A lens includes a central optically active part, and a peripheral optically inactive part surrounding the optically active part. The optically inactive part includes a first surface, an opposite second surface, and a side surface connected between the first surface and the second surface. The side surface includes a first support area, a glue guide area, and a second support area in the order written. The glue guide area has a first groove defined therein. The first groove extends from a first side of the glue guide area adjacent to the first support area to an opposite second side of the glue guide area next to the second support area.