An active infrared induction instrument powered by a dry battery capable of reducing power consumption through the adjustment of the emitter pulse width. The infrared emitted LED emits infrared signals, which, after being reflected by an object, are received by the infrared photodiode. The infrared signals received the infrared signals received by the infrared photodiode then enter an integrated circuit chip through a comparator. The pulse widths of the infrared emission pulse signals are dynamically adjusted after the width of the pulse series is received by the discrimination chip, thus reducing the emission power consumption to save energy.