Patent ID: 6898010

Claim:
A beam-shaping device which comprises: a first surface having a first grating through which passes a beam of light emitted from a light emitting point on an optical axis; and a second surface having a second grating through which passes the beam of light having passed through said first surface; wherein said first grating and said second grating are designed, so as to maintain, when the wavelength of said emitted beam of light varies, a prescribed relationship between (1) the displacement of a first virtual light emitting point, in a first meridian plane containing said optical axis, associated with the beam of light having passed through said first surface and said second surface and (2) the displacement of a second virtual light emitting point, in a second meridian plane perpendicular to said first meridian plane, containing said optical axis, associated with the beam of light having passed through said first surface and said second surface, wherein a sectional shape of said first grating is a sawtooth shape with sharp edges facing toward said optical axis in said first meridian plane, and sharp edges facing away from said optical axis in said second meridian plane, and a sectional shape of said second grating is a sawtooth shape with sharp edges either (A) facing toward said optical axis in said first meridian plane or (B) facing away from said optical axis in said first meridian plane, and sharp edges facing toward said optical axis in said second meridian plane.