| 摘要 |
PROBLEM TO BE SOLVED: To accurately adjust exposure by a small-sized device, at low cost and with low power consumption by detecting the quantity of light received by a solar battery in accordance with the quantity of electrical energy generated when electric load is connected to the solar battery and controlling light transmittance by driving a liquid crystal cell in accordance with the light quantity detected. SOLUTION: The solar battery 11 has both functions of a power source and an illuminance (light quantity) detecting sensor, and DC electromotive voltage is generated between a grounding conductor GND and a positive potential cable Vcc by converting light energy into the electrical energy, so that the level of electromotive voltage Vcc generated in accordance with the illuminance of the light received at a light receiving surface is changed. A sample-and-hold circuit 25 and a voltage comparator circuit 27 detect the quantity of the light received by the solar battery 11 in accordance with the quantity of the electrical energy generated when the electric load 24 is connected to the solar battery 11, and a driving circuit 28 controls the light transmittance by driving the liquid crystal cell 13 by taking the electrical energy generated by the solar battery 11 as the power source in accordance with the detected quantity of light. |
