Image matching and object detection, how to perform detection for small object?

Question

I am using SIFT feature the matching between two images or it can be considered as object detection.

First matching. I used SIFT feature for matching and it failed when the object is small.

Second matching. However, it woks when I cropped that object out from that image.

Any suggestions or ideas to improve the first matching without cropping?

Example images are shown below.

Image A: http://www.mathworks.com/matlabcentral/answers/uploaded_files/21827/imageA.png

Image B: http://www.mathworks.com/matlabcentral/answers/uploaded_files/21828/imageB.png

Image C cropped out from image B: mathworks.com/matlabcentral/answers/uploaded_files/21829/imageC.png

Answer 1

the standard approach is to do sliding window detection, i.e start with a window size, slide it over the image and take the window (at some position x,y) which matches best, this thing can be done with windows of multiple sizes.