Optical elements like lenses and prisms continue to evolve with advances in design technologies, from spherical to aspherical shapes, and from axisymmetric to free-form surfaces. In the case of optical elements that demand nanometer-order levels of precision (a nanometer is one millionth of 1mm), conventional production technologies are incapable of achieving free-form surfaces involving large curvature differences. Such applications require the development of new processing and measurement systems.

Free-Form Processing Machine (A-Former)

For its free-form processing machine, Canon developed various proprietary technologies to enable the high-precision control of the highspeed cutting tool, including highly rigid air bearings and a highperformance controlling system. The company's free-form measurement machine, which makes possible the ultra high-precision measurement of the entire surface of optical elements through contact probes that are in contact with the element, also employs a variety of advanced technologies. A metrology box with a unique box-shaped structure provides the system's precision standard while a laser interferometer comprising a work guide sandwiched between six mirrors is used to cancel contact-probe motion errors, making possible measurements of nanometer-order precision.

Free-Form Measurement Machine (A-Ruler)