LOW-COST SPECTROMETRY SYSTEM FOR END-USER FOOD ANALYSIS

• US 20140320858A1
• Filed: 10/31/2012
• Published: 10/30/2014
• Est. Priority Date: 11/03/2011
• Status: Active Grant

• Current Assignee: Verifood, Ltd.
• Original Assignee: Verifood, Ltd.
• Inventors: Goldring, Damian, Sharon, Dror
• Granted Patent: US 9,377,396 B2
• Time in Patent Office: Days
• US Class Current: 356/416
• CPC Class Codes: G01J 2003/1226 Interference filters
• CPC Class Codes: G01J 3/0208 using focussing or collimating elements, e.g. lenses or mirrors; performing aberration correction
• CPC Class Codes: G01J 3/0256 Compact construction
• CPC Class Codes: G01J 3/26 using multiple reflection, e.g. Fabry-Perot interferometer, variable interference filters
• CPC Class Codes: G01J 3/2803 using photoelectric array detector
• CPC Class Codes: G01J 3/36 Investigating two or more bands of a spectrum by separate detectors
• CPC Class Codes: G01N 21/255 Details, e.g. use of specially adapted sources, lighting or optical systems

Abstract

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.

Claims

1. A compact spectrometer system for obtaining the 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; and

,

a first Fourier transform focusing element;

wherein said compact spectrometer system does not contain any dispersive optical elements.

2. The compact spectrometer system according to claim 1, wherein said optical filter is a non-tunable filter.

3. The compact spectrometer system according to claim 1, wherein said first Fourier transform focusing element is disposed between said optical filter and said optical detector such that light passing through said optical filter is dispersed by said at least one focusing element onto the light-sensitive surface of said detector.

4. The compact spectrometer system according to claim 1, wherein the center wavelength of said optical filter varies with the incidence angle of light impinging thereupon.

5. The compact spectrometer system according to claim 1, wherein said optical filter comprises a plurality of sub-filters with different center wavelengths.

6. The compact spectrometer system according to claim 5, wherein said optical filter comprises a plurality of substantially parallel strips, each of which comprises a sub-filter.

7. The compact spectrometer system according to claim 5, wherein said optical filter comprises a plurality of substantially rectangular areas, each of which comprises a sub-filter.

8. The compact spectrometer system according to 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.

9. The compact spectrometer system according to claim 1, wherein said first Fourier transform focusing element is a plano-convex lens disposed such that its flat face faces said optical detector and its curved face faces said optical filter.

10. The compact spectrometer system according to claim 1, further comprising a second Fourier transform focusing element.

11. The compact spectrometer system according to claim 10, wherein said Fourier transform focusing elements are plano-convex cylindrical lenses disposed such that:

the flat face of each lens faces said optical detector;

the curved face of each lens faces said optical filter;

the focal lines of the two lenses are oriented along different axes in the x-y plane; and

,

the focal planes of said Fourier transforming focusing elements substantially coincide.

12. The compact spectrometer system according to claim 11, wherein the focal planes of said Fourier transforming focusing elements are substantially coincident with light-sensitive surface of said optical detector.

13. The compact spectrometer system according to claim 11, wherein the focal lines of said Fourier transform focusing elements are perpendicular.

14. The compact spectrometer system according to claim 1, further comprising a micro-lens array.

15. The compact spectrometer system according to claim 14, wherein said micro-lens array is located in the focal plane of said first Fourier transform focusing element.

16. The compact spectrometer system according to claim 14, wherein said detector is located at a plane substantially perpendicular to the optical axis such that the micro-lenses form multiple images of said optical filter on said optical detector.

17. The compact spectrometer system according to claim 14, wherein said optical filter comprises a plurality of sub-filters with different center wavelengths.

18. The compact spectrometer system according to claim 14, further comprising a second Fourier transforming focusing element, wherein said micro-lens array comprises an array of cylindrical lenses and is located at the focal plane of first of two said focusing elements and said optical detector is located at the focal plane of second of two said focusing elements.

19. The compact spectrometer system according to claim 1, further comprising a diffuser disposed between said sample and said optical filter.

