| 摘要 |
PURPOSE:To obtain binary signal corresponding to bar code irrespective of variation of amplitude value of optical signal or background level by a method wherein white or black bars in bar code applied to a measuring specimen are converted into electric binary signals and two comparators act as floating level comparators. CONSTITUTION:Bar codes 71-73 applied to a measuring specimen are arranged so that bar code 72 is delayed with respect to bar code 71 by 1/4 cycle for pitch P of a pair of bars, and bar code 73 is delayed with respect to bar code 71 by 1/4 cycle. Optical signals a1-a3 obtained from optical fibers 62-64 corresponding to bar codes 71-73 are amplified by amplifiers 8-10, respectively. Output of the amplifier 8 is entered in one input of a comparator 20 and output of the amplifier 9 supplied thereto as reference signal, and further output of the amplifier 9 is entered in one input of a comparator 30 and output of the amplifier 10 is supplied thereto as reference signal, thus binary signals are obtained. Since the comparators 20, 30 act as floating level comparators, phase difference and duty ratio of the binary signals are constant. |
