Fizeau Interferometer

• Technical mass products with flat surfaces specified to better than 0.1µm over a few cm are produced by millions per month.
• The production processes are lapping & polishing - and, increasingly more often, micro-machining; 90% have diameters under 50mm.
• ISO 9000 requires tight inspection often 100%.
• The most common tool for this is The Interferometer
• An esteemed value to engineers as does the stethoscope for the medical practitioner.

Principle :
Interferometer is shown in Figure 1 (The basic layout of a Fizeau Autocollimator). A laser source is spatial y filtered via a microscope objective. This microscope objective is located at the focal point of a collimating lens. Between the microscope objective and lens is a cube beam-splitter. The collimated beam encounters a slightly wedged glass plate. This is the heart of the interferometer. The surface adjacent to the collimating lens is of good optical quality.

However, the next surface is of exceptional optical quality, ?/10 peak to valley (PV) or better. This is the reference surface and part of the collimated beam is reflected by this surface. Part of the collimated beam continues on to interrogate the component being tested. The return beam contains information on aberration introduced by the test surface. The two wave fronts recombine inside the interferometer.

The cube beam-splitter diverts the combined beam towards a recording medium, either film or a CCD. An intermediate lens forms an image of the test surface onto the recording plane.

Technical Specifications:

	Model - FAC-30	Model - FAC-60	Model - FAC-100
Orientation:	Vertical	Vertical	Vertical
Light Source- He-Ne Laser	< 2 mW	< 2 mW	< 2 mW
Clear Aperture:	25 mm	55 mm	95 mm
Reference Flat:	Lambda/10	Lambda/10	Lambda/10
Work Table (Tilt Table) Dimension:	3" x 3"	4" x 4"	6" x 6"
1/2"  CCD Camera:	640 x 570 pixels	640 x 570 pixels	640 x 570 pixels
Viewing : Alignment and Fringe viewing	Yes	Yes	Yes
Dimensions : L x B X H	300 x 250  x 470	300 x 250 x 570	300 x 250 x 800
Weight :	27 Kgs	38 Kgs	45 Kgs