Is it possible to train an Object Detector (e.g. SSD), to detect when something is not in the image. Imagine an assembly line that transports some objects. Each object needs to have 5 screws. If the Object Detector detects 4 screws, we know that one is missing, hence there is an anomaly.
Actually this is an Anomaly Detection task where there is something else than a screw (e.g. a hole), but unsupervised anomaly detectors are hard to train and not as stable as object detectors.
Is my assumption correct, that even though it is not really an object detection task, one can use such methods?