Abstract: A blister pack scanning device for detection and removal of overfilled or defective pharmaceutical blister packs is comprised of a photoelectric LED transmitter and sensor with a scanning beam channel bar disposed therebetween. The blister pack web is passed below the bar through a space precisely equivalent to the thickness of a properly filled blister. Overfilled or improperly molded blisters will contact a beveled edge of the bar as the web passes thereunder and the lateral movement forces the bar and its two end plates which are in juxtaposition to the transmitter and receiver respectively, to move upward, thereby interfering with the beams transmission. The interference created thereby shuts off the blister production machine and sounds an alarm for removal of the defective package.