Patent ID: 11949973
Assignee: CANON KABUSHIKI KAISHA
Field: Audio-visual technology (Electrical engineering)
Classification: CPC G  H | IPC H

Claim 5:
6. An optical system comprising:
an imaging optical system; and
an attachment optical system attachable to and detachable from the imaging optical system,
wherein the attachment optical system includes:
a first converter optical system attachable to an object side of the imaging optical system; and
a second converter optical system attachable to an image side of the imaging optical system,
wherein the first converter optical system includes a first unit consisting of a dome-shaped cover, and
wherein the following inequality is satisfied:

0.9<|skcw/skmw|<1.5, where skcw is a distance on an optical axis from a lens surface closest to an image plane of the imaging optical system to the image plane while the attachment optical system is attached to the imaging optical system in water, and skmw is a distance on the optical axis from the lens surface closest to the image plane of the imaging optical system to the image plane while the attachment optical system is not attached to the imaging optical system in air.