Image measuring instrument calibration considerations are as follows:

Glass optical ruler, using 1 1um level precision:

Image measuring instrument calibration accuracy is generally in the characterization of 50mm 100mm 1mm,the distance between the optical linear glass scale, the error must be less than the nominal error of measurementinstruments, need to use the 1um level precision optical ruler. Let the length of the corrected for instrument, a grid of measurement, wire clamping strict alignmentmeasurement results and deviation of not greater than linear precision value; test finished, let the back test theorigin, coincident accuracy cannot be greater than the nominal value of the instrument. Influence of measurement process to reduce the man-made error online are not allowed, get the key index for the comprehensive performance of instrument.

2, do not use the workpiece as the basis for testing:

(1) because of the influence of environmenttemperature, do not use the thermal expansioncoefficient of the metal material workpiece as the measured sample.

(2) must use optical ruler line clear, to avoid the errorcaused by inaccurate alignment of contrast andselection, as close to the true value. Especially the useof shaft device, image measuring transition surface projection angiography not will cause the technical limitations of large error, namely the need to avoid theprinciple limitation, try to obtain image measuring instrument in the normal use of the precision value.