Meaning
The adjustment and verification of non-contact, light-based dimensional measurement instruments use highly accurate physical references to ensure measurement traceability. This optical micrometer calibration is necessary to correct for optical drift, thermal expansion, and mechanical wear in the instrument’s laser or LED transmitter and receiver arrays. It ensures that the sub-micron measurements taken during production are accurate and consistent.
Calibration Standard
Certified gauge blocks or specialized chrome-on-glass reticles with certified dimensions are positioned within the measuring path of the instrument. During optical micrometer calibration, the instrument takes multiple readings across these known references to calculate correction factors. These reference objects must have a calibration certificate from an accredited national laboratory to establish the chain of traceability.
This step is repeated at multiple points across the measurement range.
Environmental Variable
Ambient temperature and dust levels must be strictly controlled because they directly influence the behavior of the light beam. Since changes in temperature can warp the reference blocks or alter the refractive index of the air, optical micrometer calibration should be executed in a temperature-stabilized room held at twenty degrees Celsius. Even minor temperature deviations can cause the instrument to fail the calibration process.
Technical Consequence
Failing to complete this process on schedule leads to the invalidation of all dimensional measurements taken by the instrument since its last successful test.
