Procedure for enhancing resolution of spectral information

• US 5,400,265 A
• Filed: 06/30/1993
• Issued: 03/21/1995
• Est. Priority Date: 02/18/1991
• Status: Expired due to Term

• Current Assignee: Temet Instrument Oy
• Original Assignee: Temet Instrument Oy
• Inventors: Kauppinen, Jyrki
• Primary Examiner(s): Voeltz, Emanuel T.
• Assistant Examiner(s): PIPALA, EDWARD J
• Application Number:
  US08/081,365
• Time in Patent Office: 629 Days
• Field of Search: 364/574, 364/498, 364/576, 364/525, 356/345, 356/346
• US Class Current: 702/77
• CPC Class Codes: G01J 3/453 by correlation of the amplitudes
• CPC Class Codes: G01R 33/56 Image enhancement or correction, e.g. subtraction or averaging techniques , e.g. improvement of signal-to-noise ratio and resolution
• CPC Class Codes: G06F 17/141 Discrete Fourier transforms

Abstract

A procedure for enhancing the resolution of spectral data, in which the Fourier self-deconvolution method FSD is used to produce from the input spectrum a data set in an interval 0-L_t, the maximum entropy method MEM is used to compute prediction error filter coefficients {a_k } from this data, and by the linear prediction method LP, using coefficients {a_k } and data points 0 to M. Data are predicted in the interferogram I(x) beyond L_t, whereby output spectrum maximum line narrowing with minimum distortion is achieved.

Claims

1. A method of examining a sample to determine the presence or absence of a component therein comprising:

producing a spectral image of a sample in the form of spectral data,

spectroscopically producing spectral data from a sample representing the composition of said sample,

producing from said spectral data an interferogram of said sample between 0 and L_f ;

producing by the Fourier self-deconvolution method FSD a data set from the obtained interferogram in an interval from 0 to L_t where L_t <

L_f, said data set comprising data points O to M where M is the number of data points in said data set;

computing from said data set by the maximum entropy method MEM prediction error filter coefficients {a_k }, where k=0,1,2,. . .M;

predicting data beyond L_t in the interferogram using said prediction error filter coefficients {a_k }, and the data points 0 to M in said data set to achieve maximum line narrowing with minimum distortion in the resulting spectrum, and

examining lines in said spectrum to detect presence or absence of a component in the composition of said sample, whereby the narrowing of the lines and the minimization of distortion facilitates the examination and detection of said component.

2. A method according to claim 1, comprising applying said FSD to form said interferogram I(x) whose output line shape is consistent with a sinc function.

3. A method according to claim 1, comprising, prior to computing the final spectrum apodizing the expanded interferogram I(x) to alter the line shape in the final spectrum.

4. A method according to claim 1, comprising determining the extra data points in the linear prediction by the formula:

##EQU18##

5. A method according to claim 1, comprising establishing the point x=L_t in the time domain to corresponds to stays in the point where the signal is substantially equal to the noise.

6. A method according to claim 1, comprising rendering said interferogram substantially free of noise.

7. A method according to claim 1, comprising providing the spectral data with a signal/noise ratio of 1000, 100, 10 or about 3.

8. A method according to claim 1, wherein said sample is solid, liquid or gaseous.