Photoelectric opposite-type bidirectional length measuring apparatus

The utility model relates to a steel pipe automatic length measuring apparatus on a finishing line of a steel pipe plant, in particular to a photoelectric opposite-type bidirectional length measuring apparatus which adopts photoelectric opposite-type positioning and bidirectional movable measurement. The photoelectric opposite-type bidirectional length measuring apparatus is formed by two symmetrically arranged length measuring units. Each length measuring unit comprises a base; oriented linear guide rails and a sliding block, a gear and a rack both for transferring power, a power element, photoelectric opposite-type switches, a speed reduction switch, zero switches and a drag chain unit are installed on the base; the power element consists of a moving trolley with a sliding block, a servo motor and a speed reduction unit; the photoelectric opposite-type switches and the speed reduction switch are used for detecting a steel pipe; the zero switch is used for judging a starting point; and the drag chain unit co