A single lens homogenizer for converting a wide, parallel, in-phase Gaussian beam into a narrow uniform-power beam and shooting an object with the narrow uniform-power beam is proposed. A tilt error induces beam deformation. A single lens homogenizer which can reduce the beam deformation induced by the tilt error is proposed. A suitable homogenizer is a convex/flat lens having a convex aspherical surface on the light source side and a flat surface on the object side. Another preferable homogenizer is a convex/convex lens having a convex surface on the light source side and a convex surface on the object side. At least one of the convex surfaces is an aspherical convex surface.