Sensor and method of detecting the condition of a turf grass

Abstract

A method of detecting the condition of a turf grass is described. According to one aspect of the invention, the method comprises steps of attaching an active sensor to a mower; traversing a section of turf grass; and processing the output of the sensor. A device for detecting the condition of turf grass is also disclosed. The device comprises an array of illuminating devices generating a pattern of illuminating light; a detecting device receiving a pattern of reflected light which is coincident with the pattern of illuminating light; a detecting device adapted to detect stray light from the may of illuminating devices; and a feedback loop controlling the array of illuminating devices. A system employing the device is also disclosed.

1 . A method of detecting a condition of a turf grass, said method comprising the steps of:
 providing a plurality of illumination devices;   coupling a feedback circuit to adjust an output of each illuminating device of said plurality of illuminating devices;   detecting an irradiance of each illuminating device of said plurality of illuminating devices; and   adjusting the irradiance of an illuminating device of said plurality of illuminating devices.   
     
     
         2 . The method of  claim 1  wherein said step of providing a plurality of illumination devices comprises providing a plurality of illumination devices in concentric circles. 
     
     
         3 . The method of  claim 2  wherein said step of adjusting an irradiance of an illuminating device of said plurality of illuminating devices comprises adjusting illumination devices based upon said concentric circles. 
     
     
         4 . The method of  claim 2  further comprising a step of providing different frequencies per concentric circles. 
     
     
         5 . A device for detecting a condition of turf grass, said device comprising:
 an array of illuminating devices generating a pattern of illuminating light;   a detecting device receiving a pattern of reflected light which is coincident with said pattern of illuminating light;   a detecting device adapted to detect an entity proportional to a light output from said array of illuminating devices; and   a feedback loop controlling said array of illuminating devices.   
     
     
         6 . The device of  claim 5  wherein said array of illuminating devices comprises LEDs having a plurality of modulation frequencies. 
     
     
         7 . The device of  claim 5  wherein said feedback loop comprises a first demodulator for a first frequency and a second demodulator for a second frequency. 
     
     
         8 . The device of  claim 5  wherein said detecting device detects stray light from said array of illuminating devices. 
     
     
         9 . A device for detecting a condition of turf grass, said device comprising:
 an array of LEDs generating a cone of illuminating light;   a photodetector receiving a cone of reflected light which is coincident with said cone of illuminating light;   one or more photodetectors adapted to detect light from said array of LEDs; and   a feedback loop controlling said array of LEDs based upon light from said array of LEDs.   
     
     
         10 . The device of  claim 9  wherein said array of LEDs comprises LEDs having a plurality of modulation frequencies. 
     
     
         11 . The device of  claim 9  wherein said feedback loop comprises a first demodulator for a first frequency and a second demodulator for a second frequency. 
     
     
         12 . The device of  claim 9  further comprising a circuit for providing offset correction. 
     
     
         13 . The device of  claim 12  wherein said circuit for providing offset correction comprises a first offset correction circuit for a first frequency and a second offset correction circuit for a second frequency. 
     
     
         14 . The device of  claim 9  further comprising a background light subtraction circuit. 
     
     
         15 . The device of  claim 9  wherein said detecting device detects stray light from said array of illuminating devices. 
     
     
         16 . The device of  claim 5  wherein said feedback loop comprises more than one demodulator for more than one frequency. 
     
     
         17 . An apparatus comprising:
 a plurality of light-emitting diodes;   at least one photodiode; and   circuitry operative to provide a constant output by the plurality of light-emitting diodes in response a representative portion of light sensed by the at least one photodiode;   wherein the plurality of light-emitting diodes and the at least one photodiode are positioned with respect to one another to provide an even weighting of light into the at least one photodiode.   
     
     
         18 . The apparatus of  claim 17  wherein the plurality of light-emitting diodes and the at least one photodiode are arranged in a circular array. 
     
     
         19 . The apparatus of  claim 18 , wherein a distance between one of the at least one photodiode and one of the plurality of light-emitting diodes is given by:
     d   i   =x ·cos(θ i )+√{square root over ( x   2 ·cos 2 (θ i )− x   2   +r   i   2 )}
   
       Where r is a radius of the circular array, x is the distance from a center of the circular array to the one of the at least one photodiode, and θ is an angle between a normal to the one of the at least one photodiode and the one of the plurality of light-emitting diodes.