| 摘要 |
A Fresnel lens of the prior art is split into two Fresnel lenses to allow easier control of the horizontal and vertical viewing angles. In a second embodiment, the Fresnel lens is entirely eliminated. Instead, the diffuser contains elliptical microstructures so that the diffusing cones in orthogonal directions are different, eliminating the need for a Fresnel lens to perform this function. To compensate for the absence of the light collimation provided by the Fresnel lens, a diffuser with spatially varying diffusing angles is used.
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