LENGTH & DIMENSIONAL

The standard is based on a femtosecond fibre laser frequency comb. The output of the laser is a sequence of pulses that are essentially copies of the same pulse separated by the round-trip time. The spectrum of such a pulse train is a frequency comb separated by the repetition rate (the inverse of the round-trip time) of the laser. The repetition rate and the carrier-envelope offset frequency of the frequency comb are locked to a 10 MHz reference signal from a Hydrogen Maser, the primary frequency standard.

NMC is able to calibrate absolute frequency of lasers with wavelength from 530 nm to 2100 nm. The best measurement uncertainty is in the order of a few hundred Hz.

Services Provided:

• Frequency of stabilized laser
  

The standards of linear dimensions are realized through the laser interferometry, mechanical contact comparison, and optical non-contact comparison. The main instruments include Gauge Block Interferometer (GBI), Gauge Block Comparator (GBC), Universal Length Measuring (ULM) machine, Quick Vision (QV) Measuring system, Coordinate Measuring Machine (CMM) and Laser Confocal Microscope, etc.

NMC is able to calibrate various length instruments and standards, including end standards (gauge blocks, length bars, rod, step/gap/thickness gauges), line standards (line scales, stage micrometers, grid plates, 1D/2D grating, linewidth, tape, wire, etc.), diameter standards (plug, pin, wire, ring, ball), and standards of 1D point-to-point dimensions.

The measurement range of linear dimension at NMC is up to 1200 mm, and the best measurement uncertainty is at the sub-nanometer level.

Services Provided:

• Central length of gauge blocks (steel, ceramic, and tungsten carbide)
• Line spacing of glass scales and stage micrometers
• Grid point coordinates of grid plates
• Pitch of 1-D and 2D gratings
• Diameter of external cylinders (plug, pin, wire)
• Diameter of internal cylinders (ring)
• Diameter of spheres (ball)

NMC is able to calibrate optical polygon, angle artifacts and angle prism, etc. The main instruments for angle calibrations include the autocollimator, index table and small angle generator. The measurement range is from 0 ˚ up to 360 ˚, and the best uncertainty for angle calibrations can be as low as 0.08 ". The services for non-standard angle measurements and calibrations can be also provided according to customers’ requests.

Services Provided:

• Free angle of optical polygons
• Error of indicated angle of autocollimator
• Angle of angle blocks

The main instruments for form calibrations in NMC include the laser flatness measurement system, roundness measurement system, stylus instrument, laser confocal microscope, white light interferometer and large range metrological AFM. The form related calibration and measurement capabilities are:

• Flatness: the measurement range is from 0.02 µm to 5 µm, and the best uncertainty is 32 nm.
• Roundness: the measurement range is from 0 µm to 2 µm, and the best is at the sub 10 nm level.
• Step height: the measurement range is from 0.005 µm to 1000 µm, and the best uncertainty is 1.5 nm.
• Roughness: the measurement range is from 0.01 µm to 50 µm for Ra, and 10 µm to 500 µm for Rsm; and the best uncertainty is 9 nm for Ra and 98 nm for Rsm.

The services for straightness standards, cylindricity standards and optical standards such as lens, radius standards are also provided.

Services Provided:

• Flatness of optical flats and optical parallels
• Parallelism
• Roundness of external cylinders (plug, pin, wire)
• Roundness of internal cylinders (ring)
• Roundness of spheres (ball, hemisphere)
• Depth and step height of standards
• Roughness (Ra, Rq, Rz, Rt, Rsm)
• Straightness, cylindricity, lens radius

NMC is able to calibrate the following complex geometry standards:

• CMM artifacts such as step gauge, ball plate, ball bar and large CMM artifact, etc. The measurement range is up to 1,200 mm, and the best uncertainty is as low as 0.51 µm. The services for non-standard CMM artifact measurements and calibrations can be also provided.
• The calibration and measurement capabilities for screw standards and gear standards are under developing, and the related services will be provided soon.

Services Provided:

• Complex geometry standards (CMM artefacts and standards)
• Mechanical elements and parts