Whats most popular (otherwise known as LDR) is a sensitive Receiver that changes resistance with light intensity. It is of the normal principle that some resistant materials can be changed by the intensity of light. A photo sensor 's main functions are to detect whether or not there is sufficient light, measure the energy in light and convert this into an electrical signal. Technology characteristics of photo sensors include wide spectral response range, high sensitivity, low dark current, and fast-response time. The industry features photo sensors are very diverse and include automatic lighting controls, solar power sensing grids for systems such as this is a good example today and object detection in robotics and factory automation systems.