector means being operative for detecting said postsample intensities of said green and red lights.

12. An apparatus for detecting the presence of hemoglobin in a fluid which comprises

means for providing a substantially green light having, when said light is energized, a postsample intensity after said light is directed through the sample;

means for providing a substantially red light having, when said light is energized, a postsample intensity after said light is directed through the sample;

means for alternately energizing said green and red lights;

means for detecting said postsample intensities of said green and red lights;

means for generating a first analog signal that is proportional to said postsample intensity of said green light;

means for comparing said first analog signal with an other signal and for generating a succession of scaling factors which

incrementally increase in value if said first analog signal is greater than said other signal,

incrementally decrease in value if said first analog signal is less than said other signal, and

remain constant in value if said first analog signal is equal to said other signal,

means for generating a second analog signal that is proportional to said postsample intensity of said red light; and

means operatively connected with said second analog signal generating means and said comparing means for generating a succession of said other signals by multiplying said second analog signal with said successive scaling factors and for transmitting said succession of said other signals to said comparing means,

whereby said scaling factor, once constant, comprises the ratio of the absorbance of said first green and said red light.

13. An apparatus according to claim 12

wherein said comparing means comprises a comparator having two inputs, one of which is operatively connected with said first analog signal generating means, and an output, and

wherein said other signal generating means includes a digital to analog converter having one input operatively connected with said second analog signal generating means, another input operatively connected with said output of said up/down counter, and an output operatively connected with said second input of said comparing means.

14. A method for detecting hemoglobin in a fluid which comprises the steps of:

energizing a substantially green light;

alternately energizing a substantially red light;

directing the green light and the red light through the sample and detecting the radiation intensity of each light after it has passed through the sample;

generating a first analog signal that is proportional to the intensity of the first light after it has passed through the sample;

comparing the first analog signal with an other signal and then generating a succession of scaling factors which

incrementally increase in value if the first analog signal is greater than the other signal,

incrementally decrease in value if the first analog signal is less than the other signal, and

remain constant in value if the first analog signal is equal to the other signal,

generating a second analog signal that is proportional to the intensity of the second light after it has passed through the sample, and

generating a succession of the other signals by multiplying the second analog signal with the successive scaling factors,

whereby the scaling factor, once constant, comprises the ratio of the absorbance of the green light and the red light.

15. A method for detecting hemoglobin in a fluid which comprises the steps of:

energizing a substantially green light;

alternately energizing a substantially red light;

directing the green and red lights through the sample and detecting the radiation intensity from each light after it has passed through the sample;

providing to a comparator a signal that is proportional to the detected intensity from said green light;

providing to a digital to analog converter a signal that is proportional to the detected intensity from said red light;

coupling the output of said comparator to the up/down input of an up/down counter;

coupling the output of said up/down counter to another input of the digital to analog converter; and

coupling the output of the digital to analog converter to the other input of said comparator.