Patent ID: 7961371

Claim:
A light beam generator including: a light source for outputting coherent light; and an optical phase modulation element which receives the light output from the light source to modulate a phase of the light depending on a position on a beam cross section of the light, and outputs the light after the phase modulation; wherein a polar coordinate system (r, θ) having an origin at a beam center position is set on the beam cross section of the light input in the optical phase modulation element, and when domains A 0 to A p are defined on the beam cross section and centers of the domains A 0 to A p are placed commonly at the beam center position, on these domains A 0 to A p , a phase modulation amount Φ at each position inside an even-numbered domain counted from the beam center is expressed by a formula of Φ=qθ and a phase modulation amount Φ at each position inside an odd-numbered domain counted from the beam center is expressed by a formula of Φ=qθ+π, provided that p is a natural number corresponding to a radial exponent and q is a non-zero integer number corresponding to a declination component.