Spectrum optimization for artificial illumination

• US 10,188,046 B2
• Filed: 09/24/2013
• Issued: 01/29/2019
• Est. Priority Date: 09/24/2012
• Status: Active Grant

• Current Assignee: Heliospectra AB
• Original Assignee: Heliospectra AB
• Inventors: Wik, Torsten, Carstensen, Anna-Maria, Pocock, Teresa
• Primary Examiner(s): Williams, Monica L
• Assistant Examiner(s): Rodziwicz, Aaron M
• Application Number:
  US14/430,323
• Publication Number:
  US 20150250106A1
• Time in Patent Office: 1,953 Days
• Field of Search: 47 581 LS
• CPC Class Codes: A01G 7/045 with electric lighting
• CPC Class Codes: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: H05B 45/22 using optical feedback
• CPC Class Codes: Y02P 60/14 Measures for saving energy, e.g. in green houses

Abstract

The present invention relates to a method for artificial illumination of a plant, wherein the illumination of the plant is controlled based on the amount of light being reflected from the plant. The invention also relates to a corresponding illumination system, use of the illumination system and a computer program product.

Claims

1. A method of using an illumination system for artificial illumination of a plant, the illumination system comprising a first and a second light source and at least one sensor configured to receive light reflected from the plant, wherein the first and the second light sources are configured to emit light within a first and a second predetermined wavelength range, respectively, the method comprising:

controlling the first and the second light source to illuminate the plant with a first and a second predetermined base level radiant flux, respectively;

introducing a minor variation to at least one of the first and the second base level radiant flux;

determining, by the at least one sensor, a first level of reflected light within the first wavelength range and a second level of reflected light at the second wavelength range;

estimating a marginal reflectance based on the first and the second levels of reflected light from the plant within each of the first and second wavelength ranges, wherein the marginal reflectance comprises a derivative of the first or the second levels of reflected light with respect to the first and the second predetermined base level radiant flux, respectively; and

adjusting a radiant flux of light emitted by the first light source such that the marginal reflectance within the first wavelength range stands in a predetermined relation to the marginal reflectance within the second wavelength range.

2. The method according to claim 1, wherein the marginal reflectance within the first wavelength range is equal to the marginal reflectance within the second wavelength range.

3. The method according to claim 2, wherein the marginal reflectance of the first lighting wavelength correlates to the marginal reflectance of the second lighting wavelength based on a predetermined scaling matrix.

4. The method according to claim 1, wherein the minor variation is introduced to the first and the second base level radiant flux.

5. The method according to claim 3, wherein the scaling matrix is dependent on at least one of a type of plant, a growth cycle of the plant, or an ambient temperature, humidity, ambient light condition in a vicinity of the plant.

6. The method according to claim 1, further comprising controlling the radiant flux of light emitted by the first and the second light source such that the marginal reflectance within the first wavelength range corresponds to the marginal reflectance within the second wavelength range.

7. The method according to claim 1, wherein said marginal reflectance is estimated by an incremental reflectance given by:

8. The method according to claim 1, wherein said marginal reflectance is based on a derivative of the first level of reflected light from the plant with respect to said first base level radiant flux and a derivative of the second level of reflected light from the plant with respect to said second base level radiant flux at the first and second wavelengths ranges respectively.

9. The method according to claim 1, further comprising:

estimating a matrix K according to an equation given by

10. The method according to claim 1, wherein said marginal reflectance is a ratio between a variation in reflected light in a wavelength range and a variation in applied power to induce the variation in reflected light.

11. An illumination system for artificial illumination of a plant, the illumination system comprising:

a first and a second light source;

a sensor configured to receive light reflected from the plant, and

a control unit, the control unit being electrically coupled to the sensor and the first and the second light source, wherein the control unit is configured to;

control the first and the second light source to illuminate the plant with a first and a second predetermined base level radiant flux, respectively;

introduce a minor variation to at least one of the first and the second base level radiant flux;

determine, by the at least one sensor, a first level of reflected light within the first wavelength range and a second level of reflected light within the second wavelength range;

estimate a marginal reflectance based on the first and the second levels of reflected light from the plant within the first and second wavelengths ranges, wherein the marginal reflectance comprises a derivative of the first or the second levels of reflected light with respect to the first and the second predetermined base level radiant flux, respectively; and

adjust a radiant flux of light emitted by the first light source such that the marginal reflectance within the first wavelength range stands in a predetermined relation to the marginal reflectance within the second wavelength range.