Display device and optical device

1. A display device comprising:

a visual target; and

a backlight adapted to illuminate the visual target from the rear, the backlight including:

a plurality of first light sources disposed on the rear of the visual target and on one side of a given direction along the rear surface of the visual target to produce light of a first wavelength;

second light sources disposed on the rear of the visual target and on the one side of the given direction to produce light of a second wavelength different from the first wavelength and smaller in number than the first light sources; and

a light guide plate disposed to be opposed to the rear surface of the visual target so as to radiate the light, produced by the first and second light sources, across the rear surface of the visual target while at the same time guiding the light toward another side of the given direction, wherein

the light guide plate has a plurality of projecting portions on a side surface portion thereof upon which the light, produced by the plurality of first and second light sources is incident, the projecting portions being arranged, along the side surface portion and project toward the one side of the given direction,

the plurality of first light sources are disposed to be opposed to the tip surfaces of the plurality of projecting portions, and

the second light sources are disposed to be opposed to the bottom surfaces of recessed portions formed between the plurality of projecting portions.

2. The display device of claim 1 further comprising

a plurality of sensors disposed in a distributed manner at positions on a plane overlapping the visual target and light guide plate, the sensors being adapted to detect the light of the second wavelength which has passed through the visual target from the rear side and has been reflected by a detection target which is located on the front of the visual target.

3. The display device of claim 2 , wherein

the first wavelength is a visible light wavelength, and

the second wavelength is an invisible light wavelength.

4. The display device of claim 1 , wherein

projections and recesses are formed on the tip surfaces of the plurality of projecting portions and the bottom surfaces of the recessed portions to scatter light, and

the projections and recesses on the bottom surfaces of the recessed portions are formed smaller than those on the tip surfaces of the plurality of projecting portions.

5. The display device of claim 1 , wherein

a light-scattering substance is mixed in the light guide plate, and

the light-scattering substance is relatively higher in concentration in the region surrounding the region with which the visual target coincides and to which the second light sources are opposed as seen in plan view.

6. An optical device comprising:

a plurality of first light sources adapted to produce light of a first wavelength;

second light sources adapted to produce light of a second wavelength different from the first wavelength and smaller in number than the first light sources; and

a light guide member adapted to guide the light, produced by the first and second light sources, in a given direction, wherein

the light guide member has a plurality of projecting portions on a surface portion thereof upon which the light from the plurality of first light sources and from the second light sources is incident, the plurality of projecting portions being arranged along the surface portion,

the plurality of first light sources are disposed to be opposed to the tip surfaces of the plurality of projecting portions, and

the second light sources are disposed to be opposed to the bottom surfaces of recessed portions formed between the plurality of projecting portions.