A Finite Impulse Response filter is implemented in software on a general purpose processor in a manner which reduces the number of memory accesses as compared to conventional methods. The polymerizable compound has two or more polymerizable functional groups in a molecule thereof, wherein one of the two or more polymerizable functional groups of the polymerizable compound is an acrylamide group having the below-mentioned formula. A noise-insensitive determination of the position of local antennas with high precision is achieved. The software commands may be called up via the call-up means only if these means are in an unlocked state. An image forming apparatus identifies a reflection surface on which a light beam is incident by using the period of an FG signal.