Light sensing instrument with modulated polychromatic source
First Claim
1. A light sensor for measuring the reflectance of an object, comprising:
- (a) a polychromatic light source simultaneously emitting visible light and infrared light with a modulator of the light source, and apparatus to set and monitor optical power of the light source;
(b) a reflected light receiver comprised of an array of photodetectors comprised of at least one photodetector sensitive to visible light positioned to receive reflected light originating from the light source and including ambient light compensation means for reducing the effects of ambient light on the photodetector and a first output, and at least one photodetector sensitive to nonvisible light positioned to receive reflected light originating from said light source and including an ambient light compensator for reducing the effects of ambient light on said second photodetector and a second output;
(c) a detector for distinguishing the light originating from the light source and light reflected by the object from ambient light; and
(d) a computational device for performing calculations based on reading the first output, reading the second output and the light source power.
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Accused Products
Abstract
An apparatus is described for assessing plant status using biophysical and biochemical properties of the plant remotely sensed by the invention thereby allowing selective monitoring, elimination or treatment of individual plants. In a preferred embodiment, a single polychromatic emitter provides coincident light beams; one beam substantially in the visible portion of the spectrum (400 nm to 700 nm) and the other in the near infrared (NIR) portion of the spectrum (700 nm to 1100 nm). This light beam illuminates a small surface area on the ground, which may be bare ground, desired plants or undesired weeds. The beam of light may be focused, collimated or non-focused. A detector array, usually composed of a visible detector and a NIR detector, detects portions of this polychromatic light beam reflected by the surface area and provides a signal indicative of whether the detected light was reflected by a plant or by some non-plant object such as soil. A controller analyzes this signal and, assuming a plant is detected, responds by activating a device to take some action with respect to the plant or stores the analyzed signal with corresponding DGPS position in the controller'"'"'s memory for later analysis. A number of actions may be taken by the controller. For instance, if the plant is a weed, the desired action might be to spray herbicide on the weed. Or, if the plant is a crop that is determined to be lacking in nutrient, the desired action may be to apply fertilizer. Additionally, if the plant under test is a turf landscape, such as found on golf courses and sporting fields, plant biomass may be mapped and geo-located using GPS for later, comparative analysis.
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Citations
18 Claims
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1. A light sensor for measuring the reflectance of an object, comprising:
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(a) a polychromatic light source simultaneously emitting visible light and infrared light with a modulator of the light source, and apparatus to set and monitor optical power of the light source; (b) a reflected light receiver comprised of an array of photodetectors comprised of at least one photodetector sensitive to visible light positioned to receive reflected light originating from the light source and including ambient light compensation means for reducing the effects of ambient light on the photodetector and a first output, and at least one photodetector sensitive to nonvisible light positioned to receive reflected light originating from said light source and including an ambient light compensator for reducing the effects of ambient light on said second photodetector and a second output; (c) a detector for distinguishing the light originating from the light source and light reflected by the object from ambient light; and (d) a computational device for performing calculations based on reading the first output, reading the second output and the light source power. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A light sensor for measuring the fluorescence of a plant, comprising:
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(a) a polychromatic light source simultaneously emitting visible light and infrared light with a modulator of the light source, and apparatus to set and monitor optical power of the light source; (b) a reflected light receiver comprising a first photodetector sensitive to light between about 690 nm and about 720 nm and positioned to receive emitted light originating from the plant due to the excitation by the light source;
an ambient light compensator for reducing the effects of ambient light on the first photodetector; and
a first output;
a second photodetector sensitive to light between about 720 nm and about 780 nm positioned to receive emitted light originating from the plant due to excitation by the light source;
an ambient light compensator for reducing the effects of ambient light on the second photodetector; and
a second output;(c) a detection means for distinguishing the light originating from the light source and emitted by the plant from ambient light; and (d) a computational device to calculate a measurement based on reading the first output and reading the second output and light source power. - View Dependent Claims (13)
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14. A light sensor for measuring the reflectance of an object, comprising:
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(a) a solid-state polychromatic light source emitting light simultaneously in the visible spectrum and the infrared spectrum, a means of modulation of the light source, and a means to set and monitor optical power of the light source; (b) a reflected light receiver comprising a first photodetector sensitive to visible light positioned to receive reflected light originating from the light source, ambient light compensation means for reducing the effects of ambient light on the first photodetector; and
a first output, a second photodetector sensitive to nonvisible light positioned to receive reflected light originating from said light source, and ambient light compensation means for reducing the effects of ambient light on said second photodetector; and
a second output;(c) a detection means for distinguishing the light originating from said light source and reflected by an object from ambient light; and (d) a computational device to perform a calculation based on reading said first output, said second output and said light source power.
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15. A method for measuring the reflectance of a plant, comprising the steps of:
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(a) simultaneously projecting light of a first, visible wavelength from a solid-state polychromatic light source and light of a second, infrared wavelength from the light source, modulating the light source, and setting and monitoring optical power of the light source; (b) receiving reflected visible light originating from the light source in a reflected light receiver comprising a first photodetector sensitive to visible light, and reducing the effects of ambient light on the first photodetector in an ambient light compensator; and
a first output;(c) positioning a second photodetector sensitive to infrared light to receive reflected infrared light originating from the light source, and reducing the effects of ambient light on said second photodetector in an ambient light compensator; and
a second output;(c) distinguishing the light originating from said light source and reflected by the object from ambient light; and (d) calculating in a computational device a vegetative index based on reading said first output and said second output and light source power. - View Dependent Claims (16, 17)
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18. A light sensor for measuring the reflectance of an object, comprising:
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(a) a single light source that simultaneously illuminates a substantially identical area with both visible and nonvisible light with a modulator of the light source, and apparatus to set and monitor optical power of the light source; (b) a reflected light receiver comprised of an array of photodetectors comprised of at least one photodetector sensitive to visible light positioned to receive reflected light originating from the light source and including ambient light compensation means for reducing the effects of ambient light on the photodetector and a first output, and at least one photodetector sensitive to nonvisible light positioned to receive reflected light originating from said light source and including an ambient light compensator for reducing the effects of ambient light on said second photodetector and a second output; (c) a detector for distinguishing the light originating from the light source and light reflected by the object from ambient light; and (d) a computational device for performing calculations based on reading the first output, reading the second output and the light source power.
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Specification