Display apparatus having collimated illumination
View Patent ↗A display apparatus ( 30 ) has an LC device ( 14 ) exhibiting its maximum contrast with incident light at an oblique angle φ from normal, wherein oblique angle φ is greater than about +/−10 degrees from normal. A backlight unit ( 32 ) provides substantially collimated illumination with a central ray at an incident angle θ 2 with respect to the LC device ( 14 ), wherein incident angle θ 2 within about +/−5 degrees of oblique angle φ. The full-width half-maximum intensity of the illumination is within about +/−10 degrees of the central ray at incident angle θ 2 .
1. A method for forming an image comprising:
(a) providing an LC device exhibiting its maximum contrast with incident light at an oblique angle φ from normal, wherein oblique angle φ is greater than about +/−10 degrees from normal; and,
(b) directing a substantially collimated illumination as incident light to the LC device, with a central ray at an incident angle θ 2 with respect to the LC device within about +/−5 degrees of oblique angle φ and wherein the full-width half-maximum intensity of the illumination is within about +/−10 degrees of the central ray at incident angle θ 2 .
2. The method of claim 1 wherein the step of providing an LC device comprises the step of providing a twisted nematic LC device.
3. The method of claim 1 wherein oblique angle φ is between about +/−10 degrees from normal and +/−25 degrees from normal.
4. The method of claim 1 wherein directing a substantially collimated illumination comprises the step of disposing a light redirecting film between a light guiding plate and the LC device.
5. The method of claim 1 wherein directing a substantially collimated illumination comprises the step of disposing a collimating film between a light providing surface and the LC device.