An object of the present invention is to suppress fragmentation occurring due to repeated storing and deleting small capacity file data, while effectively storing large capacity real time file data. The method can be used to form gels that can be used for the transportation of volatile organic solvents like gasoline, cooking oil, and contaminated organic liquids to be incinerated. The primary electromagnetic coil and the secondary electromagnetic coil comprising copper and nickel. According to the above optical element, it is possible to appropriately suppress an influence of shift of the position between the first and second microlens array units, and it becomes possible to produce the optical element with ease. The switch element outputs either one of the first signal and the second signal in accordance with a distance and e positional relationship between a light collection point of the light output from the collection light system and the track.