A system comprising a sharpener and a light-emitting surface, the sharpener comprising: a cylindrical inner louver portion and a cylindrical outer louver portion, which are concentrically disposed around an axis that extends forward from the center of the light-emitting surface, wherein a back end of the inner louver portion and a back end of the outer louver portion are disposed nearer to the light-emitting surface, and a front end of the inner louver portion and a front end of the outer louver portion are disposed farther from the light-em itting surface, and the front end of the inner louver portion is disposed nearer to the light-emitting surface than the front end of the outer louver portion is, and wherein the back end of the inner louver portion is disposed nearer to the light-emitting surface than the back end of the outer louver portion is, and wherein in a cross section of the sharpener, the cross section being cut by a plane that includes the axis, when the axis is used to define a boundary to divide into a first side and a second side in the cross section, and when a straight line that passes through a back end side inner periphery edge (c) of the outer louver portion located on the first side and also passes through a front end side inner periphery edge (d) of the outer louver portion located on the second side is defined as a first reference line, a portion of a front end side outer periphery edge (b) of the inner louver portion appeared on the first side in the cross section is located on the first reference line or forward than the first reference line, characterised in that the distance from the axis to a back end side outer periphery edge (a) of the inner louver portion is longer than the distance from the axis to an edge portion of the light-emitting surface. a cylindrical inner louver portion and a cylindrical outer louver portion, which are concentrically disposed around an axis that extends forward from the center of the light-emitting surface, wherein a back end of the inner louver portion and a back end of the outer louver portion are disposed nearer to the light-emitting surface, and a front end of the inner louver portion and a front end of the outer louver portion are disposed farther from the light-em itting surface, and the front end of the inner louver portion is disposed nearer to the light-emitting surface than the front end of the outer louver portion is, and wherein the back end of the inner louver portion is disposed nearer to the light-emitting surface than the back end of the outer louver portion is, and wherein in a cross section of the sharpener, the cross section being cut by a plane that includes the axis, when the axis is used to define a boundary to divide into a first side and a second side in the cross section, and when a straight line that passes through a back end side inner periphery edge (c) of the outer louver portion located on the first side and also passes through a front end side inner periphery edge (d) of the outer louver portion located on the second side is defined as a first reference line, a portion of a front end side outer periphery edge (b) of the inner louver portion appeared on the first side in the cross section is located on the first reference line or forward than the first reference line, characterised in that the distance from the axis to a back end side outer periphery edge (a) of the inner louver portion is longer than the distance from the axis to an edge portion of the light-emitting surface.