Light deflection device and optical device
An object is to provide a light deflection device and an optical device having a simple structure suitable for reducing the size and weight where a deflection angle can be increased. The light deflection device includes: a light deflection element that deflects incident light in one in-plane direction to be emitted; a driving unit that drives the light deflection element; a light collecting element that is disposed on a light emission side of the light deflection element; and an angle increasing optical element consisting of a diffraction element in which a periodic structure pitch gradually changes from a center of deflection of the light deflection element toward an outer side.
1. A light deflection device comprising:
a light deflection element that deflects incident light to be emitted;
a driving unit that drives the light deflection element;
an angle increasing optical element that is disposed downstream of the light deflection element in a light traveling direction and increases an angle range of a deflection angle of light emitted from the light deflection element, the angle increasing optical element consisting of a diffraction element having different periodic structure pitches in a plane; and
a light collecting element that is disposed downstream of the light deflection element in the light traveling direction;
wherein the angle increasing optical element is a liquid crystal diffraction element, and
the liquid crystal diffraction element includes an optically-anisotropic layer that is formed using a composition including a liquid crystal compound and has a liquid crystal alignment pattern in which a direction of an optical axis derived from the liquid crystal compound changes while continuously rotating in at least one in-plane direction.
2. The light deflection device according to claim 1 ,
wherein an optical path length between centers of the angle increasing optical element and the light collecting element is shorter than a focal length of the light collecting element.
3. The light deflection device according to claim 1 ,
wherein the diffraction element in the angle increasing optical element is a diffraction element in which the periodic structure pitch gradually changes from a center of the deflection angle of the light deflection element toward an outer side.
4. An optical device comprising:
the light deflection device according to claim 1 ;
a light source that emits light to the light deflection element of the light deflection device; and
a light-receiving element.
5. The light deflection device according to claim 2 ,
wherein the diffraction element in the angle increasing optical element is a diffraction element in which the periodic structure pitch gradually changes from a center of the deflection angle of the light deflection element toward an outer side.
6. The light deflection device according to claim 1 ,
wherein the liquid crystal alignment pattern of the optically-anisotropic layer is a concentric circular pattern having a concentric circular shape where the one in-plane direction in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating moves from an inner side toward an outer side.
7. The light deflection device according to claim 1 ,
wherein the optically-anisotropic layer includes a liquid crystal compound that is twisted and aligned along a helical axis extending in a thickness direction.
8. The light deflection device according to claim 7 ,
wherein the liquid crystal diffraction element includes two optically-anisotropic layers having opposite twisted directions in which the liquid crystal compound is twisted and aligned along the helical axis extending in the thickness direction.
9. The light deflection device according to claim 8 ,
wherein the optically-anisotropic layer in which the liquid crystal compound is not twisted and aligned is provided between the two optically-anisotropic layers.
10. The light deflection device according to claim 1 ,
wherein the light collecting element is a condenser lens element.
11. The light deflection device according to claim 1 ,
wherein the light collecting element is a diffraction element having different periodic structure pitches in a plane.
12. The light deflection device according to claim 11 ,
wherein the light collecting element is a liquid crystal diffraction element.
13. The light deflection device according to claim 12 ,
wherein the light collecting element is a liquid crystal diffraction element including an optically-anisotropic layer that is formed using a composition including a liquid crystal compound and has a liquid crystal alignment pattern in which a direction of an optical axis derived from the liquid crystal compound changes while continuously rotating in at least one in-plane direction.
14. The light deflection device according to claim 13 ,
wherein the liquid crystal alignment pattern of the optically-anisotropic layer in the light collecting element is a concentric circular pattern having a concentric circular shape where the one in-plane direction in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating moves from an inner side toward an outer side.
15. The light deflection device according to claim 13 ,
wherein the optically-anisotropic layer in the light collecting element includes a liquid crystal compound that is twisted and aligned along a helical axis extending in a thickness direction.
16. The light deflection device according to claim 1 ,
wherein the light deflection element is an optical phase modulation element.
17. The light deflection device according to claim 1 ,
wherein the light deflection element is a liquid crystal optical phase modulation element.
18. The light deflection device according to claim 1 ,
wherein the light deflection element is a MEMS light deflection element.
19. A light deflection device comprising:
a light deflection element that deflects incident light to be emitted;
a driving unit that drives the light deflection element;
an angle increasing optical element that is disposed downstream of the light deflection element in a light traveling direction and increases an angle range of a deflection angle of light emitted from the light deflection element, the angle increasing optical element consisting of a diffraction element having different periodic structure pitches in a plane; and
a light collecting element that is disposed downstream of the light deflection element in the light traveling direction;
wherein the light collecting element is a diffraction clement having different periodic structure pitches in a plane.