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 for detecting light emanating from said sample;
an optical filter located between said sample and said detector to provide an angularly encoded spectrum;
a Fourier transform focusing element disposed between said optical filter and said detector; and
a diffuser disposed between said sample and said optical filter,
wherein the Fourier transform focusing element transforms the angularly encoded spectrum into a spatially encoded spectrum of light of different wavelengths, the spatially encoded spectrum arriving at a plurality of positions on the detector with each of the plurality of positions on the detector correlated to a wavelength of the spatially encoded spectrum.
2. The compact spectrometer system of claim 1 , wherein said optical filter comprises a plurality of sub-filters with different center wavelengths, and wherein said optical filter comprises a plurality of substantially rectangular surface areas, each of which comprises a sub-filter.
3. The compact spectrometer system of claim 1 , wherein said optical filter is chosen from the group consisting of (a) Fabry-Perot filter, (b) thin-film filter, and (c) interference filter.
4. The compact spectrometer system of claim 1 , further comprising a micro-lens array.
5. The compact spectrometer system of claim 4 , wherein said micro-lens array is located in a focal plane of said Fourier transform focusing element.
6. The compact spectrometer system of claim 4 , wherein said detector is located at a plane substantially perpendicular to an optical axis such that the micro-lens array forms multiple images of said optical filter on said optical detector.
7. The compact spectrometer system of claim 4 , wherein said optical filter comprises a plurality of sub-filters with different center wavelengths.
8. The compact spectrometer system of claim 4 , further comprising a second Fourier transforming focusing element, wherein said micro-lens array comprises an array of cylindrical lenses and is located at a focal plane of the Fourier transforming focusing element and said optical detector is located at a focal plane of the second Fourier transform focusing element.
9. The compact spectrometer system of claim 1 , further comprising a diffuser disposed between said sample and said optical filter.
10. The compact spectrometer system of claim 1 , further comprising a light source adapted to illuminate said sample.
11. The compact spectrometer system of claim 10 , wherein said light source is a laser.
12. The compact spectrometer system of claim 10 , wherein said light source is a light-emitting diode.
13. The compact spectrometer system of claim 10 , further comprising a focusing system adapted to focus light from said light source at a predetermined location relative to said sample.
14. The compact spectrometer system of claim 13 , wherein said focusing system is an autofocus system.
15. The compact spectrometer system of claim 13 , wherein said focusing system controls a position of a lens that focuses light produced by said light source onto said sample.
16. The compact spectrometer system of claim 13 , wherein said focusing system controls optical properties of a lens that focuses light produced by said light source onto said sample.
17. The compact spectrometer system of claim 13 , wherein said focusing system comprises a voice-coil motor.
18. The compact spectrometer system of claim 13 , wherein said focusing system comprises a piezoelectric motor.
19. The compact spectrometer system of claim 13 , wherein said focusing system comprises a micro-electrical-mechanical-system (MEMS) motor.
20. The compact spectrometer system of claim 1 , further comprising means for communicating with a communication network.
21. The compact spectrometer system of claim 20 , wherein said communication network is a wireless communication network.
22. The compact spectrometer system of claim 20 , wherein said compact spectrometer system is enclosed within a mobile communication device associated with said communication network.
23. The compact spectrometer system of claim 22 , wherein said mobile communication device is a cellular telephone.
24. The compact spectrometer system of claim 20 , further comprising a database of spectral information in communication with said communication network.
25. The compact spectrometer system of claim 24 , wherein said database is continuously updatable in real time.