Canon Patent: RF-S 14-30mm f/4-6.3 And RF 20-50mm f/4-5.6

May 28, 2024
Canon Patents
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Here is a new Canon patent application, one for a RF-S and one for a RF lens.

Canon patent application 2024072459 (Japan, 5/28/2024) discusses optical formulas for two RF-mount lenses:

RF-S 14-30mm f/4-6.3 [for APS-C imaging sensors]
RF 20-50mm f/4-5.6

From the patent literature:

The present invention provides a zoom lens that is both compact and lightweight and has high image quality, has a short focal length at the wide-angle end, is easy to manufacture, is inexpensive, and allows high-speed zoom operations.
BACKGROUND ART
Zoom lenses used in imaging devices are required to be small and lightweight, have various aberrations including chromatic aberration well corrected, and have high optical performance. Additionally, there is a demand for a zoom lens that has a short focal length at the wide-angle end, is easy to manufacture, and is inexpensive. Furthermore, there is a demand for a zoom lens that allows high-speed zoom operations.
In order to provide such a zoom lens, the arrangement of the aspherical lens is important. If an aspherical lens is placed in the second lens group, which is placed adjacent to the image side of the first lens group closest to the object and has a high axial ray height, the required precision of the aspherical lens will be high, making it difficult to manufacture. As the power increases, it becomes difficult to provide an inexpensive zoom lens. On the other hand, if an aspherical lens is not disposed in the second lens group, it will be difficult to suppress aberrations generated in the second lens group, making it difficult to achieve high image quality. Furthermore, in order to provide a zoom lens that can realize high-speed zoom operations, it is effective to fix the first lens group with a large lens diameter and move only the lens group with a small lens diameter. However, by fixing the first lens group closest to the object, aberration correction deteriorates and it becomes difficult to achieve high image quality.
Patent Document 1 describes a compact and lightweight zoom lens that includes a first lens group with negative refractive power, a second lens group with positive refractive power, and a second lens group with negative refractive power, which are arranged in order from the object side. A zoom lens has been proposed that includes a third lens group and a fourth lens group with positive refractive power. The first lens group is fixed relative to the image plane during zooming.
The present invention provides a zoom lens that is both compact and lightweight and has high image quality, has a short focal length at the wide-angle end, is easy and inexpensive to manufacture, and allows high-speed zoom operations.

Example 1