Distance compensation for infrared sensors used for total temperature measurements of large area canopy

Measuring the total temperature of large area crop canopy is of great significance for grasping crop growth conditions. However, it is difficult to realize real-time measurements of the total temperature of large area canopy with traditional methods. The previously developed sensor based on the infrared detection technique for canopy temperature measurements achieved a large field of view (FOV) of 53.2° through the designed infrared optical system. The developed sensor allows the no-contact measurement of the total temperature of large area canopy. However, due to the influence of atmospheric transmission efficiency, the output data of the sensor are affected by the measurement distance. In this paper, we analyzed the influencing mechanism of the measurement distance on the measurement results and provided the distance compensation model to eliminate the influences of the measurement distance. With the distance compensation model, the measurement errors caused by the measurement distance are reduced from 1.4 °C to 0.2 °C. In addition, we added an ultrasonic module to the original sensor and designed a new type of sensor. After the verification through field experiments, the experiment results show that the advanced sensor can weaken the influence of the measurement distance effectively