A range finder includes a laser transmitter, a laser receiver, a large-aperture objective lens unit, an image sensing device, a display device and a microphone. The laser transmitter is configured to emit a laser beam to a measured object. The laser receiver is configured to receive a reflected laser beam reflected by the measured object. The objective lens unit is configured to allow visible light reflected by the measured object to pass therethrough, includes an objective lens and a focusing lens and has a length defined by the objective lens and the focusing lens. The image sensing device is configured to receive the visible light passing through the objective lens and generate an image signal. The length is constant when the objective lens unit is moved with respect to the image sensing device for focusing operation.