| 摘要 |
A micro image pickup optical system is provided to obtain f-number about 2.8 and angle of view over 60 degrees, to secure high resolution, and to improve various aberrations. A micro image pickup optical system is composed of an aperture stop(AS); a first lens(L1) having the positive refractive force, wherein the surface of the first lens facing an object is convex; a second lens(L2) having the negative refractive force; a third lens(L3) having the positive refractive force; and a fourth lens(L4) having the negative refractive force. The size of the optical system in an optical axial direction satisfies the following formula 1, 1.225. Refractive indexes of the first and second lenses satisfy the following formula 3, Nd2-Nd1>0.15. TL is the distance from the aperture stop to an upside(IP). F is an effective focal distance of the optical system. Vd1 is an abbe number of the first lens and Vd2 is an abbe number of the second lens. Nd1 is a refractive index of the first lens and Nd2 is a refractive index of the second lens.
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