An object detection system and method includes: an optical image sensor arranged to perform the following steps: capturing a calibration image during a calibration stage, dividing the calibration image into a plurality of quadrants, and calculating a parameter for each of the quadrants; capturing a plurality of raw images during a detection stage, dividing each image of the raw images into a plurality of quadrants, and calculating a parameter for each of the quadrants; comparing the respective parameters of each quadrant of a raw image with the respective parameters of each quadrant of the calibration image to generate a ratio value for each quadrant; and comparing the ratio value of each quadrant with a predetermined threshold. When each ratio value of specific quadrants of the quadrants is greater than the predetermined threshold, object detection is confirmed.