In this patent application (2024-053967) Canon is looking to improve the ability of the cameras to calibrate the eye control focus with the photographer. The eye control focus is featured on older EOS film cameras and more notably, the Canon EOS R3. Eye Control AF differs from Eye AF, as Eye Control AF moves the focus point to where you are looking through the viewfinder, and Eye AF locks onto the target's eye as the focus point.
The camera does eye control by shining infrared light into your eye and measuring the relative location of your pupil. Using that, the camera can calculate where you are looking. Because of this, and because it's a very individual measurement, each person has to be calibrated to use eye control autofocus. Canon in this patent is looking at increasing the precision without necessarily increasing the time it takes to calibrate eye control.
According to Canon's machine-translated patent-speak;
An object of the present invention is to provide a line of sight detection device that can perform highly accurate correction while reducing the burden on the user.
According to the patent application, it appears as if the detection is sensitive to the diameter of the user's pupil. This surprised me, but it does stand to reason because Canon does specify that you need to take calibration indoors and outdoors – which would cause users to have a different pupil size with the variation in light intensity. It should probably be noted that it may even be a good thing to expand on the calibration to include overcast conditions, etc.
According to Canon Europe;
You have to confirm that you're looking at it, then it will move, and you need to follow it with your eye. This needs to be done with the camera in horizontal and vertical orientation, both inside and outside, but you don't have to do it all at once. You can come back to a calibration.
So anything that Canon can to do make the calibration of the camera's eye control auto focus easier and more accurate is welcomed. It will be interesting to see how Canon advances this technology over time.
As with all patent applications, this is a look into Canon's research and may not end up in an actual patent or product.
Source: Japan Patent Application 2024-053967
eyeface cup for the R3?