An image sensor includes: a group of autofocus sensor units; neighboring sensor units adjacent to and surrounding the group of autofocus sensor units, wherein each of the neighboring sensor units has a first side close to the group of autofocus sensor units, and a second side away from the group of autofocus sensor units. The image sensor further includes: a first light shielding structure disposed between the group of autofocus sensor units and the neighboring sensor units; a first extra light shielding structure laterally extending from the first light shielding structure and disposed on at least one of the first side and the second side of one or more of the neighboring sensor units.