Polarizing turning film using total internal reflection
View Patent ↗A light redirecting article redirects light toward a target angle. The light redirecting article has an input surface for accepting incident illumination over a range of incident angles and an output surface with a plurality of light redirecting structures, each light redirecting structure having an internal reflection surface oriented at a first angle with respect to the plane of the input surface and an exit surface for emitting an output light at an emitted light angle, wherein the exit surface is oriented at a second angle relative the plane of the input surface. For incident illumination at a principal angle greater than 60 degrees from normal, light is reflected from the internal reflection surface and emitted from the exit surface at an emitted light angle that is within 5 degrees of the target angle.
1. A light redirecting article for redirecting light toward a target angle, said light redirecting article comprising:
(a) an input surface for accepting incident illumination over a range of incident angles;
(b) an output surface comprising a plurality of light redirecting structures each light redirecting structure having
(i) an internal reflection surface oriented at a first angle with respect to the plane of the input surface;
(ii) an exit surface for emitting an output light at an emitted light angle, wherein the exit surface is oriented at a second angle relative the plane of the input surface,
whereby for incident illumination at a principal angle greater than 60 degrees from normal, light is reflected from the internal reflection surface and emitted from the exit surface at an emitted light angle that is within 5 degrees of the target angle.
2. The light redirecting article of claim 1 comprising a material having a refractive index greater than 1.6.
3. The light redirecting article of claim 1 whereby, for incident illumination at either of at least two different principal angles, each principal angle being greater than 60 degrees from normal and said principal angles having a difference of 5 degrees or greater, the emitted light angle is within 5 degrees of the target angle.
4. The light redirecting article of claim 1 wherein the output light for the principal angle has transmittance of one polarization in excess of 95 percent.
5. The light redirecting article of claim 1 wherein the output light for the principal angle further has a transmittance of one polarization in excess of 90 percent.
6. The light redirecting article of claim 5 wherein the output light for the principal angle has a transmittance of less than 55 percent for the orthogonal polarization.
7. The light redirecting article of claim 5 wherein the output light for the principal angle has a transmittance of less than 50 percent for the orthogonal polarization.
8. The light redirecting article of claim 1 wherein for incident illumination at each of at least three different principal angles, each principal angle being greater than 60 degrees from normal and said angles having a difference of 5 degrees or greater from each other, the emitted light angle is within 5 degrees of the target angle.
9. The light redirecting article of claim 1 wherein the target angle is normal with respect to the plane of the light redirecting article.
10. The light redirecting article of claim 1 wherein a plurality of the light redirecting structures are substantially parallel and extend from one edge of the output surface to the other.
11. The light redirecting article of claim 1 comprising at least two materials, wherein the materials have different indices of refraction.
12. The light redirecting article of claim 1 wherein, for incident illumination wherein the principal angle is 70 degrees or less, said illumination is directed at an incident angle within +/−11 degrees of Brewster's angle at the input surface and said light is incident at the exit surface at an angle that is within +/−11 degrees of Brewster's angle at the exit surface.
13. The light redirecting article of claim 1 wherein, for incident illumination wherein the principal angle is 70 degrees or more, said illumination is directed at an incident angle within +/−16 degrees of Brewster's angle at the input surface and said light is incident at the exit surface at an incident angle that is within +/−16 degrees of Brewster's angle at the exit surface.
14. The light redirecting article of claim 1 wherein the internal reflection surface has a portion that is curved.
15. The light redirecting article of claim 1 wherein the exit surface has a portion that is curved.
16. The light redirecting article of claim 1 wherein the exit surface comprises more than one slope.
17. The light redirecting article of claim 1 wherein the light redirecting structures are truncated.
18. The light redirecting article of claim 1 wherein the light redirecting structures are extended in an arcuate pattern.
19. A display apparatus comprising:
(a) an illumination source for emitting illumination over a range of angles;
(b) a light redirecting article for redirecting light toward a target angle, the light redirecting article comprising:
(i) an input surface for accepting incident illumination over a range of incident angles;
(ii) an output surface comprising a plurality of light redirecting structures each light redirecting structure having an internal reflection surface oriented at a first angle with respect to the plane of the input surface and an exit surface for emitting an output light at an emitted light angle, wherein the exit surface is oriented at a second angle relative the plane of the input surface, whereby for incident illumination at a principal angle greater than 60 degrees from normal, light is reflected from the internal reflection surface and emitted from the exit surface at an emitted light angle that is within 5 degrees of the target angle; and
(c) a light gating device for forming an image by modulating the output light from the light redirecting article.