An optical member that refracts a light beam to diverge or focus the light beam, includes: at least three pairs of opposing surfaces. Each of the three pairs of opposing surfaces include a lens. Curvatures of the lenses at one side surfaces of the respective three pairs of surfaces are all the same, or curvatures of the lenses at one side surfaces of respective pairs of at least two pairs of the three pairs of surfaces are different from each other, and respective shortest distances between optical axes of the lenses at the one side surfaces of respective pairs of the at least two pairs of surfaces, and reference sides which are each any one of respective sides surrounding surfaces including the lenses are different from each other.

An optical member that refracts a light beam to diverge or focus the light beam, includes: at least three pairs of opposing surfaces. Each of the three pairs of opposing surfaces include a lens. Curvatures of the lenses at one side surfaces of the respective three pairs of surfaces are all the same, or curvatures of the lenses at one side surfaces of respective pairs of at least two pairs of the three pairs of surfaces are different from each other, and respective shortest distances between optical axes of the lenses at the one side surfaces of respective pairs of the at least two pairs of surfaces, and reference sides which are each any one of respective sides surrounding surfaces including the lenses are different from each other.

An anamorphic optical element and an adjustment mechanism for selectively rotating the optical element either around an axis substantially in a vertical direction, an axis substantially in an optical axis direction, an axis substantially in a plane formed by the vertical direction and the optical axis direction, or combination of axes thereof is used to vary a vertical separation between two or more spots.

A prism block is provided at least one notch to propagate in the light flux in air, on an optical path from entrance of a light flux via a first portion of the prism block to exit of the light flux via a second portion of the prism block. The notch is configured such that the light flux exiting from inside of the prism block via a first interface of the notch between the prism block and the air re-enters the prism block via a second interface between the air and the prism block, the second interface facing the first interface.

A prism block is provided at least one notch to propagate in the light flux in air, on an optical path from entrance of a light flux via a first portion of the prism block to exit of the light flux via a second portion of the prism block. The notch is configured such that the light flux exiting from inside of the prism block via a first interface of the notch between the prism block and the air re-enters the prism block via a second interface between the air and the prism block, the second interface facing the first interface.