Various embodiments disclosed herein include techniques for determining autofocus for a camera on a mobile device. In various instances, a depth imaging system (e.g., a time-of-flight autofocus system (ToF-AF system)) is used to determine distance of a subject in order to determine autofocus for a camera. In some instances, however, the ToF-AF system may be unable to detect a subject that is very close to the camera when the objects are below a minimum detectable distance of the ToF-AF system. In such instances, an existing IR detector outside of the ToF-AF system may be implemented to measure reflected signals from the ToF-AF system. A power ratio may be determined from the reflected signals and used to determine information about the distance of the subject from the camera.