Canon Patent For Various RF Mount Zoom Lenses

December 6, 2019
Canon Patents
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Canon patent application US20190369372 discusses optical formulas for various zoom lenses for the Canon EOS R system.

Among the discussed optics in this Canon patent application is a 28-280mm f/2.8 lens. All lenses seem to be designed for the EOS R full frame mirrorless system.

A zoom lens includes, in order from an object side, a positive first unit, a negative second unit, a positive intermediate group consisting of one or two units and including a third unit located on a most object side, a negative unit, and a rear group consisting of one or two units including a positive unit located on a most object side. Conditional expressions are satisfied with respect to amounts of movement of the second and third units from a wide angle end to a telephoto end, a distance at the wide angle end from a most object side surface vertex in the first unit to a most object side surface vertex in the third unit, an Abbe number of a most object side lens in the first unit, a focal length of the second unit, and focal lengths at the wide angle end and at the telephoto end.
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A zoom lens of the disclosure includes a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, an intermediate lens group having a positive refractive power and including one or two lens units inclusive of a third lens unit located on an object side, a lens unit having a negative refractive power, and a rear lens group including one or two lens units inclusive of a lens unit which is located on the object side and has a positive refractive power, which are arranged in order from the object side to an image side. Here, an interval between every two adjacent lens units is configured to be variable for zooming. In the meantime, a total length of the zoom lens is reduced by keeping the first lens unit unmoved relative to an image plane while varying the intervals between the lens units during the zooming. The first lens unit includes three or more lenses and mainly corrects a spherical aberration and an axial chromatic aberration on a telephoto side. The second lens unit includes three or more lenses and mainly suppresses variations in curvature of field and in chromatic aberration of magnification during the zooming. In order to achieve correction of aberrations and reduction in size at the same time, it is preferable to form each of the first lens unit and the second lens unit by use of three or four lenses.