Here is a new Canon patent application, yet for another RF mount lens. A rather interesting one, although it refers to ab already released lens: the Canon RF 100-300mm f/2.8L IS USM.
Canon patent application 2023117937 (Japan, published 8/24/2023) discusses optical formulas for a fast telephoto zoom lens, a telephoto zoom that keeps f/2.8 over the zoom range.
Excerpt from the patent literature:
A zoom lens, an imaging device having the same, and an imaging system.
An object of the present invention is to provide a lightweight zoom lens that has high optical performance over the entire zoom range and all object distances.
Description of the Related Art
In recent years, zoom lenses used in image pickup apparatuses are required to have high optical performance at all object distances from infinity to the shortest distance, and to be quiet during focusing. In order to meet these demands, a zoom lens has been proposed that performs focusing by moving two lens groups along different trajectories (see Patent Documents 1 and 2).
In a large-aperture telephoto zoom lens with a long focal length and a small F-number, if the focus group is arranged near the diaphragm or closer to the object side than the diaphragm, the lens diameter of the focus group increases, making it difficult to reduce the weight . As a result, the load on the actuator for driving the focus group increases, making it difficult to perform quiet and high-speed focusing. In order to reduce the weight of the focus group, it is important to appropriately set the arrangement of the focus group and the refractive power of the front and rear lens groups.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a lightweight zoom lens that has high optical performance over the entire zoom range and object distance.
- Focal length: 103.00-292.00
- F-value: 2.89-2.91
- Half angle of view: 11.86-4.24
- Image height: 21.64
- Overall length: 334.46
- Back focus: 32.73
- Focal length: 120.00-294.00
- F-value: 2.91
- Half angle of view: 10.22-4.21
- Image height: 21.64
- Total length: 350.00
- Back focus: 37.47
As I said at the beginning, the Canon patent application refers to an already released lens. More Canon patent applications are listed here.