Measuring Instruments » Optical Flat

Speedfam optical flats provide the fast, sure and accurate method of obtaining flatness measurement under Monochromatic Checklite. It is always necessary to have reflective, clean and dry surface of finished component before measuring its flatness. Flatness measurements are accomplished by reading interference (light) bands which appear on the surface of the work piece when placed under a Speedfam optical flat. Fringes appear when the flat is placed gently on work piece surface under Monochromatic Checklite. The optical flats are available in various diameters.

Optical flats are available in Borosilicate glass material with flatness accuracies as ?4, ?6, ?10. These are available either Single side or Double side surfaces. Sizes available are 1", 2", 3", 4", 5", 6", as standards and other sizes on request.

Light bands or lines & their interpretation is illustrated as below.


Straight,parallel lines or bands indicate true flatness

The flatness is read from the no. of bands intersected by a tangent line to any curve, counted from the point of greatest curvature to one side of piece. Above work piece is 1band out-of-flat.

Illustration shows low area or grove in work piece of 1/2 band deep and a drop-off area at lower right hand edge of 1band.

Shown here is edge rounding or "Dubbing" of 1/2 band.

If broadening of light bands occurs when pressed at the center, the piece is concave

Either concave or convex pieces may show as a "Bulls-Eye" design. If Bulls-Eye" moves toward point of pressure when pressed on edge the piece is convex.

Applications : To measure flatness on polished components w.r.t. checklite.