PRISM OPTICAL SYSTEM, IMAGE DISPLAY DEVICE USING PRISM OPTICAL SYSTEM, AND IMAGING DEVICE USING PRISM OPTICAL SYSTEM

摘要

[Problem] To provide a prism optical system that: includes an optical element that is very small, is light-weight, and has a high degree of flexibility in terms of shape; has a high resolution performance up to the periphery of an image; and can project an image from an image display element to an observer's eye as a virtual image. [Solution] A prism optical system 1 is characterized by having at least three optical surfaces having an optical action, and by including an optical element 10 in which incident light forms an image upon exiting after making at least three internal reflections, said optical element 10 having an entrance-side reflecting surface 12 that reflects light immediately after the light enters, an exit-side reflecting surface 14 that reflects light immediately before the light exits, and an intermediate reflecting surface 13 that reflects light on the light path between the entrance-side reflecting surface 12 and the exit-side reflecting surface 14. The prism optical system 1 is further characterized in that, if the direction along the advancing direction of a central main light path that passes through the center of an entrance pupil, which is the origin, and is perpendicular to the surface forming the entrance pupil is taken to be the positive direction of the Z-axis, the plane containing the Z-axis and the center of an image surface is taken to be the Y-Z plane, the direction that passes through the origin and is orthogonal to the Y-Z plane is taken to be the positive direction of the X-axis, and the axis that forms a right-hand orthogonal coordinate system with the X-axis and the Z-axis and heads in the direction approaching the center of the image surface from the origin is taken to be the Y-axis, the thickness Tn of an intermediate region An containing the intermediate reflecting surface 13 in the X-Z plane is greater than the thickness Tc of an entrance-side region Ac containing the entrance-side reflecting surface 12, or the thickness Ts of an exit-side region As containing the exit-side reflecting surface 14.