Illuminator

An illuminator including a pair of an ultraviolet light-emitting discharge tube and a white visible light-emitting discharge tube that are alternately and periodically placed in a lighted state and an unlighted state, such that a state of illumination using only one of said ultraviolet light-emitting discharge tube and said white visible light-emitting discharge tube is realized in at least part of a time domain during a period, the illuminator comprising:

• a plurality of pairs of light sources for ultraviolet light and white visible light,
• a hot-cathode tube used for at least one of said ultraviolet light-emitting discharge tube and said white visible light-emitting discharge tube, said hot-cathode tube being arranged in a state where a heating power supply for heating filaments, and an illuminating power supply for enabling motion of thermoelectrons within said hot-cathode tube and at a same time periodic repetition of the lighted state and unlighted state, are capable of executing and interrupting application of voltage, independently of each other, and
• a computer which controls selection of a pair of light sources and periodic application of voltages from power supplies to the selected pair of light sources.