PURPOSE: To resolve the inaccuracy of manual check by providing a specific circuit to display the intermediate brightness on an LCD panel and detecting a defect of transverse stripes at the time of displaying the intermediate brightness.

CONSTITUTION: A color camera 1 for picture input, an input circuit 2 which converts inputted picture information to a digital signal, a picture memory 3 where converted picture information is stored, and a projection circuit 4 which projects stored picture information in the horizontal direction to obtain the cumulative sum of picture information are provided. A binarizing circuit 5 which performs binarization with a designated threshold and a measuring circuit 6 which measures the number of binarized picture data and their areas and positions are provided to display the intermediate brightness on an LCD panel 10. Thus, the difference of check result by checkers is prevented.