Optical member
An optical member includes a light guide body. The light guide body has an incident surface on which an outside light is incident, a first surface having flat portions and prism portions, an incident light incident on the incident surface reaching the first surface for the first time, and a second surface arranged opposite to the flat portions. The flat portions totally reflect the incident light toward the second surface. The second surface totally reflects a reflected light reflected by the flat portion toward the first surface. The prism portion has an ejection surface to emit the incident light to outside.
1. An optical member comprising:
a light guide body having an incident surface on which an outside light is incident,
a first surface having a plurality of flat portions and a plurality of prism portions, an incident light incident from the incident surface reaching the first surface for the first time, and
a second surface arranged opposite to the plurality of flat portions, wherein
the plurality of flat portions is a first reflecting surface to totally reflect the incident light toward the second surface,
the second surface is a second reflecting surface to totally reflect a reflected light, reflected by the first reflecting surface, toward the first surface,
the plurality of prism portions has an ejection surface to emit a part of the incident light or a part of light reflected by the second surface to outside,
the plurality of prism portions arranged on the first surface is a first prism portion,
the light guide body has an incident portion having a plurality of second prism portions, and
the incident surface comprises an outer surface of each of the plurality of second prism portions and is parallel to the ejection surface of the first prism portions.
2. The optical member according to claim 1 , wherein
an incident angle of the incident light with respect to a flat surface formed by the plurality of flat portions and an incident angle of the light reflected by the flat portion with respect to the second surface are defined as Φ,
a refractive index of the light guide body is defined as n 1 ,
a refractive index of a medium in contact with the light guide body is defined as n 2 , and
the light guide body satisfies a relationship of sin Φ>n 2 /n 1 .
3. The optical member according to claim 2 , wherein
an angle between an incident direction of the outside light on the incident surface and a normal direction with respect to the flat portions is defined as θ 1 ,
an angle between the incident surface and the normal direction is defined as ψ, and
the light guide body satisfies a relationship of Φ>θ 1 and π/2−Φ>ψ.
4. The optical member according to claim 1 , wherein
the incident portion is arranged on a plane formed by the second surface.
5. The optical member according to claim 1 , wherein
a normal direction is defined with respect to a flat surface formed by the flat portions,
an end point of the incident surface opposite to the first surface is defined as a first end portion,
a distance between the first end portion and the flat surface in the normal direction is defined as a height Td,
a distance between the flat portion and the second surface in the normal direction is defined as a height To,
the incident surface satisfies a relationship of Td>To,
an end point of the second surface adjacent to the incident surface is defined as a second end portion,
an angle formed between the normal direction and a virtual straight line connecting the first end portion and the second end portion is defined as ξ,
an incident angle of the incident light with respect to the flat surface is defined as Φ, and
the light guide body satisfies a relationship of ξ<Φ.
6. The optical member according to claim 5 , wherein
the light guide body is covered with a light absorption film within a region from the first end portion to the second end portion.
7. The optical member according to claim 1 , wherein
the first surface has a plurality of regions, a ratio of widths of the prism portion and the flat portion adjacent to each other being different among the plurality of regions,
a ratio of the width of the flat portion to the width of the prism portion is smaller as the plurality of regions is located farther from the incident surface, and
the width of the flat portion is zero in a region farthest from the incident surface.
8. The optical member according to claim 7 , wherein
the number of the plurality of regions is defined as m+1 (m: natural number of 1 or more),
a width of the prism portion is defined as Wpk and a width of the flat portion is defined as Wsk in a k-th (1≤k≤m) region from the incident surface among the plurality of regions, and
the k-th region satisfies a relationship of Wsk/(Wpk+Wsk)= (m+1−k)/(m+2−k).
9. The optical member according to claim 7 , wherein
a height To is defined as a distance between the second surface and the flat portion in a normal direction of the flat portion,
the incident light has an incidence angle Φ relative to the normal direction of the flat portion, and
a width WI of the incident portion is within a range ±10% of a value represented by 2To×tan Φ.
10. The optical member according to claim 1 , wherein
the plurality of flat portions is parallel to the second surface.
11. The optical member according to claim 1 , wherein
the ejection surface is parallel to the incident surface.
12. The optical member according to claim 1 , wherein
a width of the prism portion is defined as Wp and a width of the flat portion adjacent to the prism portion is defined as Ws,
an angle formed between an incident direction of the outside light on the incident surface and a normal direction with respect to a flat surface formed by the flat portions is defined as θ 1 , and
the first surface satisfies a relationship pf (Wp+Ws)cos θ 1 <2 mm.
13. The optical member according to claim 1 , wherein
the prism portion has a facing surface facing the ejection surface,
an angle formed between the facing surface and a normal direction with respect to a flat surface formed by the flat portions is defined as δ,
an angle formed between the emission light emitted outward from the ejection surface and the normal direction is defined as θ 2 , and
the facing surface satisfies a relationship of δ≥θ 2 .
14. The optical member according to claim 1 , wherein
at least a part of the prism portions has a trapezoidal shape with a top side adjacent to the ejection surface.
15. The optical member according to claim 14 , wherein
each of the prism portions has a trapezoidal shape with a top side,
one of the prism portions has a first end point that is an end point of the ejection surface adjacent to the flat portion,
another prism portion adjacent the one of the prism portions has a second end point that is an end point of the top side opposite to the ejection surface,
an angle ε is formed by a virtual straight line connecting the first end point and the second end point and a normal direction with respect to a flat surface formed by the flat portions,
an angle θ 2 is formed by an emission light emitted outward from the emission surface and the normal direction, and
the prism portion having the trapezoidal shape satisfies a relationship of ε>θ 2 .
16. The optical member according to claim 1 , wherein
the first surface along which the first prism portions are arranged is not flush with the incident portion along which the second prism portions are arranged.
17. The optical member according to claim 1 , wherein
the second prism portions are located adjacent to each other without a flat portion.
18. The optical member according to claim 1 , wherein
the incident portion is an outer surface that connects the first surface and the second surface.
19. The optical member according to claim 18 , wherein
the incident portion is opposite to a third surface, through which a part of the incident light that is repeatedly reflected by the reflection surface and the second surface, and does not reach the prism portion, escapes to the outside as afterglow.