Backlight unit and head-up display device

1. A backlight unit, comprising:

at least one light source;

a light collecting member that collects light emitted from the light source;

an optical member that includes a concave reflecting surface and reflects light incident from the light collecting member toward a light transmissive liquid crystal display element by the reflecting surface; and

a diffusion plate that is arranged on an optical path between the optical member and the liquid crystal display element, wherein

the reflecting surface of the optical member includes a plurality of micromirrors,

one or more groups of the plurality of micromirrors are arranged in the reflecting surface in a first direction and a second direction orthogonal to the first direction, and

each of the micromirrors includes a convex or concave curved surface.

2. The backlight unit according to claim 1 , wherein

the respective micromirrors are formed such that the curved surfaces have the same curvatures in at least one of the first direction and the second direction, and differ in a length in a direction in which the curved surfaces have the same curvature.

3. The backlight unit according to claim 2 , wherein

the respective micromirrors are formed such that a length in the direction in which the curved surfaces have the same curvature differs for each of areas obtained by dividing the reflecting surface in the direction in which the curved surfaces have the same curvature.

4. The backlight unit according to claim 2 , wherein

the respective micromirrors are formed such that lengths in the direction in which the curved surfaces have the same curvature are consecutively different.

5. The backlight unit according to claim 1 , wherein

the respective micromirrors are formed such that lengths in at least one of the first direction and the second direction are equal, and

curvatures of the curved surfaces are different in a direction in which the micromirrors have the same length.

6. The backlight unit according to claim 5 , wherein

the respective micromirrors are formed such that the curvature of the curved surface in the direction in which the micromirrors have the same length differs for each of areas obtained by dividing the reflecting surface in the direction in which the micromirrors have the same length.

7. The backlight unit according to claim 1 , wherein

the respective micromirrors are formed such that lengths in at least one of the first direction and the second direction are equal,

the curved surface is a free curved surface including a plurality of curvatures, and

the plurality of curvatures are set to be different in accordance with an angle of deviation amount of reflected light to the liquid crystal display element with respect to incident light from the light collecting member in a direction in which the micromirrors have the same length.

8. A head-up display device, comprising:

a light transmissive liquid crystal display element; and

a backlight unit, wherein

the backlight unit includes:

at least one light source;

a light collecting member that collects light emitted from the light source;

an optical member that includes a concave reflecting surface and reflects light incident from the light collecting member toward the liquid crystal display element by the reflecting surface; and

a diffusion plate that is arranged on an optical path between the optical member and the liquid crystal display element,

the reflecting surface of the optical member includes a plurality of micromirrors,

one or more groups of the plurality of micromirrors are arranged in the reflecting surface in a first direction and a second direction orthogonal to the first direction, and

each of the micromirrors includes a convex or concave curved surface.