The role of the "non -" spherical lens
The light incident in the lens gathers at one point after passing through the lens.This is one of the ideal lenses conditions.
The general camera lens uses a "spherical lens" that cuts out the surface of the spherical body.However, this spherical lens has a principle issue in which light passing through the periphery of the lens and the light passing through the center when the light is incident.
The focus position shift causes a "spherical aberration" in which the statue is blurred.In addition, the spherical lens has the property that the area around the screen is distorted, and that "color aberration", which causes color bleeding, is likely to occur.
One of the means to correct these aberrations is to combine a variety of lenses with different properties.Since spherical aberration occurs in the opposite direction in convex lenses and concave lenses, it can be corrected by stacking two lenses.
On the other hand, the "non -sphere lens" was attracting attention as a fundamental way to solve these aberration.The aspherical lens changes the curvature toward the periphery of the lens, and all light passes from the center to the peripheral part to one point, and suppresses aberration.Compared to spherical lenses that correct aberration by combining multiple lenses, the number of compositions can be reduced by effectively using aspherical lenses, resulting in miniaturization and high image quality of products.
球面レンズで発生する球面収差非球面によって焦点位置を合致Canon has begun the development of aspherical lenses since 1963, and in 1971, a single -lens reflex camera replacement lens "FD55mm F1".Released 2AL.This year is the 50th anniversary of the release of the lens.
FD55mm F1.2AL（1971年発売）関連記事Canon's first non -sphere lens "FD55mm F1".Technical explanations and effects on the official website that celebrates the 50th anniversary of the release