Method for measuring spectra of materials

• US 4,632,549 A
• Filed: 04/14/1983
• Issued: 12/30/1986
• Est. Priority Date: 04/14/1982
• Status: Expired due to Fees

• Current Assignee: Kozponti Elelmiszeripari Kutato Intezet
• Original Assignee: Kozponti Elelmiszeripari Kutato Intezet
• Inventors: Kaffka, Karoly, Horvath, Lorand, Nadai, Bela, Czabaffy, Andras
• Primary Examiner(s): Evans, F. L.
• Application Number:
  US06/485,049
• Time in Patent Office: 1,356 Days
• Field of Search: 356/319, 356/323, 356/325, 356/300, 356/326, 356/328, 364/498
• US Class Current: 356/300
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/0232 using shutters
• CPC Class Codes: G01J 3/0289 Field-of-view determination; Aiming or pointing of a spectrometer; Adjusting alignment; Encoding angular position; Size of measurement area; Position tracking
• CPC Class Codes: G01J 3/42 Absorption spectrometry; Double beam spectrometry; Flicker spectrometry; Reflection spectrometry beam switching arrangements G01J3/08
• CPC Class Codes: G01N 21/274 Calibration, base line adjustment, drift correction

Abstract

The invention provides on a method for measuring the spectrum of a material, wherein a sample (10) of the material to be tested is irradiated with a radiation of required wavelengths and the spectrum signals produced by an intensity measuring unit (34) as a result of the radiation reflected or transmitted by the sample (10) are measured. According to the present invention, a zero level signal produced by the intensity measuring unit (34) in an unradiated condition is measured and the measured zero level value is stored, then one or more spectrum signal measurements are performed at at least one wavelength and the measured one or more spectrum values are stored, then the zero level signal produced by the intensity measuring unit (34) is measured again in an unradiated condition and its value is stored, then preferably those one or more spectrum signal measurements at at least one wavelength prescribed and the storage of the measured values as well as the zero level signal measurement and the storage of the measured value are repeated as many times as required, and finally the stored spectrum values are modified by correction values generated on the basis of the stored zero level values.

Claims

1. A method for measuring the spectrum of a material comprising the steps of

irradiating a sample of the material to be tested successively by radiations of different wavelengths of the spectrum to be measured;

measuring and storing spectrum signals produced by an intensity measuring unit in response to the radiation reflected or transmitted by the sample irradiated;

measuring and storing zero level signals produced by the intensity measuring unit in the unradiated condition of the sample at least two times in the course of said spectrum signal measurements;

calculating correction values for the stored spectrum values by interpolation based on the stored zero level values; and

subtracting from the stored spectrum values the respective calculated correction values to produce corrected spectrum values.

2. The method according to claim 1, wherein said interpolation is linear.

3. The method according to claim 1, wherein said measuring and storing of the zero level signals are performed a plurality of times in the course of said spectrum signal measurements, and said interpolation is based on a function versus time approximating the stored zero level values.

4. The method according to claim 1, wherein said measuring and storing of the zero level signals are performed before and after said spectrum signal measurements at different wavelengths.

5. The method according to claim 1, wherein said measuring and storing of the spectrum signals are performed in successive groups by measuring and storing spectrum signals of substantially the same wavelength in each group a plurality of times;

and said measuring and storing of the zero level signals are performed before or after each group a plurality of times.

6. The method according to claim 5, wherein the measured spectrum signals in each group are averaged;

and the zero level signals measured before or after each group are also averaged.

7. The according to claim 5, wherein said intensity measuring unit is set to zero in the unradiated condition of the sample before the first group;

said measuring and storing of the zero level signals are performed after each group a plurality of times; and

in calculating the correction values a zero value of the zero level signal at the time of said setting to zero is also taken into account.

8. A method for measuring the spectrum of a material comprising the steps of

irradiating a sample of the material to be tested successively by radiations of different wavelengths of the spectrum to be measured;

measuring and storing spectrum signals produced by an intensity measuring unit in response to the radiation reflected or transmitted by the sample irradiated;

measuring and storing zero level signals produced by the intensity measuring unit in the unradiated condition of the sample at least two times in the course of said spectrum signal measurements;

calculating correction values for the stored spectrum values measured before the measurement of the last zero level value by interpolation based on the stored zero level values;

calcualating correction values for the stored spectrum values measured after the measurement of the last zero level value by extrapolation based on the stored zero level values; and

substracting from the stored spectrum values the respective calcualted correction values to produce corrected spectrum values.

9. The method according to claim 8, wherein said interpolation and extrapolation are linear.

10. The method according to claim 8, wherein said measuring and storing of the zero level signals are performed a plurality of times in the course of said spectrum signal measurements, and said interpolation and extrapolation are based on a function versus time approximating the stored zero level values.

11. The method according to claim 8, wherein said measuring and storing of the spectrum signals are performed in successive groups by measuring and storing spectrum signals of substantially the same wavelength in each group a plurality of times;

and said measuring and storing of the zero level signals are performed before each group a plurality of times.

12. The method according to claim 11, wherein the measured spectrum signals in each group are averaged;

and the zero level signals measured before or after each group are also averaged.

13. The method according to claim 11, wherein said intensity measuring unit is set to zero in the unradiated condition of the sample before the first measuring and storing of the zero level signal.