Error minimization apparatus and method for real-time spectral deconvolution of chemical mixtures

• US 5,585,919 A
• Filed: 10/19/1994
• Issued: 12/17/1996
• Est. Priority Date: 10/19/1994
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Kurtzberg, Jerome M., Lew, John S.
• Primary Examiner(s): Evans, F. L.
• Application Number:
  US08/325,746
• Time in Patent Office: 790 Days
• Field of Search: 356/300, 356/326, 356/328, 364/498, 364/499
• US Class Current: 356/300
• CPC Class Codes: G01N 21/314 with comparison of measurements at specific and non-specific wavelengths dual wavelength spectrometry G01J3/427

Abstract

An apparatus and method are described for determining the relative concentrations of the N constituent chemical components of a chemical combination. The spectral response, C_i, of the composite sample is measured at M wavelengths λ_i, wherein M≧N. The relative concentration of the jth constituent is X_j. The spectral response of the jth component at wavelength λ_i is A_ij. the set of M equations ##EQU1## have intersections defining values of X_j of which only those within the region defined by 0≦X_j are possible values of X_j. An error is assigned to each intersections and the intersection of minimum error defines the values of X_j. Such a determination is rapid. A profile of each of the relative concentration X_j in the sample is readily and rapidly determined.

Claims

1. An apparatus for measuring relative spectral intensities C_i at M wavelengths λ

_i, wherein i=1 to M and for using these measurements to determine relative concentrations X_j of N component chemical constituents, wherein j=1 to N, in a chemical combination using predetermined relative constituent spectral intensities A_ij of said component chemical constituents, wherein M≧

N, comprising;

means for measuring relative spectral intensities C_i of said chemical combination at said wavelengths λ

_i ;

means for storing said C_i as stored relative spectral intensities;

means for storing said A_ij as stored predetermined relative constituent spectral intensities;

means for determining said relative concentrations X_j from said stored relative spectral intensities and said stored relative constituent spectral intensities;

means for generating a set of M surfaces each of N-1 dimensions within a region defined by 0≦

X_j for j=1 to N from a set of M equations ##EQU13## means for determining a set of intersections of said M surfaces within said region;

means for assigning an error indicating how good said intersection is for said value of said relative concentrations;

means for storing said error;

means for determining which of said intersection has a minimum value of said error, said intersection having said minimum error defining said relative concentrations X_j of said component chemical constituents of said chemical combination.

2. An apparatus according to claim 1, wherein said relative spectral intensities A_ij and C_i are absorbance intensities.

3. An apparatus according to claim 1, wherein said means for measuring said relative spectral intensities C_i is an absorbance spectrometer.

4. An apparatus according to claim 1, wherein said predetermined relative spectral intensities A_ij are determined using an absorbance spectrometer.

5. An apparatus according to claim 1, wherein said means for determining is a digital computer.

6. An apparatus according to claim 5, wherein said predetermined relative spectral intensities A_ij are stored in said digital computer.

7. An apparatus according to claim 5, wherein said relative spectral intensities C_i are stored in said computer.

8. An apparatus according to claim 1, further including a means for generating said relative spectral intensities C_i at a plurality of periodic intervals in time.

9. An apparatus according to claim 8, wherein said interval of time is less than a millisecond.

10. An apparatus according to claim 1, wherein said chemical combination is selected from the group consisting of a solid, a liquid and a gas.

11. An apparatus according to claim 8, wherein said chemical combination is a solid, and further including a means for removing a portion of material at a surface of said solid, said chemical combination being said portion at each of said plurality of said time intervals, said relative concentration X_j of said chemical constituent being generated for each of said time intervals, said time interval corresponding to a depth into said surface, further including a means for generating a profile of at least one of said relative concentrations X_j versus said depth.

12. An apparatus according to claim 1, wherein each of said intersections has an error ε

, wherein ##EQU14## wherein X_j^'"'"' is the value of X_j at said intersection.

13. An apparatus according to claim 1, wherein each of said intersection has an error ε

, wherein equivalently ##EQU15## wherein X_j^'"'"' is the value of X_j at said intersection.

14. An apparatus according to claim 1, further including a means for generating said relative spectral intensities C_i at a plurality of samples of said chemical combination.

15. An apparatus according to claim 14, wherein said plurality of samples are spaced at periodic intervals of time and wherein profiles of at least one of said relative concentrations X_j are generated versus said periodic intervals of time.

16. An apparatus according to claim 14, wherein said plurality of samples are spaced at periodic spatial intervals and wherein profiles of at least one of said relative concentrations are generated versus said periodic spatial intervals.

17. An apparatus for determining, at periodic intervals of time, the relative concentrations X_j of component chemical constituents, wherein j=1 to N, in a chemical combination using predetermined relative constituent spectral intensities A_ij of said N component chemical constituents, wherein i=1 to M, wherein M≧

N, comprising;

means for measuring relative spectral intensities C_i of said chemical combination at wavelengths λ

_i at said periodic intervals of time;

means for storing said C_i as stored relative spectral intensities;

means for storing said A_ij as stored predetermined relative constituent spectral intensities;

means for determining said relative concentrations X_j from said stored relative spectral intensities and from said stored relative constituent spectral intensities;

by generating a set of M surfaces each of N-1 dimensions within a region defined by 0≦

X_j for j=1 to N from a set of M equations ##EQU16## determining a set of intersections of said M surfaces within said region;

means for assigning an error to each of said intersections indicating how good said intersection is for said value of said relative concentrations;

means for storing said error;

means for determining which of said intersections has a minimum value of said error, said intersection having said minimum error defining said relative concentrations X_j of said N component chemical constituents of said chemical combination;

an electromagnetic radiation source for providing an incident beam containing said λ

_i, said beam having an intensity I₀ (λ

_i) at each of said λ

_i ;

a container through which said chemical mixture passes, said container being transparent to said λ

_i ;

a means for directing said incident beam at said container through which said beam passes as a transported beam;

means for measuring each of said I₀ (λ

_i);

means for measuring an intensity I(λ

_i) of said transported beam at each of said λ

_i ;

means for comparing I₀ (λ

_i) and I(λ

_i ) for each of said λ

_i to determine each of said C_i ;

means for generating a profile of at least one of said relative concentrations X_j versus said periodic intervals of time.

