Optical device, and virtual image display

Abstract

There is provided an optical device including an optical waveguide upon which a group of parallel light beams different in traveling direction from each other are incident and from which the group of parallel light beams go out after propagated by repeated total reflection through it. The optical waveguide includes a first reflection-type volume hologram grating, and a second reflection-type volume hologram grating. The pitches of interference fringes on the hologram surfaces of the first and second reflection-type volume hologram gratings are equal to each other. In at least the second reflection-type volume hologram grating, the angle formed between the interference fringes and hologram surfaces are varied continuously or stepwise within the hologram in relation to the main incident light beam so as to meet the Bragg condition. Therefore, it is possible to reduce the unevenness of color and brightness due to angles of view.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of the filing date of U.S. application Ser. No. 11 / 424,338, entitled “Optical Device and Virtual Image Display,” filed on Jun. 15, 2006 which is incorporated herein by reference to the extent permitted by law. This application also claims the benefit of priority to Japanese Patent Application No. 2005-178376, filed Jun. 17, 2005, which is also incorporated herein by reference to the extent permitted by lawBACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to a thin-type optical device that guides display-image light to a viewer's pupil, and a virtual image display including the optical device and that displays a two-dimensional image as a virtual image enlarged by a virtual image optical system to the viewer.[0004]2. Description of the Related Art[0005]To display a two-dimensional image as a virtual image enlarged by a virtual image optical system to the viewer...

AI Technical Summary

Benefits of technology

This solution reduces color and brightness unevenness by equalizing diffraction efficiencies and preventing color variations across the display screen, enhancing image quality and viewer experience.

Problems solved by technology

However, the virtual image display 100 has incurred large unevenness of color and brightness in the past.

Also, in case the wavelength of light incident upon the hologram is short, the diffraction efficiency will possibly vary depending upon an angle of view and brightness will possibly be uneven.

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