PURPOSE: To provide a free space light switch system which can converge spot beams to the related array of a light detection element through the use of an objective lens constituted of few elements.

CONSTITUTION: In the free space light switch system having the objective lens 30 converging the array of the parallel beams on a space light modulation element 22, the objective lens 30 is provided with a convex tablet lens 32, a convex lens 34 which is adjacently arranged to the convex tablet lens 32, a concave lens 36 arranged by detaching it from the convex lens 34 by a prescribed distance (d) and a stopper 38 arranged immediately before the convex tablet lens 32. The array of the parallel beams enters the convex tablet lens 32 through the stopper 38 and a converged spot beam array goes out from the concave lens 36.