Method and apparatus for photometric measurement of concentration ratios

• US 3,922,088 A
• Filed: 04/15/1974
• Issued: 11/25/1975
• Est. Priority Date: 08/27/1973
• Status: Expired due to Term

• Current Assignee: Dietrich W. Lubbers, Reinhard Wodick
• Original Assignee: Dietrich W. Lubbers, Reinhard Wodick
• Inventors: Lubbers, Dietrich W., Wodick, Reinhard
• Primary Examiner(s): Smith, Alfred E.
• Assistant Examiner(s): Koren, Matthew W.
• Application Number:
  US05/461,150
• Time in Patent Office: 589 Days
• Field of Search: 356/39,40-42,179,180,184,186 250/564,574
• US Class Current: 356/40
• CPC Class Codes: A61B 5/00 Measuring for diagnostic purposes radiation diagnosis A61B6/00; diagnosis by ultrasonic, sonic or infrasonic waves A61B8/00; Identification of persons
• CPC Class Codes: G01J 2003/2866 Markers; Calibrating of scan
• CPC Class Codes: G01J 3/28 Investigating the spectrum using colour filters G01J3/51
• CPC Class Codes: G01N 21/314 with comparison of measurements at specific and non-specific wavelengths dual wavelength spectrometry G01J3/427

Abstract

A method and apparatus for photometrically measuring the concentration ratio of two components in a two-component system comprising separately directing at least three of five monochromatic light beams of different wavelengths onto a first of two components of the two-component system while the components are separated from each other; in which each of the five monochromatic light beams of different wavelengths are separately directed onto the second of the two components of the two-component system while the two components are separated from each other; in which at least three of the five monochromatic light beams are separately directed onto the object to be measured while only the first component of the two-component system is present in the object; in which the five monochromatic light beams of different wavelengths are separately directed onto the object to be measured, while only the second component of the two component system is present in the object. In each case reflectivity and/or transmissivity measurements of the resulting intensities are made; these resulting intensities determine calibration intensities. Each of the five monochromatic light beams are then directed onto the object on which the measurements are to be made, and the resulting reflected system-intensities measured. The calibrating intensities together with the measured system-intensities are then utilized to determine the relative concentration of the two components in the two-component system.

Claims

1. A method of photometrically measuring the concentration ratio of the two components of a two-component system, comprising a. directing five monochromatic light beams having respective ones of five predetermined wavelengths towards the system while only the first component is present in the system, and measuring the intensity of the five beams at portions thereof directed away from the system, these measured intensities constituting calibrating intensities;

b. directing three monochromatic light beams having respective ones of a predetermined three of the five wavelengths towards the system while only the second component is present in the system, and measuring the intensity of the three beams at portions thereof directed away from the system, these measured intensities constituting additional calibrating intensities;

c. directing five monochromatic light beams having respective ones of the five wavelengths towards the first component with the first component removed from the system and separated from the second component, and measuring the intensity of the five beams at portions thereof directed away from the first component, these measured intensities constituting further calibrating intensities;

d. directing three monochromatic light beams having respective ones of a predetermined three of the five wavelengths towards the second component with the second component removed from the system and separated from the first component, and measuring the intensity of the three beams at portions thereof directed away from the second component, these measured intensities constituting still further calibrating intensities;

e. directing five monochromatic light beams having respective ones of the five wavelengths towards the system wHile both the first and the second component are present in the system, and measuring the intensity of the five beams at portions thereof directed away from the system, these measured intensities constituting system intensities; and

f. deriving the relative concentrations of the two components in the system from the values of the calibrating intensities and of the system intensities.

2. A method as defined in claim 1, wherein in performing at least one of steps (a) to (e) at least portions of the light beams employed in the step coincide with each other.

3. A method as defined in claim 1, wherein in performing at least one of steps (a) to (e) at least portions of the monochromatic light beams employed in the step coincide and are constituent components of a beam of light having a continuous rather than a discrete spectral wavelength distribution.

4. A method as defined in claim 3, wherein the beam having a continuous spectral wavelength distribution is a beam of white light.

5. A method as defined in claim 1, wherein step (e) comprises generating five system signals corresponding to the five system intensities, wherein step (f) comprises generating five first weighted signals and five second weighted signals having values corresponding to respective ones of the five system signals multiplied by respective ones of five first weighting factors and five second weighting factors derived from the sixteen calibrating intensities measured in steps (a) to (d), adding said five first weighted signals together to form a first summed signal and adding said five second weighted signals together to form a second summed signal, generating a ratio signal by effecting division of the first summed signal by the second signal, and normalizing the ratio signal to produce a normalized ratio signal.

6. A method as defined in claim 5, wherein in steps (c) and (d) the first and the second component, respectively, is located in a test cuvette, and wherein the values of said five system signals are respectively designated by G( lambda 1), G( lambda 2), G( lambda 3), G( lambda 4) and G( lambda 5).

7. A method as defined in claim 6, wherein said calibrating intensities for each of said components at each wavelength are G1100, G3100 and G5100, for wavelengths lambda 1, lambda 3, and lambda 5, respectively, for first component k1 having a concentration of 100% as measured in said system;

G1o, G2o, G3o, G4o, and G5o for wavelengths lambda 1, lambda 2, lambda 3, lambda 4, and lambda 5, respectively, for second component k2 having a relative concentration of 100% as measured in said system;

M2100, M3100, and M4100 for wavelengths lambda 2, lambda 3, and lambda 4, respectively, for first component k1 having a relative concentration of 100% as measured in a test cuvette;

M1o, M2o, M3o, M4o, and M5o for wavelengths lambda 1, lambda 2, lambda 3, lambda 4, and lambda 5, respectively, for second component k2 having a relative concentration of 100% as measured in a test cuvette;

said first weighting factors are A1N, A2N, A3N, A4N, and A5N;

said second weighting factors are B1N, B2N, B3N, B4N, and B5N;

said weighting factors being given by A1N Po Beta A2N NoMa A3N - NoM - Po A4N NoM(1-a) A5N Po(1-a) B1N - Beta (P100 - Po) B2N aNoM B3N (P100 - Po) - NoM B4N (1 - a) NoM B5N (1 - Beta ) (P100 - Po) where NoM M3o - Beta M1o - (1 - Beta )M5o NoG G3o - Beta G1o - (1 - Beta )G5o Po aG2o + (1 - a)G4o - G3o P100 aG2100 + (1 - a)G4100 - G3100 with

8. A method as defined in claim 1, wherein said two component system has a reflection spectra curve of reflected intensity and wavelength, said curve having a relative minimum and two relative maxima, and wherein one of the five wavelengths corresponds to said relative minimum, and two further ones of the five wavelengths respectively correspond to said relative maxima.

9. A method as defined in claim 8, wherein the remaining two of the five wavelengths and also the wavelength which corresponds to said relative minimum are all associated with the same intensity value on said curve.

10. A method as defined in claim 8, wherein said two relative maxima are equal.

11. A method as defined in claim 1, wherein said first component is oxygenated hemoglobin, and said second component is deoxygenated hemoglobin.

12. An arrangement for photometrically measuring the concentration ratio of a two component system comprising a source of five monochromatic light beams of different wavelengths;

a spectrophotometer, capable of measuring the reflective intensity of said light beams from a sample comprising at least one of said components, thereby producing reflected sample intensity signals;

amplifying means connected to said spectrophotometer to multiply each of said reflected sample intensity signals by a predetermined gain factor to thereby produce weighted signals;

adding means, serving to add predetermined combinations of said weighted signals;

dividing means, serving to divide two of said predetermined combinations thereby producing an output signal; and

read-out means, serving to display said output signal.