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Machine translation
1. (WO2014122256) METHOD AND ELECTRONIC EQUIPMENT FOR DETERMINING A LEAF AREA INDEX
Note: Text based on automatic Optical Character Recognition processes. Please use the PDF version for legal matters

CLAIMS

1. A method (200; 300) for determining Leaf Area Index, or LAI, of a plant canopy sample by a portable electronic equipment (100) movable with respect to a Cartesian orthogonal reference system (X, Y, Z) fixed with respect to the ground, said reference system having a first axis (X) perpendicular to the ground and a second (Y) and third (Z) axes parallel to the ground and orthogonal to said first axis, said equipment being provided with a digital image acquisition module (40, 102) and with an accelerometer module (50) operable to detect an inclination relative to the ground of the electronic portable equipment (100), comprising the steps of: - positioning (202; 202') said portable electronic equipment (100) at the plant canopy sample to be studied;

- rotating (203) said portable electronic equipment (100) about said second axis (Y) from a first position, in which a camera lens (102) of said image acquisition module lies on a reference plane (XY) orthogonal to the ground identified by said first (X) and second (Y) axes, to a second position in which said camera lens (102) lies on a first plane (YZ) parallel to the ground identified by said second (Y) and third (Z) axes and orthogonal to the reference plane (XY);

- during the rotation of the portable electronic equipment (100), detecting, by the accelerometer module (50), the attainment of an intermediate position between said first and second position, in said intermediate position the equipment (100) being inclined with respect to the reference plane (XY) by a reference inclination angle (θ) of about 57.5°;

- acquiring (204) at least one digital image of said plant canopy sample at said intermediate position of the equipment (100);

- sending (205) said at least one acquired digital image to a processing module (10) provided for in the portable electronic equipment (100);

- processing (206; 206') said at least one digital image to measure a parameter (P0) indicative of a light radiation transfer through the plant canopy sample at said reference inclination angle (θ), said parameter (P0) being a function of the leaf area index, or LAI.

2. The method (200) according to claim 1, wherein said positioning step (202) comprises the steps of:

- positioning the portable electronic equipment (100) under the plant canopy sample to acquire a first digital image by carrying out the steps of rotating (203) the portable electronic equipment (100), detecting the attainment of the intermediate position, acquiring (204) at least one digital image and sending (205) said at least one digital image acquired at the processing module (10);

- positioning the portable electronic equipment (100) above the plant canopy sample to acquire a second digital image by carrying out the steps of rotating (203) the portable electronic equipment (100), detecting the attainment of the intermediate position, acquiring (204) at least one digital image and sending (205) said at least one digital image acquired at the processing module (10);

said processing step (206) comprising the further steps of:

- calculating (207) a first (Lb) luminance value starting from said first image; - calculating (208) a second (La) luminance value starting from said second image; said parameter (P0) measured at the reference inclination angle (θ) being proportional to a ratio of the first (Lb) and the second (La) luminance values.

3. The method (200) according to claim 2, wherein said parameter (P0) is calculated based on the equation:

wherein:

- Lb and La are the first and the second luminance values, respectively;

- β r represents a multiplication factor depending on the ratio of a radiation directed above the plant canopy sample and a radiation diffused below said sample.

4. The method (200) according to claim 2, wherein said first (Lb) and second (La) luminance values are calculated by the formula:

where

- L indicates the luminance;

- N is a first coefficient indicative of a focal ratio number;

- t is a second coefficient relating to an exposure time;

- S is a third coefficient of ISO sensitivity;

- k is a fourth coefficient;

wherein the values of said coefficients N, t, S are provided by a digital light meter included in the digital image acquisition module (40) of the portable electronic equipment (100), and said fourth coefficient k is indicative of a calibration constant of light meter on reflected light.

5. The method (200; 300) according to claim 1, wherein said acquisition step (204) of at least one digital image comprises the further steps of:

- taking (204') a plurality of digital images (F) during said rotation step (203) in a preset neighborhood of the reference inclination angle (θ); - storing (204'') a single image of the plurality of images (F) corresponding to the acquired image after reaching the reference inclination angle (θ) equal to about 57.5°, during the equipment (100) rotation.

6. The method (300) according to claim 1, wherein said positioning step (202') comprises the step of positioning the portable electronic equipment (100) only below the plant canopy sample and wherein said processing step (206') comprises the steps of:

- converting (207') said at least one digital image acquired based on the tridimensional color space model HSI (Hue, Saturation, Intensity);

- selecting (207'') pixels of the respective image obtained following said conversion, said selection step (207'') comprising a step of cumulating multiple segmentation events of the original image by identifying those image pixels falling within a preset number of color ranges, said selected pixels being equal to a first number (ηχ) ;

calculating (207a) the ratio of said first number of selected pixels (ni) and a second number (ni+^) representative of the total pixels of the converted image to estimate said parameter (P0) .

7. The method (300) according to claim 6, wherein said color intervals include, to their respective extreme limits, pairs of scalars of three-dimensional space HSI, said intervals being, for example:

from HSI (125,7,123) to HSI (189, 128, 255);

from HSI (123,12,249) to HSI (134,26,255);

from HSI (133, 15, 115) to HSI (166,51,153).

8. The method (300) according to claim 1, wherein said positioning step (202') comprises the step of positioning the portable electronic equipment (100) only below the plant canopy sample and wherein said processing step (206') comprises the steps of:

converting (208') the at least one digital image acquired to a color space of grey tones;

setting a reference threshold value in said color space of grey tones;

selecting (208'') pixels of the single image obtained following said conversion, having a grey tone value greater than the preset reference threshold, said selected pixels being equal to a further first number (n1');

calculating (208a) the ratio of said further first number (n1') of selected pixels and a further second number (η1'+n2') representative of the total pixels of the converted image to estimate said parameter (P0).

9. A portable electronic equipment (100), comprising: - a processing module (10);

- a memory module operatively connected to said processing module (10);

- a digital image acquisition module (40) operatively connected to and controlled by the processing module (10) to acquire a flow (F) of digital images to be sent to the processing module; - an accelerometer module (50) operatively connected to and controlled by the processing module (10),

said portable electronic equipment being configured to carry out the method in accordance with any of the claims 1-8.

10. The portable electronic equipment (100) according to claim 9, wherein said equipment is selected from the group consisting of:

- a smartphone,

- a tablet,

- a general portable multimedia file processing device.

11. A computer program comprising a program code loadable in a memory of a computer to carry out the steps of the method (200; 300) for determining a leaf area index, or LAI, in accordance with one of the preceding claims 1 to 8.