An apparatus for enhancing image contrast includes a micro-processor which presets a plurality of thresholds, such as a black threshold and a white threshold. When determining the brightness of an image is lower than the black threshold, the micro-processor decreases the illumination level of a light source. When determining the brightness of an image is higher than the white threshold, the micro-processor increases the illumination level of the light source. A method for enhancing image contrast includes the steps of receiving an image data; determining whether the brightness of an image is lower than the black threshold; if yes, decreasing the illumination level of the light source; determining whether the brightness of the image is higher than the white threshold; and if yes, increasing the illumination level of the light source.