Apodization filter and method of manufacturing the same

Abstract

The invention provides an apodization filter and a method of manufacturing the same. A light-blocking mask layer (3) having such light transmittance characteristics that an amount of transmitted light decreases gradually as it advances in a radial direction Fr from a center of optical axis Cs is formed on a surface of a flat transparent substrate at least having a light transmittance of 80% or higher using at least a dot pattern Pd formed of a large number of dots d, having a light transmittance of 20% or lower.

Description

technical field [0001] The present invention relates to an apodized filter having a light transmittance characteristic in which light transmittance gradually decreases as the light transmittance moves away from the center of the optical axis in a radial direction, and a method for manufacturing the same. Background technique [0002] In general, in a camera lens, blurring occurs at a defocused position, but it cannot be said that beautiful blurring (blur beauty) is necessarily produced by creating an edge effect at the edge of a captured image. For example, in the case of dots, a so-called donut-shaped blur occurs, and in the case of a single line, a so-called double-line blur occurs in which there are two lines. Therefore, inserting an apodization filter having a light transmittance characteristic in which the amount of light transmittance gradually decreases as the distance from the center of the optical axis in the radial direction is inserted into the optical path in the...

AI Technical Summary

Problems solved by technology

[0005] First, since it is composed of a plano-concave lens and a plano-convex lens, it has to be thick to a certain extent, and there is a limit to obtaining a thin apodization filter.

As a result, when the apodization filter is inserted into the camera lens, the overall lens length in the direction of the optical axis becomes longer, leading to an increase in the size of the camera lens, and on the other hand, in order to avoid the increase in size, there is Opposite difficulties such as difficulty in ensuring a good blur effect

In addition, since two lens parts with the same precision as a normal lens are required, cost increase is inevitable

In addition, since the degree of freedom in lens design is restricted, it also becomes a cause of a decrease in the functionality and performance of the lens.

[0006] Second, in terms of the structural principle of the apodization filter, the light transmittance at the center of the optical axis cannot be made 100%

That is, since the plano-concave lens needs to have dimming properties, the thickness at the center of the plano-concave lens cannot be made zero. As a result, the light transmittance at the center cannot be made 100%, and loss of light quantity is unavoidable.

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