Which type of packaging machine using encoder optic sensor?

I think,Ecoder optic sensors are used in bottle filling machines.These machines require precise measurement of the distance a conveyor belt travels,then the encoder optic sensorsare used in order to determine the exact distance the conveyor belt has moved forward.

Pepper & Fuchs incremental Rotary Encoders.

Used in precise positioning...such as packing filling on conveyors ,incremental encoders type  used