Reflective optical sensor

A reflective optical sensor comprising a light emitting element and a light receiving element, and detecting an object to be detected by reflected light emitted from the light emitting element and reflected by the object to be detected with the light receiving element;

• wherein
• provided is a case in a form of an open box integrally formed with a first concave mirror and a second concave mirror, each of which has a reflective surface comprising a partial concave surface of a rotational ellipse surface rotated around a major axis of an ellipse,
• the first concave mirror and the second concave mirror are formed open toward an open side of the case so that one focal point of the first concave mirror is coincident with one focal point of the second concave mirror as a common focal point and a first focal point, which is the other focal point of the first concave mirror, does not overlap with a second focal point, which is the other focal point of the second concave mirror,
• the light emitting element emits light from the first focal point toward the first concave mirror,
• the first concave mirror reflects the light to the object to be detected which is positioned at or near the common focal point, and the second concave mirror reflects light reflected by the object to be detected, and
• the light receiving element is configured to detect the light reflected by the second concave mirror at the second focal point.