An internal-reflective telecentric lens system includes a first lens assembly, a reflector, and a second lens assembly. The first lens assembly includes a first lens. The second lens assembly includes a second lens, a third lens, and a fourth lens, that are disposed in sequence along a light path. The first lens assembly is configured to receive and output one or more light beams towards the reflector. The reflector is configured to reflect the light beams towards the second lens assembly. The second lens assembly is configured to receive and converge the light beams reflected by the reflector at a diaphragm between the second lens and the third lens, and transmit the light beams past the diaphragm through the third and the fourth lenses for imaging.