1. A portable computer, comprising: a display screen showing a cursor; a first image sensor disposed on a first plane on which the display screen locates and configured to capture a first image toward a first direction along a front of the display screen; a second image sensor disposed on a second plane, and configured to capture a second image in a field of view thereof and toward a second direction, wherein the second plane is not parallel to the first plane, and the second direction is different from the first direction; and a processing unit configured to recognize a predetermined hand posture according to the first image, activate the second image sensor when the predetermined hand posture is recognized, control the cursor according to a hand posture position of the first image and identify a click event of an object transversely crossing the field of view of the second image sensor according to the second image.