Effects of Aspheric Surfaces on Optical Performance and Their Application to Lenses for 35mm Cinematography

Abstract

The practical use of aspheric surfaces in optical devices, such as parabolic mirrors or illuminating condensers, is well-known. Technical problems in the design and manufacture of such surfaces had to be overcome before the incorporation of aspheric surfaces into the construction of high precision optics, such as camera lenses for motion pictures and television, could be attempted. An overview of the performance of aspheric surfaces is given, and their limitations are mentioned. Spherical aberration, distortion, and astigmatism can be controlled by their use. The introduction of an aspheric surface into the design of a lens produces two types of effects: direct effects permit controlling of a specific aberration, and indirect or secondary effects may allow for the simultaneous control of another aberration. Greater lens compactness and reduction of the number of required lens elements may result. Three fundamental parameters for the measurement and evaluation of an aspheric surface are explained. A short description of various possible grinding and polishing methods is given. The accuracy of the surfaces obtained can be measured by the use of interference fringes or by means of a feeler in combination with a laser. Canon designed their first aspheric lens in 1971. It is shown that the aspheric design reduces aberration fringes, gives greater freedom from flare, and improves contrast. A series of four aspheric high speed lenses for motion-picture use was created. Some details of their design and contruction, including the “floating” focusing mechanism, are mentioned. A Class III Scientific or Technical Award from the Academy of Motion Picture Arts and Sciences resulted from this technological achievement.