18. A method for determining the relative concentrations X_j of N component chemical constituents, wherein j=1 to N, in a chemical combination using predetermined relative constituent spectral intensities A_ij of said N component chemical constituents, wherein i=1 to M, wherein M≧

N, comprising the steps of;

measuring relative spectral intensities C_i of said chemical combination at wavelengths λ

_i ;

storing said C_i as stored relative spectral intensities;

storing said A_ij as stored predetermined relative constituent spectral intensities;

generating a set of M surfaces each of N-1 dimensions within a region defined by 0≦

X_j for j=1 to N from a set of M equations ##EQU17## determining a set of intersections of said M surfaces within said region;

means for assigning an error to each of said intersections indicating how good said intersection is for said value of said relative concentrations;

means for storing said error;

determining which of said intersections has a minimum value of said error, said intersection having said minimum error defining said relative concentrations X_j of said N component chemical constituents of said chemical combination.

19. A method according to claim 18, wherein said relative spectral intensities A_ij and C_i are absorbance intensities.

20. A method according to claim 18, wherein said step of measuring said relative spectral intensities C_i is done using an absorbance spectrometer.

21. A method according to claim 18, wherein said predetermined relative spectral intensities A_ij are determined using an absorbance spectrometer.

22. A method according to claim 18, wherein said step of determining a set of intersections and said step of determining which of said intersections has a minimum value of said error are done using a computer.

23. A method according to claim 22, wherein said predetermined relative spectral intensities A_ij are stored in said computer.

24. A method according to claim 22, wherein said relative spectral intensities are stored in said computer, said particular X_j is set equal to zero.

25. A method according to claim 18, further including a step of generating said relative spectral intensities C_i at a plurality of periodic intervals in time.

26. A method according to claim 25, wherein said interval of time is less than a millisecond.

27. A method according to claim 18, wherein said chemical combination is selected from the group consisting of a solid, a liquid and a gas.

28. A method according to claim 25, wherein said chemical combination is a solid, and further including a step for removing a portion of material at a surface of said solid, said chemical mixture being said portion at each of said plurality of said periodic intervals in time, said relative concentrations X_j being generated for each of said time intervals, said time interval corresponding to a depth into said surface, further including a step of generating a profile of at least one of said relative concentrations X_j versus said depth.

29. A method according to claim 18, wherein each of said intersections has an error ε

, wherein ##EQU18## wherein x'"'"' is the value of X_j at said intersection.

30. A method according to claim 18, wherein each of said intersections has an error, ε

, wherein, equivalently, ##EQU19## wherein X_j^'"'"' is the value of X_j at said intersection.

31. A method according to claim 18 further including generating said relative spectral intensities C_i at a plurality of samples of said chemical combination.

32. A method according to claim 31, wherein said plurality of samples are spaced at periodic intervals of time and wherein profiles of at least one of said relative concentrations X_j are generated versus said periodic intervals of time.

33. A method according to claim 32, wherein said plurality of samples are spaced at periodic spatial intervals and wherein profiles of at least one of said relative concentrations are generated versus said periodic spatial intervals.

34. A method for determining, at periodic intervals of time, the relative concentrations X_j of N component chemical constituents, wherein j=1 to N, in a chemical mixture using predetermined relative constituent spectral intensities A_ij of said N component chemical constituents, wherein i=1 to M, wherein M≧

N, comprising;

measuring relative spectral intensities C_i of said chemical mixture at wavelengths λ

_i at said periodic intervals of time;

storing said C_i as stored relative spectral intensities;

storing said A_ij as stored predetermined relative constituent spectral intensities;

determining said relative concentrations X_j from said stored relative spectral intensities and from said stored relative constituent spectral intensities;

generating a set of M surfaces each of N-1 dimensions within a region defined by 0≦

X_j for j=1 to N from a set of M equations ##EQU20## determining a set of intersections of said M surfaces within said region;

each point within each of said intersections has coordinating X'"'"'_j for j=1 to N;

assigning an error to each of said intersections indicating how good said intersection is for said value of said relative concentrations;

means for storing said error;

determining which of said intersections has a minimum value of said error, said point having said minimum error defining said relative concentrations X_j of said component chemical constituents of said chemical mixture;

providing an incident electromagnetic beam containing said λ

_i, said beam having an intensity I₀ (λ

_i) at each of said λ

_i ;

passing said chemical combination through an enclosure, said enclosure being transparent to said λ

_i ;

directing said incident beam at said enclosure through which said beam passes as a transported beam;

measuring each of said I₀ (λ

i);

measuring the intensity I(λ

i) of the transported beam at each of said λ

_i ;

comparing I₀ (λ

_i) and I(λ

_i) to determine each of said C_i ;

generating a profile of an least one of said relative concentrations X_j versus said periodic intervals of time.