Posted in | Mirrors

Optical Surfaces On-Axis Paraboloids

Optical Surfaces' on-axis parabolic mirror production has been used by generations of customers. Our heritage goes back to the production of large astronomical telescope optics of over 1 metre for the Royal Greenwich Observatory and other discerning customers. During the course of the past 40 years, we have supplied many high quality mirrors for science, defence and space research.

The on-axis mirror offers some advantages over its cousin, the off-axis parabola:

  • The f-number that can be achieved is higher ("faster") therefore more energy can be concentrated.
  • It has 3-D rotational symmetry resulting in a lower price for a given specification.
  • Generally, (except for extreme f-numbers) alignment will be less critical, thus easier.
  • In view of the above, surface roughness and slope errors of low value are easier to achieve.

All on-axis mirrors undergo rigorous testing with modern interferometry. Using the latest industry standard Zygo software, we measure typically 30000 data points (this varies according to the image size being acquired). These are then analysed to produce an OPD contour map of the optic with additional characteristics shown as required. These always include p-v and RMS surface accuracy, and may include other parameters such as slope error, Strehl Ratio, PSF plot or simulated image, according to customer preference.

Each mirror is accompanied by a test report showing that tolerances have been achieved.

Standard mirrors are offered with Aluminium plus Magnesium Fluoride coating. A range of specialist coatings are also available, depending on diameter.

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