20. The compact spectrometer system according to claim 1, wherein said first Fourier transform focusing element is a lens chosen from the group consisting of (a) plano-convex lenses, (b) biconvex lenses, and (c) aspheric lenses, and further wherein said optical filter is located between said first Fourier transform focusing element and said sample.

21. The compact spectrometer system according to claim 20, wherein said optical filter comprises a plurality of sub-filters with different center wavelengths.

22. The compact spectrometer system according to claim 21, wherein said plurality of sub-filters is disposed radially about a center point.

23. The compact spectrometer system according to claim 20, wherein said optical filter is in close proximity to said optical detector.

24. The compact spectrometer system according to claim 1, wherein said optical detector is a two-dimensional image sensor.

25. The compact spectrometer system according to claim 1, further comprising a light source adapted to illuminate said sample.

26. The compact spectrometer system according to claim 25, wherein said light source is a laser.

27. The compact spectrometer system according to claim 25, wherein said light source is a light-emitting diode.

28. The compact spectrometer system according to claim 25, further comprising a focusing system adapted focus light from said light source at a predetermined location relative to said sample.

29. The compact spectrometer system according to claim 28, wherein said focusing system is an autofocus system.

30. The compact spectrometer system according to claim 28, wherein said focusing system controls the position of a lens that focuses light produced by said light source onto said sample.

31. The compact spectrometer system according to claim 28, wherein said focusing system controls the optical properties of a lens that focuses light produced by said light source onto said sample.

32. The compact spectrometer system according to claim 28, wherein said focusing system comprises a voice-coil motor.

33. The compact spectrometer system according to claim 28, wherein said focusing system comprises a piezoelectric motor.

34. The compact spectrometer system according to claim 28, wherein said focusing system comprises a micro-electrical-mechanical-system (MEMS) motor.

35. The compact spectrometer system according to claim 1, wherein said light emanating from said sample comprises light scattered by said sample upon illumination.

36. The compact spectrometer system according to claim 35, wherein said spectrum is selected from the group consisting of (a) molecular vibrational spectra, (b) molecular rotational spectra, and (c) electronic spectra.

37. The compact spectrometer system according to claim 36, wherein said spectrum is a Raman spectrum.

38. The compact spectrometer system according to claim 35, further comprising a second optical filter.

39. The compact spectrometer system according to claim 35, wherein said light scattered from said sample upon illumination comprises light reflected by said sample upon illumination.

40. The compact spectrometer system according to claim 1, wherein said light emanating from said sample comprises light produced by fluorescence emanating from said sample.

41. The compact spectrometer system according to claim 1, further comprising means for communicating with a communication network.

42. The compact spectrometer system according to claim 41, wherein said communication network is a wireless communication network.

43. The compact spectrometer system according to claim 41, wherein said compact spectrometer system is enclosed within a mobile communication device associated with said communication network.

44. The compact spectrometer system according to claim 43, wherein said mobile communication device is a cellular telephone.

45. The compact spectrometer system according to claim 41, further comprising a database of spectral information in communication with said communication network.

46. The compact spectrometer system according to claim 45, wherein said database is continuously updatable in real time.

47. The compact spectrometer system according to claim 1, further comprising a local digital processor.

48. The compact spectrometer system according to claim 47, wherein said local digital processor is programmed to perform at least one algorithm chosen from the group consisting of (a) an algorithm for operating said compact spectrometer system;

(b) an algorithm for processing raw spectral data obtained by said compact spectrometer system;

(c) an algorithm for comparing data obtained by said compact spectrometer system with data stored in a database; and

(c) an algorithm for transmitting spectral data obtained by said compact spectrometer system to a remote server.

49. The compact spectrometer system according to claim 1, further comprising local memory.

50. The compact spectrometer system according to claim 49, wherein said local memory is chosen from the group consisting of (a) fixed memory and (b) volatile memory.

51. The compact spectrometer system according to claim 49, further comprising a local database of spectral information stored within said local memory.

52. The compact spectrometer system according to claim 1, wherein said compact spectrometer system is incorporated into an oven.

53. The compact spectrometer system according to claim 52, wherein said oven is a microwave oven.

54. The compact spectrometer system according to claim 1, wherein said compact spectrometer system is incorporated into a refrigerator.

