Aspherical lenses have an ideal curvature for light to converge to a single point. Aspheric lens elements are used not only in Canon’s interchangeable lens SLR cameras, but also in broadcasting lenses, semiconductor lithography systems, astronomical telescopes, and various optical products.
Representative Canon’s aspherical lenses are △RF15-35mm F2.8 L IS USM (released in September 2019) △RF24-70mm F2.8 L IS USM (released in September 2019) △RF70-200mm F2.8 L IS USM From the F2.8 L IS USM zoom lens series for professionals and enthusiasts (released in November 2019) to the RF28-70mm F2 L USM (released in December 2018) that provides a bright F2 aperture over the entire zoom range. have. Canon’s aspherical lens reduces aberrations and realizes high image quality.
On the other hand, the spherical lens is characterized in that the parallel rays do not converge to exactly one point. This is because blurring (spherical aberration) or other optical aberration occurs in the captured image due to the spherical surface of the lens. In order to correct such spherical aberration, several spherical lenses must be used and arranged in a specific configuration. By utilizing the characteristics of the spherical lens, spherical aberration can be corrected with only one aspherical lens.
Accordingly, Canon launched a lens research and development program in 1963 to develop a lens that creates a clear and accurate image by converging all incident light at a single point. In order to mass-produce aspheric lenses, a precise processing technology of 0.1 micrometer or less and a high-precision measuring device capable of measuring up to 0.01 or less were required. Canon succeeded in developing the technology required for mass production of aspherical lenses through continuous design and processing. In March 1971, Canon released the first interchangeable lens SLR camera lens’FD55mm F1.2AL’ that adopted an aspherical lens element.
In addition, in 1973, the precision of lens processing technology was further improved by developing an ultra-high precision aspherical lens grinder at the ALG-Z nanometer level. In 1985, it launched the first interchangeable lens SLR camera lens’FD35-105mm F3.5-4.5′ (released in December 1985) using a large-diameter glass mold (GMo) aspherical lens element. Since then, Canon continues to develop high-performance lenses based on the technology used to form and measure aspherical lenses.
A Canon official said, “We plan to show products and technologies that meet the diverse needs of consumers while continuing to develop innovative optical technologies in the future.”