Patent ID: 6970294

Claim:
A beam-emission-angle compensating optical unit for correcting a beam emission angle, comprising: an optical element formed of a light-transmissive member having a refractive index n, including: a light incident surface receiving an incident light beam in an incident beam direction which is defined with respect to a reference axis; and a light emitting surface emitting an output light beam in an output beam direction which is defined with respect to the reference axis, the light incident surface and the light emitting surface forming an angle Î± therebetween and defining an imaginary normal plane, which is orthogonal to both the light incident surface and the light emitting surface and which extends along the reference axis, the output beam direction being shifted by an angle Î´ from the incident beam direction, the angle Î´ having a value that depends on the refractive index n, the angle Î±, and a rotational position of the imaginary normal plane relative to the reference axis and substantially satisfies an equation Î±=Î´/(nâˆ’1); and wherein the reference axis is defined in an xyz space, the xyz space being defined by x-axis, y-axis, and z-axis that are orthogonal to one another, the x-axis and the y-axis defining an xy plane, the x-axis and the z-axis defining an xz plane, and the y-axis and the z-axis defining a yz plane, the reference axis extending along the x-axis, the incident beam direction being shifted from the x-axis by the angle Î´, which defines an angle Î´yz between the y-axis and an orthogonal projection component of the incident light beam in the yz plane; and wherein the optical element is disposed with its imaginary normal plane being located at a rotational angle Ï† from the xy plane around the x-axis, the rotational angle Ï† being equal to the angle Î´yz to allow the light emitting surface to output the output light beam in the output beam direction that is parallel with the x axis.