OPTICAL MEASUREMENTS OF CHEMICAL CONTENT

• US 20170261427A1
• Filed: 03/14/2016
• Published: 09/14/2017
• Est. Priority Date: 03/14/2016
• Status: Abandoned Application

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Deliwala, Shrenik
• Application Number:
  US15/068,824
• Publication Number:
  US 20170261427A1
• Time in Patent Office: Days
• CPC Class Codes: G01J 2003/1213 Filters in general, e.g. dichroic, band
• CPC Class Codes: G01J 3/0256 Compact construction
• CPC Class Codes: G01J 3/0262 Constructional arrangements for removing stray light
• CPC Class Codes: G01J 3/0264 Electrical interface; User interface
• CPC Class Codes: G01J 3/10 Arrangements of light sources specially adapted for spectrometry or colorimetry
• CPC Class Codes: G01J 3/36 Investigating two or more bands of a spectrum by separate detectors
• CPC Class Codes: G01J 3/427 Dual wavelengths spectrometry
• CPC Class Codes: G01N 21/3577 for analysing liquids, e.g. polluted water
• CPC Class Codes: G01N 2201/0627 Use of several LED's for spectral resolution
• CPC Class Codes: G01N 33/18 Water

Abstract

Techniques for optical detection of target chemicals on/in samples are disclosed. Light of at least two different wavelengths, or different bands of wavelengths, interacts with a target chemical, and at least some of the light that has interacted with the target chemical is incident on at least two photodetectors. Each of the photodetectors is configured to detect light of a different wavelength, or a different band of wavelengths, that has interacted with the target chemical. A processing logic is configured to compute a ratio between a parameter indicative of the intensity of light detected by one photodetector and a parameter indicative of the intensity of light detected by the other photodetector, and to determine the presence and/or the amount of the target chemical based on the computed ratio. In this manner, a simple, compact, and non-contact optical measurement assembly for assessing chemical content using differential spectral measurements may be provided.

Claims

1. An apparatus for optical detection of a presence and/or an amount of a target chemical, the apparatus comprising:

a first photodetector configured to detect light of a first wavelength that has interacted with the target chemical;

a second photodetector configured to detect light of a second wavelength that has interacted with the target chemical; and

a processing logic configured to;

compute a ratio (R) between a first parameter indicative of at least an intensity of the light detected by the first photodetector (Int1) and a second parameter indicative of at least an intensity of the light detected by the second photodetector (Int2), and

determine the presence and/or the amount of the target chemical based on the computed ratio.

2. The apparatus according to claim 1, wherein:

the first photodetector is configured to detect light of a first band of wavelengths that has interacted with the target chemical, the first band of wavelengths including the first wavelength, and

the second photodetector is configured to detect light of a second band of wavelengths that has interacted with the target chemical, the second band of wavelengths including the second wavelength.

3. The apparatus according to claim 2, wherein the first band of wavelengths and the second band of wavelengths at least partially overlap.

4. The apparatus according to claim 3, wherein the first band of wavelengths is included within the second band of wavelengths and the ratio is computed as

5. The apparatus according to claim 2, wherein the ratio is computed as

6. The apparatus according to claim 1, wherein the first photodetector is provided at a distance less than 5 millimeters from the second photodetector.

7. The apparatus according to claim 6, wherein the first photodetector and the second photodetector are provided on the same die.

8. The apparatus according to claim 1, wherein each of the first photodetector and the second photodetector comprises a plurality of photodetecting regions, and the photodetecting regions of the first photodetector are interleaved with the photodetecting regions of the second photodetector.

9. The apparatus according to claim 1, wherein the first photodetector is configured to detect the light of the first wavelength by detecting light incident on one or more photodetecting regions of the first photodetector that has passed through a first optical filter and the second photodetector is configured to detect the light of the second wavelength by detecting light incident on one or more photodetecting regions of the second photodetector that has passed through a second optical filter.

10. The apparatus according to claim 9, wherein the first optical filter and/or the second optical filter is provided as a coating over a respective photodetector.

11. The apparatus according to claim 1, wherein:

the light of the first wavelength is modulated and the light detected by the first photodetector is locked to the modulation of the light of the first wavelength, and/or

the light of the second wavelength is modulated and the light detected by the second photodetector is locked to the modulation of the light of the second wavelength.

12. The apparatus according to claim 1, wherein the first photodetector is configured to detect light of the first wavelength substantially simultaneously with the second photodetector detecting light of the second wavelength.

13. The apparatus according to claim 1, further comprising one or more light sources configured to generate light to interact with the target chemical.

14. The apparatus according to claim 13, wherein the light generated by the one or more light sources comprises broadband light.

15. The apparatus according to claim 14, wherein a band of the light generated by the one or more light sources at least partially overlaps with a band of light that the first photodetector is configured to detect and with a band of light that the second photodetector is configured to detect.

16. The apparatus according to claim 13, wherein the one or more light sources comprise a light emitting diode centered at about 1460 nm or/and a light emitting diode centered at about 1930 nm, and the target chemical comprises water.

17. The apparatus according to claim 13, wherein the one or more light sources comprise a light emitting diode centered at about 1200 nm, and the target chemical comprises a fat.

18. The apparatus according to claim 1, further comprising a third photodetector configured to detect light of a third wavelength that has interacted with the target chemical, wherein:

the processing logic determining the ratio comprises the processing logic determining one or more ratios between the first parameter, the second parameter, and a third parameter indicative of at least an intensity of the light detected by the third photodetector (Int3), and

the processing logic determining the presence and/or the amount of the target chemical based on the computed ratio comprises the processing logic determining the presence and/or the amount of the target chemical based on the determined one or more ratios.

19. A method for optical detection of a presence and/or an amount of a target chemical, the method comprising:

computing a ratio (R) between a first parameter indicative of at least an intensity of light of a first wavelength that has interacted with the target chemical, detected by a first photodetector (Int1) and a second parameter indicative of at least an intensity of the light of a second wavelength that has interacted with the target chemical, detected by a second photodetector (Int2); and

determining the presence and/or the amount of the target chemical based on the computed ratio.

20. The method according to claim 19, further comprising performing a calibration, prior to determining the presence and/or the amount of the target chemical, by:

computing a plurality of ratios for a plurality of samples having a known presence and/or a known amount of one or more of predefined target chemicals, each ratio comprising a ratio between the first parameter indicative of at least the intensity of light of the first wavelength that has interacted with the predefined target chemical and the second parameter indicative of at least the intensity of light of the second wavelength that has interacted with the predefined target chemical; and

storing the plurality of computed ratios in association with identifications of the plurality of samples.