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Canon Patent: Variable Apodization Using Electrochromic Elements (Defocus Smoothing technology)

Devocus Smoothing
Drawing from the patent literature

This Canon patent application might point to the next generation of Canon’s Defocus Smoothing technology.

Canon patent application 2022124678 (Japan) discusses technology and optical formulas to obtain Defocus Smoothing by the mean of electrochromic elements (EC). Defocus Smoothing is Canon’s technology to improve bokeh (see short video below for an explanation).

From the patent literature:


An electrochromic (hereinafter sometimes referred to as “EC”) element is an element having a pair of electrodes and an EC layer disposed between the electrodes. It is an optical element that adjusts the hue and amount of light in the visible light band by applying a voltage between them to oxidize or reduce the compounds in the EC layer.

EC elements have already been applied to products such as variable transmittance windows for aircraft and anti-glare mirrors for automobiles. Attempts have been made to apply it to The apodization filter is an optical element that smoothes the outline of a blurred image, and has a transmittance distribution in which the transmittance decreases with increasing distance from the optical axis.

In the conventional EC device described above, a desirable transmittance distribution is achieved by defining the resistance range of the electrodes, but the setting of the constituent requirements was not sufficient. That is, the transmittance distribution of the solution-type EC element depends on the resistance ratio between the electrode resistance and the solution resistance per unit width. , depending on the resistivity of the electrochromic layer (solution). Therefore, it was necessary to define these in order to achieve a desirable transmittance distribution.

An object of the present invention is to provide an EC element capable of realizing a suitable transmittance distribution in a solution-type EC element in which power is supplied from the outer periphery of the dimming area, and furthermore, a suitable transmittance by following the aperture diameter of the mechanical aperture of the lens. It is an object of the present invention to provide an EC device capable of forming an index distribution. Another object of the present invention is to provide a lens unit and an image pickup apparatus having excellent optical characteristics using such an EC element.

To me it appears this might be the next generation of the Defocus Smoothing technology.

More patents are listed here.

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