Optical device

An optical device configured to display an external scene image of a blind spot area for a viewer when an obstacle is within a view field of the viewer, the optical device comprising:

• a light guide having
• an incident surface on which an external scene light coming from a blind area is incident,
• a first surface having a plurality of flat portions and a plurality of prism portions, the external scene light that is incident from the incident surface reaching the first surface for a first time, and
• a second surface located opposite to the plurality of flat portions of the first surface;
• a light shielding portion provided so as to block an outside light from entering the light guide, wherein
• the plurality of flat portions of the first surface totally reflects the external scene light traveling inside the light guide toward the second surface,
• the second surface totally reflects the external scene light reflected by the plurality of flat portions toward the first surface,
• each of the plurality of prism portions has an exit surface for outward emitting a part of the external scene light that is incident from the incident surface and a part of the external scene light reflected by the second surface, and an inclined surface located opposite to the viewer with respect to the exit surface,
• the light shielding portion has a first light shielding portion configured to block-an the outside light that is incident on the inclined surface and a second light shielding portion configured to block the outside light that is incident in a predetermined direction on a flat portion from among the plurality of flat portions,
• in a cross-sectional view including a normal to the exit surface and a normal to the flat portion,
• θ is an angle formed between the normal to the flat portion and a line connecting a center of a predetermined exit surface and an eyepoint center of the viewer,
• L is a distance between the center of the predetermined exit surface and the eyepoint center,
• DL is a distance between the eyepoint center and an outer edge of an eyelips of the viewer away from the light guide in a direction perpendicular to the line connecting the center of the predetermined exit surface and the eyepoint center,
• θ min is an angle represented by θ−tan−1 (DL/L),
• a straight line A passes through a point where the exit surface and the inclined surface intersect with each other and the straight line A is incident on the flat portion with the angle θ min symmetrical relative to the normal to the flat portion,
• a straight line B is parallel to the straight line A and incident on a point where the inclined surface and the flat portion intersect with each other,
• a point P1 where the straight line A intersects with the flat portion,
• a point P2 where the straight line B intersects with the flat portion,
• a point P3 where the exit surface intersects with the flat portion,
• a distance Fa is defined between the point P1 and the point P3,
• a distance Fb is defined between the point P2 and the point P3,
• Fa<Fb is satisfied,
• the second light shielding portion is arranged so as to overlap the straight line A and the straight line B,
• the second light shielding portion is positioned away from, and is not in contact with, the flat portion, and
• the flat portion is in contact with air.