# US 7,746,452 B2 · Portable meter to measure chlorophyll, nitrogen and water and methods

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- Number: US 7,746,452 B2
- Document ID: US7746452B2
- Status: Granted
- Kind: B2
- Application number: 12/089,902
- Filed: 2006-11-21
- Published: 2008-10-02
- Granted: 2010-06-29
- Earliest claimed: 2005-11-21
- Assignees: State of Oregon acting by and through the State Board of Higher Education on behalf of Oregon State University
- Inventors: Leslie H. Fuchigami; Pinghai Ding; Guy E. Barnes, Jr.
- Web page: https://patentgrep.com/patent/US7746452B2

## CPC

- G01N 21/3151: {using two sources of radiation of different wavelengths (G01N21/33 - G01N21/39 take precedence)}
- G01N 2001/021: {Correlating sampling sites with geographical information, e.g. GPS}
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)

## Abstract

Methods for determining chlorophyll content comprise providing a sample, subjecting the sample to light at a first wavelength and detecting a first wavelength response, subjecting the sample to light at a second wavelength and detecting a second wavelength response, and calculating a chlorophyll content of the sample based on at least the first wavelength response and the second wavelength response. Optional approaches include detecting the nitrogen content and/or water content of the sample. Associated apparatus for determining chlorophyll content, which may comprise a handheld device, is also disclosed.

## Claims

### Claim 1

A method for determining chlorophyll content, comprising:
providing a sample;
subjecting the sample to light at a first wavelength and detecting a first wavelength response;
subjecting the sample to light at a second wavelength and detecting a second wavelength response;
subjecting the sample to light at a third wavelength and detecting a third wavelength response; and
calculating a chlorophyll content of the sample with a device for determining chlorophyll content based on at least the first wavelength response, the second wavelength response, and the third wavelength response.

### Claim 2 (depends on 1)

The method of claim 1, further comprising:
subjecting the sample to light at a fourth wavelength and detecting a fourth wavelength response,
wherein calculating a chlorophyll content of the sample is also based on the fourth wavelength response.

### Claim 3 (depends on 1)

The method of claim 1, wherein the device for determining chlorophyll content is a handheld device, and wherein subjecting the sample to light at a first wavelength, subjecting the sample to light at a second wavelength, and subjecting the sample to light at a third wavelength are performed with the handheld device.

### Claim 4 (depends on 1)

The method of claim 1, wherein subjecting the sample to light at a first wavelength comprises subjecting the sample to light at a wavelength of about 520 nm to about 580 nm.

### Claim 5 (depends on 1)

The method of claim 1, wherein subjecting the sample to light at a first wavelength comprises subjecting the sample to light at a wavelength selected to indicate chlorophyll content.

### Claim 6 (depends on 1)

The method claim 1, wherein subjecting the sample to light at a second wavelength comprises subjecting the sample to light at a wavelength of about 690 nm to about 740 nm.

### Claim 7 (depends on 1)

The method of claim 1, wherein subjecting the sample to light at a second wavelength comprises subjecting the sample to light at a far-red wavelength selected to indicate nitrogen content.

### Claim 8 (depends on 1)

The method of claim 1, wherein subjecting the sample to light at a third wavelength comprises subjecting the sample to light at a wavelength of about 800 nm to about 1100 nm.

### Claim 9 (depends on 1)

The method of claim 1, wherein subjecting the sample to light at a third wavelength comprises subjecting the sample to light at an infrared wavelength selected to account for at least one of thickness and texture of the sample.

### Claim 10 (depends on 2)

The method of claim 2, wherein subjecting the sample to light at a fourth wavelength comprises subjecting the sample to light at a wavelength of about 1420 nm to about 1510 run.

### Claim 11 (depends on 2)

The method of claim 2, wherein subjecting the sample to light at a fourth wavelength comprises subjecting the sample to light at an infrared wavelength selected to indicate water content.

### Claim 12 (depends on 1)

The method of claim 1, further comprising storing position information regarding the sample's location.

