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In this patent application (2024-072582) Canon discusses improving the magnets that drive the motors on various lenses that attach to the camera. This is to prevent the magnetic flux from causing image artifacts especially at high ISO when the sensor is operating at a extremely high level of amplification and thus, sensitivity.
I seem to recall this in the early days when certain lenses would cause banding, etc. but I can't remember any issues now.
However, with mirrorless, the distance between the motors on the lenses, and the sensor has been reduced, and even more so when you consider that today's lenses because of that lowered focal plane distance, usually have the focus motors and aperture motors further to the rear of the lens.
So I think that is where this patent becomes more important because as lenses get smaller, the magnets move closer to the sensor. Magnetic field strength is governed by inverse square law, so if you half the distance, you will dramatically increase the field strength that can influence the sensor. What Canon is concerned about is the leakage flux generated by the coils and the impact that may pertain to the image sensor's performance.
Canon describes the problem as;
In imaging devices such as digital cameras having an imaging element, when magnetic field noise is interlinked with the imaging element, the captured image is disturbed due to the magnetic field noise. In recent years, the ISO sensitivity of imaging devices has increased, and small electronic components such as transformers and inductors, which were not a problem in the past, are now used as the components. Image distortion also occurs due to the weak magnetic field noise that is generated.
Canon looks to resolve this by creating a different coil arrangement and moving it so that the leakage flux will not impact the sensor.
I'm not going to even pretend to completely understand this patent application but any improvements that Canon can make to the lenses and cameras to improve high ISO operability is a good thing.
As with all patent applications, this may never end up in an actual product – I don't think we'd be able to tell if it did or not, except that lenses attached to our cameras would simply “just work”.
Source: Japan Patent Application 2024-072582
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