When pixel row 3 is determined to have the correlation with pixel row 2 that is the reference line (Yes in S144), pixel row 3 is set to the correlation line for pixel row 2 (S145). Then, determination unit 32 determines whether the pixel row immediately below pixel row 3 has the correlation with the reference line (S146). Specifically, determination unit 32 determines whether pixel row 4 that is the pixel row immediately below pixel row 3 has the correlation with pixel row 2 that is the reference line. In this case, pixel row 2 is an example of the first pixel row and the first comparison reference line, and the pixel rows (for example, pixel rows 3 to N) that includes pixel row 3 and is located below pixel row 2 are an example of the second pixel row.
When determining that pixel row 4 has the correlation with pixel row 2 (Yes in S146), determination unit 32 sets pixel row 4 to the correlation line for pixel row 2 (S145). Then, determination unit 32 determines whether the pixel row immediately below pixel row 3 has the correlation with the reference line (S146). As described above, determination unit 32 sequentially determines the correlation between the reference line and pixel row 22 along the scanning direction of gate driver 25. Determination unit 32 repeatedly performs the pieces of processing in steps S145 and S146 until the negative determination is made in step S146. Consequently, the pixel row except for the reference line is set to the correlation line for pixel row 2 as long as the pixel row except for the reference line has the correlation with pixel row 2 that is the reference line selected in step S110.