An apparatus includes a probe sized to be at least partially inserted into an intraoral cavity of a patient and an illumination unit 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 and being configured to: overlap a plurality of light beams of the light within the light focusing assembly; and focus the light to a plurality of external focal planes to illuminate the patient's teeth. The apparatus includes a detector to measure one or more characteristics of incident light returning from the 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 returning from the illuminated patient's teeth.