Making traceable measurements
High quality calibration scales are required for making traceable measurements with non-contacting imaging and vision measurement systems. NPL designs and calibrates a range of optical scales and reference patterns for quantitative microscopy, image analysis and non-contact measurement systems.
Our extensive range of measurement facilities provides sub-micrometer accuracy for the following types of scales:
Stage micrometers - NPL offers a UKAS and CIPM-MRA accredited service for the calibration of stage micrometers (and other linescales or calibration standards) up to 150 mm in length. NPL also offers calibration service for scales from 150 mm to 400 mm in length. Scales are measured using a microscope with a travelling stage. The displacement of the stage is measured by means of a helium-neon laser interferometer, providing an uncertainty of 0.2 µm or better for scale length of 50 mm with direct traceability to the metre.
High precision line scales - Line scales offer a practical means of traceably verifying the measurement performance of optical measurement equipment. NPL-designed high precision line scales are available in lengths from 1 mm to 400 mm. Scales can be traceably calibrated by NPL.
Optical dimensional standard - A single high-precision calibration artefact, bearing a vast range of different scales designed to meet virtually all optical dimensional calibration needs. Where high precision calibration and verification of the imaging system is required, a multi-functional Optical Dimensional Standard is available, consisting of a single high-precision calibration plate bearing a vast range of different scales, designed to meet virtually all optical dimensional calibration needs. Optical instrumentation companies, vision machine and image analysis developers, system integrators and end-users can all benefit from using the NPL Optical Dimensional Standard.
Our Optical Dimensional Standard is a 100mm square quartz plate bearing many thousands of bright chrome structures ranging in sizes between 1µm to 60mm. There are twenty-two patterns, scaled and repeated on the glass six times enabling it to be used at different magnifications. Additionally, there are six linear scales and an X-Y stage position calibration grid. The measurement uncertainty can be as low as ±0.05μm on the linear scales and features smaller than 100μm in size.
Further information on the Optical Dimensional Standard and pattern dimensions
Reference stage graticules
This calibration artefact contains four test areas comprising a 400 µm square grid, a 20 x 17 monosize array of 15 µm diameter spots, a Root-2 array of spots from 3 µm to 48 µm diameter, and a log-normally distributed array of 100 spots ranging from 4.5 µm to 27 µm diameter. It is ideally suited for calibrating image analyser systems and can also be used as a high precision stage micrometer.
X-Y grid plates
We have 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.
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