Scanner and distribution mechanism thereof

A scanner, comprising:

• a frame;
• a rocker arm pivoted on the frame and swinging up to an upper dead point or down to a lower dead point;
• a first gear pivoted on the frame;
• a second gear pivoted on the rocker arm and engaging the first gear;
• and
• a friction element pivoted on the rocker arm and abutting the second gear and the rocker arm;
• and
• a trail bearing the scanned object, joining the rocker arm and capable of swinging with the rocker arm, wherein when the first gear rotates the second gear, the second gear rotates the rocker arm upward or downward selectively via the friction element, and when the rocker arm swings up to the upper dead point or down to the lower dead point, the second gear maintains rotation of the friction element with respect to the rocker arm.