Canon Patent application for Improved flare control for DO elements

One of Canon's many lens innovations, DO elements starting off with the 70-300 DO lens has been undergoing continual improvements.

This is a possible improvement as Canon looks to improve the DO element's abilities in the infrared band to reduce flare.

An image pickup apparatus for the long wavelength band of 8~14μm uses light (hereinafter, the far referred to as long wavelength infrared region). Therefore, if the diffraction efficiency of the diffractive optical element with respect to a specific diffraction order is low in a part of the far-infrared region, diffracted light having a diffraction order unnecessary for imaging can be generated. This is not preferable because it causes flare.

 US Patent Application 20180045975