Optical Element, Holding Structure Therefor, And Optical Device

An optical element having a first surface, a second surface on the opposite side of the first surface, an optical surface provided on at least one of the first and second surfaces, and a protruding part, the protruding part being held in a prescribed position by being in contact with a holding member, wherein

• the protruding part comprises:
• a first protruding part that is formed on the first surface and comprises a first contact part that is a convex circular arc shape on at least one longitudinal plane and partly comes into contact with the holding member, and
• a second protruding part that is formed on the second surface and comprises a second contact part that is a convex circular arc shape on at least one longitudinal plane and partly comes into contact with the holding member, and
• a circular arc that constitutes the first contact part and a circular arc that constitutes the second contact part are present in at least one cross-section that passes through a contact point between the first contact part and the holding member as well as a contact point between the second contact part and the holding member, and the center of the circular arc that constitutes the first contact part is aligned with the center of the circular arc that constitutes the second protruding part.