Cigarette rod optical inspection

A method of inspecting cigarettes or other continuous rods of the tobacco industry comprising disposing a plurality of focussed light emitter-detector units at circumferentially-spaced positions around a rod being inspected, each unit being arranged to propagage focused light onto a defined surface region of the rod and to receive the light reflected from that surface region and further arranged to generate an electrical signal related to the intensity of the received light;

• multiplexing the intensity related signals from said units;
• transferring the multiplexed signals to a remote location;
• demultiplexing the signals at said remote location;
• and processing the signal from each unit by continually averaging the signal, comparing the averaged signal with the instantaneous signal from that unit, and generating a fault signal if the instantaneous signal differs from the averaged signals by more than a preset percentage.

An inspection device for a continuous cigarette rod comprising means for guiding a continuous cigarette rod along a predetermined path extending through an inspection station;

• means including a plurality of light emitters for directing focused beams of light at circumferentially-spaced positions around said rod at said inspection station;
• means including a plurality of light detectors at circumferentially-spaced positions around the path of the rod at said inspectin station for detecting light from respective light emitters after reflection from said rod and for producing respective electrical signals representative thereof;
• multiplexing means for multiplexing the signals produced by said light detectors at said inspection station and for transmitting said multiplexed signals to a remote location;
• and control means at said remote location which is responsive to said multiplexed signals for generating a fault signal when any one of said multiplexed signals falls below a predetermined value.