| 摘要 |
PURPOSE: A slim lens unit is provided to improve performance of the unit by compensating spherical aberration and coma aberration by using a non-spherical plastic lens. CONSTITUTION: A slim lens unit includes a first lens(10), a second lens(20), a diaphragm(30), and a third lens(40) implemented sequentially from an object side. The first lens has a negative refractive index. The second lens has a positive refractive index and includes convex portions at both ends thereof. The diaphragm adjusts an amount of light. The third lens has a positive refractive index and has a meniscus formation. The refractive indexes of the first and the third lens satisfy 0.8<abs(f1/fT) <0.9 and 3.2<abs(f3/fT)<3.4, where abs(a) means an absolute value of a, fT is a focal distance of the overall system, f1 is a focal distance of the first lens, and f3 is a focal distance of the third lens.
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