Thread Subject: circle detection hough transform

Hi,
I am using hough transform for circle detection..it is detecting the circles properly where ever in image. But sometimes it gives false detections..i.e. at that place in image no circle is there..then also it detects. I am using CircularHough_Grd() function which is available on file exchange of mathworks. Also I have done some preprocessing on image such as histogram equalization, thresholding, dilation , erosion and finally edge detection . Then the edge detected image I am giving to CircularHough_Grd.

Could some one tell me whether steps followed by me are correct or not? How to remove false detections?

Thanks and regards,
Nishtha