referring now specifically to the drawings , and the illustrative embodiments depicted therein , a combine or harvester 10 , according to the invention , includes a laser assembly 11 having at least one laser source 12 projecting a laser in the nature of a beam of photons “ b ” positioned to intersect the stalk of a plant “ p ” ( fig1 and 2 ). laser assembly 11 is supported by a vehicle 14 . vehicle 14 may be a conventional harvester of the type disclosed in u . s . pat . no . 4 , 408 , 441 , the disclosure of which is hereby incorporated herein by reference . as such , laser assembly 14 may be a retrofit kit to replace the mechanical cutters of the harvester while utilizing the propulsion system and gathering arms of the combine . alternatively , laser assembly 11 may be supported by a vehicle 14 having pneumatic tires 18 and a lightweight frame to reduce compaction of the soil . wheels 18 may be mounted with hydraulic lifts ( not shown ) and a control to keep the body of vehicle 14 level , notwithstanding variation in terrain . pneumatic tires 18 are less likely to loosen the upper surface of the soil . moreover , support 14 has a weight that is significantly less than that of mechanical combines . accordingly , the tendency for tires 18 to compact the soil is significantly reduced over mechanical combines . a generator 16 , which may be supported by vehicle 14 , is provided to supply electrical energy to power laser assembly 11 . preferably , assembly 11 is a plurality of lasers 12 laterally arranged in a laser , as illustrated in fig2 . most preferably , the plurality of lasers is moved , such as by scanning , or the like , laterally from the solid line position illustrated in fig2 to the phantom position illustrated in fig2 . this allows a fewer number of lasers to be utilized to cut the stalks of plants “ p .” in the illustrated embodiment , lasers 12 cover a cutting distance “ d ” laterally of the movement of support 14 . preferably , distance “ d ” is on the order of one foot and is , most preferably , in the range of 12 inches to 14 inches . generator 16 is sized to supply the power requirements of lasers 12 . by way of example , if eight laser assemblies are utilized , and each require 1 kilowatt of power , then generator 16 would be at least 8 kilowatts in size . in the illustrated embodiment , support 14 scans lasers 12 at a rate of on the order of one cycle per second . however , other rates may be appropriate for the application . the lasers 12 may be moved by a purely lateral motion , as illustrated in fig2 . alternatively , they can be swept in a fan shape motion as would be suggested to the skilled artisan . laser 12 has a focal length that is less than one foot in length , and may be less than one - half of a foot in length , and may be four inches or less . this reduces the necessity for shielding around lasers 12 to protect individuals in the area in which combine 10 is operating from damage resulting from contact with beam “ b ,” such as by the beam contacting the eyes of the individual . it is advantageous to reduce the necessity for any special shielding around laser 12 because such shield may reduce the effectiveness of its operation in cutting the stalks of plants “ p .” an advantage of combine 10 is that it cauterizes the stalk , as seen in fig5 in which the surface of the cut is relatively uniform and exposes channels in the stalk . this is an advantage over the cut produced by mechanical cutting of the stalk , as illustrated in fig4 in which glucose may ooze from the many exposed channels ch in the cut thereby reducing the yield of sugar . advantageously , by cauterizing the cut , the present invention facilitates the cutting of the stalk into multiple short pieces , or segments , s , as illustrated in fig3 by a series of cuts c to each stalk p . combine 10 may cut the sugarcane into lengths of less than one foot , less than one - half of a foot , and even as low as approximately four inches or less without concern from glucose weeping from each cut c . as seen in fig3 the producing of multiple short pieces of stalk results in a cutting of the foliage f thereby cutting excess lengths of foliage f from the stalk . this allows the foliage to be removed at the site , such as by tumbling the stack while passing the stalk and foliage through a fluid jet , such as a jet of compressed air . an example of an apparatus that may discharge the separated excess foliage is as disclosed in u . s . pat . no . 5 , 092 , 110 , the disclosure of which is hereby incorporated herein by reference . this separates the foliage from the stalk such that the foliage may be immediately returned to the soil without being hauled to and from the processing plant . this reduces the cost of processing the foliage . furthermore , the stalk can be more quickly processed without the necessity for a separate stalk - removing procedure at the processing plant . this further increases the yield of sugar because of the initiation of conversion of glucose to sugar begins as soon as the plant is cut . in the illustrated embodiment , combine 10 initially cuts the stalk close to the ground with the remaining cuts that divide the stalk into small pieces being performed when the stalk is supported by support 14 . in order to control the height of the initial cut “ c ,” a height control mechanism 20 may be provided to control the height of laser assembly 11 . height control mechanism 20 is a non - contact sensor that senses distance to the soil and a control that adjusts to that level selected by an operator . height control mechanism 20 may be a laser - based control , a camera - based control , an ultrasonic - based control , a radar - based control , a mechanical sensor , or the like , which are known in the art . by way of example , such height control mechanism may be of the type disclosed in u . s . pat . no . 5 , 327 , 345 , the disclosure of which is hereby incorporated herein by reference . because height control mechanism 20 is capable of guiding position of laser assembly 1 without constant intervention by an operator , it is no longer necessary to burn the foliage around plants to allow an operator to view the interface between the soil and the sugarcane . this avoids the problems created by burning in the past . another laser assembly ( not shown ) may be supported by vehicle 14 in a position to cut off tops of the sugarcane stalks . this additional laser assembly may be manually controlled in vertical height by an operator , which is feasible because sugarcane stalk tops are somewhat consistent in height . however , a height control similar to mechanism 20 could also be used to control a laser assembly to cut sugarcane stalk tops . thus , it is seen that the present invention provides a unique combine and method of harvesting a plant having a stalk , which is more efficient at processing the stalks , as set forth above . in addition to facilitating the removal of foliage at the site , wherein the foliage can be immediately returned to the soil , the present invention produces less soil compaction and less disturbing of the top layer of the soil . this reduces the need for subsequent aeration of the soil and the likelihood that the trucks hauling the sugarcane to the processing plant will transfer loose soil from the field to the road . furthermore , the necessity for hauling only the stalk , and not the foliage , to the processing plant reduces the number of loads that must be hauled for each unit of output . furthermore , the need to burn foliage is advantageously removed . the present invention makes use of commercially available lasers , which are capable of having their photon beam focused in response to an output from a control . however , the invention may also be used with a laser whose photon beam is permanently focused at a focal length “ f ” selected in the manner set forth above . although the invention is most advantageous in harvesting sugarcane , its use in other stalk - based crops , such as corn , will be apparent to those skilled in the art . furthermore , as set forth above , the invention may be applied to other uses , such as a bush hog , or the like . changes and modifications in the specifically described embodiments can be carried out without departing from the principles of the invention , which is intended to be , limited only by the scope of the appended claims , as interpreted according to the principles of patent law including the doctrine of equivalents .
a method of harvesting a stalk - based plant , such as sugarcane , includes generating at least one laser beam and causing the at least one laser beam to at least momentarily come into contact with the sugarcane stalk . this severs the stalk and cauterizes the stalk where severed .