Abstract: An optical device includes a range finding module. The range finding module includes a first light condenser unit, a light emitting unit and a light receiving unit. The first light condenser unit defines an optical axis and a hole disposed along the optical axis. The first light condenser unit, the light emitting unit and the light receiving unit are sequentially arranged along the optical axis. The light is emitted by the light emitting unit, passes through the hole, reaches an object, is reflected by the object, is converged by the first light condenser unit and is received by the light receiving unit to generate an electrical signal.