Optical sectioning is a non-destructive method of measuring irregular shapesthat are often difficult to reach by other measuring methods.

The procedure consists of focusing on a edge of light perpendicular to the part,then viewing the edge of light at 90° to the projected light source. When properly aligned, the edge of light appears as a very narrow cross section line of the area viewed. Optical Gaging Products' optical design utilizes a cube beamsplitter in front of the objective lens which combines the part image and a 1:1 reticle image beforepassing through the objective lens. The focal length is 4 2".

The superimposed images are then viewed in the microscope eyepiece or by moving a mirror into the light path. The images are then focused on the video camera and viewed on the monitor. A major advantage of this system is that the reticles are made at a 1:1 ratio and mounted in individual cells for quick change over from part to part. The part image and reticle formed are each set to equal and perfect focus through the beam splitter and single objective lens and therefore any optical or electronic distortion does not change the relationship of the two superimposed images. The use of optical sectioning means a large number of parts can be checked rapidly and with less fatigue, as compared to mechanical probe tracing of section outlines or the use of 1:1 sight templates. Continuity of the entire edge can be checked as the part is passed through the band of light.