Optical Flat - Single & Double Sided

Produced from Quartz, Kemet Optical Flats are available in single and double sided, 1/4* light band accuracy, in sizes from 25mm up to 600mm diameter**. They are supplied with Certificate of Conformity with full traceability to international standards. Special optical flats are available on request. Kemet offers an optical flat reconditioning and calibration service.

* Higher accuracy available on request.
** Larger sizes made to order with configurations such as square optical flats, rectangle optical flats, donut optical flats and custom optical flat thickness are available.

optical flat

For reconditioning of Optical Flats, please contact us for a quote.

1/4 light band optical flats (Lambda/8)
Diameter Single sided Double sided
25mm 361220 361237
50mm 361222 361215
75mm 361224 361705
100mm 361226 361210
125mm 361228 361242
150mm 361123 361216
200mm 361232 361219
250mm 361234 361217
300mm 361218 361246
1/10 light band optical flats (Lambda/20)
Diameter Single sided Double sided
25mm 361221 361238
50mm 361223 361239
75mm 361225 361240
100mm 361227 361241
125mm 361229 361214
150mm 361231 361243
200mm 361233 361244
250mm 361235 361245
300mm 361236 361247

Large Optical Flats

Diameter Flatness Single Sided Double Sided
mm Inches
330 13 1/2 light band. Lambda/4
350 14 1/2 light band. Lambda/4
400 16 1/2 light band. Lambda/4
450 18 1/2 light band. Lambda/4
500 20 1/2 light band. Lambda/4
600 24 2 light band. Lambda4  

* Within any 300mm Dia

Optical Flat Stands are required for the above Optical Flats

Accessories for Optical Flats

Optical Flat Cleaning/Care Kit

This Kit is used for cleaning Optical Flats. Taking special care of these will ensure accuracy and long service.

optical flat cleaning kit

Optical Flat Stands

Stands for large optical flats (250mm diameter and above) for protection of optical flat.

optical flat stand

Using Optical Flats with Monolights

The surface being examined must be smooth and reflective so that light will be reflected back through the optical flat.

On very hard materials, such as hardened alloy steel, the lapped finish will generally reflect sufficient light to give accurate readings. On soft materials, such as brass, copper, mild steel etc., it is necessary to polish the surface by rubbing the part on a polishing medium.

The operator, while using a figure of eight motion similar to that used in hand lapping, should hold the part in such a way that no distortion occurs to the polished surface. Most parts will polish more efficiently if thoroughly cleaned of all lapping vehicle and abrasive.

Optical Flat Adjustment

After the part has been polished to achieve reflectivity, it is placed under the monochromatic light source. Both the optical flat and the part must be clean and dry. If necessary, clean with a lintless material such as lens tissue or camels hair brush.

The optical flat should be placed or removed directly from the surface to be checked. Never slide the flat across the part surface as this will scratch the flat and shorten its useful life.

The width of the light bands is dependant upon the thickness of the air wedge which always exists between two parts. Minute particles of dust or dirt on either surface will hold the flat far enough away from the part so that the light bands will be very narrow and close together. The thickness of the air wedge can be decreased either by more cleaning or by gently pressing on the optical flat to force out some of the air. As the air wedge thickness decreases the light bands become wider. The width of the light bands or the number of bands does not affect the surface measurement, only the ease of making an accurate reading. The bands need only to be as wide as necessary for an accurate interpretation of their curvature.