What is the principle of automatic correction device for PE extrusion laminating machine ?

What is the principle of automatic correction device for PE extrusion laminating machine? Which sensors (ultrasonic, photoelectric, pneumatic, etc.) are commonly used?

What is the difference between these sensors?

The automatic correction device is a system that automatically detects and controls the lateral position of the tape. It is through the sensor to detect the edge or edge of the tape (substrate), the use of the control system to calculate the lateral position of the fluctuations or errors, and issued an error correction instructions, by the implementing agencies to correct the horizontal position of the tape.

Commonly used sensors are ultrasonic sensors, photoelectric sensors and pneumatic sensors. Ultrasonic sensors are available for all materials and are generally used for heel. Photoelectric sensors are mainly used for the line, but can not be used in the transparent substrate with the edge. Pneumatic sensors are suitable for all materials with the edge, but the general accuracy is low.