Liquid crystal optical element and image display device
View Patent ↗According to one embodiment, liquid crystal optical element includes: first board; second board; liquid crystal layer; first electrodes; second electrodes; third electrodes; and fourth electrode. The liquid crystal optical element generates refractive index distribution functioning as a lens. The first electrodes are at positions corresponding to end portions of the lens and on the liquid crystal layer side of the first board. The second electrodes are at positions corresponding to discontinuity points of the lens and on the liquid crystal layer side of the first board. The third electrodes are at positions corresponding to lens surfaces of the lens and on the liquid crystal layer side of the first board. The fourth electrode is provided to the whole surface on the liquid crystal layer side of the second board and includes first cutout portions formed at parts opposing the third electrodes.
1. A liquid crystal optical element comprising:
a first board;
a second board;
a liquid crystal layer sandwiched between the first board and the second board, the liquid crystal optical element being configured to generate a refractive index distribution functioning as a Fresnel lens by application of a voltage to the liquid crystal layer;
a plurality of first electrodes provided at first positions corresponding to end portions of the Fresnel lens and on the liquid crystal layer side of the first board;
a plurality of second electrodes provided at second positions on the liquid crystal layer side of the first board between the first positions;
a plurality of third electrodes provided at third positions on the liquid crystal layer side of the first board, the third positions between the second positions;
a fourth electrode provided to a surface on the liquid crystal layer side of the second board and comprising first slits formed at parts overlapping the third electrodes by partially removing the fourth electrode, wherein
a width of each of the first slits is formed to be greater than a width of each of the third electrodes opposing each of the first slits; and
first, second, and third voltages are provided between the fourth electrode and the first, second, and third electrodes, respectively, in order to generate the refractive index distribution.
2. The liquid crystal optical element of claim 1 , wherein, as viewed in an opposing direction of the first board and the second board, an area to which each of the first slits is provided comprises a whole area of each of the third electrodes opposing the each of the first slits.
3. The liquid crystal optical element of claim 1 , wherein
the third electrodes are arranged between a central axis of the Fresnel lens and each of the first electrodes, and
a width of each of the first slits opposing each of the third electrodes is formed greater in a width as a distance between the each of the third electrodes and the central axis decreases.
4. The liquid crystal optical element of claim 1 , wherein
a plurality of the first slits are arranged in the second board, and,
as viewed in an opposing direction of the first board and the second board, each of the first slits is formed greater in a width as a distance between a central axis of the Fresnel lens and a position of an area to which the each of the first slits is provided decreases.
5. The liquid crystal optical element of claim 1 , wherein
the first electrodes and the second electrodes are embedded in an insulation layer provided to the liquid crystal layer side of the first board, and
the third electrodes are provided at a position on the liquid crystal layer side of the insulation layer.
6. The liquid crystal optical element of claim 1 , wherein second slits are provided at positions corresponding to the second electrodes and on the fourth electrode.
7. The liquid crystal optical element of claim 6 , wherein
the second electrodes are arranged between a central axis of the Fresnel lens and each of the first electrodes, and
each of the second slits opposing the second electrodes is formed greater in a width as a distance between each of the second electrodes and the central axis decreases.
8. The liquid crystal optical element of claim 6 , wherein
a plurality of the second slits are arranged in the second board, and,
as viewed in an opposing direction of the first board and the second board, each of the second slits is formed greater in a width as a distance between the central axis and a position of an area to which the each of the second slits is provided decreases.
9. The liquid crystal optical element of claim 1 , wherein the first electrodes, the second electrodes, and the third electrodes are provided in symmetry with respect to a central axis of the Fresnel lens.
10. The liquid crystal optical element of claim 1 , further comprising:
a fifth electrode provided at a position corresponding to a central axis of the Fresnel lens and on the liquid crystal layer side of the first board.
11. An image display device comprising:
the liquid crystal optical element of claim 1 ; and
an image display module comprising a display stacked on the liquid crystal optical element and causing light including image information to be incident on the liquid crystal layer comprised in the liquid crystal optical element.