Canon Patent Application: Diffractive Optical Element improvements
In this patent Canon describes how to manufacturer a diffractive optical element with a refractive resin component attached to it to further reduce chromatic aberrations.
Canon continues to work on DO optics and elements, showing that like Nikon, they are pressing forward with this technology to make lenses physically smaller.
in a refractive optical system using the refraction of light, lenses formed from glass materials having different dispersion characteristics are used together in combination to reduce the chromatic aberration. For example, in the case of an object lens of a telescope or the like, a glass material having low dispersion and a glass material having high dispersion are used in combination as a positive lens and a negative lens, respectively, to correct the chromatic aberration which appears on the axis.
US Patent Application 20180143350
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