A management center registers user information that includes user identification information for identifying a user terminal and improvement-information identification information for identifying improvement information recorded in an optical disk and processed by the user terminal. An imaging system may include an image acquisition system, a pre-processor and a coding engine. Each stage is arranged to generate a stage output signal in response to the latched state of the stage. For example, programming reliability and consistency is achieved by forming the conductive layers with varied thickness and forming the polysilicon layers with varied doping profiles, to provide more precise localized regions in which fusing events readily occur.