The present invention is directed to a method for joining two parts together and the unit derived therefrom. It is a method, processes, and apparatus for measurement and analysis of variables of different type and origin. The element-side lens and the identification mark are separated from each other by a distance that is at least the radius of the element-side lens. When accelerating from rest or a slow speed, the speed at which the driving force control operation shifts into the execution mode is increased as the accelerator position becomes larger. The light-absorbing film 3 is made of an Si film 3, which absorbs a part of the incident light so that the temperature of the information layer 4 increases.