PURPOSE: To easily detect deviation of joints of plural photoelectric conversion elements by including a 1st process leading out an image pickup signal, a 2nd process leading out a visual output picture and a 3rd process superimposing an output picture and a grating pattern and detecting the joint deviation in the scanning direction of joints of plural photoelectric conversion elements depending on the state of obtained moire stripes.

CONSTITUTION: At first, a test chart 18 is carried in a subscanning direction (in a direction of arrow X) at a picture scanning section 10 and a picture read section 12 reads longitudinal lines 22 and lateral lines 24. In an output picture, the longitudinal lines 22 and the lateral lines 24 recorded on the test chart 18 are overlapped while being tilted by a tilt angle θ. In this case, a moire stripe is caused in the reproduction picture of the longitudinal lines 22 based on a spatial frequency caused by a pitch of the longitudinal lines 22, a spatial frequency caused by a pitch of an output picture with nonmagnification output and the tilt angle θ. Similarly, a moire strip is caused on the reproduction picture of the lateral lines 24.