1. An apparatus for ranging an object comprising: an illuminator to illuminate a field of view potentially including the object; an imager to capture a first image having reflected signals from the field of view when the field of view is illuminated by the illuminator and a second image having reflected signals from the field of view when the field of view is not illuminated by the illuminator; a circuit coupled to said imager to synchronously control said illuminator and said imager, and to generate a subtraction image of the field of view as the pixel difference between the first image and the second image; and wherein the imager captures one of the first image and second image while the other one of the second image and first image is still captured in the imager.