1. An image processing method, applied to an image processing apparatus comprising a light source and an image sensor, wherein the image sensing method comprises: acquiring a first image via the image sensor when the light source does not emit light; acquiring a second image via the image sensor when the light source emits light; acquiring a third image via the image sensor when the light source operates does not emit light; generating a combined image based on only part of contents of the first image and only part of contents of the third image, but not based on the second image; and acquiring a target image after background noise removing via subtracting the combined image from second image.