Measuring bilirubin in blood using light at two wavelengths

Claim 1

A method of measuring the concentration of bilirubin in blood serum comprising the steps of: directing light rays through a sample of said serum and forming said light rays into a beam of light directed along an established principal optical path; dividing said light rays of said beam into two substantially equal amounts at one point in said principal optical path and directing each of said equal amounts of light rays along a different discrete branch path wherein the total amount of light in each branch path is equal; filtering at one point in one of said branch paths substantially all wavelengths of the light therein but that for which bilirubin in serum has a maximum absorbance; filtering at one point in the other of said branch paths substantially all wavelengths of the light therein but that for which hemoglobin in blood serum has substantially the same absorbance as it has for the light of said first-mentioned wavelength, said first and last-mentioned wavelengths of light being of different frequencies; and adjusting the amount of light of one of said frequencies to equality with the amount of light of different frequency by operation of adjustable aperture stop means disposed in one of said branch paths whereby the extent of adjustment of said stop means may be interpreted in terms of the concentration of bilirubin in said sample.

Claim 2

A method of measuring the concentration of bilirubin in blood serum comprising the steps of: directing light rays through a sample of said serum and forming said light rays into a beam of light directed along an established principal optical path; dividing said light rays of said beam into two substantially equal amounts at one point in said principal optical path and directing each of said equal amounts of light rays along a different discrete branch path wherein the total amount of light in each branch path is equal; filtering at one point in one of said branch paths substantially all wavelengths of the light therein but that for which bilirubin in serum has a maximum absorbance; filtering at one point in the other of said branch paths substantially all wavelengths of the light therein but that for which hemoglobin in blood serum has substantially the same absorbance as it has for the light of said first-mentioned wavelength, said first and last-mentioned wavelengths of light being of different frequencies; and adjusting the amount of light of one of said frequencies to equality with the amount of light of different frequency by operation of adjustable aperture stop means disposed in one of said branch paths whereby the extent of adjustment of said stop means may be interpreted in terms of the concentration of bilirubin in said sample.

Claim 6

A system for measuring the concentration of bilirubin in a sample of blood serum comprising: a source of light; a sample holder positioned to receive light rays emitted by said source wherewith a blood sample placed in said holder is transilluminated; projection lens means arranged to receive at least a substantial amount of said light rays transmitted through said holder and sample for forming and prOjecting a beam thereof along a principal optical path in said system; a beam splitter in said principal path constructed and arranged to divide said light rays of said beam into two parts of substantially equal amounts and direct each part discretely along an individual branch path; a band-pass filter in each branch path through which substantially only light rays of one wavelength are permitted to pass; an electrical photodetector so positioned in each branch path as to receive only respective light rays of the one wavelength; projection lens means between said photodetector and band-pass filter in each branch path for receiving and directing said light rays into incidence upon respective photodetectors in said paths; an adjustable light attenuator in one of said branch paths for regulating the amount of light rays received by the particular photodetector in said one path; a meter for indicating relative electrical responses of said photodetectors to light rays received thereby; and a scale moveable in conjunction with adjustment of said attenuator, said scale being calibrated to read bilirubin concentration in terms of the amount of regulation of light effected by operation of said attenuator for a given indication of relative responses of said photodetectors on said meter.

Claim 7

A system for measuring the concentration of bilirubin in a sample of blood serum comprising: a source of light; a sample holder positioned to receive light rays emitted by said source wherewith a blood sample placed in said holder is transilluminated; projection lens means arranged to receive at least a substantial amount of said light rays transmitted through said holder and sample for forming and prOjecting a beam thereof along a principal optical path in said system; a beam splitter in said principal path constructed and arranged to divide said light rays of said beam into two parts of substantially equal amounts and direct each part discretely along an individual branch path; a band-pass filter in each branch path through which substantially only light rays of one wavelength are permitted to pass; an electrical photodetector so positioned in each branch path as to receive only respective light rays of the one wavelength; projection lens means between said photodetector and band-pass filter in each branch path for receiving and directing said light rays into incidence upon respective photodetectors in said paths; an adjustable light attenuator in one of said branch paths for regulating the amount of light rays received by the particular photodetector in said one path; a meter for indicating relative electrical responses of said photodetectors to light rays received thereby; and a scale moveable in conjunction with adjustment of said attenuator, said scale being calibrated to read bilirubin concentration in terms of the amount of regulation of light effected by operation of said attenuator for a given indication of relative responses of said photodetectors on said meter.