Patent ID: 11971607
Assignee: CANON KABUSHIKI KAISHA
Field: Optics (Instruments)
Classification: CPC G | IPC G

Claim 17:
18. An image pickup apparatus comprising:
an optical system with a fixed focal length; and
an image sensor configured to capture an image formed by the optical system,
wherein the optical system includes:
a front lens unit closest to an object side;
a rear lens unit having a negative refractive power closest to an image plane; and
a middle group having a positive refractive power as a whole, including one or more lens units, and disposed between the front lens unit and the rear lens unit,
wherein a distance between adjacent lens units changes during focusing,
wherein the rear lens unit includes an air lens having a negative refractive power,
wherein the front lens unit includes a negative meniscus lens having a convex surface facing an image side,

wherein the rear lens unit includes two or more positive lenses, and
wherein the following conditional expressions are satisfied:

—0.40≤f/fr≤−0.12

65≤vdpl 

0.00<|fpl/fr|≤0.60

−10.0≤(R1+R2)/(R1-R2)<0.0, where f is a focal length of the optical system, fr is a focal length of the rear lens unit, vdpl and fpl are an Abbe number and a focal length of a positive lens having the largest Abbe number in the rear lens unit, respectively, R1 is a radius of curvature of a surface on the object side of the air lens, and R2 is a radius of curvature of a surface on the image side of the air lens.