PURPOSE: To prevent the tracking performance from being spoiled even against a sudden variation of a luminance level by providing an average value calculating circuit and a subtracter in an input stage of image data, eliminating a DC component from the image data and executing a correlation operation by using only an AC component of the image data.

CONSTITUTION: An average value calculating circuit 1 calculates an average value of a one-line portion, outputs an average value signal (b) to a subtracter 2, and the subtracter 2 subtracts the signal (b) from input image data (a), and outputs image data (c) from which a DC portion is eliminated, to a correlation arithmetic circuit 3 and a template memory 5. As for the image data, the correlation arithmetic circuit 3 calculates an expression in accordance with the image data (c) outputted from the subtracter 2. In the expression, the number of samples in a template data area, the number of samples of input image data, luminance of template data, and luminance of the input image data are denoted as (m), (n), TK, and Xi, respectively, and at the time of (i)=A, the minimum correlation value signal Di is obtained. In such a way, [A+(m-1)/2] can be obtained as a target position signal (e).