| 摘要 |
PROBLEM TO BE SOLVED: To provide grism capable of preventing the incident angle of light from exceeding the critical angle even when the apex of the prism is increased, improving efficiency, being mass-produced and reducing cost. SOLUTION: The grism has a first prism with a high refractive index, a second prism with a high refractive index and a volume phase hologram as a diffraction grating and is formed by interposing the volume phase hologram between the first prism and the second prism with the apex of the first prism and the apex of the second prism facing each other.
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