Monitoring the number and size of pests based on modulated infrared beam sensing technology

in order to identify the number and size of pests, a sensor based on modulated infrared sensing technology with narrow-line laser beam was developed. a mathematical model between the light current change and time was established when a pest passed through the sensor. this model indicated that the factors that influence light current change not only involved the pest dimensions but also other dimensions, such as the width of narrow-line laser beam and the height between the taper collecting mouth and the narrow-line laser beam. therefore, information on pest numbers and dimensions, obtained from similar sensors in previous literature was inaccurate. however, quantitative analysis of the model showed that the external dimensions could be neglected if an appropriate width of the narrow-line laser beam was selected. hence, it was set at 0.0005 m in this sensor. experimental results indicated that the sensor could eliminate the influence of ambient light and had a good precision of pest counting and classifying, which were larger than 98 and 86.7% respectively.