智能照明-人類偏好自動調光

　　自動調光是首選的工作環境，如工廠和辦公室，以確保最佳照明的工人完成他們的任務，同時最大限度地減少照明的整體能源消耗。環境光傳感器（ALS）是有效地幫助確定正確的亮度設置，以實現最佳的照明相結合的電力照明與自然光。

　　ALS Principles

　　ALS suppliers such as Vishay typically tune the spectral response of sensors to mimic the human eye using optical filters. In practice， this enables an electronic dimmer to adjust lamp brightness continuously to ensure the illumination always meets the needs of human workers as natural light levels vary during the day. Other sensor characteristics， however， can depend on factors such as detector size， lot-to-lot manufacturing variations， and whether the sensor has a phototransistor or photodiode output.

　　If the base of a silicon transistor is exposed to visible light， ionization occurs that produces charge pairs which have the same effect as an externally applied base current. If connections are made to the base and collector only， the device acts as a photodiode and a small current will flow depending on the intensity of the incident light and the photosensitivity of the chip. On the other hand， biasing the device as a transistor produces amplification of the photodiode current. In this case， the output current depends on the transistor gain as well as the photosensitivity of the chip.