The utility model discloses an optical
system suitable for stage
light beam lamp. The optical
system includes the focusing lens module, the middle lens module and the front lens module who sets gradually from object side to image side along the
optical axis direction, and the front lens module, the middle lens module all have positive focal power, and the focusing lens module has negative focal power, the front lens module includes at least one front group lens piece, and the image side surface of front group lens piece is the convex surface, the middle lens module includes the third lens piece, the second lens piece and the first lens piece who sets in order along the
optical axis direction, and the first and second lens piece are all
meniscus positive lens, and the third lens piece is
meniscus negative lens, and the second and third lens piece are glued and are connected as an integral structure, and the focusing lens module includes at least one focusing lens piece, and the focusing lens module is translated before and after along the
optical axis between the middle lens module and the
light source, to adjust the spot definition to different
projection distance. The utility model can shorten the length of overall
optical path while guaranteeing the spot definition and the beam sharpness.