| 摘要 |
PURPOSE:To stably detect a bar code even if a bar code detection distance varies by permitting an automatic focussing means to adjust a distance between a light converging means and an image sensor and forming the image of reflected light from the bar code on an image sensor. CONSTITUTION:Assuming that the bar code 2 lies in a position (distance from the light converging means 3) X 240mm, the distance (y) between the image sensor 4 and the light converging means 3 is set to 34.0mm. Since the field depth (x) equals 240+ or -30mm (A'), the bar code can be detected. If the bar code is shifted to a position x=58mm (B), it is out of the field depth A, and therefore the bar code 2 cannot be detected. However, a distance measuring part detects the position of the bar code 2, and shifts the position of the light converging means 3, thereby y=46.5mm can be obtained. The field depth changes to x=128+ or -30mm (B'), and the bar code can be detected.
|
