1. Verification of non-linear error
The non-linear error is due to the over-correction of the instrument software or other abnormal reasons, the measurement values given by the lens meter in different axial directions of the lens are inconsistent, and the displayed values change irregularly. To put it simply, when the lens meter measures the astigmatism lens or the ball-cylindrical combination lens, the cylinder power values displayed on different axes are different, and there is a deviation, and the error is asymmetrical. At present, there are many non-linear indicators of domestic automatic focusmeters in the market that cannot meet the requirements. In order to pass the metrological verification, some focusmeter manufacturers have adopted abnormal software correction methods to artificially adjust the vertex power indications to match those of standard lenses. The nominal value of is exactly the same, so that the nonlinear error is zero. For this abnormal situation, the test personnel must treat it with caution, and cannot easily conclude that the nonlinear error is qualified.
2. Verification of spherical mirror power indication error
Put the standard lenses one by one on the lensometer support, and perform the verification when the cross cursor is turned on at the center of the lensometer display. When verifying some domestic brands of auto-focusmeters, the author found that for standard lenses with larger nominal values, the cross cursor of the instrument does not open at the center of the display screen, but at a place far away from the center. . In this case, it must not be easy to simply interpret the indication error of the spherical power.
