Imaging lens system, camera module, in-vehicle system, and vehicle

An imaging lens system comprising, sequentially from an object side toward an image side:

• a first lens having negative power with an image-side surface whose concave surface faces the image side:
• a second lens having negative power with an image-side surface whose concave surface faces the image side:
• a third lens having positive power with an object-side surface whose convex surface faces the object side, an iris, a fourth lens having positive power with an image-side surface whose convex surface faces the image side, and a fifth lens and a sixth lens constituting a cemented lens, one of the lenses having negative power and another of the lenses having positive power, wherein
• the imaging lens system satisfies the following Conditional Expressions (1) to (2):
• 2.3
• <
• f
• ⁢
• 4
• /
• f
• <
• 3.9
• ,
• and
• (
• 1
• )
• vd
• ⁢
• 4
• >
• 55
• (
• 2
• )
• where f4 is defined as a focal length of the fourth lens, f is defined as a focal length of an entire optical system, and vd4 is defined as an Abbe's number of a d-line of the fourth lens.