An optical system includes: a splitter reflecting a portion of a laser beam to form a reflected laser beam, and transmitting a portion of the laser beam to form a transmitted laser beam; a reflection module reflecting the laser beam from the splitter; an inversion module including a first lens having a first focal length and a first incident surface and a first exit surface opposite to the first incident surface, and a second lens having a second focal length and including a second incident surface and a second exit surface opposite to the second incident surface, in which the laser beam sequentially passes through the first lens and the second lens so that the transmitted laser beam is converted into an inverted laser beam; and a combiner reflecting the laser beam reflected from the reflection module and transmitting the inverted laser beam emitted from the inversion module.