asphericon Company

Measurement

For the measurement of aspheric components both tactile as well as interferometrical systems are used. Our equipment is compliant with the current world standard.

For the tactile measurements, a probe with a spherical ruby or diamond tip is moved across the surface on a cross-section trajectory. A laser-interferometric system is used to measure the amplitude of the probe from which the surface-irregularity of the object is being computed. Having devices with a resolution of 1.5 and 12nm we can measure surfaces with an accuracy of 100 to 200nmand an area of up to 250mm diameter.

Furthermore the equipment can be used to measure surface-roughness as low as 1nm. Our software allows to compute the errors either based on the trajectory or the X-plane.

In contrast to spheres, the measuring of aspheres with Fizeau-interferometers is more complex because an aspheric wave-front is needed as a reference. The aspheric wave-front is generated with diffractive elements also known as computer generated holograms (CGH). The Fizeau-interferometer in conjunction with the CGH enables us to measure the entire surface with an accuracy of up to lambda by 20.