METHOD OF DETERMINING QUALITY OF TUBULAR BULB

PURPOSE:To improve the reliability of quality determination by geneating a defective product signal only when the electric signal level caused by the transparent light from a bulb exceeds the integrated signal level. CONSTITUTION:A projection light source 2 illuminates the bulb surface of a fluorescent lamp 1 and transparent light is detected by a photoelectric conversion camera 3 by circumferentially rotating the bulb. The optical signal of a dark and shade picture on the bulb surface condensed by a lens is focused on an internal photoelectric conversion element and each photoelectric conversion element generates the electric signal in proportion to the dark and shade picture. The electric signal is directly input to a comparator 6 and is converted into an integrated signal by an integrated circuit 5 through an amplifier circuit 4 and then is input to the comparator 6. The comparator 6 compares the electric signal with the integrated signal. When there is a defect on the bulb surface, since the electric signal level of the photoelectric conversion camera 3 instantaneously exceeds the integrated signal level of the integrated circuit 5, a defective device signal is generated from a logic memory circuit 7 in this case.