Face detection algorithm for 15x15 pixels face?

I'd like to know if you are aware of any algorithm to detect开发者_运维技巧 low-resolution faces in an image. The image could have any resolution and the faces resolution could be as low as 10x10 or 15x15. I am using OpenCV but I don't think the Haar classifiers provided allow me to work with resolutions so small. Are there any other alternative? Thanks

The Eigenface technique is (IIRC) known to work fairly well on low-resolution images. Human faces have a distinct pattern to them that's still visible at low quality, and I believe that using a sliding window technique in conjunction with this algorithm might produce good results.