We have been investigating a system to detect moving objects correctly at the place where luminous intensity is changing because of the influence of incident light such as sunlight, fluorescent light and car headlight. The object detection system consists of a smart image sensor and a modulated LED light, and it is possible to suppress the influence of the change of background light by using a different value between two image values when the LED light is turned on and off. Because the speed of modulation is high for accurate detection of moving objects, electric charges from a photodiode are distributed into two capacitors by switching in sync with the LED light in a pixel circuit of the sensor. Also, the sensor has a subtraction function by a current mirror circuit to reduce the same charges from two capacitors before saturation. By the frequent subtractions, it is possible to increase only the influence of the modulated light and reconstruct wide dynamic range images at outside of the sensor by using the information of subtractions and the voltage value of each capacitor.