An optical apparatus is disclosed, with which focus detection areas of different size andor position can be stored. The invention further provides an object detection device and a system including the device. When the cable carries a high frequency signal, a capacitive impedance is provided between the neck portion and an outer shield of the cable to reduce electromagnetic signal leakage. Unlike a typical DTI scan, the ADC measurements of the present invention are treated in a \u201creconstruction\u201d phase as if the gradients were applied in different directions.