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Retroreflective Microscope Illuminator

IP.com Disclosure Number: IPCOM000046742D
Original Publication Date: 1983-Aug-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Johnson, M: AUTHOR

Abstract

Microscopic viewing of specularly reflecting objects may be greatly simplified by placing retroreflective sheet material close to the object being viewed. Microscopes are widely used for the inspection of small components, such as electronic chips, small gold plated parts, silicon optical benches, etc. For good subjective viewing of the topography of the device it is convenient in many cases to tilt it. Unfortunately, an illumination problem occurs when the usual coaxial illuminator is used, as the device may have a high specular reflectivity, and little light is recaptured by the microscope objective. A typical example of this is in inspection of 'V-grooves' in etched substrates. The normal solution is to adjust external light sources until the feature of interest eventually comes into satisfactory view.

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Retroreflective Microscope Illuminator

Microscopic viewing of specularly reflecting objects may be greatly simplified by placing retroreflective sheet material close to the object being viewed. Microscopes are widely used for the inspection of small components, such as electronic chips, small gold plated parts, silicon optical benches, etc. For good subjective viewing of the topography of the device it is convenient in many cases to tilt it. Unfortunately, an illumination problem occurs when the usual coaxial illuminator is used, as the device may have a high specular reflectivity, and little light is recaptured by the microscope objective. A typical example of this is in inspection of 'V-grooves' in etched substrates. The normal solution is to adjust external light sources until the feature of interest eventually comes into satisfactory view. A simple technique which eases this problem is to place a retroreflective region near to the object, such as may be created easily, for example, with sheet material like SCOTCHLITE*. This is a plastic sheet material with a coating of high index beads. Another retroreflective sheet material is a vinyl replicated retroreflector array manufactured by the Reflexite Corporation.

These materials scatter any incident light back along its original path into the microscope (Fig. 1). Positioning is not critical.

Various types of light-tent arrangements will occur to the reader. A second application area for retroreflector augmented i...