DEVICE TO RECOGNIZE OBJECTS, PREDOMINANTLY AGRICULTURAL PLANTS AND METHOD DETERMINING LOCATION OF PLANT Russian patent published in 1999 - IPC

FIELD: selective killing of weeds when treating cultivated crops. SUBSTANCE: high-speed modulation of two light radiators 201, 202 is employed to ensure selective killing of weeds. Each radiator emits radiation with different length of wave. Modulation realized with use of switching on and off of one radiator is phase shifted through approximately 90 deg relative to modulation of illuminated section of surface. Light beams 203, 204 formed by radiator are reflected from plant 206 or ground and are received by photodetector. As plants have typical spectral reflecting power within range of electromagnetic spectrum that can be distinguished from reflecting power of background relative amplitudes of reflected radiation on two lengths of waves of radiators vary depending on reflection of radiation from plant or ground. Ratio of radiations on two lengths of waves received by photodetector is converted to phase. This phase is compared with initial reference phase of modulation of one of radiators. Controller 221 uses this phase information to determine presence or absence of plant and then initiates killing of weed. EFFECT: improved efficiency of device and method. 41 cl, 8 dwg