AVX System User Guide
8.3 Performing Monthly Zoom Optics Alignment Verification The system’s zoom optics (if applicable) should be verified monthly for parfocality, parcentricity, and squareness to ensure accurate measurement. Verification is straightforward and can be performed as often as desired.
Caution
While optical alignment verification may be performed by an operator, optical alignment correction should only be performed by an authorized service technician. If alignment discrepancies are found, contact Starrett or your local Starrett representative to schedule authorized service.
8.3.1 Zoom Optics Parfocality and Focus
Definition
Parfocality is the condition in which the video image remains in focus as the magnification is adjusted from highest to lowest. Starrett zoom optics are designed to maintain parfocality throughout their magnification range. To check parfocality, always reference a flat, sharp edge. Do not select a rough or sloping feature. The magnification checker provided with the system is an ideal part to check parfocality.
Procedure
To check parfocality, perform the following steps:
1. Place the magnification checker or other suitable inspection part on the stage and secure properly. 2. Backlight the image as necessary using the M3 software. 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 changing the viewing distance. 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.
8.3.2 Zoom Optics Parcentricity
Definition
Parcentricity describes the condition where a feature remains 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.
Procedure
To check parcentricity, perform the following steps:
1. Place the magnification checker or other suitable inspection part on the stage and secure properly.
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