Figure 25. Inline Clean Air Kit Filter
8.5 Verifying Zoom Optics Alignment
The system’s zoom optics (if ordered) should be verified regularly to ensure accurate measurement. Parfocality, parcentricity and squareness verifications are straightforward and can be performed as often as desired. Focus is adjusted as needed by changing the distance between the lens and the surface being viewed. Note : Optical alignment verification can be performed by any qualified operator. However, optical alignment correction should only be performed by an authorized technician. Report any observed alignment discrepancies and contact the factory or your local Starrett representative to schedule authorized service.
8.5.1 Zoom Optics Parfocality and Focus
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. A magnification (mag) checker is an ideal part to check parfocality.
To check parfocality, perform the following steps:
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 the 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.
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