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Moire Metrical Topography with Micrometer Resolution

IP.com Disclosure Number: IPCOM000049589D
Original Publication Date: 1982-Jun-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Drollinger, B: AUTHOR [+3]

Abstract

A moire set up is modified in that the test grating on the sample surface is generated by two plain waves brought to interference in the same area.

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Moire Metrical Topography with Micrometer Resolution

A moire set up is modified in that the test grating on the sample surface is generated by two plain waves brought to interference in the same area.

In the figure, the exit beam of laser 1 is expanded by collimator optics 2 and reflected from two plain mirrors 3a, 3b, forming a roof mirror with a variable angle theta /2. The reflected beams 4, 5 with plain wavefronts are brought to interference in the area of object 6, thus generating a space grating with a grating constant g equals lambda /2 sin theta. This interference field has maximum contrast on the entire surface of object 6 and is not subject to depth of focus problems encountered when material gratings are imaged onto the test surface.

The test grating on the object is imaged by lens 7 onto a reference grating 8 where moire fringes appear that can be recorded by TV camera 9 and displayed on monitor 10. The moire fringes represent contour lines of object 6.

If scattering objects 6 are to be examined, the optical axis of imaging lens 7 is preferably oriented vertically to the object plane; this configuration requires only a relatively small depth of field for imaging the entire object 6 onto reference grating 8. A high resolution optical system 7 can thus be chosen which again permits the use of small grating constants (down to 10 micrometers), thus yielding a high measuring sensitivity.

The measuring range of the set up in the figure can easily be changed...