Browse Prior Art Database

Surface Contour Measuring Instrument

IP.com Disclosure Number: IPCOM000043826D
Original Publication Date: 1984-Sep-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 2 page(s) / 62K

Publishing Venue

IBM

Related People

Goodman, DS: AUTHOR [+2]

Abstract

Imperfections in flat surfaces may be measured by projecting onto the test surface a transparency having a variation in optical density. An irregular surface will bend the projected equi-brightness contours, which may be viewed or detected in various ways. In the traditional light section or Schmaltz microscope (Fig. 1), surface contours are measured by projecting the image of a slit onto a surface at an angle. Contours result in bending of the projected slit. In the device here disclosed, the slit is replaced by a transparency having an optical density gradient (Fig. 2). The density variation of the transparency is in one direction, so that when it is projected onto a flat surface, the image has parallel loci of equal brightness. The steps could be linear, logarithmic, etc., as dictated by other requirements.

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Surface Contour Measuring Instrument

Imperfections in flat surfaces may be measured by projecting onto the test surface a transparency having a variation in optical density. An irregular surface will bend the projected equi-brightness contours, which may be viewed or detected in various ways. In the traditional light section or Schmaltz microscope (Fig. 1), surface contours are measured by projecting the image of a slit onto a surface at an angle. Contours result in bending of the projected slit. In the device here disclosed, the slit is replaced by a transparency having an optical density gradient (Fig. 2). The density variation of the transparency is in one direction, so that when it is projected onto a flat surface, the image has parallel loci of equal brightness. The steps could be linear, logarithmic, etc., as dictated by other requirements. The brightness variation could be continuous, or there could be discrete steps. If the surface has bumps or depressions, the loci of equal brightness will be curved (Fig. 3). There are a number of ways this principle could be exploited. One system is shown in Fig. 4. A linear detector is imaged onto the central line of constant brightness for a flat surface of proper height. The surface is then translated beneath the optical system. Surface contours are read out from the detector array. If the surface is flat, the outputs of the detector elements are identical. If it is flat, but is not of the proper height, the detector...