Browse Prior Art Database

Achromatic Oblique Viewing Microscope

IP.com Disclosure Number: IPCOM000114934D
Original Publication Date: 1995-Feb-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 69K

Publishing Venue

IBM

Related People

Chastang, J: AUTHOR [+3]

Abstract

Disclosed is an achromatic oblique viewing microscope capable of operating at a plurality of wavelengths and obliquities. This invention eliminates two of the limitations associated with the original oblique viewing microscope (1) which could only work at a fixed wavelength and a fixed obliquity.

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Achromatic Oblique Viewing Microscope

      Disclosed is an achromatic oblique viewing microscope capable
of operating at a plurality of wavelengths and obliquities.  This
invention eliminates two of the limitations associated with the
original oblique viewing microscope (1)  which could only work at a
fixed wavelength and a fixed obliquity.

      The technique of oblique illumination and microscopic oblique
viewing is advantageous in the study of the topography of small
samples and has been used by IBM* to determine the relative volume of
C4 solder balls (2).

      The principle of the achromatic oblique viewing microscope is
similar to that of the original oblique viewing microscope.  However,
the replacement of the afocal relay lens with a commercial optical
systems and the replacement of the simple microscope optics with long
working distance optics allows the new microscope to operate at a
variety of wavelengths and obliquities.

      The commercial optical system is the Offner lens (3).  This
system consists of two mirrors: a large primary and a smaller
secondary.  These mirrors are concentric.  Under the name of
Micralign objectives, such systems were at one time widely used for
photolithographic applications.  In this invention, the Micralign
objective is used to image the sample onto the diffraction grating in
the manner shown in the Figure.  Note the presence of an illumination
arm whose axis makes an angle 2 alpha with the optical axis of the
Micralign objecti...