A mobile device having an external housing that includes a housing camera lens cover made of graded index (GRIN) material is described herein. The housing camera lens cover has one face that faces a camera lens of a camera module included in the mobile device and another face that is exposed to the exterior of the mobile device. By using the GRIN material in the housing camera lens cover, the light rays are bent by the GRIN material before the light rays reach the camera lens. This bending of the light rays reduces the optical total track length (TTL) of the camera module and also reduces high Chief Ray Angle (CRA) such that the z-height of the camera module may be reduced while maintaining the camera's imaging performance.