PURPOSE: To eliminate the necessity for an expensive mechanical restriction mechanism by selecting a single system of exposure filter and CCD element by a level of incident luminous energy, in a CCD camera, in the case of supervising a running line by the CCD camera and automatic traveling while correcting displacement from a running route.

CONSTITUTION: In the case of adjusting exposure of a CCD camera against input luminous energy markedly changed in accordance with an external environmental condition, reflecting light from a running line 10 is converged by a lens 11, and this converged light is input to each one-dimensional CCD element 12 via each exposure filter 14. Here by conversion into an electric signal on the other hand by a level of separately measured incident luminous energy, using what system of the exposure filter 14 and CCD element 12 is selected by a signal switching device 15. A selecting result is output to an image processing device 2, to adjust exposure of the CCD camera 1. In the image processing device 2, displacement between a conveyer and the running line 10 is calculated to correct a running direction of a running drive motor 4.