National Physical Laboratory

X-Y Grid Plates

Grid PlatesX-Y Two-Dimensional Grid Plate

NPL has developed range of non-contact dimensional standards designed to calibrate the co-planar axes of industrial imaging systems and vision inspection machines.

The standards are chrome on glass and have working areas from 250 mm x 250 mm to 650 mm x 650 mm. The chrome layer bears metrology structures composed of target dies, set on a square grid that has a nominal pitch of 25 mm. Each die is made up of chrome and clear circles, crosses and squares. The nominal external dimensions of these features start from 30 µm, with each successive feature being twice the size of the previous, up to 1 mm.

This enables the co-ordinates of the features to be measured using different optical magnifications. Each artefact has supplementary patterns including linear scales, grids and optical linewidths, designed for the linear calibration of a vision system's optical viewing head.

Grid Plates Supplimentary Patterns

A choice of types of standard is available:

  Chromium on glass Photographic emulsion on glass Polyester film encapsulated in glass
Maximum size: 650 mm square 500 x 400 mm 500 x 400 mm
Line quality: Excellent Good Good
Positional uncertainty: Typically 0.8 µm Typically 3 µm Typically 10+ µm
Dimensional stability: Good Good Satisfactory in the short term
Durability: Excellent Excellent with cover plate Good
Cost: Relatively high Moderate Relatively low

Uncertainties:

On high specification grid plates sub-micrometre measurement uncertainties can potentially be achieved.

Key features:

  • Standards are available for sale, or customer supplied artefacts can be measured
  • Traceable to the Iodine Stabilised Laser
  • A wide variety of scale designs and artefact dimensions can be accommodated
  • Measurements can be made with transmitted or reflected illumination
  • Various scale supporting mechanisms available

Contact

Customer Service tel: +44 20 8943 6245
E-mail: optics_enquiries@npl.co.uk

Last Updated: 18 Aug 2015
Created: 12 Nov 2009

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