Abstract: At least two luminescent materials are intermingled within a security feature. The materials are selected from among a larger set of luminescent materials each having a different individual exponential decay characteristic (decay constant and initial amplitude response to the degree of excitation) for photo-luminescent emission from the respective material following excitation. The ratio of the decay constants for any two materials is greater than or equal to about 1.5. The selected materials are mixed in one of a plurality of predetermined ratios. The combined emissions from the intermingled materials appear, to an unsophisticated measuring device, to have a single exponential decay constant. Based on measurements for the decay of the combined emissions following excitation, estimates of the individual decay constants and associated initial emission amplitudes allow decoding of the particular combination of materials and/or their ratios to validate the security feature, authenticating the article.

Abstract: At least two luminescent materials are intermingled within a security feature. The materials are selected from among a larger set of luminescent materials each having a different individual exponential decay characteristic (decay constant and initial amplitude response to the degree of excitation) for photo-luminescent emission from the respective material following excitation. The ratio of the decay constants for any two materials is greater than or equal to about 1.5. The selected materials are mixed in one of a plurality of predetermined ratios. The combined emissions from the intermingled materials appear, to an unsophisticated measuring device, to have a single exponential decay constant. Based on measurements for the decay of the combined emissions following excitation, estimates of the individual decay constants and associated initial emission amplitudes allow decoding of the particular combination of materials and/or their ratios to validate the security feature, authenticating the article.

Abstract: At least two luminescent materials are intermingled within a security feature. The materials are selected from among a larger set of luminescent materials each having a different individual exponential decay characteristic (decay constant and initial amplitude response to the degree of excitation) for photo-luminescent emission from the respective material following excitation. The ratio of the decay constants for any two materials is greater than or equal to about 1.5. The selected materials are mixed in one of a plurality of predetermined ratios. The combined emissions from the intermingled materials appear, to an unsophisticated measuring device, to have a single exponential decay constant. Based on measurements for the decay of the combined emissions following excitation, estimates of the individual decay constants and associated initial emission amplitudes allow decoding of the particular combination of materials and/or their ratios to validate the security feature, authenticating the article.

Abstract: We disclose measurement systems and methods for measuring analytes in target regions of samples that also include features overlying the target regions. The systems include: (a) a light source; (b) a detection system; (c) a set of at least first, second, and third light ports which transmit light from the light source to a sample and receive and direct light reflected from the sample to the detection system, generating a first set of data including information corresponding to both an internal target within the sample and features overlying the internal target, and a second set of data including information corresponding to features overlying the internal target; and (d) a processor configured to remove information characteristic of the overlying features from the first set of data using the first and second sets of data to produce corrected information representing the internal target.

Abstract: We disclose measurement systems and methods for measuring analytes in target regions of samples that also include features overlying the target regions. The systems include: (a) a light source; (b) a detection system; (c) a set of at least first, second, and third light ports which transmit light from the light source to a sample and receive and direct light reflected from the sample to the detection system, generating a first set of data including information corresponding to both an internal target within the sample and features overlying the internal target, and a second set of data including information corresponding to features overlying the internal target; and (d) a processor configured to remove information characteristic of the overlying features from the first set of data using the first and second sets of data to produce corrected information representing the internal target.

Abstract: At least two luminescent materials are intermingled within a security feature. The materials are selected from among a larger set of luminescent materials each having a different individual exponential decay characteristic (decay constant and initial amplitude response to the degree of excitation) for photo-luminescent emission from the respective material following excitation. The ratio of the decay constants for any two materials is greater than or equal to about 1.5. The selected materials are mixed in one of a plurality of predetermined ratios. The combined emissions from the intermingled materials appear, to an unsophisticated measuring device, to have a single exponential decay constant. Based on measurements for the decay of the combined emissions following excitation, estimates of the individual decay constants and associated initial emission amplitudes allow decoding of the particular combination of materials and/or their ratios to validate the security feature, authenticating the article.

Abstract: We disclose measurement systems and methods for measuring analytes in target regions of samples that also include features overlying the target regions. The systems include: (a) a light source; (b) a detection system; (c) a set of at least first, second, and third light ports which transmit light from the light source to a sample and receive and direct light reflected from the sample to the detection system, generating a first set of data including information corresponding to both an internal target within the sample and features overlying the internal target, and a second set of data including information corresponding to features overlying the internal target; and (d) a processor configured to remove information characteristic of the overlying features from the first set of data using the first and second sets of data to produce corrected information representing the internal target.

Abstract: The invention relates to systems and methods for measuring properties of samples with standardized spectroscopic systems. The methods can include (i) measuring, with a first spectroscopic system, spectra of at least three different reference targets; (ii) calibrating the first spectroscopic system; (iii) measuring, with the first spectroscopic system, a spectrum of a known reference specimen having a known value of the property; (iv) generating a model for the measured property using the spectrum of the known reference specimen; (v) measuring, with a second spectroscopic system, the spectra of at least three different reference targets; (vi) calibrating the second spectroscopic system; (vii) applying the model to the second spectroscopic system; (viii) measuring a spectrum of the sample using the second spectroscopic system; and (ix) determining a value of the property using the model.

Abstract: We disclose measurement systems and methods for measuring analytes in target regions of samples that also include features overlying the target regions. The systems include: (a) a light source; (b) a detection system; (c) a set of at least first, second, and third light ports which transmit light from the light source to a sample and receive and direct light reflected from the sample to the detection system, generating a first set of data including information corresponding to both an internal target within the sample and features overlying the internal target, and a second set of data including information corresponding to features overlying the internal target; and (d) a processor configured to remove information characteristic of the overlying features from the first set of data using the first and second sets of data to produce corrected information representing the internal target.

Abstract: We disclose measurement systems and methods for measuring analytes in target regions of samples that also include features overlying the target regions. The systems include: (a) a light source; (b) a detection system; (c) a set of at least first, second, and third light ports which transmit light from the light source to a sample and receive and direct light reflected from the sample to the detection system, generating a first set of data including information corresponding to both an internal target within the sample and features overlying the internal target, and a second set of data including information corresponding to features overlying the internal target; and (d) a processor configured to remove information characteristic of the overlying features from the first set of data using the first and second sets of data to produce corrected information representing the internal target.

Abstract: Methods and systems for calculating tissue oxygenation, e.g., oxygen saturation, in a target tissue are disclosed. In some embodiments, the methods include: (a) directing incident radiation to a target tissue and determining reflectance spectra of the target tissue by measuring intensities of reflected radiation from the target tissue at a plurality of radiation wavelengths; (b) correcting the measured intensities of the reflectance spectra to reduce contributions thereto from skin and fat layers through which the incident radiation propagates; (c) determining oxygen saturation in the target tissue based on the corrected reflectance spectra; and (d) outputting the determined value of oxygen saturation.

Abstract: Within a method of making an optical interference filter, sample spectra and measurements of a predetermined characteristic associated with respective spectra are provided. Upon selection of an initial number of filter layers and a thickness for each layer, a transmission spectrum is determined. Each sample spectrum is applied to a regression formula that relates interaction of light with the transmission spectrum to a regression value. A comparison relationship between the calculated regression values and the sample measurements is defined and optimized, wherein thickness of each layer is an optimization variable.