Abstract: A displacement detection apparatus can reduce a measurement error even when a diffraction grating is displaced and/or tilted to a direction other than the measurement direction. A displacement detection apparatus includes a light source which emits light, a luminous flux-splitting section, a diffraction grating, a diffracted light-reflecting section, a correcting lens, a luminous flux-coupling section, and a light-receiving section. The diffracted light-reflecting section reflects a first luminous flux and a second luminous flux so as to be perpendicular to one of measuring planes of the diffraction grating and be parallel to each other. The correcting lens is arranged between the diffracted light-reflecting section and the diffraction grating.

Abstract: A displacement detection apparatus can reduce a measurement error even when a diffraction grating is displaced and/or tilted to a direction other than the measurement direction. A displacement detection apparatus includes a light source which emits light, a luminous flux-splitting section, a diffraction grating, a diffracted light-reflecting section, a correcting lens, a luminous flux-coupling section, and a light-receiving section. The diffracted light-reflecting section reflects a first luminous flux and a second luminous flux so as to be perpendicular to one of measuring planes of the diffraction grating and be parallel to each other. The correcting lens is arranged between the diffracted light-reflecting section and the diffraction grating.

Abstract: There is provided a light distribution control member with a plurality of first prisms that have inclined surfaces of which each edge of a hexagon is a base edge, and a plurality of second prisms that have inclined surfaces of which each edge of a triangle is a base edge. The first prisms are arranged in a houndstooth pattern, and the second prisms are arranged in areas surrounded by three first prisms.

Abstract: An illuminator includes a light source unit having an emitting surface for emitting light, and a light distribution control member having a prism surface including a plurality of prisms that have inclined surfaces and are arranged in a plane for two-dimensionally controlling light distribution of light emitted from the light source unit, wherein the prism surface has flat parts. With the light distribution control member, in the light distribution properties of the illumination light of the illuminator, the luminous intensity angular distribution is properly adjusted to have uniform illuminance distributions.