Optoelectronic device for automatically inspecting a group of cigarettes or the like

An optoelectronic apparatus for detecting when a cigarette is missing from a preformed group of cigarettes and when a cigarette in said group is improperly filled, said group normally having a predetermined number of cigarettes arranged in columns and rows, said group being conveyed to a position proximate said apparatus, said apparatus comprising:

• a plurality of photodetectors equal in number to said predetermined number, said photodetectors being arranged in columns and rows corresponding to said columns and rows of cigarettes in said group such that there is a one-to-one correspondence between a photodetector and each cigarette in said group;
• each said photodetector including a light-emitting source for illuminating the end portion of a cigarette registered with said photodetector when power is applied thereto and a photoelectric transducer for producing a signal in response to light reflected from the end portion of said registered cigarette;
• sequence circuitry connected to said light-emitting sources for controlling power to said light-emitting sources, said sequence circuitry modulating the power applied to said light-emitting sources at a high frequency so that the intensity of said light-emitting sources alternately increases and decreases producing modulated light;
• AC-coupling circuitry connected to said photoelectric transducers for passing only high frequency components of said photoelectric transducer signals resulting from modulated light reflected from said end portions;
• amplifier circuitry connected to said AC-coupling circuitry for amplifying said high frequency components of said photoelectric transducer signals passed by said AC-coupling circuitry;
• rectifier circuitry connected to said amplifier circuitry for converting said high frequency components passed by said AC-coupling circuitry and amplified by said amplifier circuitry to a DC signal;
• filter circuitry connected to said rectifier circuitry for smoothing said DC signal;
• threshold adjusting circuitry for presetting a threshold signal that each said DC signal must equal or exceed to indicate the presence of a properly filled cigarette;
• and
• comparison circuitry connected to said filter circuitry and to said threshold adjusting circuitry for producing a reject signal when at least one said smoothed DC signal is less than said threshold signal.

A method for detecting when a cigarette is missing from a preformed group of cigarettes and when a cigarette in the group is improperly filled, the group normally having a predetermined number of cigarettes arranged in columns and rows, including the steps of:

• conveying the group to a position proximate a plurality of photodetectors equal in number to the predetermined number, the photodetectors being arranged in columns and rows corresponding to the columns and rows of cigarettes in the group such that there is a one-to-one correspondence between a photodetector and each cigarette in the group, each photodetector including a light-emitting source for illuminating the end portion of a cigarette registered with the photodetector when power is applied thereto and a photoelectric transducer for producing a signal in response to light reflected from the end portion of the registered cigarette;
• modulating power to the light-emitting sources at a high frequency such that light emanating from each light-emitting source alternately increases and decreases in intensity as the end portion of each cigarette in the group is illuminated;
• comparing the high frequency components of each photoelectric transducer signal with a preselected threshold signal;
• and
• producing a reject signal when the high frequency components of at least one photoelectric transducer signal are less than the preselected threshold signal;
• thereby minimizing the effects of varying ambient light on the accuracy with which missing and improperly filled cigarettes are detected.