| 摘要 |
The present invention is a technique for fabrication of a holographic optical element combiner having a high diffraction efficiency at a central portion and gradually decreasing diffraction efficiencies for peripheral portions at locations further from the central portion. The holographic optical element combiner is constructed by exposing a photosensitive material and either selectively diffusing the construction beam with moving diffuser plate or plates or selectively blocking the construction beam with opaque plate or plates. The peripheral portions are directly exposed for a gradually decreasing fraction of the exposure time for locations further from the central portion. The preferred embodiment employs diffuser plate or plates in order to achieve the same exposure bias level throughout the photosensitive material. When a holographic optical element combiner of this construction is employed in a head up display, the visibility of the edge of the combiner is reduced. In the preferred embodiment the holographic optical element combiner is embedded in a windshield glass structure.
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