Method of interpreting spectrometric data

• US 5,991,023 A
• Filed: 05/19/1998
• Issued: 11/23/1999
• Est. Priority Date: 05/19/1997
• Status: Expired due to Term

• Current Assignee: Monster, Inc. (Atlantic Acquisition, Inc.), Measurement Microsystems A-Z, Inc. (Lumentum Holdings Inc.)
• Original Assignee: Measurement Microsystems A-Z, Inc. (Lumentum Holdings Inc.)
• Inventors: Slima, Mohamed B., Miekina, Andrzej, Barwicz, Andrzej, Morawski, Roman Z.
• Primary Examiner(s): HANTIS, KAREN
• Application Number:
  US09/081,440
• Time in Patent Office: 553 Days
• Field of Search: 356/326, 356/328, 356/301, 356/330-334, 250/339.13, 250/339.07, 250/339.01, 250/338.5, 702/28
• US Class Current: 356/326
• CPC Class Codes: G01J 2003/2866 Markers; Calibrating of scan
• CPC Class Codes: G01J 3/0259 Monolithic
• CPC Class Codes: G01J 3/28 Investigating the spectrum using colour filters G01J3/51

Abstract

A method for spectral measurement is disclosed. The method uses a low-resolution grating to disperse light and thereby image a spectrum thereof. The imaged spectrum is converted into a digital electrical signal and is processed in order to enhance the spectral information. The resulting spectral information is analogous to that captured using a higher resolution spectral imager with optical processing of the spectral data. The method is equally applicable to enhancing resolution of spectra captured using high resolution spectral imaging devices.

Claims

1. A method of spectral measurement comprises the steps of:

capturing data representative of a first spectrum of a sample using a spectral transducer;

comparing the data representative of the first spectrum to data representative of a known spectrum for a sample substantially identical to the first sample and determining calibration data for transforming, according to a determined transformation, the data representative of the first spectrum into an approximation of the data representative of the known spectrum;

capturing data representative of a spectrum of a second sample using the spectral transducer; and

,

estimating an ideal spectrum for the second sample using the calibration data, the estimation performed using the determined transformation.

2. The method of spectral measurement as defined claim 1 wherein the spectral transducer has a resolution R>

5 nm.

3. The method of spectral measurement as defined claim 1 wherein the spectral transducer has a resolution R, 1 nm≦

R≦

15 nm.

4. A method of spectral measurement as defined in claim 1 wherein

the data representative of the first spectrum is defined by {y_n^cal },

the known spectrum is defined by x^cal (λ

), and

wherein the calibration data is determined by the steps of;

choosing a form of an ideal peak v_s (λ

,l) and of projection operator and reconstruction operator

pre-processing the data representative of the first spectrum {y_n^cal };

determining parameters p of projection operator and parameters p of reconstruction operator ; and

,

storing calibration data comprising the determined parameters in memory.

5. A method of spectral measurement as defined in claim 1 wherein the step of estimating the ideal spectrum comprises the steps of:

estimating positions l of peaks within a spectrum of the second sample on the basis of an estimate s(λ

) of s(λ

;

l,a);

estimating magnitudes a of the peaks; and

,

iteratively correcting the estimates of the parameters of the peaks.

6. A method of spectral measurement as defined in claim 5 wherein the steps of estimation of the magnitudes a and iterative correction of estimates of magnitudes a and positrons l of the peaks is performed using one of the following:

space="preserve" listing-type="equation">l=arg.sub.l inf{∥

{y.sub.n }-G[s(λ

;

l,a);

p.sub.G ]∥

.sub.q |lε

L}

and,

space="preserve" listing-type="equation">l=arg.sub.l inf{∥

s(λ

)-s(λ

;

l,a)∥

.sub.q |lε

L}

with L being a set of feasible solutions having the following options;

q=2 and L.OR right.R^k ;

q=∞ and

L.OR right.R^k ;

q=2 and L.OR right.R₊^k ;

q=∞ and

L.OR right.R₊^k.

7. A method of spectral measurement as defined in claim 1 comprising the step of preprocessing the data representative of the first spectrum.

8. A method of spectral measurement as defined in claim 7 wherein the step of preprocessing includes a step of normalising the data representative of the first spectrum.

9. A method of spectral measurement as defined in claim 7 wherein the step of preprocessing includes a step of smoothing the data representative of the first spectrum.

10. A method of spectral measurement as defined in claim 7 wherein the step of preprocessing includes a step of performing baseline correction.

11. A method of spectral measurement as defined in claim 1 wherein the calibration data comprising a mathematical transform of captured spectral data, said mathematical transform for converting the data into an approximation of the ideal spectral data.

12. A method of spectral measurement as defined in claim 1 wherein the calibration data comprises information relating to defects in the spectral transducer.

13. A method of spectral measurement as defined in claim 1 wherein the data captured by the spectral transducer includes insufficient information for a specific task and wherein the estimated ideal spectrum includes sufficient information for said task.

14. A method spectral measurement as defined in claim 1 wherein the spectral transducer is a low-resolution spectral transducer.

15. A method of spectral measurement as defined in claim 1 wherein the estimated ideal spectrum has a resolution of at least 5 times the resolution of the spectral transducer.

16. A method of spectral measurement as defined in claim 1 wherein the estimated ideal spectrum has a resolution of at least 10 times the resolution of the first spectral transducer.

17. A method of spectral measurement as defined in claim 1 wherein the step of estimating an ideal spectrum for the second sample using the calibration data, the estimation performed using the determined transformation results in an estimated spectrum, the estimated spectrum corrected for imperfections in the spectral transducer.

18. A method of spectral measurement as defined in claim 17 comprising the step of:

estimating parameters l and a on the basis of an estimate s(λ

) of the second spectrum s(λ

;

l,a).