| 摘要 |
A small-sized optical system is provided to decrease a size of an electronic device by arranging the small-sized optical system using four lenses. A small-sized optical system includes a first lens(G1), a second lens(G2), a third lens(G3), and a fourth lens(G4), which are sequentially arranged from an object side to an image side. The first lens has a positive refractive power. The second lens has a negative refractive power and is made of a glass material. A relation, -1.5 < f2/tt1 < -0.5, is satisfied, where f2 is a focal length of the second lens and ttl is a distance between an object side surface of the first lens to the image side.
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