Inner focus macrolens and image pickup device using the same

An inner focus macrolens comprising sequentially from an object side:

• a first lens unit;
• an aperture stop;
• a second lens unit having a positive refractive power;
• a third lens unit having a negative refractive power;
• and
• a fourth lens unit having a positive refractive power, wherein
• the first lens unit comprises a negative lens as the closest powered lens to the object side and a positive lens,
• the second lens unit comprises sequentially from the object side:
• a negative meniscus lens having a convex surface facing the image side, a positive meniscus lens having a convex surface facing the image side, and a biconvex positive lens,
• the third lens unit comprises a negative lens,
• the fourth lens unit comprises a positive lens,
• wherein focusing is performed by moving the third lens unit toward an image side, and the inner focus macrolens satisfies conditional expressions (1) and (2):
• −5<=(1−β32)×β42<=−2 (1)
• −4<=(R2f+R2r)/(R2f−R2r)<=0.4 (2)
• wherein beta3 is a lateral magnification of the third lens unit in focusing on an infinity object, beta4 is a lateral magnification of the fourth lens unit in focusing on the infinity object, R2f is a radius of curvature of an object side surface of the object side negative lens, and R2r is a radius of curvature of an image side surface of the object side negative lens.