1. An image generation apparatus comprising: a grip unit configured to grip a target object by a hand with a plurality of fingers; an image capturing unit configured to capture an image of at least one of the target object and said grip unit; an image processing unit configured to process an image; and a grip controller configured to control said grip unit; and an image capturing controller configured to control said image capturing unit, wherein said image capturing controller controls said image capturing unit to capture, as a grip-state image for a predetermined orientation, said grip unit and the target object when said grip controller controls said grip unit to grip the target object by the hand in a grip state and place the target object in the predetermined orientation relative to said image capturing unit, wherein the image capturing controller stores the orientation and position of the hand in the grip state, wherein said image capturing controller controls said image capturing unit to capture, as a non-grip-state image for the predetermined orientation, said grip unit when said grip controller controls said grip unit not to grip the target object, to be in the stored position and orientation that are coincident with the position and orientation in which said grip unit gripped and placed the target object in the predetermined orientation, and to be positioned and oriented in the same way of opening the fingers of the hand when said grip unit gripped the target object by the hand, and wherein said image processing unit generates the target object image representing the target object in the predetermined orientation based on a difference between the grip-state image for the predetermined orientation and the non-grip-state image for the predetermined orientation.