| Popis: |
Two optical methods were investigated for accurately measuring the gap, or chamber spacing, that separates two closely spaced transparent plates. The first method uses a special microscope in which the main feature is a unit-magnification catadioptric system that gives an aberration-free image of the chamber outside the plates, where it is accessible to a high-power objective. The second method is based upon the light section principle, where by the image of a slit is projected on to the boundaries of the chamber and is thus doubled. The reflected images are observed with a microscope and the degree of separation, which is proportional to the chamber spacing, is measured. Accuracy better than 2 µm is obtained for the two techniques. The choice of the appropriate method depends on the surface quality of the chamber boundaries. |
