PURPOSE: To expand an emission pupil without expanding a relay optical system or reducing a projection image by using an NA expanding element arranged on either a position conjugate with a display surface corresponding to the relay optical system or its vicinity.
CONSTITUTION: A relaly lens system 2 is arranged on the display surface side of an LCD 1, a plane diffusion plate 3 is arranged on a position conjugate with the display surface corresponding to the system 2 and an eyepiece optical system 4 is arranged in the optical axis direction. The light flux 5b of a display image displayed on the LCD 1 is transmitted by the lens system 2 and forms an image on the surface conjugate with the display surface. The NA of the light flux 5b made incident upon the plate 3 is expanded and emitted by the diffusing action by the plate 3. Thereby the diameter of an emission pupil 10 is expanded in accordance with the expansion of the NA by the plate 3. Consequently an observer can easily search the setting position of his (or her) pupil.
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