Correction of non-linearities in detectors in fourier transform spectroscopy

US4927269A · kind A · utility

Assignee

• Bruker Analytische Messtechnik GmbH · DE

Inventors

• Axel Keens · Karlsruhe, DE
• Arno Simon · Ettlingen, DE

Key dates

• Filing date: Jan 31, 1989
• Grant date: May 22, 1990
• Expiry date: Jan 31, 2009

Classification

• Technology area (CPC G): Physics
• CPC primary: G01J3/45
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

An interferogram is formed as in the prior art by dividing a beam of radiation from the source into two beams and interfering these beams so as to form an interferogram on the detector. A Fourier transform is then made of this interferogram. This transform has a signal spectrum above the cutoff frequency of the detector; and because of non-linearities in the detector and in the electronic signal processing circuitry, this transform also has a spectrum below the cutoff frequency of the detector. In accordance with the invention, two correction factors are calculated from this Fourier transform and these correction factors are then used to calculate a corrected interferogram. The first correction factor is evaluated by determining from the portion of the spectrum below the cutoff frequency a valve for the spectral signal at zero frequency. In addition, the integral of the square of the spectrum signal above the cutoff frequency is determined and the correction factor is found by dividing the signal at zero frequency by the integral of the square of the spectrum above the cutoff. The second correction factor is a function of the first correction factor and the integral of the spectrum…