7Kocher M F, Lan Y, Chen C, et al. Opto-electronic sensor system for rapid evaluation of planter seed spacing uniformity[J]. Transactions of the ASAE, 1998,41 ( 1 ) :237 - 245.
8Onal Okan, Onal Ismet. Development of a computerized measurement system for in-row seed spacing accuracy[J]. Turkish Journal of Agriculture and Forestry, 2009,33 (2) :99 - 109.
9Lan Y, Kocher M F, Smith J A. Opto-electronic sensor system for laboratory measurement of planter seed spacing with small seeds [ J ]. Journal of Agricultural Engineering Research, 1999,72 (2) : 119 - 127.