Photometric apparatus and method

Claim 2

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.

Claim 3

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.

Claim 4

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

Claim 5

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.

Claim 6

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.

Claim 7

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.

Claim 8

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.

Claim 15

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.

Claim 16

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.

Claim 19

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.