Method and instrument combination for producing comparability of spectrometer measurements

• US 6,049,082 A
• Filed: 08/26/1997
• Issued: 04/11/2000
• Est. Priority Date: 12/27/1995
• Status: Expired due to Fees

• Current Assignee: Bran+Luebbe GmbH
• Original Assignee: Bran+Luebbe GmbH
• Inventors: Methfessel, Jennifer
• Primary Examiner(s): Hannaher, Constantine
• Assistant Examiner(s): Israel, Andrew
• Application Number:
  US08/945,929
• Time in Patent Office: 959 Days
• Field of Search: 250/339.09, 356/300, 356/326, 356/319
• US Class Current: 250/339.09
• CPC Class Codes: G01J 3/2803 using photoelectric array detector
• CPC Class Codes: G01N 21/274 Calibration, base line adjustment, drift correction

Abstract

A method provides the comparability of spectrometer measurements with a plurality of measuring instrument individuals of the same type in a family, and a spectrometer for performing the method is used with automatic standardization is also described. By this method and with this spectrometer, a substantial improvement in comparability as well as accuracy of spectral measurements is possible, since the measurement values are replicable by means of a calibration of the spectrometers, and varying consistencies or dimensions among specimens are balanced out or compensated for.

Claims

1. A method for providing the comparability of spectrometer measurements, in particular for measurements with diffuse reflection, using a plurality of measuring instrument individuals of the same type in one family, characterized by the following method steps:

storage in memory of set-point spectra or immobilized standard specimens in a spectrometer individual of the family;

ascertaining a number of comparison spectra of the standard specimens with the spectrometer individual of the family;

calculating parameters of an approximation for the deviation in the comparison spectrum from the set-point spectrum per wavelength base point on the standard specimens;

storage in memory of the parameters per wavelength base point in the instrument;

measurement of the spectrum of an unknown specimen;

calculation of true values for each wavelength base point of a measured value of the spectrum of the unknown specimen, using an equation that is obtained from the approximation function, which is at least second or higher order.

2. The method for providing the comparability of spectrometer measurements, in accordance with claim 1, characterized in that a plurality of standard specimens, in particular more than seven specimens, are used, with diffuse straight reflectances of 2%, 5%, 10%, 20%, 40%, 50%, 60%, 80%, and 99%.

3. The method for providing the comparability of spectrometer measurements, in accordance with claim 1, characterized in that at least three measurements of comparison spectra per reflectance are performed, whose values are averaged for each wavelength base point.

4. The method for providing the comparability of spectrometer measurements, in accordance with claim 1, characterized in that the quality of the approximation function is determined by calculating the standard deviation or the correlation coefficient at each wavelength base point.

5. A spectrometer for measuring spectra for using the method in accordance with claim 1, 2, 3, or 4, characterized in that it has a first memory (1) for a plurality of set-point spectra, a second memory (2) for comparison spectra of different standard specimens, and means for calculation of true values for each wavelength base point of a measured value of the spectrum of the unknown specimen using an equation that is obtained from the approximation function of at least second or higher order.

6. A spectrometer for measuring spectra in accordance with claim 5, characterized in that it has a unit (3) for calculating parameters of an approximation function for each wavelength base point by comparison of the comparison spectra with the set-point spectra of the standard specimens.

7. A spectrometer for measuring spectra in accordance with claim 5, characterized in that it has a third memory (4) for parameters for each wavelength base point of an approximation function.

8. A spectrometer for measuring spectra in accordance with claim 5, characterized in that it has a fifth memory (5) for storing a spectrum of an unknown specimen.

9. A spectrometer for measuring spectra in accordance with claim 5, characterized in that it has an arithmetic unit (6) for calculating actual values by means of an equation determined by the approximation function per wavelength base point of an unknown specimen.

10. A spectrometer for measuring spectra in accordance with claim 5, characterized in that it has an arithmetic unit (6) for calculating the quality of the approximation function.

11. A spectrometer for measuring spectra in accordance with claim 5, characterized in that it has an output unit (8) for outputting the corrected spectrum as an actual spectrum.

12. A spectrometer for measuring spectra in accordance with claim 5, characterized in that the spectrometer is assigned a set of standard specimens, which are furnished for providing the comparability of spectrometer measurements of the spectrometers.

13. A spectrometer for measuring spectra in accordance with claim 5, characterized in that it has a memory-programmable controller for performing the method.

15. A spectrometer for measuring spectra for using the method in accordance with claim 1, 2, 3, 4, or 14, characterized in that it has a first memory (1) for a plurality of set-point spectra, a second memory (2) for comparison spectra of different standard specimens, and means for calculation of true values for each wavelength base point of a measured value of the spectrum of the unknown specimen using an equation that is obtained from the approximation function, and using the spectra of the specimens with different reflectances per wavelength base point to calculate parameters of the approximation function.

16. A spectrometer for measuring spectra for using the method in accordance with claim 1, 2, 3, 4, or 14, characterized in that it has a first memory (1) for a plurality of set-point spectra, a second memory (2) for comparison spectra of different standard specimens, and the specimens for instruments of the same type are received in a holder of identical dimensions, and the holder is indexed so that changes in length are also averted.

14. A method for providing the comparability of spectrometer measurements, in particular for measurements with diffuse reflection, using a plurality of measuring instrument individuals of the same type in one family, characterized by the following method steps:

storage in memory of set-point spectra or immobilized standard specimens in a spectrometer individual of the family;

ascertaining a number of comparison spectra of the standard specimens with the spectrometer individual of the family;

calculating parameters of an approximation for the deviation in the comparison spectrum from the set-point spectrum per wavelength base point on the standard specimens;

storage in memory of the parameters per wavelength base point in the instrument;

measurement of the spectrum of an unknown specimen;

calculation of true values for each wavelength base point of a measured value of the spectrum of the unknown specimen, using an equation that is obtained from the approximation function, and the spectra of the specimens with different reflectances per wavelength base point are used to calculate parameters of the approximation function.