55. The compact spectrometer system according to claim 1, further comprising GPS positioning means for determining the location of said spectrometer system.

56. The compact spectrometer system according to claim 1, wherein said sample comprises food.

73. The method according to claim 56, wherein said spectrum is selected from the group consisting of (a) molecular vibrational spectra, (b) molecular rotational spectra, and (c) electronic spectra.

74. The method according to claim 73, wherein said spectrum is a fluorescence spectrum.

75. The method according to claim 73, wherein said spectrum is a Raman spectrum.

76. The method according to claim 75, further comprising a step of separating the Raman signal from the fluorescence signal.

57. A method of obtaining a spectrum of a sample without using dispersive optics, wherein said method comprises:

providing a sample;

causing light emanating from said sample to impinge on an optical filter, the center wavelength of which depends on the angle of incidence of the light impinging upon it;

passing said light to a first Fourier transform focusing element;

measuring the intensity of light as a function of position in a predetermined plane P₁; and

,

converting the intensity of light as a function of position in said plane P₁ to a spectrum.

58. The method according to claim 57, wherein said step of measuring the intensity of light as a function of position in a predetermined plane P₁ comprises measuring the intensity of light as a function of position in a plane substantially coincident with the focal plane of said first Fourier transform focusing element.

59. The method according to claim 57, wherein said step of causing light emanating from said sample to impinge on an optical filter precedes said step of passing said light to a first Fourier transform focusing element, whereby the light passing through said optical filter is angle-encoded according to its wavelength and said light is transformed by said Fourier transform focusing element to spatially encoded.

60. The method according to claim 57, wherein said step of passing said light to a first Fourier transform focusing element precedes said step of causing light emanating from said sample to impinge on an optical filter.

61. The method according to claim 57, further comprising a step of placing in said predetermined plane P₁ an image sensor adapted to measure the intensity of light impinging upon said image sensor as a function of position.

62. The method according to claim 57, wherein said step of passing said light to a first Fourier transform focusing element comprises a step of passing said light to a plano-convex lens, the curved surface of which is facing said optical filter.

63. The method according to claim 57, wherein said step of causing light emanating from said sample to impinge on an optical filter comprises a step of causing light emanating from said sample to impinge on an optical filter comprising a plurality of sub-filters.

64. The method according to claim 63, further comprising:

placing a micro-lens array in a predetermined plane P₂ oriented such that each micro-lens samples the optical Fourier transform formed at said plane P₂, thereby creating a micro-image of the aperture of said optical filter at a predetermined plane P₃, and thereby decomposing the sampling points of said optical Fourier transform according to the origin of the light at a particular sub-filter reaching said micro-lens.

65. The method according to claim 64, wherein said predetermined plane P₂ is substantially identical to the focal plane of said first Fourier transform focusing element.

66. The method according to claim 64, further comprising a step of placing an image sensor adapted to measure the intensity of light impinging upon said image sensor as a function of position in said predetermined plane P₃.

67. The method according to claim 64, further comprising:

placing said plurality of sub-filters along a single axis; and

,

passing said angle-encoded light through a second Fourier transform focusing element disposed such that the spatially encoded light produced by said second Fourier transform focusing element is encoded at an angle relative to the orientation of the spatially encoded light produced by said first Fourier transform focusing element and such that the focal plane of said second Fourier transform focusing element is substantially identical with said predetermined plane P₃;

wherein said step placing a micro-lens array between said first Fourier transform focusing element and said predetermined plane P₃ further comprises placing a micro-lens array comprising cylindrical micro-lenses disposed such that the light passing through said micro-lens array is disposed in said plane along an axis parallel to said single axis.

68. The method according to claim 67, wherein said step of passing said angle-encoded light to a first Fourier transform focusing element comprises a step of passing said angle-encoded light to a first plano-convex cylindrical lens, the curved surface of which is facing said optical filter, and said step of passing said angle-encoded light through a second Fourier transform focusing element comprises a step of passing said angle-encoded light to a second plano-convex cylindrical lens, the curved surface of which is facing said optical filter.

