Square grid pattern generated in a dielectric barrier discharge device is adopted by CCD digital camera. By using 2-D
Fourier spectrum analyzing, it is found that the dot-line pattern is selected by two modes and the hexagonal pattern is
selected by single mode, while the square grid pattern is formed by three wave resonance. For further investigation, the
intensity distribution of square grid pattern is analyzed. Results show that the structures of square grid pattern is perfect
and the intensity distribution along a line contains two types of intensity peaks, indicating that each cell of square grid
pattern is composed of eight spots.