Low-cost spectrometry system for end-user food analysis
A compact spectrometer is disclosed that is suitable for use in mobile devices such as cellular telephones. In preferred embodiments, the spectrometer comprises a filter, at least one Fourier transform focusing element, a micro-lens array, and a detector, but does not use any dispersive elements. Methods for using the spectrometer as an end-user device for performing on-site determinations of food quality, in particular, by comparison with an updatable database accessible by all users of the device, are also disclosed.
1. A compact spectrometer system for obtaining a spectrum of a sample, comprising:
an optical detector configured to detect light emanating from said sample;
a plurality of optical filters configured to be disposed between said sample and said optical detector, said plurality of optical filters having different central wavelengths; and,
a micro-lens array disposed between said optical detector and said plurality of optical filters, wherein said micro-lens array is configured to sample and decompose light received from said plurality of optical filters to form a plurality of light components corresponding to respective optical filters of said plurality of optical filters at a plurality of positions of a light sensitive surface of said optical detector, wherein said optical detector is configured to measure optical intensity as a function of said plurality of positions.
2. The compact spectrometer system of claim 1 , wherein said plurality of optical filters are configured to angle-encode light passing through said plurality of optical filters according to wavelength.
3. The compact spectrometer system of claim 1 , wherein dispersive optical elements are absent in said compact spectrometer system.
4. The compact spectrometer system of claim 1 , wherein said optical detector comprises a two-dimensional detector array and wherein said plurality of optical filters comprises a filter array having a plurality of filter elements.
5. The compact spectrometer system of claim 1 , further comprising a diffuser configured to be disposed between said sample and said plurality of optical filters.
6. The compact spectrometer system of claim 1 , further comprising a light source configured to illuminate said sample.
7. The compact spectrometer system of claim 1 , further comprising a communication module, wherein said communication module is configured to transmit optical intensity data measured from said optical detector to a remote processing unit, wherein said remote processing unit is configured to generate said spectrum of said sample based at least in part on said optical intensity data.
8. The compact spectrometer system of claim 7 , wherein said compact spectrometer system is enclosed within a mobile communication device comprising said communication module.
9. The compact spectrometer system of claim 7 , wherein said communication module or said remote processing unit is in communication with a database of spectral information.
10. The compact spectrometer system of claim 9 , wherein said database of spectral information comprises one or more of raw detector data, pre-processed detector data, and post-processed detector data.
11. The compact spectrometer system of claim 1 , further comprising a first Fourier transform focusing element disposed between said plurality of optical filters and said micro-lens array, wherein said micro-lens array is disposed in a focal plane of said first Fourier transform focusing element.
12. The compact spectrometer system of claim 11 , wherein said first Fourier transform focusing element is configured to spatially encode light passing through said first Fourier transform focusing element.
13. The compact spectrometer system of claim 12 , further comprising a second Fourier transforming focusing element disposed between said first Fourier transform focusing element and said micro-lens array, wherein said optical detector is located at a focal plane of said second Fourier transform focusing element.
14. The compact spectrometer system of claim 13 , wherein a first focal line of said first Fourier transforming focusing element is not aligned with a second focal line of said second Fourier transforming focusing element.
15. The compact spectrometer system of claim 14 , wherein a first focal line of said first Fourier transforming focusing element is substantially perpendicular to a second focal line of said second Fourier transforming focusing element.
16. The compact spectrometer system of claim 11 , wherein said first Fourier transform focusing element comprises a plano-convex cylindrical lens, wherein a planar surface of said plano-convex cylindrical lens faces said optical detector and a curved surface of said plano-convex cylindrical lens faces said plurality of optical filters.
17. The compact spectrometer system of claim 1 , wherein said optical detector is located at a plane substantially perpendicular to an optical axis such that the micro-lenses form multiple images of said optical filter on said optical detector.
18. The compact spectrometer system of claim 1 , wherein said plurality of filters are aligned along a single axis.
19. The compact spectrometer system of claim 1 , wherein said micro-lens array is disposed such that light dispersed on said optical detector is along an axis parallel to an axis on which said plurality of sub-filters are aligned.
20. The compact spectrometer system of claim 1 , wherein said micro-lens array is a cylindrical micro-lens array.