Abstract: A safe following distance warning system for a vehicle includes a forward-looking image capturing unit, a speed sensor, a processor, and a warning output device. The forward-looking image capturing unit is for capturing images forward of the vehicle. The forward-looking image capturing unit includes a taking lens, an image sensor disposed behind the taking lens, an image processing unit, and a lens driving unit. The image processing unit is for calculating an in-focus position of the taking lens. The speed sensor is for sensing a current speed of the vehicle. The processor is for calculating a following distance from the vehicle to a vehicle directly forward of the vehicle and comparing the following distance to an applicable safe distance parameter. The warning output device is for outputting an alarm to the driver of the vehicle when the following distance is less than the applicable safe distance parameter.