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Light sensor with modulated radiant polychromatic sourceRelated Patent Categories: Radiant Energy, Photocells; Circuits And Apparatus, Optical Or Pre-photocell System, Controlled By Article, Person, Or AnimalLight sensor with modulated radiant polychromatic source description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060208171, Light sensor with modulated radiant polychromatic source. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] This invention is a continuation in part to U.S. patent application Ser. No. 10/703,256 BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] This invention relates to a structure and a method for determining changes in the chlorophyll status of a plant via remote sensing of the plant's reflectance spectrum spanning from approximately 650 nm to 800 nm. [0004] 2. Description of Related Art [0005] In order to manage our natural resources in an efficient and cost-effective manner, producers and turf professionals need a way in which to measure and assess the health and performance of their landscapes. For example, the need to know when and how much fertilizer (nitrogen) and other nutrients to apply to a plant to elicit the appropriate growth response is primarily guess work to the producer. Because nitrogen is required by the plant in the greatest quantities and because nitrogen is rather mobile in soils, producers have practiced a one time application of nitrogen to cover the crops need for the entire growing season. However, over application of nitrogen on agricultural and commercial landscapes has resulted in the contamination of ground and surface waters. The primary vectors for water contamination are run-off and leaching. Nitrate-nitrogen is the most common contaminant found in U.S. groundwater. Nitrate contamination is increasing both in area and concentration, particularly beneath landscapes dominated by corn production. It is estimated that 1.8.times.10.sup.9 kilograms of nitrates wash into the Gulf of Mexico from the Mississippi River basin each year. Of this amount, 55% of the nitrogen released into the basin can be attributed to agricultural fertilizers with only a 3% contribution attributable to non-agricultural fertilizer application primarily on turf for lawns and recreational land (CAST, 1999). [0006] Techniques to remotely measure crop status include the use of a spectroradiometer and other instruments (Bausch et al. 1994; Chappelle et al. 1992; Maas and Dunlap, 1989), aerial photography (Benton et al, 1976), and satellite imagery. [0007] The techniques listed above are not without their limitations. For example, early research by Resource21.TM. determined that during the optimal fly over times between 10 a.m. and 11 a.m. for satellite imaging, cloud cover had adverse affects on visibility. It was found that during the 10 am to 11 am time frame, fields in Colorado were visible approximately 80% of the time while eastern Nebraska fields were visible approximately 50% of the time. This trend in decreased visibility continued the farther east that data was collected. Also, spatial resolution for satellite imagery is poor (Landsat, 20 meter and panchromatic, 10 meter). Similar problems plague aerial photographic methods as well. While aerial imagery has better spatial resolution (typically less than 3 meters) than satellite imaging, partial cloud cover can shade sections of fields giving biased or incorrect reflectance measurements. Both techniques, however, suffer from the need for extensive data processing (performed by third party providers at high cost and long lead time) and geo-referencing issues. Even with spectroradiometric methods using sunlight as the ambient light source, cloud cover and time of day (8 a.m. to 8 p.m.) demands limit the mainstream acceptance of the technology for addressing the nitrogen rate over-loading problem. What is needed is an on-the-go type sensor that overcomes the time of day and fair-weather issues surrounding the aforementioned measurement techniques. [0008] In certain crops or plant varieties, nutrient deficiencies constitute only part of the management problem. In particular, the basic problem of determining or monitoring plant status with respect to stress whether it stems from nutrient, water, pest, disease, or otherwise is of primary concern. For instance, turf stress determination is of major concern for the turf manager. Earlier detection can protect the health of the grass but also reduce the cost of restoring the badly damaged turf to good health. Turf stress can be due to many causes such as water, pest, nutrient, heat, disease, and the like. By detecting changes in the turf landscape early, turf quality can be maintained and costly restoration operations can be reduced or eliminated. On the other hand, being able to control the degree of stress is important for some producers. Grape producers, for example, like to control the degree of water stress prior to harvesting in order to control disease and increase the sugar content of the grape. SUMMARY OF THE INVENTION [0009] The new sensor of the present invention overcomes the time-of-day and fair weather limitations of passive technologies by incorporating its own radiant source and by rejecting the influence of ambient light on the measured canopy reflectance. Unlike passive sensor technology, this sensor will be able to operate under completely dark or full sun conditions. Additionally, the new sensor apparatus is an improvement both in performance and cost over competing active-sensor technologies commercially available. [0010] As discussed above, the invention presented here will be advantageous in a number of commercial applications. For site-specific agricultural applications, the developed sensor would allow the producer to reduce the amount of nitrogen fertilizer applied to a crop or facilitate spoon-feeding the crop during the growing season, thus having the potential for lowering production costs and enhancing environmental quality. Also, by being able to determine the appropriate fertilizer needs of the crop at any given location in the field, the producer can apply only the fertilizer needed to prevent yield loss or degradation of product quality (i.e., protein content in wheat and barley or sugar content in sugar beets). Subsequently, decreased fertilizer rates will substantially lower nitrogen runoff and leaching losses, which will improve the health of our watersheds, waterways, lakes, and oceans. In addition, data produced by the sensor may be used to produce relative yield maps for forecasting crop production. As for turf grass applications, the sensor technology would allow turf managers to map changes occurring on turf landscapes or for monitoring the status of turf quality. [0011] In accordance with the present invention, structures and methods are provided for assessing plant status using the chlorophyll status changes and/or biomass properties of the plant remotely sensed, in the red-edge portion of the vegetative reflectance spectrum (.about.650 nm to .about.800 nm), thereby allowing selective monitoring or treatment of individual plants. [0012] When incorporated into variable rate applicator and/or sprayers systems, the present invention significantly reduces the use of fertilizers by precisely applying agricultural products to individual plants to be treated or eliminated. Moreover, the present invention is operable under a wide variety of conditions including cloudy conditions, bright sunlight, artificial illumination, or even total darkness. The advantage to the producer is that field operations do not have to be timed to daytime sunlight hours for operation. [0013] All embodiments of the invention can be used in two primary ways. The first method of use includes the application of the invention to handheld instrumentation. Here the invention is utilized to measure plant canopies held in hand by a producer, turf manager, researcher, and the like. The invention includes the use of GPS for geo-referencing data collected by the invention. A second method of use includes applications where the sensor is mounted a moving object such as a tractor, mower, center pivot/linear irrigator, or the like. Again, data may be geo-referenced using GPS for mapping and data layer (GPS maps, soil maps, etc.) integration. Problem areas can be logged and reviewed later by the producer or land manager for analysis and site management decisions. [0014] An object of the invention is to provide a sensor for remotely sensing plant status using biophysical and biochemical properties of the plant thereby allowing selective monitoring, elimination, or treatment of individual plants. [0015] This and other objects of the invention will be made apparent to those skilled in the art upon a review of this specification, the associated drawings and the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS [0016] FIG. 1 is a graphical representation of the effect of nitrogen rate on the plant reflectance curve over the visible and near infrared portion of the spectrum. [0017] FIG. 2 is a graphical representation of plant reflectance curves over the visible and near infrared portion of the spectrum with the red-edge portion of the spectrum emphasized. [0018] FIG. 3 is a side and bottom view of a sensor of the present invention. [0019] FIG. 4 is a functional block diagram of a preferred embodiment of the present invention. [0020] FIG. 5 is a diagram of a circuit used to generate a light source of the present invention. [0021] FIG. 6 shows diagrammatically a sensor based mapping system of the present invention. Continue reading about Light sensor with modulated radiant polychromatic source... Full patent description for Light sensor with modulated radiant polychromatic source Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Light sensor with modulated radiant polychromatic source patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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