Non-Contact 3D Measurements of Optical Surfaces with the LuphoScan Platform

The LuphoScan platforms are interferometric, scanning metrology units based on multi-wavelength interferometry (MWLI®) technology. They are capable of performing non-contact, ultra-precision, 3D form measurements of rotationally symmetric surfaces e.g., concave and convex aspheric lenses.

These platforms make taking form measurements of flats, aspheres, spheres, steep slopes, profiles exhibiting inflection points and slight freeforms straightforward.

Key Features

The main features of the LuphoScan platforms are given below:

  • Almost all types of materials, whether transparent, opaque, specular, polished, or ground, can be analyzed
  • Rapid measurement speeds
  • Large spherical departures
  • High flexibility with regard to unusual surface shapes
  • Maximum object diameters up to 420 mm
  • Investigation of any rotationally symmetric surface
  • Highly accurate (better than +/- 50 nm) with reproducible results

Main Applications

The stage layout is designed in such a way as enable the 3D topologies of all lenses that fit in the machine to be determined.

The standard operation mode requires a theoretical description of the surface to be tested to be provided, based on the conic constant, the radius of curvature and the even and uneven aspheric coefficients. The platform’s software package enables measurement of ground or polished parts by default.

Apart from the basic measurement applications, the LuphoScan platforms can also be applied in the total characterization of optical elements, with the aid of the LuphoSwap extension. This tool enables determination of wedge and decentre errors, and thickness measurement of lenses.

There are also many add-on software modules that can assist in straightforward measurement of discontinuous optics such as segmented surfaces, e.g., rectangular parts, annular optics, or surfaces with diffractive steps, and axicons.

LuphoSwap Extension

This enables total form error characterization of optical components. LuphoSwap is offered as an extension for LuphoScan 260 and LuphoScan 420 platforms. It can handle consecutive characterization of both surfaces of a lens. It is possible to attain absolute correlation of the results measured on both sides, meaning that the LuphoSwap simultaneously measures the lens thickness, the wedge and decentre errors of the two surfaces and their rotational orientation, and the form errors. It is also possible to assess the lens–mount position.

LuphoSwap is based on the absolute measurement capability of the LuphoSmart sensor technology, an additional (runout) reference sensor, and an innovative holder concept.

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