FILTERS FOR SPECTRAL ANALYSIS DATA
First Claim
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1. A method of locating and removing spike noise from spectral data comprising:
- collecting a plurality of replicates of spectral data, wherein;
each collected replicate comprises a plurality of pixels, each pixel having an associated intensity value; and
the plurality of replicates represents discrete instances of spectral data obtained sequentially, from a sample under interrogation;
performing replicate processing to condition the intensity values of the collected replicates for subsequent pixel processing and spike noise filtering;
performing pixel processing to identify outliers corresponding to noise spikes within the plurality of replicates by collectively evaluating the conditioned intensity values of the plurality of replicates as a function of pixel position, wherein performing pixel processing further includes transforming the replicates by adjusting the intensity values of the plurality of replicates based upon a predetermined function; and
performing spike noise filtering by removing each identified outlier from its replicate and by replacing the removed outlier value with a computed approximation of an intensity value of a noise-free signal at that removed outlier pixel position.
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Abstract
Cosmic spike filters are provided, which remove noise spikes in spectral data. Spikes are eliminated by locating, smoothing and filtering the spikes using replicates to improve the accuracy of the spike detection process compared to when only one replicate is used. Cosmic spike filters are also provided that combine a data collection approach and a statistical approach to remove cosmic spike noise from the collected signal without distorting the true signal. Still further, a statistical approach is provided to identify and remove negative peaks from a spectrum, where the negative peaks are caused by bad pixels in a charge coupled device.
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Citations
20 Claims
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1. A method of locating and removing spike noise from spectral data comprising:
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collecting a plurality of replicates of spectral data, wherein; each collected replicate comprises a plurality of pixels, each pixel having an associated intensity value; and the plurality of replicates represents discrete instances of spectral data obtained sequentially, from a sample under interrogation; performing replicate processing to condition the intensity values of the collected replicates for subsequent pixel processing and spike noise filtering; performing pixel processing to identify outliers corresponding to noise spikes within the plurality of replicates by collectively evaluating the conditioned intensity values of the plurality of replicates as a function of pixel position, wherein performing pixel processing further includes transforming the replicates by adjusting the intensity values of the plurality of replicates based upon a predetermined function; and performing spike noise filtering by removing each identified outlier from its replicate and by replacing the removed outlier value with a computed approximation of an intensity value of a noise-free signal at that removed outlier pixel position. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method of locating and removing noise spikes from spectral data comprising:
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obtaining a first raw replicate of spectral data, wherein the first raw replicate represents a first instance of spectral data obtained from a sample under investigation; obtaining a second raw replicate of spectral data, wherein the second raw replicate represents a second instance of spectral data obtained from the sample under investigation; computing a first smoothed replicate from the first raw replicate; computing a second smoothed replicate from the second raw replicate; determining whether at least one noise spike is present in at least one of the first raw replicate and the second raw replicate by comparing select ones of;
the first raw replicate, the first smoothed replicate, the second raw replicate and the second smoothed replicate;eliminating the effect of each located noise spike in the first raw replicate and the second raw replicate by locally re-smoothing the corresponding replicate around each located spike; and consolidating the first raw replicate and the second raw replicate into a single spectrum that is free of cosmic spikes. - View Dependent Claims (16, 17)
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18. A method of detecting bad pixel elements in a charge coupled device comprising:
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collecting a plurality of replicates of spectral data, wherein; each collected replicate comprises a plurality of pixels, each pixel having an associated intensity value; calculating a rolling median for each pixel of each collected replicate; estimating a noise level of the corresponding spectrum; identifying pixels of interest; identifying local minima; determining the height of a negative peak of select pixels; identifying large negative peaks where local minima have a height greater than a predetermined threshold; assessing negative peaks for removal; and replacing each removed negative peak with a linear interpolation between the pixel previous to the peak and the next pixel after the peak. - View Dependent Claims (19, 20)
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Specification