Imaging lens

An imaging lens comprising, in order from an object side to an image side,

• a first lens with positive refractive power,
• a second lens with negative refractive power,
• a third lens,
• a fourth lens with positive refractive power, and
• a fifth lens with negative refractive power,
• wherein said first lens has an object-side surface being convex in a paraxial region, said third lens has an image-side surface being convex in a paraxial region, and said fifth lens is formed in a biconcave shape having an object-side surface being concave and an image-side surface being concave in a paraxial region, and the following conditional expressions (1), (2), (3), (4) and (21a) are satisfied:
• −9.00<r3/r7/D2<−4.20 (1)
• 0.10<r5/r6 (2)
• r7/T2<−9.00 (3)
• 0.50<r10/(D5−T4)<9.50 (4)
• 0.20<(f4/f)+(f5/f)<0.45 (21a)
• where
• r3:
• a paraxial curvature radius of an object-side surface of the second lens,
• r7:
• a paraxial curvature radius of an object-side surface of the fourth lens,
• D2:
• a thickness along the optical axis of the second lens,
• r5:
• a paraxial curvature radius of an object-side surface of the third lens,
• r6:
• a paraxial curvature radius of an image-side surface of the third lens,
• T2:
• a distance along the optical axis from an image-side surface of the second lens to an object-side surface of the third lens,
• r10:
• a paraxial curvature radius of an image-side surface of the fifth lens,
• D5:
• a thickness along the optical axis of the fifth lens,
• T4:
• a distance along the optical axis from an image-side surface of the fourth lens to an object-side surface of the fifth lens,
• f4:
• a focal length of the fourth lens,
• f5:
• a focal length of the fifth lens, and
• f:
• a focal length of the overall optical system of the imaging lens.