Optical displacement sensor

An optical displacement sensor comprising:

• a diffraction unit having diffraction gratings arranged at a predetermined period along a measurement direction;
• a light source that radiates light to the diffraction unit;
• and
• a light-receiving unit that receives light that has gone through the diffraction unit, characterized in that the optical displacement sensor comprises:
• a splitting unit that splits the light radiated from the light source into a first light ray and a second light ray that is different from the first light ray at a predetermined splitting point, and that outputs each of the first light ray and the second light ray in a direction that is in plane symmetry with respect to a plane including the splitting point;
• and
• a reflection unit having a first reflection part that reflects the light radiated from the light source and a second reflection part provided at a predetermined angle with respect to the first reflection part,
• wherein the reflection unit comprises:
• a first reflection unit including the second reflection part provided at a predetermined angle with respect to the first reflection part;
• a second reflection unit that is different from the first reflection unit and that includes the second reflection part provided at the same angle as the predetermined angle in the first reflection unit with respect to the first reflection part,
• wherein the first reflection unit and the second reflection unit are provided so that the first reflection parts and the second reflection parts are arranged in plane symmetry with respect to the plane including the splitting point, the plane being defined as a symmetry plane,
• wherein the first reflection part of the first reflection unit is incident with one of the first light ray and the second light ray output from the splitting unit and reflects the incident light to the second reflection part of the first reflection unit,
• wherein the first reflection part of the second reflection unit is incident with the other one of the first light ray and the second light ray output from the splitting unit and reflects the incident light to the second reflection part of the second reflection unit, and
• wherein the light-receiving unit receives the first light ray and the second light ray that have gone through the first reflection unit and the second reflection unit.