In order to achieve index of thin film production

using linear array CCD to carry out data acquisition and measurement

reflective infrared photoelectric sensor as feedback control

and field programmable gate array（ FPGA） is used as core controller

design a high precision thin film width control instrument. The device can detect width of the produced thin film accurately

at the same time

compare it with setting value of production requirements

then realize pneumatic switch control. Through experimental analysis

the system improves precision and reliability of the whole production process.