Canon Patent For 12-48mm f/1.8-4.0 Lens For EOS M System

Canon Patent

Canon patent application 2019-120821 (Japan) describes the optical formula for a 12-48mm f/1.8-4 lens for the Canon EOS M mirrorless camera system.

An excerpt from the Canon patent:

[…] provide a zoom lens which is small in the whole lens system, has a wide angle of view, a high zoom ratio, and a large aperture ratio and has high optical performance over an entire zoom range. 
[Means for solving]A 1 lens group having negative refractive power, a 2 lens group having positive refractive power, a 3 lens group having negative refractive power, and a 4 lens group having positive refractive power arranged in this order from the object side to the image side, and the 1 lens group is stationary at the time of zooming. In this zoom lens, a 2 lens group, a 3 lens group, and a 4 lens group are moved and an interval between adjacent lens groups is changed. The 4 lens group has 2 or more lenses, and appropriately sets a focal length f 2 of the 2 lens group, a focal length fw of the entire system at the wide-angle end, a moving amount M 2 of the 4 lens group during zooming from the wide-angle end to the telephoto end, and a moving amount M 4 of the second lens group during zooming from the wide-angle end to the telephoto end. 

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