Technology

Optocraft delivers powerful multi-functional solutions for optics testing and laser beam characterization. The centerpiece of each product is the Shack-Hartmann wavefront sensor, which we combine with industrial image processing systems and additional optical sensor systems.

Shack-Hartmann wavefront sensor

The original idea was published by Johannes Hartmann in 1904. To measure the imaging quality of objective lenses, he placed a hole mask into the beam path and observed the resulting dot pattern on a photographic plate. From the position of the dots he was able to conclude the quality of the objective under test. In the 1970s, Roland Shack further developed this technique by using microlenses instead of holes. By doing so he improved the light efficacy and opened the way to automated wave-front evaluation by using digital cameras.

The fundamental principle, however, stays the same: the local inclination of the wave-front across the microlens array causes a distortion of the spot array. Each spot is deviated from the local optical axis of its microlens depending on the ray direction. Thus, the spot position is a measure for the wave-front inclination and the ensemble of all measurement points can be used to reconstruct the wave-front by using numerical methods.

Depending on the application, further data analyis and evaluation can be done to calculate the parameters containing the relevant information on the specific sample under test (see also the links below), for example

  • laser beam parameters like beam waist, divergence, M²,
  • for optical systems the point spread function, modulation transfer function,
  • for contact or intraocular lenses the refractive data, power map, etc.

and by combination of multiple measurements we can also calculate parameters like

  • field curvature
  • chromatic aberrations
  • polarization effects

Why Shack-Hartmann?

Thanks to the geometric optical principle, Shack-Hartmann sensors work without a simultaneously needed reference wavefront. This is a big advantage compared to interferometry. Also, the requirements concerning environmental conditions and the light sources are much more relaxed:
  • “Single shot” technique, i.e. wave-front evaluation of single camera frame is possible
  • High intrinsic stability
  • Usable within broad spectral range
  • Usable with low coherent light

Why Optocraft?

For more than 20 years we focus on optics testing. You will find this expertise in our software and in the layout of our instruments as well as when talking to one of our colleagues.

Optocraft’s wavefront sensors and systems offer a set of additional advantages:

  • Excellent unreferenced accuracy
  • Extreme dynamic range
  • Fast wavefront reconstruction

This high accuracy is particularly helpful in applications like e.g. laser beam or laser system testing where a referencing of the wavefront sensor with an ideal wavefront is often difficult or impossible. SHSLab’s outstanding wavefront mesurement accuracy allows working without additional reference measurements.

Furthermore SHSLab uses unique algorithms that enable measurement of wavefronts with extreme dynamics, i.e. with very strong aberrations and large tilt and defocus.

Industrial image processing

With industrial image processing we refer to the application of dedicated cameras, optics and algorithms. Optocraft applies industrial imaging processing to

  • locate the position of lenses precisely
  • detect marks and engravings on optical surfaces,
  • measure geometric properties and shape,
  • and also to gain information on cleanliness and intactness of the sample under test

For this, we use only high quality components that meet the demands of the corresponding application. In addition to standard components available in the market, Optocraft develops light sources, optical systems and algorithm on their own to optimize functionality and performance of their systems.

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