| 摘要 |
PURPOSE:To measure the length of a medium and to take an accurate measurement without any influence of variation in feed speed nor backing by counting up and down in a feed direction in response to each pulse generated for every constant movement extent. CONSTITUTION:The measuring circuit is equipped with measuring elements (light emission parts 12 and 14 and photodetection parts 11 and 13), pulse generating parts 31, and 33-39 which generate one pulse for every constant movement extent, and pulse generating parts 40 and 41 which count up and down in the feed direction in response to the pulse. When the photodetection parts 11 and 13 detect a medium 19, the pulse generating part 31 generates a pulse, which is inputted to and counted by the counter circuit 40. When a pulse motor is in backward operation, on the other hand, the circuit 40 counts down. When the medium 19 exits from below the photodetection part 11, the circuit 40 stops the counting operation and a microprocessor reads its counted value. Therefore, the value (length) corresponding to the number of movement pulses of the pulse motor in the period from the entrance and exit of the medium into and from the photodetection part 11 is counted accurately regardless of variation in feed speed and backing in the middle. |