69. The method according to claim 67, further comprising:

placing said micro-lens array in the focal plane of said first Fourier transform focusing element; and

,

placing said optical detector in the focal plane of said second Fourier transform focusing element.

70. The method according to claim 57, further comprising passing said light through a diffuser.

71. The method according to claim 57, further comprising illuminating said sample with a light source.

72. The method according to claim 71, wherein said step of illuminating said sample comprises illuminating said sample with a light source chosen from the group consisting of lasers and light emitting diodes.

77. The method according to claim 71, further comprising a step of focusing light emanating from said light source to a predetermined location relative to said sample.

78. The method according to claim 77, wherein said step of focusing light emanating from said light source comprises a step of focusing light emanating from said light source using an autofocus system.

79. The method according to claim 78, wherein said step of focusing light emanating from said light source using an autofocus system further comprises:

analyzing in real time the signal obtained by said spectrometer; and

,

commanding said autofocus system accordingly, so that said light is focused to the optimal signal extraction point at the sample.

80. The method according to claim 57, further comprising analyzing the spectrum obtained by comparison with a database of spectral information.

81. The method according to claim 80, wherein said step of analyzing comprises at least one step chosen from (a) comparing said spectrum with spectra in a spectral database;

(b) comparing said spectrum with spectra in a spectral database by using Principal Components Analysis;

(c) comparing said spectrum with spectra in a spectral database by using Partial Least Squares analysis; and

(d) comparing said spectrum with spectra in a spectra database by using a neural network algorithm.

82. The method according to claim 80, further comprising adding said spectrum to said spectral database.

83. The method according to claim 80, further comprising:

transmitting said spectrum to a remote processing unit;

using said remote processing unit to perform said step of analyzing; and

,

transmitting the results of said step of analyzing to the user.

84. The method according to claim 83, wherein said steps of transmitting are performed by transmitting over a wireless network.

85. The method according to claim 83, further comprising performing a preliminary analysis of said spectrum obtained in said step of converting the intensity of light as a function of position in the focal plane of said first Fourier transform focusing element.

86. The method according to claim 85, wherein said step of performing a preliminary analysis of said spectrum is performed using a local processing unit.

87. The method according to claim 85, wherein said step of performing a preliminary analysis of said spectrum is performed remotely.

88. The method according to claim 85, wherein said step of performing a preliminary analysis of said spectrum further comprises at least one step chosen from the group consisting of:

averaging a plurality of independent measurements;

compensating for optical aberrations; and

,

reducing detector noise using a noise reduction algorithm.

89. The method according to claim 57, further comprising a step of transmitting to a predetermined remote location the location at which said spectrum is obtained.

90. The method according to claim 57, wherein said step of transmitting to a predetermined remote location the location at which said spectrum is obtained further comprises a step of determining the location at which said spectrum by use of a GPS.

91. The method according to claim 57, wherein said steps of:

causing light emanating from said sample to impinge on an optical filter, the center wavelength of which depends on the angle of incidence of the light impinging upon it;

passing said light to a first Fourier transform focusing element; and

,

measuring the intensity of light as a function of position in said plane P₁;

are performed by using optical elements, all of which are disposed within or upon a mobile communication device.

92. The method according to claim 91, wherein said mobile communication device is a cellular telephone.

93. The method according to claim 57, wherein said steps of:

causing light emanating from said sample to impinge on an optical filter, the center wavelength of which depends on the angle of incidence of the light impinging upon it;

passing said light to a first Fourier transform focusing element; and

,

measuring the intensity of light as a function of position in said plane P₁;

are performed by using optical elements, all of which are disposed within or upon an oven.

94. The method according to claim 93, wherein said oven is a microwave oven.

95. The method according to claim 57, wherein said steps of:

causing light emanating from said sample to impinge on an optical filter, the center wavelength of which depends on the angle of incidence of the light impinging upon it;

passing said light to a first Fourier transform focusing element; and

,

measuring the intensity of light as a function of position in said plane P₁;

are performed by using optical elements, all of which are disposed within or upon a refrigerator.

96. The method according to claim 57, wherein said sample comprises food.

97. The method according to claim 57, wherein said sample comprises medication.