| 摘要 |
A compact, preferably monolithic optical element converts an incident beam of light into a dispersed exit beam. A transmissive optical grating is supported between two reflective surfaces such that a beam is reflected to pass through the same grating at least twice to form the exit beam. In the preferred embodiment the grating is a volume hologram cemented between two optically transmissive substrates which include outwardly oriented surfaces that are parallel to one another and to the grating, and the internal reflections occur at these surfaces. Mirrors may also be used. A preferred method of grating formation is also disclosed.
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