Abstract

FT-IR imaging employing a focal plane array (FPA) detector is often plagued by low signal-to-noise ratio (SNR) data. A mathematical transform that re-orders spectral data points into decreasing order of SNR is employed to reduce noise by retransforming the ordered data set using only a few relevant data points. This approach is shown to result in significant gains in terms of image fidelity by examining microscopically phase-separated composites termed polymer dispersed liquid crystals (PDLCs). The actual gains depend on the SNR characteristics of the original data. Noise is reduced by a factor greater than 5 if the noise in the initial data is sufficiently low. For a moderate absorbance level of 0.5 a.u., the achievable SNR by reducing noise is greater than 100 for a collection time of less than 4 min. The criteria for optimal application of a noise-reducing procedure employing the minimum noise fraction (MNF) transform are discussed and various variables in the process quantified. This noise reduction is shown to provide high-quality images for accurate morphological analysis. The coupling of mathematical transformation techniques with spectroscopic Fourier transform infrared (FT-IR) imaging is shown to result in high-fidelity images without increasing collection time or drastically modifying hardware. Index Headings: Fourier transform infrared microspectroscopy; Imaging; Minimum noise fraction; Principal components; Signal-tonoise ratio; Morphological analysis; Polymer dispersed liquid crystals.

Recent applications of FT-IR spectroscopy to polymer systems

J. L. Koenig and M. K. Antoon
Appl. Opt. 17(9) 1374-1385 (1978)

Accurate infrared transmittance measurements on optical filters using an FT-IR spectrometer

David A. C. Compton, John Drab, and Howard S. Barr
Appl. Opt. 29(19) 2908-2912 (1990)

Image gathering and processing: information and fidelity

Friedrich O. Huck, Carl L. Fales, Nesim Halyo, Richard W. Samms, and Kathryn Stacy
J. Opt. Soc. Am. A 2(10) 1644-1666 (1985)

Correction of interferogram data acquired using a focal plane FT-IR spectrometer system

Cong Gao, Jianhua Mao, and Ren Chen
Appl. Opt. 57(10) 2434-2440 (2018)

Image-gathering system design for information and fidelity

Friedrich O. Huck, Carl L. Fales, Judith A. McCormick, and Stephen K. Park
J. Opt. Soc. Am. A 5(3) 285-299 (1988)