Turning film having multiple slopes

1. A light redirecting article for redirecting light toward a target angle, the light redirecting article comprising:

(a) an input surface comprising a plurality of light redirecting structures each light redirecting structure having:

(i) a near surface having two slopes, sloping away from normal in one direction as defined by a first inclination base angle β 1 , a second inclination angle β 2 , and a first half apex angle α 2 , for accepting incident illumination over a range of incident angles;

(ii) a far surface sloping away from normal, in the opposite direction relative to the near surface, as defined by a second base angle γ 1 and a second half apex angle α 1 ; and

(b) an output surface opposing to the input surface wherein the near and far surfaces are opposed to each other at an angle (α 1 +α 2 ) that is in the range from 60 to 70 degrees, and the base angle β 1 is in the range from 82 to 87 degrees.

2. The light redirecting article of claim 1 wherein the near surface has four slopes, sloping away from normal in one direction as defined by the first inclination base angle β 1 , the second inclination angle β 2 , a third inclination angle β 3 , a fourth inclination angle β 4 , and the first half apex angle α 2 , for accepting incident illumination over a range of incident angles.

3. The light redirecting article of claim 1 wherein the near surface has a curved surface.

4. The light redirecting article of claim 1 wherein the light redirecting structure is formed of a material having a refractive index between 1.15 and 1.46.

5. The light redirecting article of claim 1 wherein the difference between α 1 and α 2 is less than 5 degrees.