A first light source arrangement pattern is defined by: defining segments opposing to each other and arranged at end positions out of three segments in a first unit and three segments in a second unit, as light source arrangement positions; and defining one of three segments in a third unit, at the same position as the segment defined as the light source arrangement position in the first unit, as a light source arrangement position. A second light source pattern is defined by defining segments out of the segments in the first unit, the second unit, and the third unit, at end positions opposite to the segments defined as the light source arrangement positions in the first light source arrangement pattern, as light source arrangement positions. The first light source arrangement pattern and the second light source arrangement pattern are alternately arranged in the vertical direction.