| 摘要 |
PURPOSE:To control the quantity of light projected from a bubble shutter in steps or steplessly by changing the quantity of heat generation of a heat generating body in steps or steplessly. CONSTITUTION:The current supply, i.e. heat generation, of the heat generating body 13 is changed on the basis of a command signal from a control circuit 14. At the time of suppressing the current supply to a low level, bubbles generated in a solution 12 are small. Thereby, an optical path of incident light beams passed into the solution 12 is expanded and the quantity of projected light is reduced. In case of increasing the heat generation of the heat generating body 13, bubbles are expanded sharply in an optical path direction. Thereby, the optical path of incident light beams passed into the solution 12 is shortened and the quantity of projected light is increased. Thus, the heat generation of the heat generating body 13 is changed in steps or steplessly through the control circuit 14 to obtain the quantity of projected light increased/decreased in accordance with the change in the heat generation.
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