opencv中的特征检测和级联分类器有什么区别？

Question

opencv 2.4.9支持以下功能检测器类型：

"FAST" – FastFeatureDetector
"STAR" – StarFeatureDetector
"SIFT" – SIFT (nonfree module)
"SURF" – SURF (nonfree module)
"ORB" – ORB
"BRISK" – BRISK
"MSER" – MSER
"GFTT" – GoodFeaturesToTrackDetector
"HARRIS" – GoodFeaturesToTrackDetector with Harris detector enabled
"Dense" – DenseFeatureDetector
"SimpleBlob" – SimpleBlobDetector

opencv 2.4.9支持以下级联分类器类型：

Haar Feature based Cascade Classifier for Object Detection
Lbp feature based Cascade Classifier for Object Detection
HOG feature based Cascade Classifier for Object Detection

找到对象哪个方法在实时图像中返回对象的方向？ 哪种方法支持实时图像中的多个对象检测？ 对象发现技术中特征检测和级联分类器之间的主要区别是什么？

提前致谢。