Abstract: A structure for positioning a plurality of noncircular lenses relative to a lens holding frame which holds the noncircular lenses precisely. The structure includes a first lens frame which holds a first noncircular lens, and a second lens frame which holds a second noncircular lens. A first coupling part of the first lens frame has a first connecting surface which is perpendicular to a centering axis of the first noncircular lens, and a second coupling part of the second lens frame has a second connecting surface, contacting with the first connecting surface, which is perpendicular to the centering axis of the first noncircular lens. When the first coupling part is connected to the second coupling part, they are prevented from rotating relative to each other around the centering axis which is perpendicular to both the first and second connecting surfaces, by a mechanism which prevents a mutual rotation between the first coupling part and the second coupling part of the lens frame.

Abstract: A structure for positioning a plurality of noncircular lenses relative to a lens holding frame which holds the noncircular lenses precisely. The structure includes a first lens frame which holds a first noncircular lens, and a second lens frame which holds a second noncircular lens. A first coupling part of the first lens frame has a first connecting surface which is perpendicular to a centering axis of the first noncircular lens, and a second coupling part of the second lens frame has a second connecting surface, contacting with the first connecting surface, which is perpendicular to the centering axis of the first noncircular lens. When the first coupling part is connected to the second coupling part, they are prevented from rotating relative to each other around the centering axis which is perpendicular to both the first and second connecting surfaces, by a mechanism which prevents a mutual rotation between the first coupling part and the second coupling part of the lens frame.

Abstract: A structure for positioning a plurality of noncircular lenses relative to a lens holding frame which holds the noncircular lenses precisely. The structure includes a first lens frame which holds a first noncircular lens, and a second lens frame which holds a second noncircular lens. A first coupling part of the first lens frame has a first connecting surface which is perpendicular to a centering axis of the first noncircular lens, and a second coupling part of the second lens frame has a second connecting surface, contacting with the first connecting surface, which is perpendicular to the centering axis of the first noncircular lens. When the first coupling part is connected to the second coupling part, they are prevented from rotating relative to each other around the centering axis which is perpendicular to both the first and second connecting surfaces, by a mechanism which prevents a mutual rotation between the first coupling part and the second coupling part of the lens frame.

Abstract: A structure for holding a decentered lens inside a lens barrel, as well as an axisymmetrical lens. The structure includes: a lens barrel with a lens receiving part projecting inwardly and radially from an inner surface thereof; a decentered lens, with a first lens surface as a reference surface a centering axis of which is made to coincide with an axis of the lens barrel, and a second lens surface, which includes an annular flat surface around the second lens surface, in which the annular flat surface forms a recessed surface relative to the second lens surface, in which the annular flat surface is perpendicular to the axis of the lens barrel, and in which the annular flat surface contacts the lens receiving part of the lens barrel; and a washer, installed on the inner surface of the lens barrel, to fixedly hold the decentered lens, relative to the lens barrel, by pinching the decentered lens between the washer and the lens receiving part of the lens barrel.