An apparatus includes a probe and a light source configured to output light. The apparatus includes a light focusing assembly comprising an image space lens, an object space lens and a focus changing assembly between the image space lens and the object space lens. The focus changing assembly is configured to focus the light to a plurality of external focal planes to illuminate a patient's teeth, wherein at least a portion of the focus changing assembly is located at a back focal length of the object space lens. The apparatus includes a detector to measure characteristics of incident light returning from an illuminated patient's teeth and a processor coupled to the detector and configured to generate data representative of a topography of the patient's teeth based on the one or more measured characteristics of the incident light.