Technology Where It Counts
Canon’s innovations put your images on film quickly, quietly, and easily with outstanding results.
Diffractive Optics
Another world’s first in camera lens optical design, Canon introduced new technology in order to build a super telephoto that complements its latest compact film and digital SLR cameras. This cutting-edge technology employs
that the ray goes through a change in direction before passing through the lens. The change in direction is caused by a diffraction grating — very fine parallel grooves or slits on the surface. Canon found that using a concentric diffraction grating that gets smaller toward the
Ultrasonic Motors (USM)
The Ultrasonic Motor (USM) in Canon EF lenses is the world’s first lens-based motor. Based on a totally new technology, the motor spins by ultrasonic oscillation energy. The USM is quiet and quick. It has made EF lenses almost noiseless and autofocusing fast, precise, and practical. The direct-drive construction is very simple, with no gear train. This makes it durable and efficient. It also consumes little power. Two types of USM are used: Ring-type USM and Micro USM. The former type is found in large-aperture and super telephoto lenses, while the latter is used in more compact lenses. Using the optimum type of USM in the lens results in maximum efficiency and effectiveness.
MRing-type USM
Aspherical Lenses
Ordinary spherical elements have an inherent flaw in that the point of focus for the lens center does not match that of the lens periphery. Spherical aberrations of large-aperture lenses and distortion by ultra-wide-angle lenses cannot be resolved with spherical elements alone. The Aspherical lens element was therefore developed. The curvature of the lens element is calculated and shaped to achieve the ideal single point of focus. The result is high contrast with minimal flare even with a large- aperture lens. Distortion can also be effectively corrected in ultra-wide-angle lenses. Canon started to develop manufacturing technology for Aspherical elements early on. We eventually succeeded in establishing a mass- production grinding and polishing process with a polishing precision of 5/10,000 mm. In 1971, Canon marketed the FD 55mm f/1.2AL lens, the world’s first large-aperture Aspherical lens for SLRs. This was followed by many other Canon lenses incorporating Aspherical elements and they were well received.
Also, Canon developed mass-production technology for glass-molded aspherical elements and replicated Aspherical lenses. The former was produced by an ultra-high-precision aspherical lens- molding machine which shaped the glass directly. For the latter, the Aspherical surface was formed by ultraviolet- hardened resin film applied on a spherical element. Canon has developed numerous compact-size lenses, taking full advantage of Aspherical elements to attain high image quality.
diffractive optical elements that use the principle of diffraction to change the direction of the lightwave’s path. This revolutionary element has Aspherical characteristics, which help define superior maximum aperture image quality, as well as optical qualities superior to UD-glass to totally correct color fringing. The Multi-Layer Diffractive Optical Elements exhibit outstanding ability to correct chromatic aberrations (color defects), and are especially effective in super telephoto lens design where these specific types of optical defects are most likely to happen. You can see how well the technology works in your own pictures by examining the straight edges of a subject in your picture. You will see a crisp, clear edge without the telltale, prismatic color fringing that is visible with images shot using inferior optics.
Diffractive grating
Glass lenses
Multi-Layer Diffractive Optical Element Construction
Refractive Optical Element
Chromatic aberrations
Refractive Optical
Element and Multi- Layer Diffractive
Optical Element
Image formation inCombined the blue, green, and
red wavelength order
Multi-Layer Diffractive
Optical Element
Chromatic aberrations reversed from that of a
edges — some as fine as tenths of a micrometer — solved many of one inherent physical limitations of camera optics. The design also makes it possible to obtain the same effect as an Aspherical lens. And taking the technology a step beyond, we actually use two single-layer diffractive optical elements whose diffraction gratings are bonded together face-to-face. Since longer wavelengths form an image closer to the lens due to the large diffractive angle, and shorter wavelengths form an image farther from the lens due to the smaller diffractive angle, putting the DO elements with conventional glass optics actually cancels out each other’s chromatic aberrations and is exceptionally effective in correcting this optical defect. The diffraction that occurs with Canon’s Multi-Layer Diffractive optical elements actually corrects the optical system’s chromatic aberrations and improves the image formation performance.
The net result of Canon’s DO technology is a lens design with reduced size and weight while offering higher image quality than a comparable focal length lens that incorporates conventional glass optical elements. It means a new generation of high-performance lenses that complement the more compact designs of our latest SLR film and digital cameras.
400mm f/4 Lens Designed with a Refractive Optical Element Only
Micro USM
Spherical aberration of spherical lens.
Convergence of parallel light rays by an Aspherical lens.
refractive optical element Chromatic aberration canceled out
Image formation in the red, green, and blue wavelength order
Red Green Blue
Correction of Chromatic Aberration by the Multi-Layer Diffractive Optical Element
Glass lens elements refract, or bend lightwaves, as they pass through to form an image. That’s simply the naturally occurring physics of light. We use multiple elements and special glass to help keep the waves focused like a pinpoint instead of spreading them into the rainbow of color seen when light passes through a glass prism. To diffract a lightwave means
317mm | Weight: 3,000g |
UD element | |
Fluorite | |
400mm f/4 DO IS USM
(Incorporates Multi-Layer Diffractive Optical Element)
| | |
| | |
| 232.7mm | Weight: 2,080g |
Multi-layer diffractive optical element | (Including removable |
Fluorite | tripod collar) |
Lens Downsizing with the Multi-Layer Diffractive Optical Element
Note: If a very bright spotlight like a mercury lamp is photographed with a DO lens, a ring of light may occasionally appear around the light source, due to the imaging characteristics of the Multi-Layer Diffractive Optical Element.