### Claim 13 (depends on 12)

The method of claim 12, wherein storing position information regarding the sample's location comprises storing GPS coordinates representing the sample's location.

### Claim 14 (depends on 1)

The method of claim 1, wherein subjecting the sample to light at a first wavelength, subjecting the sample to light at a second wavelength, and subjecting the sample to light at a third wavelength comprises causing light to impinge upon the sample, and wherein detecting a first wavelength response, detecting a second wavelength response and detecting a third wavelength response comprise measuring reflectance from the sample.

### Claim 15 (depends on 1)

The method of claim 1, wherein subjecting the sample to light at a first wavelength, subjecting the sample to light at a second wavelength, and subjecting the sample to light at a third wavelength comprises causing light to impinge upon the sample, and wherein detecting a first wavelength response, detecting a second wavelength response and detecting a third wavelength response comprise measuring transmittance from the sample.

### Claim 16 (depends on 1)

The method of claim 1, further comprising determining a water content of the sample, and wherein the water content is a factor is calculating a chlorophyll content of the sample.

### Claim 17 (depends on 1)

The method of claim 1, further comprising determining the sample's exterior characteristics, and wherein the exterior characteristics are a factor in calculating a chlorophyll content of the sample.

### Claim 18

A device for determining chlorophyll content, comprising:
a sample receiving area configured to accommodate a sample during testing;
a light source positioned adjacent the sample receiving area and operable to subject a sample in the sample receiving area to at least three different wavelengths of light;
a photodetector operatively arranged adjacent the sample receiving area and configured to detect responses to the at least three different wavelengths of light; and
a microprocessor connected to the light source and to the photodetector, the microprocessor controlling the light source and the photodetector and calculating a chlorophyll value of a sample based on at least the responses to the at least three different wavelengths of light.

### Claim 19 (depends on 18)

The device of claim 18, further comprising a lens positioned to focus light from the light source on a sample in the sample receiving area.

### Claim 20 (depends on 18)

The device of claim 18, wherein the device is a handheld device.

### Claim 21 (depends on 18)

The device of claim 18, wherein the light source comprises at least one light emitting diode (LED).

### Claim 22 (depends on 18)

The device of claim 18, wherein the light source comprises at least one LED capable of generating the at least three different wavelengths of light.

### Claim 23 (depends on 18)

The device of claim 18, wherein the light source is capable of generating light at four different wavelengths, including a first wavelength of about 520 nm to about 580 nm, a second wavelength of about 690 nm to about 740 nm, a third wavelength of about 800 nm to about 1100 nm and a fourth wavelength of about 1420 nm to about 1510 nm.

### Claim 24 (depends on 18)

The device of claim 18, further comprising a lens positioned between the light source and the sample receiving area, the lens defining an optical axis extending towards the sample receiving area, wherein the light source comprises multiple LED elements, and wherein an LED element capable of generating light at the first wavelength is spaced farther from the optical axis than an LED element capable of generating light at a third wavelength.

### Claim 25 (depends on 21)

The device of claim 21, wherein the photodetector is capable of sensing light at the first wavelength, at the second wavelength and at the third wavelength.

### Claim 26 (depends on 18)

The device of claim 18, wherein the photodetector comprises a Si/PBS photodetector.

### Claim 27 (depends on 18)

The device of claim 18, further comprising a GPS receiver connected to the microprocessor, the GPS receiver being capable of determining a current position.

### Claim 28 (depends on 21)

The device of claim 21, further comprising a personal digital assistant connected to the microprocessor, the personal digital assistant having a display, an input device and a memory in which a program for interacting with the device is stored, the display and input device being used to control the operation of the device.

### Claim 29 (depends on 28)

The device of claim 28, further comprising a GPS receiver connected to the microprocessor, and wherein the personal digital assistant is operable to display selected position information relative to a background map.

### Claim 30 (depends on 18)

The device of claim 18, further comprising a biasing circuit and an amplifier.

