REGISTERED MAIL COPYING DEVICE

摘要

PURPOSE:To obtain the focal position of an image pickup lens with high resolution even in the case where the thickness of a registered mail as the object exceeds the depth of field of the image pickup lens for a registered mail copying device and to pickup a focused object image of good quality. CONSTITUTION:An ultrasonic sensor 4 on a transmission side is installed in such a position not interrupting the optical path of the object image, and high- frequency directional ultrasonic waves are emitted toward the object. An ultrasonic sensor 5 on a reception side is arranged at even distance across the optical axis of the image pickup lens 2 from the ultrasonic sensor 4 on the transmission side, and the sensors are fixed with an inclination so that center normals of respective transmitting/receiving surfaces of the sensors 4 and 5 may cross each other on the optical axis of the image pickup lens, and the reflected ultrasonic waves reflected on the object are received by the sensor 5. And a distance from the image pickup lens 2 to the surface of the object is measured based on a time difference between the transmission by the sensor 4 and the reception by the sensor 5.