Canon News shows that a new patent indicates Canon is investigating using multiple resin layers to suppress short wavelength light in its “diffractive optics” (DO) lenses.
DO lenses, such as the much-loved 400mm f/4 DO II, use a Fresnel lens structure to significantly reduce the length of a lens, lower its weight, and usually improve its balance. Early versions, such as the 500mm f/4 DO Mark I suffered from low contrast and busy bokey. The technology has been improved slowly but consistently since its first use.
The use of resins to change the diffractive properties of a lens design was heralded with much fanfare during the launch of the breathtakingly-sharp Canon 35mm f/1.4 II. Fudgy wording in those marketing materials led forum dwellers to humorously call the technology “blue goo,” which has stuck ever since. It appears that Canon has since used the technology a few additional times, but has not been vocal about it; perhaps because the use of plastics connotes a cheapness that – in this case – isn’t deserved.