1. A detection device for detecting a plurality of classes of object data, comprising: an input unit, configured to input data to be detected; and a joint classifier comprising strong classifiers, the number of which corresponds to the number of the classes and which are used for detecting a corresponding class of the object data respectively, wherein each of the strong classifiers is obtained from a combination of a group of weak classifiers, and each of the weak classifier performs a weak classification on the data to be detected using a feature, wherein the joint classifier comprises a shared features list, and each feature in the shared features list is shared by one or more weak classifiers respectively belonging to different strong classifiers; and the weak classifiers using a same feature and belonging to different strong classifiers have parameter values different from one another.