Steps to check parfocality: 1. Place the MAG checker or other suitable inspection part on the stage and secure properly. 2. Backlight the image as necessary. Set light levels as needed to avoid blooming. 3. At low magnification, select a flat, sharp edge in the center of the field of view (FOV). 4. Select highest magnification, and carefully refocus the image by physically moving the Z-axis up or down. 5. While observing the feature, slowly adjust the magnification lower. Verify that the feature remains focused as the magnification is lowered. 6. Report any observed discrepancy. If the error is verified, contact your Starrett representative for authorized service. 6.2.2 Parcentricity Parcentricity describes the condition wherein a feature will remain at the optical center of the video image throughout the magnification range. Like parfocality, parcentricity requires that the feature be first located at highest magnification. Steps to check parcentricity: 1. Place the MAG checker or other suitable inspection part on the stage and secure properly. 2. Select the M3 crosshair image tool and place the crosshair at its defined center position. The crosshair is to remain at this position during the parcentricity test. 3. Zoom to low magnification, and adjust the stage position so that the crosshair is centered on the X-Y axis of the calibration standard (or another suitable feature if the standard is not used). 4. Change to high magnification and refocus the image. 5. Adjust the stage position as needed to recenter the crosshair on the feature. 6. While observing the feature, slowly adjust the magnification lower. Verify that the feature remains at the center of the crosshair as the magnification is lowered. 7. Report any observed discrepancy. If the error is verified, contact your Starrett representative for authorized service. 6.2.3 Squareness Squareness refers to the alignment of the camera relative to the motion of the metrology stage. If the camera is misaligned (out of square), an image will appear to drift diagonally across the video image as the stage position is moved along one axis. Stepsto check Squareness: 1. Place the MAG checker or other suitable inspection part on the stage and secure properly. 2. Select the crosshair image tool and verify that it is at its defined center position, 3. At low mag, select a point-like feature such as a corner or the standard’s X-Y origin. Using the stage, position it to the center of the crosshair. 4. Zoom to high magnification, then refocus and recenter the point as needed. 5. While observing the feature, slowly move the stage X axis ONLY. (Do not move the stage Y axis.) Verify that the point remains aligned on the X axis of the crosshair as the feature is moved to the left and right within the field of view 6. Report any observed discrepancy. If the error is verified, contact your Starrett representative for authorized service.
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