A lens system (10) includes a main lens (12) having a first surface (12a) and a second surface (12b) configured opposite to each other, a first film lens (11) and a second film lens (13) respectively secured on the first surface and the second surface of the main lens. The first film lens and/or the second film lens are radial gradient index lenses, which refractive index progressively decreases from the centers to the outmost sides. All of the main lens, the first film lens and the second film lens are converging lens, and the axles of them are overlapped one to another.