Canon Patent Application: Improved Sub-Wavelength Coatings

In this patent application (2024-063513), Canon is looking at improving the subwavelength coatings for optical elements.

In an optical system constituted by optical elements, reflection of incident light on the surface and inner surface of the optical element is undesirable because it causes a loss in the amount of transmitted light and reflection ghosts. Therefore, a technique is known in which a fine uneven structure is provided on the surface of an optical element to prevent reflection.

Canon in this patent application seems concerned that even though the recesses between the nanostructures are completely random, with a completely random formation, patterns may still occur which can degrade optical performance. Imagine if you flip a coin and get heads 5 times in a row, completely statistically possible.

A highly magnified view of the coating sitting on top of the element is shown above.

Since the positions where the recesses and the upper recesses are formed are completely random, there is a possibility that the reflectance will be biased. Accordingly, an object of the present invention is to improve the optical characteristics of an optical element. 

Any improvements that result in improvements in image quality due to reduced flare and reflections are completely welcomed.

Japan Patent Application 2024-063513

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