PURPOSE: To read the length of an original accurately by disposing two pieces of photosensors in the feed direction of the original at the spacing slightly larger than the diameter of the punched hole of an original paper.

CONSTITUTION: The preceding end of an original 3 fed in an arrow direction is detected through reflection by a photosensor 1. When a punched hole P passes under the sensors 1, 2, the presence of the paper 3 is detected by either of the sensors 1, 2 because the spacing (d) between the sensors 1, and 2 is slightly larger than the diameter of the hole P; therefore, the succeeding end of the original paper is detected with the sensor 2. The length of the paper 3 detected with the sensor is thus longer by (d) than the actual size and is longer by d/v (v is the traveling speed of the original 3) in time. To correct such errors, the pulses 6 of the frequency proportional with the (v) are generated by an encoder, and are consumed by as much as the count number equal to the time d/v by a counter 7, and the pulses 8 after such consumption are counted, whereby the length of the original is obtained accurately.