| 摘要 |
PURPOSE:To perform the measurement of amount of light with high accuracy by adjusting the amount of light that reaches the amount of light sensor via a variable opening that is provided in front of the sensor. CONSTITUTION:An opening changeable section 1 consists of liquid crystal plate that has a plurality of concentric electrodes, and an electrode is selected by an opening diameter selection circuit to select an opening diameter. The light that comes in the direction of an arrow mark goes through the liquid crystal plate 1 and goes into a measurement sensor 2. The output of the sensor 2 is supplied to a CPU5 through an amplifier 3 and an A/D converter 4. At the CPU5 it is judged whether or not the data belongs to the linear section or non-linear section of the characteristic curve of the sensor 2. In the case of the data of non-linear section, opening diameter change signal 8 is sent to a selection signal 7. After the opening is adjusted, light measurement is performed again. The data on the amount of light is sent to a display device 6. Accordingly high precision measurement is performed. |
