Canon Patent Application: Switchable teleconverter

In this patent application. Canon discusses a switchable teleconvertor.

They are looking at this because;

• switching between multiple teleconverters increases the chances of dust or moisture entering the camera or rear of the lens.
• adding a built in teleconverter such as the 200-400 increases the bulk of the lens, even if you don't need the teleconverter

Canons alternative discussed in this application is to provide a teleconverter that will switch between 1.4x and 2.0x.

The super telephoto embodiments listed in this could certainly be for the Canon RF system, and not the Canon EF system.  As an example this one for a 600mm F4.0 super telephoto lens;

focal length 590.00   
f-number 4.16   
field angle 2.10   
image height 21.64   
total lens length 502.80   
BF 40.53

The Back focus (BF) distance is a little too tight for Canon EF, especially when you consider it has to also fit an extender as teleextenders atypically protrude slightly into the lens itself, and require a back focus distance, greater than that of the flange distance (in Canon EF's case that is 44mm)

There's nothing in the patent showing the mechanical nature of switching the teleconverters, and it seems to be a pretty generic patent.  As with all patents, there's a possibility it could be used in a future product.  There's also the possibility it's simply pure exploratory research that Canon is doing.

Japan Patent Application 2019-095629

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