| 摘要 |
PROBLEM TO BE SOLVED: To provide a compact image pickup optical system which is a bright optical system and favorably corrects various aberration.SOLUTION: The image pickup optical system having five lenses includes in order from an object side: a first lens having a biconvex shape and positive refractive power; a second lens having negative refractive power; a third lens having a meniscus shape with a concave surface thereof directed toward the object side and negative refractive power; a fourth lens having a meniscus shape with a concave surface thereof directed toward the object side and positive refractive power; and a fifth lens having negative refractive power. The third lens and the fourth lens are joined, and the negative refractive power at a central portion of the third lens increases gradually toward a peripheral portion thereof, and the positive refractive power at a central portion of the fourth lens decreases gradually toward a peripheral portion thereof. A joined surface of the third lens and the fourth lens is an aspheric surface, and the cemented surface becomes a concave surface all the time with respect to the object side, at the central portion and the peripheral portion. |
