| 摘要 |
PURPOSE:To correct an aberration of an optical system at a low cost, and to realize a desired soft focusing function by providing a heating element on a prescribed position of a transparent medium whose refractive index has a temperature dependence, and controlling a heating of the heating element. CONSTITUTION:A trasparent heater 11 is provided on the inside of a transparent supporting body 10 and connected to a power source, and a medium 12 whose refractive index is varied by a temperature is provided so as to contact with the supporting body 10. When the heater 11 is heated by making a current flow, such a temperature gradient as shown by a broken line is generated in the medium 12. In case when a variation of a refractive index (a temperature coefficient of a refractive index) to a temperature of the medium 12 is negative, the refractive index of the medium increases gradually toward the outside from the vicinity of the heater 11, and it has an operation of a concave lens. In case when the temperature coefficient of the refractive index of the medium 12 is positive, it has an operation of a convex lens. By placing this optical element 10a in the vicinity of a diaphragm 15 of an optical system consisting of lenses 21-26, an aberration of the optical system is corrected at a low cost, and a desired soft focusing function is realized. |
