I tried an algorithm with some math calculations to detect circles.

1- Convert image to grayscale

2- Apply median filter to eliminate noise

3- Apply canny to get binary image

4- Find contours with the efficient parameters

5- Apply minAreaRect function to get the fitted rectangles for each contour

6- Filter contours by their length not to get small contours(noisy contours)

7- Get the center of fitted recttangles

8- Compare each contour's point with the center of fitted rectangles

9- Make a comparison and get the results

This algorithm works well in these conditions:

1- The pictures should be taken parallel to surface(camera should be parallel to target circles)

2- Shadows shouldn't exist or they should be eliminated

3- Occlusion