Light flux diameter-expanding element and display apparatus

摘要

A light flux diameter-expanding element (pupil expanding element) which is used in a retina scanning type display apparatus includes a first diffraction grating having a grating pattern extending in a first direction X, a second diffraction grating, a third diffraction grating, and a fourth diffraction grating, and expands a diameter of the incident light flux in a second direction Y so as to emit the light. In addition, the light flux diameter-expanding element includes a fifth diffraction grating having a grating pattern extending in the second direction Y, a sixth diffraction grating, a seventh diffraction grating, and an eighth diffraction grating, and expands a diameter of the incident light flux in the first direction X so as to emit the light.

主权项

1. A light flux diameter-expanding element comprising:
a first diffraction grating that is provided with concave portions or convex portions extending in a first direction, which are periodically arranged; a second diffraction grating that is disposed opposite to the first diffraction grating, and is provided with concave portions or convex portions extending in the first direction, which are periodically arranged; a third diffraction grating that is disposed at a side opposite to the first diffraction grating with respect to the second diffraction grating in a facing manner, and is provided with concave portions or convex portions extending in the first direction, which are periodically arranged; and a fourth diffraction grating that is disposed at a side opposite to the second diffraction grating with respect to the third diffraction grating in a facing manner, and is provided with concave portions or convex portions extending in the first direction, which are periodically arranged, wherein the first diffraction grating, the second diffraction grating, the third diffraction grating, and the fourth diffraction grating are disposed so that grating periods of the concave portions or the convex portions are respectively same.