### Claim 31 (depends on 18)

The device of claim 18, wherein the device is portable and includes a source of DC power.

### Claim 32 (depends on 18)

The device of claim 18 , wherein the device determines chlorophyll content without harming the sample.

### Claim 33 (depends on 1)

The method of claim 1, wherein calculating the chlorophyll content comprises:
obtaining a baseline transmittance value for each wavelength of light to which the sample is subjected;
obtaining a measured transmittance value for each wavelength of light; and
computing at least one index based on the measured transmittance values and the actual transmittance values.

### Claim 34 (depends on 33)

The method of claim 33, further comprising computing a polynomial equation based on the at least one index.

### Claim 35 (depends on 34)

The method of claim 34, wherein the polynomial equation is a quadratic equation.

### Claim 36 (depends on 33)

The method of claim 33, further comprising computing an exponential equation in which the exponent is the index.

### Claim 37 (depends on 33)

The method of claim 33, further comprising computing a power equation in which the index is raised to a power.

### Claim 38 (depends on 33)

The method of claim 33, further comprising comparing the at least one index to corresponding stored values for a particular plant, and outputting a result.

### Claim 39 (depends on 38)

The method of claim 38, wherein the stored values are for a particular plant variety.

### Claim 40 (depends on 33)

The method of claim 33, wherein the baseline and measured transmittance values are directly proportional to voltage values.

### Claim 41 (depends on 33)

The method of claim 33, wherein a first transmittance ratio is equal to the measured transmittance at the first wavelength divided by the baseline transmittance at the first wavelength,
wherein a third transmittance ratio is equal to the measured transmittance at the third wavelength divided by the baseline transmittance at the third wavelength, and
wherein computing at least one index includes computing a first index equal to the third transmittance ratio divided by the first transmittance ratio.

### Claim 42 (depends on 41)

The method of claim 41, wherein a second transmittance ratio is equal to the measured transmittance at the second wavelength divided by the baseline transmittance at the second wavelength, and
wherein computing at least one index includes computing a second index equal to the third transmittance ratio divided by the second transmittance ratio.

### Claim 43 (depends on 41)

The method of claim 41, wherein computing at least one index includes computing a third index equal to a quotient of the third transmittance ratio minus the first transmittance ratio divided by the third transmittance ratio plus the first transmittance ratio.

### Claim 44 (depends on 41)

The method of claim 41, wherein computing at least one index includes computing a fourth index equal to a quotient of the third transmittance ratio minus the second transmittance ratio divided by the third transmittance ratio plus the second transmittance ratio.

### Claim 45 (depends on 33)

The method of claim 33, wherein the at least one index is a first index, and multiple indices are computed, further comprising comparing each of the multiple indices to corresponding stored values, selecting one of the indices based on a predetermined criterion, and outputting results based on the selected one of the indices.

### Claim 46

A method for determining chlorophyll content, comprising:
providing a sample;
subjecting the sample to light at multiple different wavelengths;
detecting a response for each of the different wavelengths;
determining a water content of the sample;
calculating a chlorophyll content of the sample with a device for determining chlorophyll content based on the response for each of the different wavelengths and the determined water content of the sample.

### Claim 47 (depends on 46)

The method of claim 46, wherein calculating chlorophyll content of the sample with a device for determining chlorophyll content comprises using the determined water content of the sample to address any confounding factor based on the sample's water content in the response for each of the different chlorophyll-determining wavelengths.

### Claim 48 (depends on 28)

The device of claim 28, wherein the personal digital assistant is connected to the microprocessor via a wireless connection.

### Claim 49 (depends on 1)

The method of claim 1, wherein one of the first wavelength, second wavelength and third wavelength is in a red edge portion of the light spectrum.

### Claim 50 (depends on 1)

The method of claim 1, wherein one of the first wavelength, the second wavelength and the third wavelength is in a range of about 800 nm to about 1100 nm, and wherein the response to the about 800 nm to about 1100 nm wavelength is used in calculating a chlorophyll content of the sample and in calculating a water content of the sample.