A method of determining information carried by light using a multivariate optical analysis system , the method comprising: filtering a source light through at least one spectral element ; reflecting the filtered light through an inner annular region of a concentric tube in a first direction of a sample (W) to be measured, wherein said concentric tube in addition defines an outer annular region disposed about the inner annular region , said concentric tube being configured to separate said filtered light reflected to the sample (W) from the light reflected from the sample (W); focusing the reflected light proximate the sample (W); reflecting the focused light from the sample (W) through the outer annular region of the concentric tube in a second direction of a beamsplitter , the light being reflected from the sample (W) carrying data from the sample (W); splitting the data carrying light with the beamsplitter into a first light and a second light; optically filtering the data of the first light with a multivariate optical element into a plurality of orthogonal components; directing the first light filtered by the multivariate optical element onto a first photodetector ; determining said plurality of orthogonal components of the first light, wherein each of the components has a predetermined shape with respect to a property of the first light that varies over a predetermined wavelength range; determining respective weightings for the orthogonal components so that the magnitude of the orthogonal components in the first light, weighted by the weightings, is proportional to information present in the first light in a predetermined relationship; directing the second light onto a second photodetector ; and comparing the orthogonal components to information present in the second light to determine a property of the sample (W). filtering a source light through at least one spectral element ; reflecting the filtered light through an inner annular region of a concentric tube in a first direction of a sample (W) to be measured, wherein said concentric tube in addition defines an outer annular region disposed about the inner annular region , said concentric tube being configured to separate said filtered light reflected to the sample (W) from the light reflected from the sample (W); focusing the reflected light proximate the sample (W); reflecting the focused light from the sample (W) through the outer annular region of the concentric tube in a second direction of a beamsplitter , the light being reflected from the sample (W) carrying data from the sample (W); splitting the data carrying light with the beamsplitter into a first light and a second light; optically filtering the data of the first light with a multivariate optical element into a plurality of orthogonal components; directing the first light filtered by the multivariate optical element onto a first photodetector ; determining said plurality of orthogonal components of the first light, wherein each of the components has a predetermined shape with respect to a property of the first light that varies over a predetermined wavelength range; determining respective weightings for the orthogonal components so that the magnitude of the orthogonal components in the first light, weighted by the weightings, is proportional to information present in the first light in a predetermined relationship; directing the second light onto a second photodetector ; and comparing the orthogonal components to information present in the second light to determine a property of the sample (W). <EOS>